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@@ -0,0 +1,253 @@
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+/*
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+ * common.c - C code for kernel entry and exit
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+ * Copyright (c) 2015 Andrew Lutomirski
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+ * GPL v2
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+ *
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+ * Based on asm and ptrace code by many authors. The code here originated
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+ * in ptrace.c and signal.c.
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+ */
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+
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+#include <linux/kernel.h>
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+#include <linux/sched.h>
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+#include <linux/mm.h>
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+#include <linux/smp.h>
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+#include <linux/errno.h>
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+#include <linux/ptrace.h>
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+#include <linux/tracehook.h>
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+#include <linux/audit.h>
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+#include <linux/seccomp.h>
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+#include <linux/signal.h>
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+#include <linux/export.h>
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+#include <linux/context_tracking.h>
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+#include <linux/user-return-notifier.h>
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+#include <linux/uprobes.h>
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+
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+#include <asm/desc.h>
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+#include <asm/traps.h>
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+
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+#define CREATE_TRACE_POINTS
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+#include <trace/events/syscalls.h>
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+
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+static void do_audit_syscall_entry(struct pt_regs *regs, u32 arch)
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+{
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+#ifdef CONFIG_X86_64
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+ if (arch == AUDIT_ARCH_X86_64) {
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+ audit_syscall_entry(regs->orig_ax, regs->di,
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+ regs->si, regs->dx, regs->r10);
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+ } else
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+#endif
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+ {
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+ audit_syscall_entry(regs->orig_ax, regs->bx,
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+ regs->cx, regs->dx, regs->si);
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+ }
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+}
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+
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+/*
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+ * We can return 0 to resume the syscall or anything else to go to phase
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+ * 2. If we resume the syscall, we need to put something appropriate in
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+ * regs->orig_ax.
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+ *
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+ * NB: We don't have full pt_regs here, but regs->orig_ax and regs->ax
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+ * are fully functional.
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+ *
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+ * For phase 2's benefit, our return value is:
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+ * 0: resume the syscall
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+ * 1: go to phase 2; no seccomp phase 2 needed
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+ * anything else: go to phase 2; pass return value to seccomp
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+ */
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+unsigned long syscall_trace_enter_phase1(struct pt_regs *regs, u32 arch)
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+{
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+ unsigned long ret = 0;
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+ u32 work;
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+
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+ BUG_ON(regs != task_pt_regs(current));
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+
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+ work = ACCESS_ONCE(current_thread_info()->flags) &
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+ _TIF_WORK_SYSCALL_ENTRY;
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+
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+ /*
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+ * If TIF_NOHZ is set, we are required to call user_exit() before
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+ * doing anything that could touch RCU.
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+ */
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+ if (work & _TIF_NOHZ) {
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+ user_exit();
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+ work &= ~_TIF_NOHZ;
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+ }
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+
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+#ifdef CONFIG_SECCOMP
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+ /*
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+ * Do seccomp first -- it should minimize exposure of other
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+ * code, and keeping seccomp fast is probably more valuable
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+ * than the rest of this.
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+ */
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+ if (work & _TIF_SECCOMP) {
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+ struct seccomp_data sd;
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+
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+ sd.arch = arch;
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+ sd.nr = regs->orig_ax;
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+ sd.instruction_pointer = regs->ip;
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+#ifdef CONFIG_X86_64
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+ if (arch == AUDIT_ARCH_X86_64) {
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+ sd.args[0] = regs->di;
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+ sd.args[1] = regs->si;
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+ sd.args[2] = regs->dx;
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+ sd.args[3] = regs->r10;
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+ sd.args[4] = regs->r8;
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+ sd.args[5] = regs->r9;
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+ } else
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+#endif
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+ {
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+ sd.args[0] = regs->bx;
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+ sd.args[1] = regs->cx;
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+ sd.args[2] = regs->dx;
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+ sd.args[3] = regs->si;
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+ sd.args[4] = regs->di;
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+ sd.args[5] = regs->bp;
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+ }
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+
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+ BUILD_BUG_ON(SECCOMP_PHASE1_OK != 0);
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+ BUILD_BUG_ON(SECCOMP_PHASE1_SKIP != 1);
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+
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+ ret = seccomp_phase1(&sd);
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+ if (ret == SECCOMP_PHASE1_SKIP) {
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+ regs->orig_ax = -1;
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+ ret = 0;
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+ } else if (ret != SECCOMP_PHASE1_OK) {
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+ return ret; /* Go directly to phase 2 */
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+ }
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+
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+ work &= ~_TIF_SECCOMP;
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+ }
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+#endif
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+
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+ /* Do our best to finish without phase 2. */
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+ if (work == 0)
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+ return ret; /* seccomp and/or nohz only (ret == 0 here) */
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+
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+#ifdef CONFIG_AUDITSYSCALL
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+ if (work == _TIF_SYSCALL_AUDIT) {
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+ /*
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+ * If there is no more work to be done except auditing,
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+ * then audit in phase 1. Phase 2 always audits, so, if
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+ * we audit here, then we can't go on to phase 2.
