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@@ -0,0 +1,1364 @@
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+/*
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+ * Utility functions for x86 operand and address decoding
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+ *
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+ * Copyright (C) Intel Corporation 2017
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+ */
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+#include <linux/kernel.h>
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+#include <linux/string.h>
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+#include <linux/ratelimit.h>
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+#include <linux/mmu_context.h>
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+#include <asm/desc_defs.h>
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+#include <asm/desc.h>
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+#include <asm/inat.h>
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+#include <asm/insn.h>
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+#include <asm/insn-eval.h>
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+#include <asm/ldt.h>
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+#include <asm/vm86.h>
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+
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+#undef pr_fmt
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+#define pr_fmt(fmt) "insn: " fmt
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+
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+enum reg_type {
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+ REG_TYPE_RM = 0,
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+ REG_TYPE_INDEX,
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+ REG_TYPE_BASE,
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+};
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+
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+/**
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+ * is_string_insn() - Determine if instruction is a string instruction
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+ * @insn: Instruction containing the opcode to inspect
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+ *
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+ * Returns:
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+ *
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+ * true if the instruction, determined by the opcode, is any of the
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+ * string instructions as defined in the Intel Software Development manual.
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+ * False otherwise.
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+ */
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+static bool is_string_insn(struct insn *insn)
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+{
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+ insn_get_opcode(insn);
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+
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+ /* All string instructions have a 1-byte opcode. */
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+ if (insn->opcode.nbytes != 1)
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+ return false;
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+
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+ switch (insn->opcode.bytes[0]) {
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+ case 0x6c ... 0x6f: /* INS, OUTS */
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+ case 0xa4 ... 0xa7: /* MOVS, CMPS */
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+ case 0xaa ... 0xaf: /* STOS, LODS, SCAS */
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+ return true;
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+ default:
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+ return false;
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+ }
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+}
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+
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+/**
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+ * get_seg_reg_override_idx() - obtain segment register override index
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+ * @insn: Valid instruction with segment override prefixes
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+ *
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+ * Inspect the instruction prefixes in @insn and find segment overrides, if any.
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+ *
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+ * Returns:
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+ *
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+ * A constant identifying the segment register to use, among CS, SS, DS,
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+ * ES, FS, or GS. INAT_SEG_REG_DEFAULT is returned if no segment override
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+ * prefixes were found.
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+ *
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+ * -EINVAL in case of error.
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+ */
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+static int get_seg_reg_override_idx(struct insn *insn)
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+{
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+ int idx = INAT_SEG_REG_DEFAULT;
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+ int num_overrides = 0, i;
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+
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+ insn_get_prefixes(insn);
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+
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+ /* Look for any segment override prefixes. */
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+ for (i = 0; i < insn->prefixes.nbytes; i++) {
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+ insn_attr_t attr;
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+
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+ attr = inat_get_opcode_attribute(insn->prefixes.bytes[i]);
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+ switch (attr) {
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+ case INAT_MAKE_PREFIX(INAT_PFX_CS):
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+ idx = INAT_SEG_REG_CS;
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+ num_overrides++;
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+ break;
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+ case INAT_MAKE_PREFIX(INAT_PFX_SS):
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+ idx = INAT_SEG_REG_SS;
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+ num_overrides++;
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+ break;
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+ case INAT_MAKE_PREFIX(INAT_PFX_DS):
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+ idx = INAT_SEG_REG_DS;
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+ num_overrides++;
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+ break;
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+ case INAT_MAKE_PREFIX(INAT_PFX_ES):
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+ idx = INAT_SEG_REG_ES;
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+ num_overrides++;
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+ break;
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+ case INAT_MAKE_PREFIX(INAT_PFX_FS):
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+ idx = INAT_SEG_REG_FS;
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+ num_overrides++;
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+ break;
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+ case INAT_MAKE_PREFIX(INAT_PFX_GS):
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+ idx = INAT_SEG_REG_GS;
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+ num_overrides++;
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+ break;
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+ /* No default action needed. */
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+ }
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+ }
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+
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+ /* More than one segment override prefix leads to undefined behavior. */
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+ if (num_overrides > 1)
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+ return -EINVAL;
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+
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+ return idx;
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+}
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+
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+/**
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+ * check_seg_overrides() - check if segment override prefixes are allowed
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+ * @insn: Valid instruction with segment override prefixes
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+ * @regoff: Operand offset, in pt_regs, for which the check is performed
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+ *
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+ * For a particular register used in register-indirect addressing, determine if
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+ * segment override prefixes can be used. Specifically, no overrides are allowed
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+ * for rDI if used with a string instruction.
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+ *
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+ * Returns:
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+ *
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+ * True if segment override prefixes can be used with the register indicated
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+ * in @regoff. False if otherwise.
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+ */
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+static bool check_seg_overrides(struct insn *insn, int regoff)
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+{
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+ if (regoff == offsetof(struct pt_regs, di) && is_string_insn(insn))
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+ return false;
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+
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+ return true;
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+}
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+
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+/**
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+ * resolve_default_seg() - resolve default segment register index for an operand
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+ * @insn: Instruction with opcode and address size. Must be valid.
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+ * @regs: Register values as seen when entering kernel mode
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+ * @off: Operand offset, in pt_regs, for which resolution is needed
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+ *
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+ * Resolve the default segment register index associated with the instruction
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+ * operand register indicated by @off. Such index is resolved based on defaults
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+ * described in the Intel Software Development Manual.
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+ *
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+ * Returns:
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+ *
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+ * If in protected mode, a constant identifying the segment register to use,
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+ * among CS, SS, ES or DS. If in long mode, INAT_SEG_REG_IGNORE.
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+ *
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+ * -EINVAL in case of error.
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+ */
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+static int resolve_default_seg(struct insn *insn, struct pt_regs *regs, int off)
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+{
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+ if (user_64bit_mode(regs))
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+ return INAT_SEG_REG_IGNORE;
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+ /*
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+ * Resolve the default segment register as described in Section 3.7.4
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+ * of the Intel Software Development Manual Vol. 1:
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+ *
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+ * + DS for all references involving r[ABCD]X, and rSI.
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+ * + If used in a string instruction, ES for rDI. Otherwise, DS.
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+ * + AX, CX and DX are not valid register operands in 16-bit address
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+ * encodings but are valid for 32-bit and 64-bit encodings.
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+ * + -EDOM is reserved to identify for cases in which no register
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+ * is used (i.e., displacement-only addressing). Use DS.
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+ * + SS for rSP or rBP.
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+ * + CS for rIP.
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+ */
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+
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+ switch (off) {
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+ case offsetof(struct pt_regs, ax):
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+ case offsetof(struct pt_regs, cx):
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+ case offsetof(struct pt_regs, dx):
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+ /* Need insn to verify address size. */
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+ if (insn->addr_bytes == 2)
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+ return -EINVAL;
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+
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+ case -EDOM:
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+ case offsetof(struct pt_regs, bx):
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+ case offsetof(struct pt_regs, si):
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+ return INAT_SEG_REG_DS;
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+
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+ case offsetof(struct pt_regs, di):
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+ if (is_string_insn(insn))
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+ return INAT_SEG_REG_ES;
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+ return INAT_SEG_REG_DS;
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+
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+ case offsetof(struct pt_regs, bp):
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+ case offsetof(struct pt_regs, sp):
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+ return INAT_SEG_REG_SS;
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+
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+ case offsetof(struct pt_regs, ip):
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+ return INAT_SEG_REG_CS;
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+
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+ default:
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+ return -EINVAL;
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+ }
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+}
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+
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+/**
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+ * resolve_seg_reg() - obtain segment register index
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+ * @insn: Instruction with operands
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+ * @regs: Register values as seen when entering kernel mode
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+ * @regoff: Operand offset, in pt_regs, used to deterimine segment register
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+ *
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+ * Determine the segment register associated with the operands and, if
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+ * applicable, prefixes and the instruction pointed by @insn.
