bpf, x64: remove ld_abs/ld_ind

Since LD_ABS/LD_IND instructions are now removed from the core and
reimplemented through a combination of inlined BPF instructions and
a slow-path helper, we can get rid of the complexity from x64 JIT.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

arch/x86/net/Makefile

@@ -5,6 +5,5 @@
 ifeq ($(CONFIG_X86_32),y)
         obj-$(CONFIG_BPF_JIT) += bpf_jit_comp32.o
 else
-        OBJECT_FILES_NON_STANDARD_bpf_jit.o += y
-        obj-$(CONFIG_BPF_JIT) += bpf_jit.o bpf_jit_comp.o
+        obj-$(CONFIG_BPF_JIT) += bpf_jit_comp.o
 endif

arch/x86/net/bpf_jit.S

@@ -1,154 +0,0 @@
-/* bpf_jit.S : BPF JIT helper functions
- *
- * Copyright (C) 2011 Eric Dumazet (eric.dumazet@gmail.com)
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License
- * as published by the Free Software Foundation; version 2
- * of the License.
- */
-#include <linux/linkage.h>
-#include <asm/frame.h>
-
-/*
- * Calling convention :
- * rbx : skb pointer (callee saved)
- * esi : offset of byte(s) to fetch in skb (can be scratched)
- * r10 : copy of skb->data
- * r9d : hlen = skb->len - skb->data_len
- */
-#define SKBDATA	%r10
-#define SKF_MAX_NEG_OFF    $(-0x200000) /* SKF_LL_OFF from filter.h */
-
-#define FUNC(name) \
-	.globl name; \
-	.type name, @function; \
-	name:
-
-FUNC(sk_load_word)
-	test	%esi,%esi
-	js	bpf_slow_path_word_neg
-
-FUNC(sk_load_word_positive_offset)
-	mov	%r9d,%eax		# hlen
-	sub	%esi,%eax		# hlen - offset
-	cmp	$3,%eax
-	jle	bpf_slow_path_word
-	mov     (SKBDATA,%rsi),%eax
-	bswap   %eax  			/* ntohl() */
-	ret
-
-FUNC(sk_load_half)
-	test	%esi,%esi
-	js	bpf_slow_path_half_neg
-
-FUNC(sk_load_half_positive_offset)
-	mov	%r9d,%eax
-	sub	%esi,%eax		#	hlen - offset
-	cmp	$1,%eax
-	jle	bpf_slow_path_half
-	movzwl	(SKBDATA,%rsi),%eax
-	rol	$8,%ax			# ntohs()
-	ret
-
-FUNC(sk_load_byte)
-	test	%esi,%esi
-	js	bpf_slow_path_byte_neg
-
-FUNC(sk_load_byte_positive_offset)
-	cmp	%esi,%r9d   /* if (offset >= hlen) goto bpf_slow_path_byte */
-	jle	bpf_slow_path_byte
-	movzbl	(SKBDATA,%rsi),%eax
-	ret
-
-/* rsi contains offset and can be scratched */
-#define bpf_slow_path_common(LEN)		\
-	lea	32(%rbp), %rdx;\
-	FRAME_BEGIN;				\
-	mov	%rbx, %rdi; /* arg1 == skb */	\
-	push	%r9;				\
-	push	SKBDATA;			\
-/* rsi already has offset */			\
-	mov	$LEN,%ecx;	/* len */	\
-	call	skb_copy_bits;			\
-	test    %eax,%eax;			\
-	pop	SKBDATA;			\
-	pop	%r9;				\
-	FRAME_END
-
-
-bpf_slow_path_word:
-	bpf_slow_path_common(4)
-	js	bpf_error
-	mov	32(%rbp),%eax
-	bswap	%eax
-	ret
-
-bpf_slow_path_half:
-	bpf_slow_path_common(2)
-	js	bpf_error
-	mov	32(%rbp),%ax
-	rol	$8,%ax
-	movzwl	%ax,%eax
-	ret
-
-bpf_slow_path_byte:
-	bpf_slow_path_common(1)
-	js	bpf_error
-	movzbl	32(%rbp),%eax
-	ret
-
-#define sk_negative_common(SIZE)				\
-	FRAME_BEGIN;						\
-	mov	%rbx, %rdi; /* arg1 == skb */			\
-	push	%r9;						\
-	push	SKBDATA;					\
-/* rsi already has offset */					\
-	mov	$SIZE,%edx;	/* size */			\
-	call	bpf_internal_load_pointer_neg_helper;		\
-	test	%rax,%rax;					\
-	pop	SKBDATA;					\
-	pop	%r9;						\
-	FRAME_END;						\
-	jz	bpf_error
-
-bpf_slow_path_word_neg:
-	cmp	SKF_MAX_NEG_OFF, %esi	/* test range */
-	jl	bpf_error	/* offset lower -> error  */
-
-FUNC(sk_load_word_negative_offset)
-	sk_negative_common(4)
-	mov	(%rax), %eax
-	bswap	%eax
-	ret
-
-bpf_slow_path_half_neg:
-	cmp	SKF_MAX_NEG_OFF, %esi
-	jl	bpf_error
-
-FUNC(sk_load_half_negative_offset)
-	sk_negative_common(2)
-	mov	(%rax),%ax
-	rol	$8,%ax
-	movzwl	%ax,%eax
-	ret
-
-bpf_slow_path_byte_neg:
-	cmp	SKF_MAX_NEG_OFF, %esi
-	jl	bpf_error
-
-FUNC(sk_load_byte_negative_offset)
-	sk_negative_common(1)
-	movzbl	(%rax), %eax
-	ret
-
-bpf_error:
-# force a return 0 from jit handler
-	xor	%eax,%eax
-	mov	(%rbp),%rbx
-	mov	8(%rbp),%r13
-	mov	16(%rbp),%r14
-	mov	24(%rbp),%r15
-	add	$40, %rbp
-	leaveq
-	ret