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+ */
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+ do_audit_syscall_entry(regs, arch);
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+ return 0;
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+ }
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+#endif
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+
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+ return 1; /* Something is enabled that we can't handle in phase 1 */
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+}
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+
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+/* Returns the syscall nr to run (which should match regs->orig_ax). */
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+long syscall_trace_enter_phase2(struct pt_regs *regs, u32 arch,
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+ unsigned long phase1_result)
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+{
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+ long ret = 0;
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+ u32 work = ACCESS_ONCE(current_thread_info()->flags) &
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+ _TIF_WORK_SYSCALL_ENTRY;
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+
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+ BUG_ON(regs != task_pt_regs(current));
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+
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+ /*
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+ * If we stepped into a sysenter/syscall insn, it trapped in
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+ * kernel mode; do_debug() cleared TF and set TIF_SINGLESTEP.
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+ * If user-mode had set TF itself, then it's still clear from
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+ * do_debug() and we need to set it again to restore the user
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+ * state. If we entered on the slow path, TF was already set.
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+ */
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+ if (work & _TIF_SINGLESTEP)
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+ regs->flags |= X86_EFLAGS_TF;
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+
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+#ifdef CONFIG_SECCOMP
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+ /*
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+ * Call seccomp_phase2 before running the other hooks so that
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+ * they can see any changes made by a seccomp tracer.
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+ */
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+ if (phase1_result > 1 && seccomp_phase2(phase1_result)) {
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+ /* seccomp failures shouldn't expose any additional code. */
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+ return -1;
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+ }
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+#endif
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+
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+ if (unlikely(work & _TIF_SYSCALL_EMU))
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+ ret = -1L;
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+
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+ if ((ret || test_thread_flag(TIF_SYSCALL_TRACE)) &&
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+ tracehook_report_syscall_entry(regs))
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+ ret = -1L;
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+
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+ if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
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+ trace_sys_enter(regs, regs->orig_ax);
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+
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+ do_audit_syscall_entry(regs, arch);
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+
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+ return ret ?: regs->orig_ax;
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+}
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+
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+long syscall_trace_enter(struct pt_regs *regs)
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+{
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+ u32 arch = is_ia32_task() ? AUDIT_ARCH_I386 : AUDIT_ARCH_X86_64;
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+ unsigned long phase1_result = syscall_trace_enter_phase1(regs, arch);
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+
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+ if (phase1_result == 0)
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+ return regs->orig_ax;
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+ else
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+ return syscall_trace_enter_phase2(regs, arch, phase1_result);
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+}
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+
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+void syscall_trace_leave(struct pt_regs *regs)
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+{
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+ bool step;
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+
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+ /*
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+ * We may come here right after calling schedule_user()
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+ * or do_notify_resume(), in which case we can be in RCU
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+ * user mode.
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+ */
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+ user_exit();
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+
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+ audit_syscall_exit(regs);
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+
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+ if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
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+ trace_sys_exit(regs, regs->ax);
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+
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+ /*
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+ * If TIF_SYSCALL_EMU is set, we only get here because of
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+ * TIF_SINGLESTEP (i.e. this is PTRACE_SYSEMU_SINGLESTEP).
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+ * We already reported this syscall instruction in
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+ * syscall_trace_enter().
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+ */
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+ step = unlikely(test_thread_flag(TIF_SINGLESTEP)) &&
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+ !test_thread_flag(TIF_SYSCALL_EMU);
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+ if (step || test_thread_flag(TIF_SYSCALL_TRACE))
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+ tracehook_report_syscall_exit(regs, step);
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+
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+ user_enter();
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+}
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+
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+/*
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+ * notification of userspace execution resumption
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+ * - triggered by the TIF_WORK_MASK flags
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+ */
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+__visible void
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+do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags)
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+{
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+ user_exit();
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+
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+ if (thread_info_flags & _TIF_UPROBE)
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+ uprobe_notify_resume(regs);
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+
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+ /* deal with pending signal delivery */
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+ if (thread_info_flags & _TIF_SIGPENDING)
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+ do_signal(regs);
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+
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+ if (thread_info_flags & _TIF_NOTIFY_RESUME) {
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+ clear_thread_flag(TIF_NOTIFY_RESUME);
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+ tracehook_notify_resume(regs);
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+ }
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+ if (thread_info_flags & _TIF_USER_RETURN_NOTIFY)
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+ fire_user_return_notifiers();
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+
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+ user_enter();
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+}
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