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+ *
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+ * The segment register associated to an operand used in register-indirect
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+ * addressing depends on:
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+ *
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+ * a) Whether running in long mode (in such a case segments are ignored, except
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+ * if FS or GS are used).
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+ *
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+ * b) Whether segment override prefixes can be used. Certain instructions and
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+ * registers do not allow override prefixes.
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+ *
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+ * c) Whether segment overrides prefixes are found in the instruction prefixes.
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+ *
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+ * d) If there are not segment override prefixes or they cannot be used, the
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+ * default segment register associated with the operand register is used.
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+ *
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+ * The function checks first if segment override prefixes can be used with the
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+ * operand indicated by @regoff. If allowed, obtain such overridden segment
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+ * register index. Lastly, if not prefixes were found or cannot be used, resolve
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+ * the segment register index to use based on the defaults described in the
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+ * Intel documentation. In long mode, all segment register indexes will be
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+ * ignored, except if overrides were found for FS or GS. All these operations
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+ * are done using helper functions.
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+ *
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+ * The operand register, @regoff, is represented as the offset from the base of
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+ * pt_regs.
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+ *
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+ * As stated, the main use of this function is to determine the segment register
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+ * index based on the instruction, its operands and prefixes. Hence, @insn
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+ * must be valid. However, if @regoff indicates rIP, we don't need to inspect
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+ * @insn at all as in this case CS is used in all cases. This case is checked
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+ * before proceeding further.
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+ *
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+ * Please note that this function does not return the value in the segment
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+ * register (i.e., the segment selector) but our defined index. The segment
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+ * selector needs to be obtained using get_segment_selector() and passing the
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+ * segment register index resolved by this function.
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+ *
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+ * Returns:
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+ *
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+ * An index identifying the segment register to use, among CS, SS, DS,
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+ * ES, FS, or GS. INAT_SEG_REG_IGNORE is returned if running in long mode.
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+ *
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+ * -EINVAL in case of error.
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+ */
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+static int resolve_seg_reg(struct insn *insn, struct pt_regs *regs, int regoff)
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+{
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+ int idx;
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+
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+ /*
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+ * In the unlikely event of having to resolve the segment register
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+ * index for rIP, do it first. Segment override prefixes should not
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+ * be used. Hence, it is not necessary to inspect the instruction,
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+ * which may be invalid at this point.
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+ */
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+ if (regoff == offsetof(struct pt_regs, ip)) {
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+ if (user_64bit_mode(regs))
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+ return INAT_SEG_REG_IGNORE;
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+ else
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+ return INAT_SEG_REG_CS;
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+ }
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+
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+ if (!insn)
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+ return -EINVAL;
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+
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+ if (!check_seg_overrides(insn, regoff))
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+ return resolve_default_seg(insn, regs, regoff);
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+
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+ idx = get_seg_reg_override_idx(insn);
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+ if (idx < 0)
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+ return idx;
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+
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+ if (idx == INAT_SEG_REG_DEFAULT)
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+ return resolve_default_seg(insn, regs, regoff);
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+
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+ /*
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+ * In long mode, segment override prefixes are ignored, except for
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+ * overrides for FS and GS.
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+ */
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+ if (user_64bit_mode(regs)) {
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+ if (idx != INAT_SEG_REG_FS &&
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+ idx != INAT_SEG_REG_GS)
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+ idx = INAT_SEG_REG_IGNORE;
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+ }
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+
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+ return idx;
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+}
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+
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+/**
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+ * get_segment_selector() - obtain segment selector
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+ * @regs: Register values as seen when entering kernel mode
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+ * @seg_reg_idx: Segment register index to use
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+ *
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+ * Obtain the segment selector from any of the CS, SS, DS, ES, FS, GS segment
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+ * registers. In CONFIG_X86_32, the segment is obtained from either pt_regs or
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+ * kernel_vm86_regs as applicable. In CONFIG_X86_64, CS and SS are obtained
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+ * from pt_regs. DS, ES, FS and GS are obtained by reading the actual CPU
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+ * registers. This done for only for completeness as in CONFIG_X86_64 segment
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+ * registers are ignored.
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+ *
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+ * Returns:
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+ *
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+ * Value of the segment selector, including null when running in
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+ * long mode.
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+ *
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+ * -EINVAL on error.
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+ */
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+static short get_segment_selector(struct pt_regs *regs, int seg_reg_idx)
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+{
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+#ifdef CONFIG_X86_64
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+ unsigned short sel;
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+
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+ switch (seg_reg_idx) {
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+ case INAT_SEG_REG_IGNORE:
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+ return 0;
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+ case INAT_SEG_REG_CS:
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+ return (unsigned short)(regs->cs & 0xffff);
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+ case INAT_SEG_REG_SS:
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+ return (unsigned short)(regs->ss & 0xffff);
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+ case INAT_SEG_REG_DS:
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+ savesegment(ds, sel);
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+ return sel;
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+ case INAT_SEG_REG_ES:
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+ savesegment(es, sel);
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+ return sel;
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+ case INAT_SEG_REG_FS:
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+ savesegment(fs, sel);
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+ return sel;
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+ case INAT_SEG_REG_GS:
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+ savesegment(gs, sel);
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+ return sel;
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+ default:
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+ return -EINVAL;
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+ }
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+#else /* CONFIG_X86_32 */
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+ struct kernel_vm86_regs *vm86regs = (struct kernel_vm86_regs *)regs;
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+
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+ if (v8086_mode(regs)) {
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+ switch (seg_reg_idx) {
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+ case INAT_SEG_REG_CS:
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+ return (unsigned short)(regs->cs & 0xffff);
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+ case INAT_SEG_REG_SS:
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+ return (unsigned short)(regs->ss & 0xffff);
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+ case INAT_SEG_REG_DS:
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+ return vm86regs->ds;
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+ case INAT_SEG_REG_ES:
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+ return vm86regs->es;
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+ case INAT_SEG_REG_FS:
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+ return vm86regs->fs;
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+ case INAT_SEG_REG_GS:
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+ return vm86regs->gs;
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+ case INAT_SEG_REG_IGNORE:
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+ /* fall through */
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+ default:
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+ return -EINVAL;
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+ }
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+ }
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+
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+ switch (seg_reg_idx) {
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+ case INAT_SEG_REG_CS:
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+ return (unsigned short)(regs->cs & 0xffff);
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+ case INAT_SEG_REG_SS:
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+ return (unsigned short)(regs->ss & 0xffff);
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+ case INAT_SEG_REG_DS:
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+ return (unsigned short)(regs->ds & 0xffff);
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+ case INAT_SEG_REG_ES:
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+ return (unsigned short)(regs->es & 0xffff);
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+ case INAT_SEG_REG_FS:
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+ return (unsigned short)(regs->fs & 0xffff);
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+ case INAT_SEG_REG_GS:
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+ /*
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+ * GS may or may not be in regs as per CONFIG_X86_32_LAZY_GS.
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+ * The macro below takes care of both cases.