arch/x86/net/bpf_jit_comp.c

@@ -17,15 +17,6 @@
 #include <asm/set_memory.h>
 #include <asm/nospec-branch.h>
 
-/*
- * Assembly code in arch/x86/net/bpf_jit.S
- */
-extern u8 sk_load_word[], sk_load_half[], sk_load_byte[];
-extern u8 sk_load_word_positive_offset[], sk_load_half_positive_offset[];
-extern u8 sk_load_byte_positive_offset[];
-extern u8 sk_load_word_negative_offset[], sk_load_half_negative_offset[];
-extern u8 sk_load_byte_negative_offset[];
-
 static u8 *emit_code(u8 *ptr, u32 bytes, unsigned int len)
 {
 	if (len == 1)
@@ -107,9 +98,6 @@ static int bpf_size_to_x86_bytes(int bpf_size)
 #define X86_JLE 0x7E
 #define X86_JG  0x7F
 
-#define CHOOSE_LOAD_FUNC(K, func) \
-	((int)K < 0 ? ((int)K >= SKF_LL_OFF ? func##_negative_offset : func) : func##_positive_offset)
-
 /* Pick a register outside of BPF range for JIT internal work */
 #define AUX_REG (MAX_BPF_JIT_REG + 1)
 
@@ -120,8 +108,8 @@ static int bpf_size_to_x86_bytes(int bpf_size)
  * register in load/store instructions, it always needs an
  * extra byte of encoding and is callee saved.
  *
- * R9  caches skb->len - skb->data_len
- * R10 caches skb->data, and used for blinding (if enabled)
+ * Also x86-64 register R9 is unused. x86-64 register R10 is
+ * used for blinding (if enabled).
  */
 static const int reg2hex[] = {
 	[BPF_REG_0] = 0,  /* RAX */
@@ -196,19 +184,15 @@ static void jit_fill_hole(void *area, unsigned int size)
 
 struct jit_context {
 	int cleanup_addr; /* Epilogue code offset */
-	bool seen_ld_abs;
-	bool seen_ax_reg;
 };
 
 /* Maximum number of bytes emitted while JITing one eBPF insn */
 #define BPF_MAX_INSN_SIZE	128
 #define BPF_INSN_SAFETY		64
 
