From 836256bf5f379c298ffa99f62e329d9f40f060ac Mon Sep 17 00:00:00 2001 From: Jiong Wang Date: Fri, 24 May 2019 23:25:26 +0100 Subject: x32: bpf: eliminate zero extension code-gen Cc: Wang YanQing Tested-by: Wang YanQing Signed-off-by: Jiong Wang Signed-off-by: Alexei Starovoitov --- arch/x86/net/bpf_jit_comp32.c | 83 +++++++++++++++++++++++++++++-------------- 1 file changed, 56 insertions(+), 27 deletions(-) (limited to 'arch/x86') diff --git a/arch/x86/net/bpf_jit_comp32.c b/arch/x86/net/bpf_jit_comp32.c index b29e82f190c7..133433d181ba 100644 --- a/arch/x86/net/bpf_jit_comp32.c +++ b/arch/x86/net/bpf_jit_comp32.c @@ -253,13 +253,14 @@ static inline void emit_ia32_mov_r(const u8 dst, const u8 src, bool dstk, /* dst = src */ static inline void emit_ia32_mov_r64(const bool is64, const u8 dst[], const u8 src[], bool dstk, - bool sstk, u8 **pprog) + bool sstk, u8 **pprog, + const struct bpf_prog_aux *aux) { emit_ia32_mov_r(dst_lo, src_lo, dstk, sstk, pprog); if (is64) /* complete 8 byte move */ emit_ia32_mov_r(dst_hi, src_hi, dstk, sstk, pprog); - else + else if (!aux->verifier_zext) /* zero out high 4 bytes */ emit_ia32_mov_i(dst_hi, 0, dstk, pprog); } @@ -313,7 +314,8 @@ static inline void emit_ia32_mul_r(const u8 dst, const u8 src, bool dstk, } static inline void emit_ia32_to_le_r64(const u8 dst[], s32 val, - bool dstk, u8 **pprog) + bool dstk, u8 **pprog, + const struct bpf_prog_aux *aux) { u8 *prog = *pprog; int cnt = 0; @@ -334,12 +336,14 @@ static inline void emit_ia32_to_le_r64(const u8 dst[], s32 val, */ EMIT2(0x0F, 0xB7); EMIT1(add_2reg(0xC0, dreg_lo, dreg_lo)); - /* xor dreg_hi,dreg_hi */ - EMIT2(0x33, add_2reg(0xC0, dreg_hi, dreg_hi)); + if (!aux->verifier_zext) + /* xor dreg_hi,dreg_hi */ + EMIT2(0x33, add_2reg(0xC0, dreg_hi, dreg_hi)); break; case 32: - /* xor dreg_hi,dreg_hi */ - EMIT2(0x33, add_2reg(0xC0, dreg_hi, dreg_hi)); + if (!aux->verifier_zext) + /* xor dreg_hi,dreg_hi */ + EMIT2(0x33, add_2reg(0xC0, dreg_hi, dreg_hi)); break; case 64: /* nop */ @@ -358,7 +362,8 @@ static inline void emit_ia32_to_le_r64(const u8 dst[], s32 val, } static inline void emit_ia32_to_be_r64(const u8 dst[], s32 val, - bool dstk, u8 **pprog) + bool dstk, u8 **pprog, + const struct bpf_prog_aux *aux) { u8 *prog = *pprog; int cnt = 0; @@ -380,16 +385,18 @@ static inline void emit_ia32_to_be_r64(const u8 dst[], s32 val, EMIT2(0x0F, 0xB7); EMIT1(add_2reg(0xC0, dreg_lo, dreg_lo)); - /* xor dreg_hi,dreg_hi */ - EMIT2(0x33, add_2reg(0xC0, dreg_hi, dreg_hi)); + if (!aux->verifier_zext) + /* xor dreg_hi,dreg_hi */ + EMIT2(0x33, add_2reg(0xC0, dreg_hi, dreg_hi)); break; case 32: /* Emit 'bswap eax' to