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+ */
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+ return get_user_gs(regs);
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+ case INAT_SEG_REG_IGNORE:
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+ /* fall through */
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+ default:
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+ return -EINVAL;
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+ }
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+#endif /* CONFIG_X86_64 */
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+}
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+
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+static int get_reg_offset(struct insn *insn, struct pt_regs *regs,
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+ enum reg_type type)
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+{
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+ int regno = 0;
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+
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+ static const int regoff[] = {
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+ offsetof(struct pt_regs, ax),
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+ offsetof(struct pt_regs, cx),
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+ offsetof(struct pt_regs, dx),
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+ offsetof(struct pt_regs, bx),
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|
|
+ offsetof(struct pt_regs, sp),
|
|
|
+ offsetof(struct pt_regs, bp),
|
|
|
+ offsetof(struct pt_regs, si),
|
|
|
+ offsetof(struct pt_regs, di),
|
|
|
+#ifdef CONFIG_X86_64
|
|
|
+ offsetof(struct pt_regs, r8),
|
|
|
+ offsetof(struct pt_regs, r9),
|
|
|
+ offsetof(struct pt_regs, r10),
|
|
|
+ offsetof(struct pt_regs, r11),
|
|
|
+ offsetof(struct pt_regs, r12),
|
|
|
+ offsetof(struct pt_regs, r13),
|
|
|
+ offsetof(struct pt_regs, r14),
|
|
|
+ offsetof(struct pt_regs, r15),
|
|
|
+#endif
|
|
|
+ };
|
|
|
+ int nr_registers = ARRAY_SIZE(regoff);
|
|
|
+ /*
|
|
|
+ * Don't possibly decode a 32-bit instructions as
|
|
|
+ * reading a 64-bit-only register.
|
|
|
+ */
|
|
|
+ if (IS_ENABLED(CONFIG_X86_64) && !insn->x86_64)
|
|
|
+ nr_registers -= 8;
|
|
|
+
|
|
|
+ switch (type) {
|
|
|
+ case REG_TYPE_RM:
|
|
|
+ regno = X86_MODRM_RM(insn->modrm.value);
|
|
|
+
|
|
|
+ /*
|
|
|
+ * ModRM.mod == 0 and ModRM.rm == 5 means a 32-bit displacement
|
|
|
+ * follows the ModRM byte.
|
|
|
+ */
|
|
|
+ if (!X86_MODRM_MOD(insn->modrm.value) && regno == 5)
|
|
|
+ return -EDOM;
|
|
|
+
|
|
|
+ if (X86_REX_B(insn->rex_prefix.value))
|
|
|
+ regno += 8;
|
|
|
+ break;
|
|
|
+
|
|
|
+ case REG_TYPE_INDEX:
|
|
|
+ regno = X86_SIB_INDEX(insn->sib.value);
|
|
|
+ if (X86_REX_X(insn->rex_prefix.value))
|
|
|
+ regno += 8;
|
|
|
+
|
|
|
+ /*
|
|
|
+ * If ModRM.mod != 3 and SIB.index = 4 the scale*index
|
|
|
+ * portion of the address computation is null. This is
|
|
|
+ * true only if REX.X is 0. In such a case, the SIB index
|
|
|
+ * is used in the address computation.
|
|
|
+ */
|
|
|
+ if (X86_MODRM_MOD(insn->modrm.value) != 3 && regno == 4)
|
|
|
+ return -EDOM;
|
|
|
+ break;
|
|
|
+
|
|
|
+ case REG_TYPE_BASE:
|
|
|
+ regno = X86_SIB_BASE(insn->sib.value);
|
|
|
+ /*
|
|
|
+ * If ModRM.mod is 0 and SIB.base == 5, the base of the
|
|
|
+ * register-indirect addressing is 0. In this case, a
|
|
|
+ * 32-bit displacement follows the SIB byte.
|
|
|
+ */
|
|
|
+ if (!X86_MODRM_MOD(insn->modrm.value) && regno == 5)
|
|
|
+ return -EDOM;
|
|
|
+
|
|
|
+ if (X86_REX_B(insn->rex_prefix.value))
|
|
|
+ regno += 8;
|
|
|
+ break;
|
|
|
+
|
|
|
+ default:
|
|
|
+ pr_err_ratelimited("invalid register type: %d\n", type);
|
|
|
+ return -EINVAL;
|
|
|
+ }
|
|
|
+
|
|
|
+ if (regno >= nr_registers) {
|
|
|
+ WARN_ONCE(1, "decoded an instruction with an invalid register");
|
|
|
+ return -EINVAL;
|
|
|
+ }
|
|
|
+ return regoff[regno];
|
|
|
+}
|
|
|
+
|
|
|
+/**
|
|
|
+ * get_reg_offset_16() - Obtain offset of register indicated by instruction
|
|
|
+ * @insn: Instruction containing ModRM byte
|
|
|
+ * @regs: Register values as seen when entering kernel mode
|
|
|
+ * @offs1: Offset of the first operand register
|
|
|
+ * @offs2: Offset of the second opeand register, if applicable
|
|
|
+ *
|
|
|
+ * Obtain the offset, in pt_regs, of the registers indicated by the ModRM byte
|
|
|
+ * in @insn. This function is to be used with 16-bit address encodings. The
|
|
|
+ * @offs1 and @offs2 will be written with the offset of the two registers
|
|
|
+ * indicated by the instruction. In cases where any of the registers is not
|
|
|
+ * referenced by the instruction, the value will be set to -EDOM.
|
|
|
+ *
|
|
|
+ * Returns:
|
|
|
+ *
|
|
|
+ * 0 on success, -EINVAL on error.
|
|
|
+ */
|
|
|
+static int get_reg_offset_16(struct insn *insn, struct pt_regs *regs,
|
|
|
+ int *offs1, int *offs2)
|
|
|
+{
|
|
|
+ /*
|
|
|
+ * 16-bit addressing can use one or two registers. Specifics of
|
|
|
+ * encodings are given in Table 2-1. "16-Bit Addressing Forms with the
|
|
|
+ * ModR/M Byte" of the Intel Software Development Manual.
|
|
|
+ */
|
|
|
+ static const int regoff1[] = {
|
|
|
+ offsetof(struct pt_regs, bx),
|
|
|
+ offsetof(struct pt_regs, bx),
|
|
|
+ offsetof(struct pt_regs, bp),
|
|
|
+ offsetof(struct pt_regs, bp),
|
|
|
+ offsetof(struct pt_regs, si),
|
|
|
+ offsetof(struct pt_regs, di),
|
|
|
+ offsetof(struct pt_regs, bp),
|
|
|
+ offsetof(struct pt_regs, bx),
|
|
|
+ };
|
|
|
+
|
|
|
+ static const int regoff2[] = {
|
|
|
+ offsetof(struct pt_regs, si),
|
|
|
+ offsetof(struct pt_regs, di),
|
|
|
+ offsetof(struct pt_regs, si),
|
|
|
+ offsetof(struct pt_regs, di),
|
|
|
+ -EDOM,
|
|
|
+ -EDOM,
|
|
|
+ -EDOM,
|
|
|
+ -EDOM,
|
|
|
+ };
|
|
|
+
|
|
|
+ if (!offs1 || !offs2)
|
|
|
+ return -EINVAL;
|
|
|
+
|
|
|
+ /* Operand is a register, use the generic function. */
|
|
|
+ if (X86_MODRM_MOD(insn->modrm.value) == 3) {
|
|
|
+ *offs1 = insn_get_modrm_rm_off(insn, regs);
|
|
|
+ *offs2 = -EDOM;
|
|
|
+ return 0;
|
|
|
+ }
|
|
|
+
|
|
|
+ *offs1 = regoff1[X86_MODRM_RM(insn->modrm.value)];
|
|
|
+ *offs2 = regoff2[X86_MODRM_RM(insn->modrm.value)];
|
|
|
+
|
|
|
+ /*
|
|
|
+ * If ModRM.mod is 0 and ModRM.rm is 110b, then we use displacement-
|
|
|
+ * only addressing. This means that no registers are involved in
|
|
|
+ * computing the effective address. Thus, ensure that the first
|
|
|
+ * register offset is invalild. The second register offset is already
|
|
|
+ * invalid under the aforementioned conditions.
|
|
|
+ */
|
|
|
+ if ((X86_MODRM_MOD(insn->modrm.value) == 0) &&
|
|
|
+ (X86_MODRM_RM(insn->modrm.value) == 6))
|
|
|
+ *offs1 = -EDOM;
|
|
|
+
|
|
|
+ return 0;
|
|
|
+}
|
|
|
+
|
|
|
+/**
|
|
|
+ * get_desc() - Obtain pointer to a segment descriptor
|
|
|
+ * @sel: Segment selector
|
|
|
+ *
|
|
|
+ * Given a segment selector, obtain a pointer to the segment descriptor.
