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Message-Id: <20180503010536.7917-6-daniel@iogearbox.net>
Date: Thu, 3 May 2018 03:05:29 +0200
From: Daniel Borkmann <daniel@...earbox.net>
To: ast@...nel.org
Cc: netdev@...r.kernel.org, Daniel Borkmann <daniel@...earbox.net>
Subject: [PATCH bpf-next 05/12] 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@...earbox.net>
Acked-by: Alexei Starovoitov <ast@...nel.org>
---
arch/x86/net/Makefile | 4 +-
arch/x86/net/bpf_jit.S | 154 --------------------------------------------
arch/x86/net/bpf_jit_comp.c | 144 ++---------------------------------------
3 files changed, 5 insertions(+), 297 deletions(-)
delete mode 100644 arch/x86/net/bpf_jit.S
diff --git a/arch/x86/net/Makefile b/arch/x86/net/Makefile
index fefb4b6..20277db 100644
--- a/arch/x86/net/Makefile
+++ b/arch/x86/net/Makefile
@@ -1,6 +1,4 @@
#
# Arch-specific network modules
#
-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
diff --git a/arch/x86/net/bpf_jit.S b/arch/x86/net/bpf_jit.S
deleted file mode 100644
index b33093f..0000000
--- a/arch/x86/net/bpf_jit.S
+++ /dev/null
@@ -1,154 +0,0 @@
-/* bpf_jit.S : BPF JIT helper functions
- *
- * Copyright (C) 2011 Eric Dumazet (eric.dumazet@...il.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
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 1c3c81d..ce08b7b 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/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 @@ xadd: if (is_imm8(insn->off))
}
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];
--
2.9.5
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