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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>
This commit is contained in:
Daniel Borkmann 2018-05-04 01:08:16 +02:00 committed by Alexei Starovoitov
parent 4e1ec56cdc
commit e782bdcf58
3 changed files with 5 additions and 296 deletions
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3
arch/x86/net/Makefile
View File

@ -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

154
arch/x86/net/bpf_jit.S
View File

@ -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

144
arch/x86/net/bpf_jit_comp.c
View File

@ -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];