|
|
|
+ * Both global and local descriptor tables are supported.
|
|
|
+ *
|
|
|
+ * Returns:
|
|
|
+ *
|
|
|
+ * Pointer to segment descriptor on success.
|
|
|
+ *
|
|
|
+ * NULL on error.
|
|
|
+ */
|
|
|
+static struct desc_struct *get_desc(unsigned short sel)
|
|
|
+{
|
|
|
+ struct desc_ptr gdt_desc = {0, 0};
|
|
|
+ unsigned long desc_base;
|
|
|
+
|
|
|
+#ifdef CONFIG_MODIFY_LDT_SYSCALL
|
|
|
+ if ((sel & SEGMENT_TI_MASK) == SEGMENT_LDT) {
|
|
|
+ struct desc_struct *desc = NULL;
|
|
|
+ struct ldt_struct *ldt;
|
|
|
+
|
|
|
+ /* Bits [15:3] contain the index of the desired entry. */
|
|
|
+ sel >>= 3;
|
|
|
+
|
|
|
+ mutex_lock(¤t->active_mm->context.lock);
|
|
|
+ ldt = current->active_mm->context.ldt;
|
|
|
+ if (ldt && sel < ldt->nr_entries)
|
|
|
+ desc = &ldt->entries[sel];
|
|
|
+
|
|
|
+ mutex_unlock(¤t->active_mm->context.lock);
|
|
|
+
|
|
|
+ return desc;
|
|
|
+ }
|
|
|
+#endif
|
|
|
+ native_store_gdt(&gdt_desc);
|
|
|
+
|
|
|
+ /*
|
|
|
+ * Segment descriptors have a size of 8 bytes. Thus, the index is
|
|
|
+ * multiplied by 8 to obtain the memory offset of the desired descriptor
|
|
|
+ * from the base of the GDT. As bits [15:3] of the segment selector
|
|
|
+ * contain the index, it can be regarded as multiplied by 8 already.
|
|
|
+ * All that remains is to clear bits [2:0].
|
|
|
+ */
|
|
|
+ desc_base = sel & ~(SEGMENT_RPL_MASK | SEGMENT_TI_MASK);
|
|
|
+
|
|
|
+ if (desc_base > gdt_desc.size)
|
|
|
+ return NULL;
|
|
|
+
|
|
|
+ return (struct desc_struct *)(gdt_desc.address + desc_base);
|
|
|
+}
|
|
|
+
|
|
|
+/**
|
|
|
+ * insn_get_seg_base() - Obtain base address of segment descriptor.
|
|
|
+ * @regs: Register values as seen when entering kernel mode
|
|
|
+ * @seg_reg_idx: Index of the segment register pointing to seg descriptor
|
|
|
+ *
|
|
|
+ * Obtain the base address of the segment as indicated by the segment descriptor
|
|
|
+ * pointed by the segment selector. The segment selector is obtained from the
|
|
|
+ * input segment register index @seg_reg_idx.
|
|
|
+ *
|
|
|
+ * Returns:
|
|
|
+ *
|
|
|
+ * In protected mode, base address of the segment. Zero in long mode,
|
|
|
+ * except when FS or GS are used. In virtual-8086 mode, the segment
|
|
|
+ * selector shifted 4 bits to the right.
|
|
|
+ *
|
|
|
+ * -1L in case of error.
|
|
|
+ */
|
|
|
+unsigned long insn_get_seg_base(struct pt_regs *regs, int seg_reg_idx)
|
|
|
+{
|
|
|
+ struct desc_struct *desc;
|
|
|
+ short sel;
|
|
|
+
|
|
|
+ sel = get_segment_selector(regs, seg_reg_idx);
|
|
|
+ if (sel < 0)
|
|
|
+ return -1L;
|
|
|
+
|
|
|
+ if (v8086_mode(regs))
|
|
|
+ /*
|
|
|
+ * Base is simply the segment selector shifted 4
|
|
|
+ * bits to the right.
|
|
|
+ */
|
|
|
+ return (unsigned long)(sel << 4);
|
|
|
+
|
|
|
+ if (user_64bit_mode(regs)) {
|
|
|
+ /*
|
|
|
+ * Only FS or GS will have a base address, the rest of
|
|
|
+ * the segments' bases are forced to 0.
|
|
|
+ */
|
|
|
+ unsigned long base;
|
|
|
+
|
|
|
+ if (seg_reg_idx == INAT_SEG_REG_FS)
|
|
|
+ rdmsrl(MSR_FS_BASE, base);
|
|
|
+ else if (seg_reg_idx == INAT_SEG_REG_GS)
|
|
|
+ /*
|
|
|
+ * swapgs was called at the kernel entry point. Thus,
|
|
|
+ * MSR_KERNEL_GS_BASE will have the user-space GS base.
|
|
|
+ */
|
|
|
+ rdmsrl(MSR_KERNEL_GS_BASE, base);
|
|
|
+ else
|
|
|
+ base = 0;
|
|
|
+ return base;
|
|
|
+ }
|
|
|
+
|
|
|
+ /* In protected mode the segment selector cannot be null. */
|
|
|
+ if (!sel)
|
|
|
+ return -1L;
|
|
|
+
|
|
|
+ desc = get_desc(sel);
|
|
|
+ if (!desc)
|
|
|
+ return -1L;
|
|
|
+
|
|
|
+ return get_desc_base(desc);
|
|
|
+}
|
|
|
+
|
|
|
+/**
|
|
|
+ * get_seg_limit() - Obtain the limit of a segment descriptor
|
|
|
+ * @regs: Register values as seen when entering kernel mode
|
|
|
+ * @seg_reg_idx: Index of the segment register pointing to seg descriptor
|
|
|
+ *
|
|
|
+ * Obtain the limit of the segment as indicated by the segment descriptor
|
|
|
+ * pointed by the segment selector. The segment selector is obtained from the
|
|
|
+ * input segment register index @seg_reg_idx.
|
|
|
+ *
|
|
|
+ * Returns:
|
|
|
+ *
|
|
|
+ * In protected mode, the limit of the segment descriptor in bytes.
|
|
|
+ * In long mode and virtual-8086 mode, segment limits are not enforced. Thus,
|
|
|
+ * limit is returned as -1L to imply a limit-less segment.
|
|
|
+ *
|
|
|
+ * Zero is returned on error.
|
|
|
+ */
|
|
|
+static unsigned long get_seg_limit(struct pt_regs *regs, int seg_reg_idx)
|
|
|
+{
|
|
|
+ struct desc_struct *desc;
|
|
|
+ unsigned long limit;
|
|
|
+ short sel;
|
|
|
+
|
|
|
+ sel = get_segment_selector(regs, seg_reg_idx);
|
|
|
+ if (sel < 0)
|
|
|
+ return 0;
|
|
|
+
|
|
|
+ if (user_64bit_mode(regs) || v8086_mode(regs))
|
|
|
+ return -1L;
|
|
|
+
|
|
|
+ if (!sel)
|
|
|
+ return 0;
|
|
|
+
|
|
|
+ desc = get_desc(sel);
|
|
|
+ if (!desc)
|
|
|
+ return 0;
|
|
|
+
|
|
|
+ /*
|
|
|
+ * If the granularity bit is set, the limit is given in multiples
|
|
|
+ * of 4096. This also means that the 12 least significant bits are
|
|
|
+ * not tested when checking the segment limits. In practice,
|
|
|
+ * this means that the segment ends in (limit << 12) + 0xfff.
