diff options
| author | Michael Smith <mikesmiffy128@gmail.com> | 2023-05-01 01:23:02 +0100 |
|---|---|---|
| committer | Michael Smith <mikesmiffy128@gmail.com> | 2023-05-01 01:23:02 +0100 |
| commit | 15ed715e5e809f9af867bcf4469024ee707a339c (patch) | |
| tree | ea7bae475d14c79928c2536f3d3258b2a58d4ca7 /src | |
| parent | 5acb8437e1a7b70341952b22ac3f1c09d77da41c (diff) | |
Correct the ModR/M cases in x86.c
Diffstat (limited to 'src')
| -rw-r--r-- | src/x86.c | 11 |
1 files changed, 6 insertions, 5 deletions
@@ -1,5 +1,5 @@ /* - * Copyright © 2022 Michael Smith <mikesmiffy128@gmail.com> + * Copyright © 2023 Michael Smith <mikesmiffy128@gmail.com> * * Permission to use, copy, modify, and/or distribute this software for any * purpose with or without fee is hereby granted, provided that the above @@ -19,17 +19,18 @@ static int mrm(uchar b, int addrlen) { // I won't lie: I don't *entirely* understand this particular logic. I - // largely based it on some public domain code I found on the internet + // largely based it on some public domain code I found on the internet. + // See: https://github.com/Nomade040/length-disassembler/blob/e8b34546/ldisasm.cpp#L14 + // Bonus route credit goes to Bill for spotting some bugs in prior versions. if (addrlen == 4 || b & 0xC0) { int sib = addrlen == 4 && b < 0xC0 && (b & 7) == 4; switch (b & 0xC0) { // disp8 case 0x40: return 2 + sib; // disp16/32 - case 0: if ((b & 7) == 5) case 0x80: return 1 + addrlen + sib; + case 0: if ((b & 7) != 5) return 1 + sib; + case 0x80: return 1 + addrlen + sib; } - // disp8/32 - if (sib && (b & 7) == 5) return b & 0x40 ? 3 : 6; } if (addrlen == 2 && b == 0x26) return 3; return 1; // NOTE: include the mrm itself in the byte count |