swap lower 4 bytes */ EMIT1(0x0F); EMIT1(add_1reg(0xC8, dreg_lo)); - /* xor dreg_hi,dreg_hi */ - EMIT2(0x33, add_2reg(0xC0, dreg_hi, dreg_hi)); + if (!aux->verifier_zext) + /* xor dreg_hi,dreg_hi */ + EMIT2(0x33, add_2reg(0xC0, dreg_hi, dreg_hi)); break; case 64: /* Emit 'bswap eax' to swap lower 4 bytes */ @@ -569,7 +576,7 @@ static inline void emit_ia32_alu_r(const bool is64, const bool hi, const u8 op, static inline void emit_ia32_alu_r64(const bool is64, const u8 op, const u8 dst[], const u8 src[], bool dstk, bool sstk, - u8 **pprog) + u8 **pprog, const struct bpf_prog_aux *aux) { u8 *prog = *pprog; @@ -577,7 +584,7 @@ static inline void emit_ia32_alu_r64(const bool is64, const u8 op, if (is64) emit_ia32_alu_r(is64, true, op, dst_hi, src_hi, dstk, sstk, &prog); - else + else if (!aux->verifier_zext) emit_ia32_mov_i(dst_hi, 0, dstk, &prog); *pprog = prog; } @@ -668,7 +675,8 @@ static inline void emit_ia32_alu_i(const bool is64, const bool hi, const u8 op, /* ALU operation (64 bit) */ static inline void emit_ia32_alu_i64(const bool is64, const u8 op, const u8 dst[], const u32 val, - bool dstk, u8 **pprog) + bool dstk, u8 **pprog, + const struct bpf_prog_aux *aux) { u8 *prog = *pprog; u32 hi = 0; @@ -679,7 +687,7 @@ static inline void emit_ia32_alu_i64(const bool is64, const u8 op, emit_ia32_alu_i(is64, false, op, dst_lo, val, dstk, &prog); if (is64) emit_ia32_alu_i(is64, true, op, dst_hi, hi, dstk, &prog); - else + else if (!aux->verifier_zext) emit_ia32_mov_i(dst_hi, 0, dstk, &prog); *pprog = prog; @@ -1713,8 +1721,13 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, case BPF_ALU64 | BPF_MOV | BPF_X: switch (BPF_SRC(code)) { case BPF_X: - emit_ia32_mov_r64(is64, dst, src, dstk, - sstk, &prog); + if (imm32 == 1) { + /* Special mov32 for zext. */ + emit_ia32_mov_i(dst_hi, 0, dstk, &prog); + break; + } + emit_ia32_mov_r64(is64, dst, src, dstk, sstk, + &prog, bpf_prog->aux); break; case BPF_K: /* Sign-extend immediate value to dst reg */ @@ -1754,11 +1767,13 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, switch (BPF_SRC(code)) { case BPF_X: emit_ia32_alu_r64(is64, BPF_OP(code), dst, - src, dstk, sstk, &prog); + src, dstk, sstk, &prog, + bpf_prog->aux); break; case BPF_K: emit_ia32_alu_i64(is64, BPF_OP(code), dst, - imm32, dstk, &prog); + imm32, dstk, &prog, + bpf_prog->aux); break; } break; @@ -1777,7 +1792,8 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, false, &prog); break; } - emit_ia32_mov_i(dst_hi, 0, dstk, &prog); + if (!bpf_prog->aux->verifier_zext) + emit_ia32_mov_i(dst_hi, 0, dstk, &prog); break; case BPF_ALU | BPF_LSH | BPF_X: case BPF_ALU | BPF_RSH | BPF_X: @@ -1797,7 +1813,8 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, &prog); break; } - emit_ia32_mov_i(dst_hi, 0, dstk, &prog); + if (!bpf_prog->aux->verifier_zext) + emit_ia32_mov_i(dst_hi, 0, dstk, &prog); break; /* dst = dst / src(imm) */ /* dst = dst % src(imm) */ @@ -1819,7 +1836,8 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, &prog); break; } - emit_ia32_mov_i(dst_hi, 0, dstk, &prog); + if (!bpf_prog->aux->verifier_zext) + emit_ia32_mov_i(dst_hi, 0, dstk, &prog); break; case BPF_ALU64 | BPF_DIV | BPF_K: case BPF_ALU64 | BPF_DIV | BPF_X: @@ -1836,7 +1854,8 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, EMIT2_off32(0xC7, add_1reg(0xC0, IA32_ECX), imm32); emit_ia32_shift_r(BPF_OP(code), dst_lo, IA32_ECX, dstk, false, &prog); - emit_ia32_mov_i(dst_hi, 0, dstk, &prog); + if (!bpf_prog->aux->verifier_zext) + emit_ia32_mov_i(dst_hi, 0, dstk, &prog); break; /* dst = dst << imm */ case BPF_ALU64 | BPF_LSH | BPF_K: @@ -1872,7 +1891,8 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, case BPF_ALU | BPF_NEG: emit_ia32_alu_i(is64, false, BPF_OP(code), dst_lo, 0, dstk, &prog); - emit_ia32_mov_i(dst_hi, 0, dstk, &prog); + if (!bpf_prog->aux->verifier_zext) + emit_ia32_mov_i(dst_hi, 0, dstk, &prog); break; /* dst = ~dst (64 bit) */ case BPF_ALU64 | BPF_NEG: @@ -1892,11 +1912,13 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, break; /* dst = htole(dst) */ case BPF_ALU | BPF_END | BPF_FROM_LE: - emit_ia32_to_le_r64(dst, imm32, dstk, &prog); + emit_ia32_to_le_r64(dst, imm32, dstk, &prog, + bpf_prog->aux); break; /* dst = htobe(dst) */ case BPF_ALU | BPF_END | BPF_FROM_BE: - emit_ia32_to_be_r64(dst, imm32, dstk, &prog); + emit_ia32_to_be_r64(dst, imm32, dstk, &prog, + bpf_prog->aux); break; /* dst = imm64 */ case BPF_LD | BPF_IMM | BPF_DW: { @@ -2051,6 +2073,8 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, case BPF_B: case BPF_H: case BPF_W: + if (!bpf_prog->aux->verifier_zext) + break; if (dstk) { EMIT3(0xC7, add_1reg(0x40, IA32_EBP), STACK_VAR(dst_hi)); @@ -2475,6 +2499,11 @@ notyet: return proglen; } +bool bpf_jit_needs_zext(void) +{ + return true; +} + struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) { struct bpf_binary_header *header = NULL; -- cgit v1.2.3 From 68a8357ec15bdce55266e9fba8b8b3b8143fa7d2 Mon Sep 17 00:00:00 2001 From: Luke Nelson Date: Fri, 28 Jun 2019 22:57:49 -0700 Subject: bpf, x32: Fix bug with ALU64 {LSH, RSH, ARSH} BPF_X shift by 0 The current x32 BPF JIT for shift operations is not correct when the shift amount in a register is 0. The expected behavior is a no-op, whereas the current implementation changes bits in the