|
|
|
+ */
|
|
|
+ limit = get_desc_limit(desc);
|
|
|
+ if (desc->g)
|
|
|
+ limit = (limit << 12) + 0xfff;
|
|
|
+
|
|
|
+ return limit;
|
|
|
+}
|
|
|
+
|
|
|
+/**
|
|
|
+ * insn_get_code_seg_params() - Obtain code segment parameters
|
|
|
+ * @regs: Structure with register values as seen when entering kernel mode
|
|
|
+ *
|
|
|
+ * Obtain address and operand sizes of the code segment. It is obtained from the
|
|
|
+ * selector contained in the CS register in regs. In protected mode, the default
|
|
|
+ * address is determined by inspecting the L and D bits of the segment
|
|
|
+ * descriptor. In virtual-8086 mode, the default is always two bytes for both
|
|
|
+ * address and operand sizes.
|
|
|
+ *
|
|
|
+ * Returns:
|
|
|
+ *
|
|
|
+ * A signed 8-bit value containing the default parameters on success.
|
|
|
+ *
|
|
|
+ * -EINVAL on error.
|
|
|
+ */
|
|
|
+char insn_get_code_seg_params(struct pt_regs *regs)
|
|
|
+{
|
|
|
+ struct desc_struct *desc;
|
|
|
+ short sel;
|
|
|
+
|
|
|
+ if (v8086_mode(regs))
|
|
|
+ /* Address and operand size are both 16-bit. */
|
|
|
+ return INSN_CODE_SEG_PARAMS(2, 2);
|
|
|
+
|
|
|
+ sel = get_segment_selector(regs, INAT_SEG_REG_CS);
|
|
|
+ if (sel < 0)
|
|
|
+ return sel;
|
|
|
+
|
|
|
+ desc = get_desc(sel);
|
|
|
+ if (!desc)
|
|
|
+ return -EINVAL;
|
|
|
+
|
|
|
+ /*
|
|
|
+ * The most significant byte of the Type field of the segment descriptor
|
|
|
+ * determines whether a segment contains data or code. If this is a data
|
|
|
+ * segment, return error.
|
|
|
+ */
|
|
|
+ if (!(desc->type & BIT(3)))
|
|
|
+ return -EINVAL;
|
|
|
+
|
|
|
+ switch ((desc->l << 1) | desc->d) {
|
|
|
+ case 0: /*
|
|
|
+ * Legacy mode. CS.L=0, CS.D=0. Address and operand size are
|
|
|
+ * both 16-bit.
|
|
|
+ */
|
|
|
+ return INSN_CODE_SEG_PARAMS(2, 2);
|
|
|
+ case 1: /*
|
|
|
+ * Legacy mode. CS.L=0, CS.D=1. Address and operand size are
|
|
|
+ * both 32-bit.
|
|
|
+ */
|
|
|
+ return INSN_CODE_SEG_PARAMS(4, 4);
|
|
|
+ case 2: /*
|
|
|
+ * IA-32e 64-bit mode. CS.L=1, CS.D=0. Address size is 64-bit;
|
|
|
+ * operand size is 32-bit.
|
|
|
+ */
|
|
|
+ return INSN_CODE_SEG_PARAMS(4, 8);
|
|
|
+ case 3: /* Invalid setting. CS.L=1, CS.D=1 */
|
|
|
+ /* fall through */
|
|
|
+ default:
|
|
|
+ return -EINVAL;
|
|
|
+ }
|
|
|
+}
|
|
|
+
|
|
|
+/**
|
|
|
+ * insn_get_modrm_rm_off() - Obtain register in r/m part of the ModRM byte
|
|
|
+ * @insn: Instruction containing the ModRM byte
|
|
|
+ * @regs: Register values as seen when entering kernel mode
|
|
|
+ *
|
|
|
+ * Returns:
|
|
|
+ *
|
|
|
+ * The register indicated by the r/m part of the ModRM byte. The
|
|
|
+ * register is obtained as an offset from the base of pt_regs. In specific
|
|
|
+ * cases, the returned value can be -EDOM to indicate that the particular value
|
|
|
+ * of ModRM does not refer to a register and shall be ignored.
|
|
|
+ */
|
|
|
+int insn_get_modrm_rm_off(struct insn *insn, struct pt_regs *regs)
|
|
|
+{
|
|
|
+ return get_reg_offset(insn, regs, REG_TYPE_RM);
|
|
|
+}
|
|
|
+
|
|
|
+/**
|
|
|
+ * get_seg_base_limit() - obtain base address and limit of a segment
|
|
|
+ * @insn: Instruction. Must be valid.
|
|
|
+ * @regs: Register values as seen when entering kernel mode
|
|
|
+ * @regoff: Operand offset, in pt_regs, used to resolve segment descriptor
|
|
|
+ * @base: Obtained segment base
|
|
|
+ * @limit: Obtained segment limit
|
|
|
+ *
|
|
|
+ * Obtain the base address and limit of the segment associated with the operand
|
|
|
+ * @regoff and, if any or allowed, override prefixes in @insn. This function is
|
|
|
+ * different from insn_get_seg_base() as the latter does not resolve the segment
|
|
|
+ * associated with the instruction operand. If a limit is not needed (e.g.,
|
|
|
+ * when running in long mode), @limit can be NULL.
|
|
|
+ *
|
|
|
+ * Returns:
|
|
|
+ *
|
|
|
+ * 0 on success. @base and @limit will contain the base address and of the
|
|
|
+ * resolved segment, respectively.
|
|
|
+ *
|
|
|
+ * -EINVAL on error.
|
|
|
+ */
|
|
|
+static int get_seg_base_limit(struct insn *insn, struct pt_regs *regs,
|
|
|
+ int regoff, unsigned long *base,
|
|
|
+ unsigned long *limit)
|
|
|
+{
|
|
|
+ int seg_reg_idx;
|
|
|
+
|
|
|
+ if (!base)
|
|
|
+ return -EINVAL;
|
|
|
+
|
|
|
+ seg_reg_idx = resolve_seg_reg(insn, regs, regoff);
|
|
|
+ if (seg_reg_idx < 0)
|
|
|
+ return seg_reg_idx;
|
|
|
+
|
|
|
+ *base = insn_get_seg_base(regs, seg_reg_idx);
|
|
|
+ if (*base == -1L)
|
|
|
+ return -EINVAL;
|
|
|
+
|
|
|
+ if (!limit)
|
|
|
+ return 0;
|
|
|
+
|
|
|
+ *limit = get_seg_limit(regs, seg_reg_idx);
|
|
|
+ if (!(*limit))
|
|
|
+ return -EINVAL;
|
|
|
+
|
|
|
+ return 0;
|
|
|
+}
|
|
|
+
|
|
|
+/**
|
|
|
+ * get_eff_addr_reg() - Obtain effective address from register operand
|
|
|
+ * @insn: Instruction. Must be valid.
|
|
|
+ * @regs: Register values as seen when entering kernel mode
|
|
|
+ * @regoff: Obtained operand offset, in pt_regs, with the effective address
|
|
|
+ * @eff_addr: Obtained effective address
|
|
|
+ *
|
|
|
+ * Obtain the effective address stored in the register operand as indicated by
|
|
|
+ * the ModRM byte. This function is to be used only with register addressing
|
|
|
+ * (i.e., ModRM.mod is 3). The effective address is saved in @eff_addr. The
|
|
|
+ * register operand, as an offset from the base of pt_regs, is saved in @regoff;
|
|
|
+ * such offset can then be used to resolve the segment associated with the
|
|
|
+ * operand. This function can be used with any of the supported address sizes
|
|
|
+ * in x86.
|
|
|
+ *
|
|
|
+ * Returns:
|
|
|
+ *
|
|
|
+ * 0 on success. @eff_addr will have the effective address stored in the
|
|
|
+ * operand indicated by ModRM. @regoff will have such operand as an offset from
|
|
|
+ * the base of pt_regs.
|
|
|
+ *
|
|
|
+ * -EINVAL on error.