-#define AUX_STACK_SPACE \
-	(32 /* Space for RBX, R13, R14, R15 */ + \
-	  8 /* Space for skb_copy_bits() buffer */)
+#define AUX_STACK_SPACE		40 /* Space for RBX, R13, R14, R15, tailcnt */
 
-#define PROLOGUE_SIZE 37
+#define PROLOGUE_SIZE		37
 
 /*
  * Emit x86-64 prologue code for BPF program and check its size.
@@ -232,20 +216,8 @@ static void emit_prologue(u8 **pprog, u32 stack_depth, bool ebpf_from_cbpf)
 	/* sub rbp, AUX_STACK_SPACE */
 	EMIT4(0x48, 0x83, 0xED, AUX_STACK_SPACE);
 
-	/* All classic BPF filters use R6(rbx) save it */
-
 	/* mov qword ptr [rbp+0],rbx */
 	EMIT4(0x48, 0x89, 0x5D, 0);
-
-	/*
-	 * bpf_convert_filter() maps classic BPF register X to R7 and uses R8
-	 * as temporary, so all tcpdump filters need to spill/fill R7(R13) and
-	 * R8(R14). R9(R15) spill could be made conditional, but there is only
-	 * one 'bpf_error' return path out of helper functions inside bpf_jit.S
-	 * The overhead of extra spill is negligible for any filter other
-	 * than synthetic ones. Therefore not worth adding complexity.
-	 */
-
 	/* mov qword ptr [rbp+8],r13 */
 	EMIT4(0x4C, 0x89, 0x6D, 8);
 	/* mov qword ptr [rbp+16],r14 */
@@ -353,27 +325,6 @@ static void emit_bpf_tail_call(u8 **pprog)
 	*pprog = prog;
 }
 
-
-static void emit_load_skb_data_hlen(u8 **pprog)
-{
-	u8 *prog = *pprog;
-	int cnt = 0;
-
-	/*
-	 * r9d = skb->len - skb->data_len (headlen)
-	 * r10 = skb->data
-	 */
-	/* mov %r9d, off32(%rdi) */
-	EMIT3_off32(0x44, 0x8b, 0x8f, offsetof(struct sk_buff, len));
-
-	/* sub %r9d, off32(%rdi) */
-	EMIT3_off32(0x44, 0x2b, 0x8f, offsetof(struct sk_buff, data_len));
-
-	/* mov %r10, off32(%rdi) */
-	EMIT3_off32(0x4c, 0x8b, 0x97, offsetof(struct sk_buff, data));
-	*pprog = prog;
-}
-
 static void emit_mov_imm32(u8 **pprog, bool sign_propagate,
 			   u32 dst_reg, const u32 imm32)
 {
@@ -462,8 +413,6 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
 {
 	struct bpf_insn *insn = bpf_prog->insnsi;
 	int insn_cnt = bpf_prog->len;
-	bool seen_ld_abs = ctx->seen_ld_abs | (oldproglen == 0);
-	bool seen_ax_reg = ctx->seen_ax_reg | (oldproglen == 0);
 	bool seen_exit = false;
 	u8 temp[BPF_MAX_INSN_SIZE + BPF_INSN_SAFETY];
 	int i, cnt = 0;
@@ -473,9 +422,6 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
 	emit_prologue(&prog, bpf_prog->aux->stack_depth,
 		      bpf_prog_was_classic(bpf_prog));
 
-	if (seen_ld_abs)
-		emit_load_skb_data_hlen(&prog);
-
 	for (i = 0; i < insn_cnt; i++, insn++) {
 		const s32 imm32 = insn->imm;
 		u32 dst_reg = insn->dst_reg;
@@ -483,13 +429,9 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
 		u8 b2 = 0, b3 = 0;
 		s64 jmp_offset;
 		u8 jmp_cond;
-		bool reload_skb_data;
 		int ilen;
 		u8 *func;
 