destination register. The following example demonstrates the bug. The expected result of this program is 1, but the current JITed code returns 2. r0 = 1 r1 = 1 r2 = 0 r1 <<= r2 if r1 == 1 goto end r0 = 2 end: exit The bug is caused by an incorrect assumption by the JIT that a shift by 32 clear the register. On x32 however, shifts use the lower 5 bits of the source, making a shift by 32 equivalent to a shift by 0. This patch fixes the bug using double-precision shifts, which also simplifies the code. Fixes: 03f5781be2c7 ("bpf, x86_32: add eBPF JIT compiler for ia32") Co-developed-by: Xi Wang Signed-off-by: Xi Wang Signed-off-by: Luke Nelson Signed-off-by: Daniel Borkmann --- arch/x86/net/bpf_jit_comp32.c | 221 +++++------------------------------------- 1 file changed, 23 insertions(+), 198 deletions(-) (limited to 'arch/x86') diff --git a/arch/x86/net/bpf_jit_comp32.c b/arch/x86/net/bpf_jit_comp32.c index b29e82f190c7..f34ef513f4f9 100644 --- a/arch/x86/net/bpf_jit_comp32.c +++ b/arch/x86/net/bpf_jit_comp32.c @@ -724,9 +724,6 @@ static inline void emit_ia32_lsh_r64(const u8 dst[], const u8 src[], { u8 *prog = *pprog; int cnt = 0; - static int jmp_label1 = -1; - static int jmp_label2 = -1; - static int jmp_label3 = -1; u8 dreg_lo = dstk ? IA32_EAX : dst_lo; u8 dreg_hi = dstk ? IA32_EDX : dst_hi; @@ -745,79 +742,23 @@ static inline void emit_ia32_lsh_r64(const u8 dst[], const u8 src[], /* mov ecx,src_lo */ EMIT2(0x8B, add_2reg(0xC0, src_lo, IA32_ECX)); - /* cmp ecx,32 */ - EMIT3(0x83, add_1reg(0xF8, IA32_ECX), 32); - /* Jumps when >= 32 */ - if (is_imm8(jmp_label(jmp_label1, 2))) - EMIT2(IA32_JAE, jmp_label(jmp_label1, 2)); - else - EMIT2_off32(0x0F, IA32_JAE + 0x10, jmp_label(jmp_label1, 6)); - - /* < 32 */ - /* shl dreg_hi,cl */ - EMIT2(0xD3, add_1reg(0xE0, dreg_hi)); - /* mov ebx,dreg_lo */ - EMIT2(0x8B, add_2reg(0xC0, dreg_lo, IA32_EBX)); + /* shld dreg_hi,dreg_lo,cl */ + EMIT3(0x0F, 0xA5, add_2reg(0xC0, dreg_hi, dreg_lo)); /* shl dreg_lo,cl */ EMIT2(0xD3, add_1reg(0xE0, dreg_lo)); - /* IA32_ECX = -IA32_ECX + 32 */ - /* neg ecx */ - EMIT2(0xF7, add_1reg(0xD8, IA32_ECX)); - /* add ecx,32 */ - EMIT3(0x83, add_1reg(0xC0, IA32_ECX), 32); - - /* shr ebx,cl */ - EMIT2(0xD3, add_1reg(0xE8, IA32_EBX)); - /* or dreg_hi,ebx */ - EMIT2(0x09, add_2reg(0xC0, dreg_hi, IA32_EBX)); - - /* goto out; */ - if (is_imm8(jmp_label(jmp_label3, 2))) - EMIT2(0xEB, jmp_label(jmp_label3, 2)); - else - EMIT1_off32(0xE9, jmp_label(jmp_label3, 5)); - - /* >= 32 */ - if (jmp_label1 == -1) - jmp_label1 = cnt; + /* if ecx >= 32, mov dreg_lo into dreg_hi and clear dreg_lo */ - /* cmp ecx,64 */ - EMIT3(0x83, add_1reg(0xF8, IA32_ECX), 