|
|
|
+ */
|
|
|
+static int get_eff_addr_reg(struct insn *insn, struct pt_regs *regs,
|
|
|
+ int *regoff, long *eff_addr)
|
|
|
+{
|
|
|
+ insn_get_modrm(insn);
|
|
|
+
|
|
|
+ if (!insn->modrm.nbytes)
|
|
|
+ return -EINVAL;
|
|
|
+
|
|
|
+ if (X86_MODRM_MOD(insn->modrm.value) != 3)
|
|
|
+ return -EINVAL;
|
|
|
+
|
|
|
+ *regoff = get_reg_offset(insn, regs, REG_TYPE_RM);
|
|
|
+ if (*regoff < 0)
|
|
|
+ return -EINVAL;
|
|
|
+
|
|
|
+ /* Ignore bytes that are outside the address size. */
|
|
|
+ if (insn->addr_bytes == 2)
|
|
|
+ *eff_addr = regs_get_register(regs, *regoff) & 0xffff;
|
|
|
+ else if (insn->addr_bytes == 4)
|
|
|
+ *eff_addr = regs_get_register(regs, *regoff) & 0xffffffff;
|
|
|
+ else /* 64-bit address */
|
|
|
+ *eff_addr = regs_get_register(regs, *regoff);
|
|
|
+
|
|
|
+ return 0;
|
|
|
+}
|
|
|
+
|
|
|
+/**
|
|
|
+ * get_eff_addr_modrm() - Obtain referenced effective address via ModRM
|
|
|
+ * @insn: Instruction. Must be valid.
|
|
|
+ * @regs: Register values as seen when entering kernel mode
|
|
|
+ * @regoff: Obtained operand offset, in pt_regs, associated with segment
|
|
|
+ * @eff_addr: Obtained effective address
|
|
|
+ *
|
|
|
+ * Obtain the effective address referenced by the ModRM byte of @insn. After
|
|
|
+ * identifying the registers involved in the register-indirect memory reference,
|
|
|
+ * its value is obtained from the operands in @regs. The computed address is
|
|
|
+ * stored @eff_addr. Also, the register operand that indicates the associated
|
|
|
+ * segment is stored in @regoff, this parameter can later be used to determine
|
|
|
+ * such segment.
|
|
|
+ *
|
|
|
+ * Returns:
|
|
|
+ *
|
|
|
+ * 0 on success. @eff_addr will have the referenced effective address. @regoff
|
|
|
+ * will have a register, as an offset from the base of pt_regs, that can be used
|
|
|
+ * to resolve the associated segment.
|
|
|
+ *
|
|
|
+ * -EINVAL on error.
|
|
|
+ */
|
|
|
+static int get_eff_addr_modrm(struct insn *insn, struct pt_regs *regs,
|
|
|
+ int *regoff, long *eff_addr)
|
|
|
+{
|
|
|
+ long tmp;
|
|
|
+
|
|
|
+ if (insn->addr_bytes != 8 && insn->addr_bytes != 4)
|
|
|
+ return -EINVAL;
|
|
|
+
|
|
|
+ insn_get_modrm(insn);
|
|
|
+
|
|
|
+ if (!insn->modrm.nbytes)
|
|
|
+ return -EINVAL;
|
|
|
+
|
|
|
+ if (X86_MODRM_MOD(insn->modrm.value) > 2)
|
|
|
+ return -EINVAL;
|
|
|
+
|
|
|
+ *regoff = get_reg_offset(insn, regs, REG_TYPE_RM);
|
|
|
+
|
|
|
+ /*
|
|
|
+ * -EDOM means that we must ignore the address_offset. In such a case,
|
|
|
+ * in 64-bit mode the effective address relative to the rIP of the
|
|
|
+ * following instruction.
|
|
|
+ */
|
|
|
+ if (*regoff == -EDOM) {
|
|
|
+ if (user_64bit_mode(regs))
|
|
|
+ tmp = regs->ip + insn->length;
|
|
|
+ else
|
|
|
+ tmp = 0;
|
|
|
+ } else if (*regoff < 0) {
|
|
|
+ return -EINVAL;
|
|
|
+ } else {
|
|
|
+ tmp = regs_get_register(regs, *regoff);
|
|
|
+ }
|
|
|
+
|
|
|
+ if (insn->addr_bytes == 4) {
|
|
|
+ int addr32 = (int)(tmp & 0xffffffff) + insn->displacement.value;
|
|
|
+
|
|
|
+ *eff_addr = addr32 & 0xffffffff;
|
|
|
+ } else {
|
|
|
+ *eff_addr = tmp + insn->displacement.value;
|
|
|
+ }
|
|
|
+
|
|
|
+ return 0;
|
|
|
+}
|
|
|
+
|
|
|
+/**
|
|
|
+ * get_eff_addr_modrm_16() - Obtain referenced effective address via ModRM
|
|
|
+ * @insn: Instruction. Must be valid.
|
|
|
+ * @regs: Register values as seen when entering kernel mode
|
|
|
+ * @regoff: Obtained operand offset, in pt_regs, associated with segment
|
|
|
+ * @eff_addr: Obtained effective address
|
|
|
+ *
|
|
|
+ * Obtain the 16-bit effective address referenced by the ModRM byte of @insn.
|
|
|
+ * After identifying the registers involved in the register-indirect memory
|
|
|
+ * reference, its value is obtained from the operands in @regs. The computed
|
|
|
+ * address is stored @eff_addr. Also, the register operand that indicates
|
|
|
+ * the associated segment is stored in @regoff, this parameter can later be used
|
|
|
+ * to determine such segment.
|
|
|
+ *
|
|
|
+ * Returns:
|
|
|
+ *
|
|
|
+ * 0 on success. @eff_addr will have the referenced effective address. @regoff
|
|
|
+ * will have a register, as an offset from the base of pt_regs, that can be used
|
|
|
+ * to resolve the associated segment.
|
|
|
+ *
|
|
|
+ * -EINVAL on error.
|
|
|
+ */
|
|
|
+static int get_eff_addr_modrm_16(struct insn *insn, struct pt_regs *regs,
|
|
|
+ int *regoff, short *eff_addr)
|
|
|
+{
|
|
|
+ int addr_offset1, addr_offset2, ret;
|
|
|
+ short addr1 = 0, addr2 = 0, displacement;
|
|
|
+
|
|
|
+ if (insn->addr_bytes != 2)
|
|
|
+ return -EINVAL;
|
|
|
+
|
|
|
+ insn_get_modrm(insn);
|
|
|
+
|
|
|
+ if (!insn->modrm.nbytes)
|
|
|
+ return -EINVAL;
|
|
|
+
|
|
|
+ if (X86_MODRM_MOD(insn->modrm.value) > 2)
|
|
|
+ return -EINVAL;
|
|
|
+
|
|
|
+ ret = get_reg_offset_16(insn, regs, &addr_offset1, &addr_offset2);
|
|
|
+ if (ret < 0)
|
|
|
+ return -EINVAL;
|
|
|
+
|
|
|
+ /*
|
|
|
+ * Don't fail on invalid offset values. They might be invalid because
|
|
|
+ * they cannot be used for this particular value of ModRM. Instead, use
|
|
|
+ * them in the computation only if they contain a valid value.
|
|
|
+ */
|
|
|
+ if (addr_offset1 != -EDOM)
|
|
|
+ addr1 = regs_get_register(regs, addr_offset1) & 0xffff;
|
|
|
+
|
|
|
+ if (addr_offset2 != -EDOM)
|
|
|
+ addr2 = regs_get_register(regs, addr_offset2) & 0xffff;
|
|
|
+
|
|
|
+ displacement = insn->displacement.value & 0xffff;
|
|
|
+ *eff_addr = addr1 + addr2 + displacement;
|
|
|
+
|
|
|
+ /*
|
|
|
+ * The first operand register could indicate to use of either SS or DS
|
|
|
+ * registers to obtain the segment selector. The second operand
|
|
|
+ * register can only indicate the use of DS. Thus, the first operand
|
|
|
+ * will be used to obtain the segment selector.
