diff options
| author | Wang YanQing <udknight@gmail.com> | 2019-04-28 10:33:02 +0800 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2019-05-01 23:40:47 +0200 |
| commit | b9aa0b35d878dff9ed19f94101fe353a4de00cc4 (patch) | |
| tree | a0e484e108a504acf6b26789acdd9d8cce5df756 /arch/x86/net | |
| parent | 711aef1bbf88212a21f7103e88f397b47a528805 (diff) | |
bpf, x32: Fix bug for BPF_ALU64 | BPF_NEG
The current implementation has two errors:
1: The second xor instruction will clear carry flag which
is necessary for following sbb instruction.
2: The select coding for sbb instruction is wrong, the coding
is "sbb dreg_hi,ecx", but what we need is "sbb ecx,dreg_hi".
This patch rewrites the implementation and fixes the errors.
This patch fixes below errors reported by bpf/test_verifier in x32
platform when the jit is enabled:
"
0: (b4) w1 = 4
1: (b4) w2 = 4
2: (1f) r2 -= r1
3: (4f) r2 |= r1
4: (87) r2 = -r2
5: (c7) r2 s>>= 63
6: (5f) r1 &= r2
7: (bf) r0 = r1
8: (95) exit
processed 9 insns (limit 131072), stack depth 0
0: (b4) w1 = 4
1: (b4) w2 = 4
2: (1f) r2 -= r1
3: (4f) r2 |= r1
4: (87) r2 = -r2
5: (c7) r2 s>>= 63
6: (5f) r1 &= r2
7: (bf) r0 = r1
8: (95) exit
processed 9 insns (limit 131072), stack depth 0
......
Summary: 1189 PASSED, 125 SKIPPED, 15 FAILED
"
Signed-off-by: Wang YanQing <udknight@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Diffstat (limited to 'arch/x86/net')
| -rw-r--r-- | arch/x86/net/bpf_jit_comp32.c | 19 |
1 files changed, 6 insertions, 13 deletions
diff --git a/arch/x86/net/bpf_jit_comp32.c b/arch/x86/net/bpf_jit_comp32.c index 8097b88d744f..b29e82f190c7 100644 --- a/arch/x86/net/bpf_jit_comp32.c +++ b/arch/x86/net/bpf_jit_comp32.c @@ -700,19 +700,12 @@ static inline void emit_ia32_neg64(const u8 dst[], bool dstk, u8 **pprog) STACK_VAR(dst_hi)); } - /* xor ecx,ecx */ - EMIT2(0x31, add_2reg(0xC0, IA32_ECX, IA32_ECX)); - /* sub dreg_lo,ecx */ - EMIT2(0x2B, add_2reg(0xC0, dreg_lo, IA32_ECX)); - /* mov dreg_lo,ecx */ - EMIT2(0x89, add_2reg(0xC0, dreg_lo, IA32_ECX)); - - /* xor ecx,ecx */ - EMIT2(0x31, add_2reg(0xC0, IA32_ECX, IA32_ECX)); - /* sbb dreg_hi,ecx */ - EMIT2(0x19, add_2reg(0xC0, dreg_hi, IA32_ECX)); - /* mov dreg_hi,ecx */ - EMIT2(0x89, add_2reg(0xC0, dreg_hi, IA32_ECX)); + /* neg dreg_lo */ + EMIT2(0xF7, add_1reg(0xD8, dreg_lo)); + /* adc dreg_hi,0x0 */ + EMIT3(0x83, add_1reg(0xD0, dreg_hi), 0x00); + /* neg dreg_hi */ + EMIT2(0xF7, add_1reg(0xD8, dreg_hi)); if (dstk) { /* mov dword ptr [ebp+off],dreg_lo */ |