64); - /* Jumps when >= 64 */ - if (is_imm8(jmp_label(jmp_label2, 2))) - EMIT2(IA32_JAE, jmp_label(jmp_label2, 2)); - else - EMIT2_off32(0x0F, IA32_JAE + 0x10, jmp_label(jmp_label2, 6)); + /* cmp ecx,32 */ + EMIT3(0x83, add_1reg(0xF8, IA32_ECX), 32); + /* skip the next two instructions (4 bytes) when < 32 */ + EMIT2(IA32_JB, 4); - /* >= 32 && < 64 */ - /* sub ecx,32 */ - EMIT3(0x83, add_1reg(0xE8, IA32_ECX), 32); - /* shl dreg_lo,cl */ - EMIT2(0xD3, add_1reg(0xE0, dreg_lo)); /* mov dreg_hi,dreg_lo */ EMIT2(0x89, add_2reg(0xC0, dreg_hi, dreg_lo)); - /* xor dreg_lo,dreg_lo */ EMIT2(0x33, add_2reg(0xC0, dreg_lo, dreg_lo)); - /* goto out; */ - if (is_imm8(jmp_label(jmp_label3, 2))) - EMIT2(0xEB, jmp_label(jmp_label3, 2)); - else - EMIT1_off32(0xE9, jmp_label(jmp_label3, 5)); - - /* >= 64 */ - if (jmp_label2 == -1) - jmp_label2 = cnt; - /* xor dreg_lo,dreg_lo */ - EMIT2(0x33, add_2reg(0xC0, dreg_lo, dreg_lo)); - /* xor dreg_hi,dreg_hi */ - EMIT2(0x33, add_2reg(0xC0, dreg_hi, dreg_hi)); - - if (jmp_label3 == -1) - jmp_label3 = cnt; - if (dstk) { /* mov dword ptr [ebp+off],dreg_lo */ EMIT3(0x89, add_2reg(0x40, IA32_EBP, dreg_lo), @@ -836,9 +777,6 @@ static inline void emit_ia32_arsh_r64(const u8 dst[], const u8 src[], { u8 *prog = *pprog; int cnt = 0; - static int jmp_label1 = -1; - static int jmp_label2 = -1; - static int jmp_label3 = -1; u8 dreg_lo = dstk ? IA32_EAX : dst_lo; u8 dreg_hi = dstk ? IA32_EDX : dst_hi; @@ -857,78 +795,22 @@ static inline void emit_ia32_arsh_r64(const u8 dst[], const u8 src[], /* mov ecx,src_lo */ EMIT2(0x8B, add_2reg(0xC0, src_lo, IA32_ECX)); - /* cmp ecx,32 */ - EMIT3(0x83, add_1reg(0xF8, IA32_ECX), 32); - /* Jumps when >= 32 */ - if (is_imm8(jmp_label(jmp_label1, 2))) - EMIT2(IA32_JAE, jmp_label(jmp_label1, 2)); - else - EMIT2_off32(0x0F, IA32_JAE + 0x10, jmp_label(jmp_label1, 6)); - - /* < 32 */ - /* lshr dreg_lo,cl */ - EMIT2(0xD3, add_1reg(0xE8, dreg_lo)); - /* mov ebx,dreg_hi */ - EMIT2(0x8B, add_2reg(0xC0, dreg_hi, IA32_EBX)); - /* ashr dreg_hi,cl */ + /* shrd dreg_lo,dreg_hi,cl */ + EMIT3(0x0F, 0xAD, add_2reg(0xC0, dreg_lo, dreg_hi)); + /* sar dreg_hi,cl */ EMIT2(0xD3, add_1reg(0xF8, dreg_hi)); - /* IA32_ECX = -IA32_ECX + 32 */ - /* neg ecx */ - EMIT2(0xF7, add_1reg(0xD8, IA32_ECX)); - /* add ecx,32 */ - EMIT3(0x83, add_1reg(0xC0, IA32_ECX), 32); - - /* shl ebx,cl */ - EMIT2(0xD3, add_1reg(0xE0, IA32_EBX)); - /* or dreg_lo,ebx */ - EMIT2(0x09, add_2reg(0xC0, dreg_lo, IA32_EBX)); - - /* goto out; */ - if (is_imm8(jmp_label(jmp_label3, 2))) - EMIT2(0xEB, jmp_label(jmp_label3, 2)); - else - EMIT1_off32(0xE9, jmp_label(jmp_label3, 5)); - - /* >= 