From 81e9b93aab9217cf7cb508f64b19fc1c0df024b5 Mon Sep 17 00:00:00 2001 From: iximeow Date: Thu, 19 Nov 2020 18:13:24 -0800 Subject: fix decoding of rex-prefixed modrm+sib operands selecting index 0b100 and base 0b101 for memory operands with a base, index, and displacement either the wrong base would be selected (register number ignored, so only `*ax` or `r8*` would be reported), or yaxpeax-x86 would report a base register is present when it is not (`RegIndexBaseScaleDisp` when the operand is actually `RegScaleDisp`) thank you to Evan Johnson for catching and reporting this bug! also bump crate version to 0.1.4 as this will be immediately tagged and released. --- test/long_mode/mod.rs | 11 +++++++++++ test/protected_mode/mod.rs | 34 ++++++++++++++++++++++++++++++++++ 2 files changed, 45 insertions(+) (limited to 'test') diff --git a/test/long_mode/mod.rs b/test/long_mode/mod.rs index 3b31dbb..8489822 100644 --- a/test/long_mode/mod.rs +++ b/test/long_mode/mod.rs @@ -109,6 +109,17 @@ fn test_modrm_decode() { test_display(&[0x41, 0x33, 0x84, 0xa5, 0x11, 0x22, 0x33, 0x44], "xor eax, [r13 + 0x44332211]"); test_display(&[0x33, 0x04, 0xe5, 0x11, 0x22, 0x33, 0x44], "xor eax, [0x44332211]"); test_display(&[0x41, 0x33, 0x04, 0xe5, 0x11, 0x22, 0x33, 0x44], "xor eax, [0x44332211]"); + + // specifically sib with base == 0b101 + // mod bits 00 + test_display(&[0x42, 0x33, 0x34, 0x25, 0x20, 0x30, 0x40, 0x50], "xor esi, [r12 * 1 + 0x50403020]"); + test_display(&[0x43, 0x33, 0x34, 0x25, 0x20, 0x30, 0x40, 0x50], "xor esi, [r12 * 1 + 0x50403020]"); + // mod bits 01 + test_display(&[0x42, 0x33, 0x74, 0x25, 0x20], "xor esi, [rbp + r12 * 1 + 0x20]"); + test_display(&[0x43, 0x33, 0x74, 0x25, 0x20], "xor esi, [r13 + r12 * 1 + 0x20]"); + // mod bits 10 + test_display(&[0x42, 0x33, 0xb4, 0x25, 0x20, 0x30, 0x40, 0x50], "xor esi, [rbp + r12 * 1 + 0x50403020]"); + test_display(&[0x43, 0x33, 0xb4, 0x25, 0x20, 0x30, 0x40, 0x50], "xor esi, [r13 + r12 * 1 + 0x50403020]"); } #[test] diff --git a/test/protected_mode/mod.rs b/test/protected_mode/mod.rs index 84448ef..dd0a51f 100644 --- a/test/protected_mode/mod.rs +++ b/test/protected_mode/mod.rs @@ -50,6 +50,40 @@ fn test_display_under(decoder: &InstDecoder, data: &[u8], expected: &'static str } #[test] +fn test_modrm_decode() { + // just modrm + test_display(&[0x33, 0x08], "xor ecx, [eax]"); + test_display(&[0x33, 0x20], "xor esp, [eax]"); + test_display(&[0x33, 0x05, 0x78, 0x56, 0x34, 0x12], "xor eax, [0x12345678]"); + test_display(&[0x33, 0x41, 0x23], "xor eax, [ecx + 0x23]"); + test_display(&[0x33, 0x81, 0x23, 0x01, 0x65, 0x43], "xor eax, [ecx + 0x43650123]"); + test_display(&[0x33, 0xc1], "xor eax, ecx"); + + // sib + test_display(&[0x33, 0x04, 0x0a], "xor eax, [edx + ecx * 1]"); + test_display(&[0x33, 0x04, 0x4a], "xor eax, [edx + ecx * 2]"); + test_display(&[0x33, 0x04, 0x8a], "xor eax, [edx + ecx * 4]"); + test_display(&[0x33, 0x04, 0xca], "xor eax, [edx + ecx * 8]"); + test_display(&[0x33, 0x04, 0x20], "xor eax, [eax]"); + test_display(&[0x33, 0x04, 0x60], "xor eax, [eax]"); + test_display(&[0x33, 0x04, 0xa0], "xor eax, [eax]"); + test_display(&[0x33, 0x04, 0xe0], "xor eax, [eax]"); + test_display(&[0x33, 0x04, 0x25, 0x11, 0x22, 0x33, 0x44], "xor eax, [0x44332211]"); + + test_display(&[0x33, 0x44, 0x65, 0x11], "xor eax, [ebp + 0x11]"); + test_display(&[0x33, 0x84, 0xa5, 0x11, 0x22, 0x33, 0x44], "xor eax, [ebp + 0x44332211]"); + test_display(&[0x33, 0x04, 0xe5, 0x11, 0x22, 0x33, 0x44], "xor eax, [0x44332211]"); + + // specifically sib with base == 0b101 + // mod bits 00 + test_display(&[0x33, 0x34, 0x25, 0x20, 0x30, 0x40, 0x50], "xor esi, [0x50403020]"); + // mod bits 01 + test_display(&[0x33, 0x74, 0x25, 0x20], "xor esi, [ebp + 0x20]"); + // mod bits 10 + test_display(&[0x33, 0xb4, 0x25, 0x20, 0x30, 0x40, 0x50], "xor esi, [ebp + 0x50403020]"); +} + +#[test] fn test_mmx() { test_display(&[0x0f, 0xf7, 0xc1], "maskmovq mm0, mm1"); test_invalid(&[0x0f, 0xf7, 0x01]); -- cgit v1.1