-		if (dst_reg == BPF_REG_AX || src_reg == BPF_REG_AX)
-			ctx->seen_ax_reg = seen_ax_reg = true;
-
 		switch (insn->code) {
 			/* ALU */
 		case BPF_ALU | BPF_ADD | BPF_X:
@@ -916,36 +858,12 @@ xadd:			if (is_imm8(insn->off))
 		case BPF_JMP | BPF_CALL:
 			func = (u8 *) __bpf_call_base + imm32;
 			jmp_offset = func - (image + addrs[i]);
-			if (seen_ld_abs) {
-				reload_skb_data = bpf_helper_changes_pkt_data(func);
-				if (reload_skb_data) {
-					EMIT1(0x57); /* push %rdi */
-					jmp_offset += 22; /* pop, mov, sub, mov */
-				} else {
-					EMIT2(0x41, 0x52); /* push %r10 */
-					EMIT2(0x41, 0x51); /* push %r9 */
-					/*
-					 * We need to adjust jmp offset, since
-					 * pop %r9, pop %r10 take 4 bytes after call insn
-					 */
-					jmp_offset += 4;
-				}
-			}
 			if (!imm32 || !is_simm32(jmp_offset)) {
 				pr_err("unsupported BPF func %d addr %p image %p\n",
 				       imm32, func, image);
 				return -EINVAL;
 			}
 			EMIT1_off32(0xE8, jmp_offset);
-			if (seen_ld_abs) {
-				if (reload_skb_data) {
-					EMIT1(0x5F); /* pop %rdi */
-					emit_load_skb_data_hlen(&prog);
-				} else {
-					EMIT2(0x41, 0x59); /* pop %r9 */
-					EMIT2(0x41, 0x5A); /* pop %r10 */
-				}
-			}
 			break;
 
 		case BPF_JMP | BPF_TAIL_CALL:
@@ -1080,60 +998,6 @@ emit_jmp:
 			}
 			break;
 
-		case BPF_LD | BPF_IND | BPF_W:
-			func = sk_load_word;
-			goto common_load;
-		case BPF_LD | BPF_ABS | BPF_W:
-			func = CHOOSE_LOAD_FUNC(imm32, sk_load_word);
-common_load:
-			ctx->seen_ld_abs = seen_ld_abs = true;
-			jmp_offset = func - (image + addrs[i]);
-			if (!func || !is_simm32(jmp_offset)) {
-				pr_err("unsupported BPF func %d addr %p image %p\n",
-				       imm32, func, image);
-				return -EINVAL;
-			}
-			if (BPF_MODE(insn->code) == BPF_ABS) {
-				/* mov %esi, imm32 */
-				EMIT1_off32(0xBE, imm32);
-			} else {
-				/* mov %rsi, src_reg */
-				EMIT_mov(BPF_REG_2, src_reg);
-				if (imm32) {
-					if (is_imm8(imm32))
-						/* add %esi, imm8 */
-						EMIT3(0x83, 0xC6, imm32);
-					else
-						/* add %esi, imm32 */
-						EMIT2_off32(0x81, 0xC6, imm32);
-				}
-			}
-			/*
-			 * skb pointer is in R6 (%rbx), it will be copied into
-			 * %rdi if skb_copy_bits() call is necessary.
-			 * sk_load_* helpers also use %r10 and %r9d.
-			 * See bpf_jit.S
-			 */
-			if (seen_ax_reg)
-				/* r10 = skb->data, mov %r10, off32(%rbx) */
-				EMIT3_off32(0x4c, 0x8b, 0x93,
-					    offsetof(struct sk_buff, data));
-			EMIT1_off32(0xE8, jmp_offset); /* call */
-			break;
-
-		case BPF_LD | BPF_IND | BPF_H:
-			func = sk_load_half;
-			goto common_load;
-		case BPF_LD | BPF_ABS | BPF_H:
-			func = CHOOSE_LOAD_FUNC(imm32, sk_load_half);
-			goto common_load;
-		case BPF_LD | BPF_IND | BPF_B:
-			func = sk_load_byte;
-			goto common_load;
-		case BPF_LD | BPF_ABS | BPF_B:
-			func = CHOOSE_LOAD_FUNC(imm32, sk_load_byte);
-			goto common_load;
-
 		case BPF_JMP | BPF_EXIT:
 			if (seen_exit) {
 				jmp_offset = ctx->cleanup_addr - addrs[i];