32 */ - if (jmp_label1 == -1) - jmp_label1 = cnt; + /* if ecx >= 32, mov dreg_hi to dreg_lo and set/clear dreg_hi depending on sign */ - /* cmp ecx,64 */ - EMIT3(0x83, add_1reg(0xF8, IA32_ECX), 64); - /* Jumps when >= 64 */ - if (is_imm8(jmp_label(jmp_label2, 2))) - EMIT2(IA32_JAE, jmp_label(jmp_label2, 2)); - else - EMIT2_off32(0x0F, IA32_JAE + 0x10, jmp_label(jmp_label2, 6)); + /* cmp ecx,32 */ + EMIT3(0x83, add_1reg(0xF8, IA32_ECX), 32); + /* skip the next two instructions (5 bytes) when < 32 */ + EMIT2(IA32_JB, 5); - /* >= 32 && < 64 */ - /* sub ecx,32 */ - EMIT3(0x83, add_1reg(0xE8, IA32_ECX), 32); - /* ashr dreg_hi,cl */ - EMIT2(0xD3, add_1reg(0xF8, dreg_hi)); /* mov dreg_lo,dreg_hi */ EMIT2(0x89, add_2reg(0xC0, dreg_lo, dreg_hi)); - - /* ashr dreg_hi,imm8 */ - EMIT3(0xC1, add_1reg(0xF8, dreg_hi), 31); - - /* goto out; */ - if (is_imm8(jmp_label(jmp_label3, 2))) - EMIT2(0xEB, jmp_label(jmp_label3, 2)); - else - EMIT1_off32(0xE9, jmp_label(jmp_label3, 5)); - - /* >= 64 */ - if (jmp_label2 == -1) - jmp_label2 = cnt; - /* ashr dreg_hi,imm8 */ + /* sar dreg_hi,31 */ EMIT3(0xC1, add_1reg(0xF8, dreg_hi), 31); - /* mov dreg_lo,dreg_hi */ - EMIT2(0x89, add_2reg(0xC0, dreg_lo, dreg_hi)); - - if (jmp_label3 == -1) - jmp_label3 = cnt; if (dstk) { /* mov dword ptr [ebp+off],dreg_lo */ @@ -948,9 +830,6 @@ static inline void emit_ia32_rsh_r64(const u8 dst[], const u8 src[], bool dstk, { u8 *prog = *pprog; int cnt = 0; - static int jmp_label1 = -1; - static int jmp_label2 = -1; - static int jmp_label3 = -1; u8 dreg_lo = dstk ? IA32_EAX : dst_lo; u8 dreg_hi = dstk ? IA32_EDX : dst_hi; @@ -969,77 +848,23 @@ static inline void emit_ia32_rsh_r64(const u8 dst[], const u8 src[], bool dstk, /* mov ecx,src_lo */ EMIT2(0x8B, add_2reg(0xC0, src_lo, IA32_ECX)); - /* cmp ecx,32 */ - EMIT3(0x83, add_1reg(0xF8, IA32_ECX), 32); - /* Jumps when >= 32 */ - if (is_imm8(jmp_label(jmp_label1, 2))) - EMIT2(IA32_JAE, jmp_label(jmp_label1, 2)); - else - EMIT2_off32(0x0F, IA32_JAE + 0x10, jmp_label(jmp_label1, 6)); - - /* < 32 */ - /* lshr dreg_lo,cl */ - EMIT2(0xD3, add_1reg(0xE8, dreg_lo)); - /* mov ebx,dreg_hi */ - EMIT2(0x8B, add_2reg(0xC0, dreg_hi, IA32_EBX)); + /* shrd dreg_lo,dreg_hi,cl */ + EMIT3(0x0F, 0xAD, add_2reg(0xC0, dreg_lo, dreg_hi)); /* shr dreg_hi,cl */ EMIT2(0xD3, add_1reg(0xE8, dreg_hi)); - /* IA32_ECX = -IA32_ECX + 32 */ - /* neg ecx */ - EMIT2(0xF7, add_1reg(0xD8, IA32_ECX)); - /* add ecx,32 */ - EMIT3(0x83, add_1reg(0xC0, IA32_ECX), 32); - - /* shl ebx,cl */ - EMIT2(0xD3, add_1reg(0xE0, IA32_EBX)); - /* or dreg_lo,ebx */ - EMIT2(0x09, add_2reg(0xC0, dreg_lo, IA32_EBX)); + /* if ecx >= 32, mov