|
|
|
+ */
|
|
|
+ *regoff = addr_offset1;
|
|
|
+
|
|
|
+ return 0;
|
|
|
+}
|
|
|
+
|
|
|
+/**
|
|
|
+ * get_eff_addr_sib() - Obtain referenced effective address via SIB
|
|
|
+ * @insn: Instruction. Must be valid.
|
|
|
+ * @regs: Register values as seen when entering kernel mode
|
|
|
+ * @regoff: Obtained operand offset, in pt_regs, associated with segment
|
|
|
+ * @eff_addr: Obtained effective address
|
|
|
+ *
|
|
|
+ * Obtain the effective address referenced by the SIB byte of @insn. After
|
|
|
+ * identifying the registers involved in the indexed, register-indirect memory
|
|
|
+ * reference, its value is obtained from the operands in @regs. The computed
|
|
|
+ * address is stored @eff_addr. Also, the register operand that indicates the
|
|
|
+ * associated segment is stored in @regoff, this parameter can later be used to
|
|
|
+ * determine such segment.
|
|
|
+ *
|
|
|
+ * Returns:
|
|
|
+ *
|
|
|
+ * 0 on success. @eff_addr will have the referenced effective address.
|
|
|
+ * @base_offset will have a register, as an offset from the base of pt_regs,
|
|
|
+ * that can be used to resolve the associated segment.
|
|
|
+ *
|
|
|
+ * -EINVAL on error.
|
|
|
+ */
|
|
|
+static int get_eff_addr_sib(struct insn *insn, struct pt_regs *regs,
|
|
|
+ int *base_offset, long *eff_addr)
|
|
|
+{
|
|
|
+ long base, indx;
|
|
|
+ int indx_offset;
|
|
|
+
|
|
|
+ if (insn->addr_bytes != 8 && insn->addr_bytes != 4)
|
|
|
+ return -EINVAL;
|
|
|
+
|
|
|
+ insn_get_modrm(insn);
|
|
|
+
|
|
|
+ if (!insn->modrm.nbytes)
|
|
|
+ return -EINVAL;
|
|
|
+
|
|
|
+ if (X86_MODRM_MOD(insn->modrm.value) > 2)
|
|
|
+ return -EINVAL;
|
|
|
+
|
|
|
+ insn_get_sib(insn);
|
|
|
+
|
|
|
+ if (!insn->sib.nbytes)
|
|
|
+ return -EINVAL;
|
|
|
+
|
|
|
+ *base_offset = get_reg_offset(insn, regs, REG_TYPE_BASE);
|
|
|
+ indx_offset = get_reg_offset(insn, regs, REG_TYPE_INDEX);
|
|
|
+
|
|
|
+ /*
|
|
|
+ * Negative values in the base and index offset means an error when
|
|
|
+ * decoding the SIB byte. Except -EDOM, which means that the registers
|
|
|
+ * should not be used in the address computation.
|
|
|
+ */
|
|
|
+ if (*base_offset == -EDOM)
|
|
|
+ base = 0;
|
|
|
+ else if (*base_offset < 0)
|
|
|
+ return -EINVAL;
|
|
|
+ else
|
|
|
+ base = regs_get_register(regs, *base_offset);
|
|
|
+
|
|
|
+ if (indx_offset == -EDOM)
|
|
|
+ indx = 0;
|
|
|
+ else if (indx_offset < 0)
|
|
|
+ return -EINVAL;
|
|
|
+ else
|
|
|
+ indx = regs_get_register(regs, indx_offset);
|
|
|
+
|
|
|
+ if (insn->addr_bytes == 4) {
|
|
|
+ int addr32, base32, idx32;
|
|
|
+
|
|
|
+ base32 = base & 0xffffffff;
|
|
|
+ idx32 = indx & 0xffffffff;
|
|
|
+
|
|
|
+ addr32 = base32 + idx32 * (1 << X86_SIB_SCALE(insn->sib.value));
|
|
|
+ addr32 += insn->displacement.value;
|
|
|
+
|
|
|
+ *eff_addr = addr32 & 0xffffffff;
|
|
|
+ } else {
|
|
|
+ *eff_addr = base + indx * (1 << X86_SIB_SCALE(insn->sib.value));
|
|
|
+ *eff_addr += insn->displacement.value;
|
|
|
+ }
|
|
|
+
|
|
|
+ return 0;
|
|
|
+}
|
|
|
+
|
|
|
+/**
|
|
|
+ * get_addr_ref_16() - Obtain the 16-bit address referred by instruction
|
|
|
+ * @insn: Instruction containing ModRM byte and displacement
|
|
|
+ * @regs: Register values as seen when entering kernel mode
|
|
|
+ *
|
|
|
+ * This function is to be used with 16-bit address encodings. Obtain the memory
|
|
|
+ * address referred by the instruction's ModRM and displacement bytes. Also, the
|
|
|
+ * segment used as base is determined by either any segment override prefixes in
|
|
|
+ * @insn or the default segment of the registers involved in the address
|
|
|
+ * computation. In protected mode, segment limits are enforced.
|
|
|
+ *
|
|
|
+ * Returns:
|
|
|
+ *
|
|
|
+ * Linear address referenced by the instruction operands on success.
|
|
|
+ *
|
|
|
+ * -1L on error.
|
|
|
+ */
|
|
|
+static void __user *get_addr_ref_16(struct insn *insn, struct pt_regs *regs)
|
|
|
+{
|
|
|
+ unsigned long linear_addr = -1L, seg_base, seg_limit;
|
|
|
+ int ret, regoff;
|
|
|
+ short eff_addr;
|
|
|
+ long tmp;
|
|
|
+
|
|
|
+ insn_get_modrm(insn);
|
|
|
+ insn_get_displacement(insn);
|
|
|
+
|
|
|
+ if (insn->addr_bytes != 2)
|
|
|
+ goto out;
|
|
|
+
|
|
|
+ if (X86_MODRM_MOD(insn->modrm.value) == 3) {
|
|
|
+ ret = get_eff_addr_reg(insn, regs, ®off, &tmp);
|
|
|
+ if (ret)
|
|
|
+ goto out;
|
|
|
+
|
|
|
+ eff_addr = tmp;
|
|
|
+ } else {
|
|
|
+ ret = get_eff_addr_modrm_16(insn, regs, ®off, &eff_addr);
|
|
|
+ if (ret)
|
|
|
+ goto out;
|
|
|
+ }
|
|
|
+
|
|
|
+ ret = get_seg_base_limit(insn, regs, regoff, &seg_base, &seg_limit);
|
|
|
+ if (ret)
|
|
|
+ goto out;
|
|
|
+
|
|
|
+ /*
|
|
|
+ * Before computing the linear address, make sure the effective address
|
|
|
+ * is within the limits of the segment. In virtual-8086 mode, segment
|
|
|
+ * limits are not enforced. In such a case, the segment limit is -1L to
|
|
|
+ * reflect this fact.
|
|
|
+ */
|
|
|
+ if ((unsigned long)(eff_addr & 0xffff) > seg_limit)
|
|
|
+ goto out;
|
|
|
+
|
|
|
+ linear_addr = (unsigned long)(eff_addr & 0xffff) + seg_base;
|
|
|
+
|
|
|
+ /* Limit linear address to 20 bits */
|
|
|
+ if (v8086_mode(regs))
|
|
|
+ linear_addr &= 0xfffff;
|
|
|
+
|
|
|
+out:
|
|
|
+ return (void __user *)linear_addr;
|
|
|
+}
|
|
|
+
|
|
|
+/**
|
|
|
+ * get_addr_ref_32() - Obtain a 32-bit linear address
|
|
|
+ * @insn: Instruction with ModRM, SIB bytes and displacement
|
|
|
+ * @regs: Register values as seen when entering kernel mode
|
|
|
+ *
|
|
|
+ * This function is to be used with 32-bit address encodings to obtain the
|
|
|
+ * linear memory address referred by the instruction's ModRM, SIB,
|
|
|
+ * displacement bytes and segment base address, as applicable. If in protected
|
|
|
+ * mode, segment limits are enforced.