dreg_hi to dreg_lo and clear dreg_hi */ - /* goto out; */ - if (is_imm8(jmp_label(jmp_label3, 2))) - EMIT2(0xEB, jmp_label(jmp_label3, 2)); - else - EMIT1_off32(0xE9, jmp_label(jmp_label3, 5)); - - /* >= 32 */ - if (jmp_label1 == -1) - jmp_label1 = cnt; - /* cmp ecx,64 */ - EMIT3(0x83, add_1reg(0xF8, IA32_ECX), 64); - /* Jumps when >= 64 */ - if (is_imm8(jmp_label(jmp_label2, 2))) - EMIT2(IA32_JAE, jmp_label(jmp_label2, 2)); - else - EMIT2_off32(0x0F, IA32_JAE + 0x10, jmp_label(jmp_label2, 6)); + /* cmp ecx,32 */ + EMIT3(0x83, add_1reg(0xF8, IA32_ECX), 32); + /* skip the next two instructions (4 bytes) when < 32 */ + EMIT2(IA32_JB, 4); - /* >= 32 && < 64 */ - /* sub ecx,32 */ - EMIT3(0x83, add_1reg(0xE8, IA32_ECX), 32); - /* shr dreg_hi,cl */ - EMIT2(0xD3, add_1reg(0xE8, dreg_hi)); /* mov dreg_lo,dreg_hi */ EMIT2(0x89, add_2reg(0xC0, dreg_lo, dreg_hi)); /* xor dreg_hi,dreg_hi */ EMIT2(0x33, add_2reg(0xC0, dreg_hi, dreg_hi)); - /* goto out; */ - if (is_imm8(jmp_label(jmp_label3, 2))) - EMIT2(0xEB, jmp_label(jmp_label3, 2)); - else - EMIT1_off32(0xE9, jmp_label(jmp_label3, 5)); - - /* >= 64 */ - if (jmp_label2 == -1) - jmp_label2 = cnt; - /* xor dreg_lo,dreg_lo */ - EMIT2(0x33, add_2reg(0xC0, dreg_lo, dreg_lo)); - /* xor dreg_hi,dreg_hi */ - EMIT2(0x33, add_2reg(0xC0, dreg_hi, dreg_hi)); - - if (jmp_label3 == -1) - jmp_label3 = cnt; - if (dstk) { /* mov dword ptr [ebp+off],dreg_lo */ EMIT3(0x89, add_2reg(0x40, IA32_EBP, dreg_lo), -- cgit v1.2.3 From 6fa632e719eec4d1b1ebf3ddc0b2d667997b057b Mon Sep 17 00:00:00 2001 From: Luke Nelson Date: Fri, 28 Jun 2019 22:57:50 -0700 Subject: bpf, x32: Fix bug with ALU64 {LSH, RSH, ARSH} BPF_K shift by 0 The current x32 BPF JIT does not correctly compile shift operations when the immediate shift amount is 0. The expected behavior is for this to be a no-op. The following program demonstrates the bug. The expexceted result is 1, but the current JITed code returns 2. r0 = 1 r1 = 1 r1 <<= 0 if r1 == 1 goto end r0 = 2 end: exit This patch simplifies the code and fixes the bug. Fixes: 03f5781be2c7 ("bpf, x86_32: add eBPF JIT compiler for ia32") Co-developed-by: Xi Wang Signed-off-by: Xi Wang Signed-off-by: Luke Nelson Signed-off-by: Daniel Borkmann --- arch/x86/net/bpf_jit_comp32.c | 63 +++++-------------------------------------- 1 file changed, 6 insertions(+), 57 deletions(-) (limited to 'arch/x86') diff --git a/arch/x86/net/bpf_jit_comp32.c b/arch/x86/net/bpf_jit_comp32.c index f34ef513f4f9..1d12d2174085 100644 --- a/arch/x86/net/bpf_jit_comp32.c +++ b/arch/x86/net/bpf_jit_comp32.c @@ -894,27 +894,10 @@ static inline void emit_ia32_lsh_i64(const u8 dst[], const u32 val, } /* Do LSH operation */ if (val < 32) { - /* shl dreg_hi,imm8 */ - EMIT3(0xC1, add_1reg(0xE0, dreg_hi), val); - /* mov ebx,dreg_lo */ - EMIT2(0x8B, add_2reg(0xC0, dreg_lo, IA32_EBX)); + /* shld dreg_hi,dreg_lo,imm8 */ + EMIT4(0x0F, 0xA4, add_2reg(0xC0, dreg_hi, dreg_lo), val); /* shl dreg_lo,imm8 */ EMIT3(0xC1, add_1reg(0xE0, dreg_lo), val); - - /* IA32_ECX = 32 - val */ - /* mov ecx,val */ - EMIT2(0xB1, val); - /* movzx ecx,ecx */ - EMIT3(0x0F, 0xB6, add_2reg(0xC0, IA32_ECX, IA32_ECX)); - /* neg ecx */ - EMIT2(0xF7, add_1reg(0xD8, IA32_ECX)); - /* add ecx,32 */ - EMIT3(0x83, add_1reg(0xC0, IA32_ECX), 32); - - /* shr ebx,cl */ - EMIT2(0xD3, add_1reg(0xE8, IA32_EBX)); - /* or dreg_hi,ebx */ - EMIT2(0x09, add_2reg(0xC0, dreg_hi, IA32_EBX)); } else if (val >= 32 && val < 64) { u32 value = val - 32; @@ -960,27 +943,10 @@ static inline void emit_ia32_rsh_i64(const u8 dst[], const u32 val, /* Do RSH operation */ if (val < 32) { - /* shr dreg_lo,imm8 */ - EMIT3(0xC1, add_1reg(0xE8, dreg_lo), val); - /* mov ebx,dreg_hi */ - EMIT2(0x8B, add_2reg(0xC0, dreg_hi, IA32_EBX)); + /* shrd dreg_lo,dreg_hi,imm8 */ + EMIT4(0x0F, 0xAC, add_2reg(0xC0, dreg_lo, dreg_hi), val); /* shr dreg_hi,imm8 */ EMIT3(0xC1, add_1reg(0xE8, dreg_hi), val); - - /* IA32_ECX = 32 - val */ - /* mov ecx,val */ - EMIT2(0xB1, val); - /* movzx ecx,ecx */ - EMIT3(0x0F, 0xB6, add_2reg(0xC0, IA32_ECX, IA32_ECX)); - /* neg ecx */ - EMIT2(0xF7, add_1reg(0xD8, IA32_ECX)); - /* add ecx,32 */ - EMIT3(0x83, add_1reg(0xC0, IA32_ECX), 32); - - /* shl ebx,cl */ - EMIT2(0xD3, add_1reg(0xE0, IA32_EBX)); - /* or dreg_lo,ebx */ - EMIT2(0x09, add_2reg(0xC0, dreg_lo, IA32_EBX)); } else if (val >= 32 && val < 64) { u32 value = val - 32; @@ -1025,27 +991,10 @@ static inline void emit_ia32_arsh_i64(const u8 dst[], const u32 val, } /* Do RSH operation */ if (val < 32) { - /* shr dreg_lo,imm8 */ - EMIT3(0xC1, add_1reg(0xE8, dreg_lo), val); - /* mov ebx,dreg_hi */ - EMIT2(0x8B, add_2reg(0xC0, dreg_hi, IA32_EBX)); + /* shrd dreg_lo,dreg_hi,imm8 */ + EMIT4(0x0F, 0xAC, add_2reg(0xC0, dreg_lo, dreg_hi), val); /* ashr dreg_hi,imm8 */ EMIT3(0xC1, add_1reg(0xF8, dreg_hi), val); - - /* IA32_ECX = 32 - val */ - /* mov ecx,val */ - EMIT2(0xB1, val); - /* movzx ecx,ecx */ - EMIT3(0x0F, 0xB6, add_2reg(0xC0, IA32_ECX, IA32_ECX)); - /* neg ecx */ - EMIT2(0xF7, add_1reg(0xD8, IA32_ECX)); - /* add ecx,32 */ - EMIT3(0x83, add_1reg(0xC0, IA32_ECX), 32); - - /* shl ebx,cl */ - EMIT2(0xD3, add_1reg(0xE0, IA32_EBX)); - /* or dreg_lo,ebx */ - EMIT2(0x09, add_2reg(0xC0, dreg_lo, IA32_EBX)); } else if (val >= 32 && val < 64) { u32 value = val - 32; -- cgit v1.2.3