|
|
|
+ *
|
|
|
+ * Returns:
|
|
|
+ *
|
|
|
+ * Linear address referenced by instruction and registers on success.
|
|
|
+ *
|
|
|
+ * -1L on error.
|
|
|
+ */
|
|
|
+static void __user *get_addr_ref_32(struct insn *insn, struct pt_regs *regs)
|
|
|
+{
|
|
|
+ unsigned long linear_addr = -1L, seg_base, seg_limit;
|
|
|
+ int eff_addr, regoff;
|
|
|
+ long tmp;
|
|
|
+ int ret;
|
|
|
+
|
|
|
+ if (insn->addr_bytes != 4)
|
|
|
+ goto out;
|
|
|
+
|
|
|
+ if (X86_MODRM_MOD(insn->modrm.value) == 3) {
|
|
|
+ ret = get_eff_addr_reg(insn, regs, ®off, &tmp);
|
|
|
+ if (ret)
|
|
|
+ goto out;
|
|
|
+
|
|
|
+ eff_addr = tmp;
|
|
|
+
|
|
|
+ } else {
|
|
|
+ if (insn->sib.nbytes) {
|
|
|
+ ret = get_eff_addr_sib(insn, regs, ®off, &tmp);
|
|
|
+ if (ret)
|
|
|
+ goto out;
|
|
|
+
|
|
|
+ eff_addr = tmp;
|
|
|
+ } else {
|
|
|
+ ret = get_eff_addr_modrm(insn, regs, ®off, &tmp);
|
|
|
+ if (ret)
|
|
|
+ goto out;
|
|
|
+
|
|
|
+ eff_addr = tmp;
|
|
|
+ }
|
|
|
+ }
|
|
|
+
|
|
|
+ ret = get_seg_base_limit(insn, regs, regoff, &seg_base, &seg_limit);
|
|
|
+ if (ret)
|
|
|
+ goto out;
|
|
|
+
|
|
|
+ /*
|
|
|
+ * In protected mode, before computing the linear address, make sure
|
|
|
+ * the effective address is within the limits of the segment.
|
|
|
+ * 32-bit addresses can be used in long and virtual-8086 modes if an
|
|
|
+ * address override prefix is used. In such cases, segment limits are
|
|
|
+ * not enforced. When in virtual-8086 mode, the segment limit is -1L
|
|
|
+ * to reflect this situation.
|
|
|
+ *
|
|
|
+ * After computed, the effective address is treated as an unsigned
|
|
|
+ * quantity.
|
|
|
+ */
|
|
|
+ if (!user_64bit_mode(regs) && ((unsigned int)eff_addr > seg_limit))
|
|
|
+ goto out;
|
|
|
+
|
|
|
+ /*
|
|
|
+ * Even though 32-bit address encodings are allowed in virtual-8086
|
|
|
+ * mode, the address range is still limited to [0x-0xffff].
|
|
|
+ */
|
|
|
+ if (v8086_mode(regs) && (eff_addr & ~0xffff))
|
|
|
+ goto out;
|
|
|
+
|
|
|
+ /*
|
|
|
+ * Data type long could be 64 bits in size. Ensure that our 32-bit
|
|
|
+ * effective address is not sign-extended when computing the linear
|
|
|
+ * address.
|
|
|
+ */
|
|
|
+ linear_addr = (unsigned long)(eff_addr & 0xffffffff) + seg_base;
|
|
|
+
|
|
|
+ /* Limit linear address to 20 bits */
|
|
|
+ if (v8086_mode(regs))
|
|
|
+ linear_addr &= 0xfffff;
|
|
|
+
|
|
|
+out:
|
|
|
+ return (void __user *)linear_addr;
|
|
|
+}
|
|
|
+
|
|
|
+/**
|
|
|
+ * get_addr_ref_64() - Obtain a 64-bit linear address
|
|
|
+ * @insn: Instruction struct with ModRM and SIB bytes and displacement
|
|
|
+ * @regs: Structure with register values as seen when entering kernel mode
|
|
|
+ *
|
|
|
+ * This function is to be used with 64-bit address encodings to obtain the
|
|
|
+ * linear memory address referred by the instruction's ModRM, SIB,
|
|
|
+ * displacement bytes and segment base address, as applicable.
|
|
|
+ *
|
|
|
+ * Returns:
|
|
|
+ *
|
|
|
+ * Linear address referenced by instruction and registers on success.
|
|
|
+ *
|
|
|
+ * -1L on error.
|
|
|
+ */
|
|
|
+#ifndef CONFIG_X86_64
|
|
|
+static void __user *get_addr_ref_64(struct insn *insn, struct pt_regs *regs)
|
|
|
+{
|
|
|
+ return (void __user *)-1L;
|
|
|
+}
|
|
|
+#else
|
|
|
+static void __user *get_addr_ref_64(struct insn *insn, struct pt_regs *regs)
|
|
|
+{
|
|
|
+ unsigned long linear_addr = -1L, seg_base;
|
|
|
+ int regoff, ret;
|
|
|
+ long eff_addr;
|
|
|
+
|
|
|
+ if (insn->addr_bytes != 8)
|
|
|
+ goto out;
|
|
|
+
|
|
|
+ if (X86_MODRM_MOD(insn->modrm.value) == 3) {
|
|
|
+ ret = get_eff_addr_reg(insn, regs, ®off, &eff_addr);
|
|
|
+ if (ret)
|
|
|
+ goto out;
|
|
|
+
|
|
|
+ } else {
|
|
|
+ if (insn->sib.nbytes) {
|
|
|
+ ret = get_eff_addr_sib(insn, regs, ®off, &eff_addr);
|
|
|
+ if (ret)
|
|
|
+ goto out;
|
|
|
+ } else {
|
|
|
+ ret = get_eff_addr_modrm(insn, regs, ®off, &eff_addr);
|
|
|
+ if (ret)
|
|
|
+ goto out;
|
|
|
+ }
|
|
|
+
|
|
|
+ }
|
|
|
+
|
|
|
+ ret = get_seg_base_limit(insn, regs, regoff, &seg_base, NULL);
|
|
|
+ if (ret)
|
|
|
+ goto out;
|
|
|
+
|
|
|
+ linear_addr = (unsigned long)eff_addr + seg_base;
|
|
|
+
|
|
|
+out:
|
|
|
+ return (void __user *)linear_addr;
|
|
|
+}
|
|
|
+#endif /* CONFIG_X86_64 */
|
|
|
+
|
|
|
+/**
|
|
|
+ * insn_get_addr_ref() - Obtain the linear address referred by instruction
|
|
|
+ * @insn: Instruction structure containing ModRM byte and displacement
|
|
|
+ * @regs: Structure with register values as seen when entering kernel mode
|
|
|
+ *
|
|
|
+ * Obtain the linear address referred by the instruction's ModRM, SIB and
|
|
|
+ * displacement bytes, and segment base, as applicable. In protected mode,
|
|
|
+ * segment limits are enforced.
|
|
|
+ *
|
|
|
+ * Returns:
|
|
|
+ *
|
|
|
+ * Linear address referenced by instruction and registers on success.
|
|
|
+ *
|
|
|
+ * -1L on error.
|
|
|
+ */
|
|
|
+void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs)
|
|
|
+{
|
|
|
+ if (!insn || !regs)
|
|
|
+ return (void __user *)-1L;
|
|
|
+
|
|
|
+ switch (insn->addr_bytes) {
|
|
|
+ case 2:
|
|
|
+ return get_addr_ref_16(insn, regs);
|
|
|
+ case 4:
|
|
|
+ return get_addr_ref_32(insn, regs);
|
|
|
+ case 8:
|
|
|
+ return get_addr_ref_64(insn, regs);
|
|
|
+ default:
|
|
|
+ return (void __user *)-1L;
|
|
|
+ }
|
|
|
+}
|