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| author | Borislav Petkov <bp@suse.de> | 2020-11-14 06:16:26 -0800 |
|---|---|---|
| committer | H.J. Lu <hjl.tools@gmail.com> | 2020-11-14 06:20:33 -0800 |
| commit | 0fa0fc8539f4451bd1ed76867ba87a335e28ff31 (patch) | |
| tree | c010ef4ef967a84d7726f9d1b7f6231350e1e22c /opcodes | |
| parent | e8b2f0d952184fac8a230db181a4b9810729cd7b (diff) | |
| download | gdb-0fa0fc8539f4451bd1ed76867ba87a335e28ff31.zip gdb-0fa0fc8539f4451bd1ed76867ba87a335e28ff31.tar.gz gdb-0fa0fc8539f4451bd1ed76867ba87a335e28ff31.tar.bz2 | |
x86: Ignore CS/DS/ES/SS segment-override prefixes in 64-bit mode
"In 64-bit mode, the CS, DS, ES, and SS segment-override prefixes have
no effect. These four prefixes are not treated as segment-override
prefixes for the purposes of multiple-prefix rules. Instead, they are
treated as null prefixes." (AMD APM v2).
However, objdump disassembles instructions containing those ignored
prefixes by still generating that segment override:
66 66 2e 0f 1f 84 00 data16 nopw %cs:0x0(%rax,%rax,1)
00 00 00 00
Print those segment override prefixes as excessive ones:
66 66 2e 0f 1f 84 00 data16 cs nopw 0x0(%rax,%rax,1)
00 00 00 00
which is what they actually are - they have no effect and the decoding
hardware ignores them.
gas/
2020-11-14 Borislav Petkov <bp@suse.de>
* testsuite/gas/i386/x86-64-segovr.d: Adjust regexes.
* testsuite/gas/i386/x86-64-nops.d: Likewise.
* testsuite/gas/i386/x86-64-nops-1.d: Likewise.
* testsuite/gas/i386/x86-64-nops-1-g64.d: Likewise.
* testsuite/gas/i386/x86-64-nops-1-core2.d: Likewise.
* testsuite/gas/i386/x86-64-nops-1-k8.d: Likewise.
* testsuite/gas/i386/x86-64-nops-2.d: Likewise.
* testsuite/gas/i386/x86-64-nops-3.d: Likewise.
* testsuite/gas/i386/x86-64-nops-4.d: Likewise.
* testsuite/gas/i386/x86-64-nops-4-core2.d: Likewise.
* testsuite/gas/i386/x86-64-nops-4-k8.d: Likewise.
* testsuite/gas/i386/x86-64-nops-5.d: Likewise.
* testsuite/gas/i386/x86-64-nops-5-k8.d: Likewise.
* testsuite/gas/i386/x86-64-nops-7.d: Likewise.
* testsuite/gas/i386/x86-64-nop-1.d: Likewise.
* testsuite/gas/i386/x86-64-align-branch-1a.d: Likewise.
* testsuite/gas/i386/x86-64-align-branch-1b.d: Likewise.
* testsuite/gas/i386/x86-64-align-branch-1c.d: Likewise.
* testsuite/gas/i386/x86-64-align-branch-1d.d: Likewise.
* testsuite/gas/i386/x86-64-align-branch-1g.d: Likewise.
* testsuite/gas/i386/x86-64-align-branch-2c.d: Likewise.
* testsuite/gas/i386/x86-64-align-branch-6.d: Likewise.
* testsuite/gas/i386/x86-64-align-branch-7.d: Likewise.
* testsuite/gas/i386/x86-64-align-branch-8.d: Likewise.
* testsuite/gas/i386/ilp32/x86-64-nops-1-core2.d: Likewise.
* testsuite/gas/i386/ilp32/x86-64-nops-1-k8.d: Likewise.
* testsuite/gas/i386/ilp32/x86-64-nops-1.d: Likewise.
* testsuite/gas/i386/ilp32/x86-64-nops-2.d: Likewise.
* testsuite/gas/i386/ilp32/x86-64-nops-3.d: Likewise.
* testsuite/gas/i386/ilp32/x86-64-nops-4-core2.d: Likewise.
* testsuite/gas/i386/ilp32/x86-64-nops-4-k8.d: Likewise.
* testsuite/gas/i386/ilp32/x86-64-nops-4.d: Likewise.
* testsuite/gas/i386/ilp32/x86-64-nops-5-k8.d: Likewise.
* testsuite/gas/i386/ilp32/x86-64-nops-5.d: Likewise.
* testsuite/gas/i386/ilp32/x86-64-nops.d:: Likewise.
ld/
2020-11-14 Borislav Petkov <bp@suse.de>
* testsuite/ld-x86-64/pe-x86-64-4.od: Adjust regexes.
* testsuite/ld-x86-64/tlsld3.dd: Likewise.
* testsuite/ld-x86-64/tlsld4.dd: Likewise.
opcodes/
2020-11-14 Borislav Petkov <bp@suse.de>
* i386-dis.c (ckprefix): Do not assign active_seg_prefix in
64-bit addressing mode.
(NOTRACK_Fixup): Test prefixes for PREFIX_DS, instead of
active_seg_prefix.
Diffstat (limited to 'opcodes')
| -rw-r--r-- | opcodes/ChangeLog | 7 | ||||
| -rw-r--r-- | opcodes/i386-dis.c | 25 |
2 files changed, 27 insertions, 5 deletions
diff --git a/opcodes/ChangeLog b/opcodes/ChangeLog index d00e549..b25132a 100644 --- a/opcodes/ChangeLog +++ b/opcodes/ChangeLog @@ -1,3 +1,10 @@ +2020-11-14 Borislav Petkov <bp@suse.de> + + * i386-dis.c (ckprefix): Do not assign active_seg_prefix in + 64-bit addressing mode. + (NOTRACK_Fixup): Test prefixes for PREFIX_DS, instead of + active_seg_prefix. + 2020-11-11 Przemyslaw Wirkus <przemyslaw.wirkus@arm.com> * aarch64-tbl.h: Enable -march=armv8.6-a+ls64. diff --git a/opcodes/i386-dis.c b/opcodes/i386-dis.c index 9338b1f..58cf001 100644 --- a/opcodes/i386-dis.c +++ b/opcodes/i386-dis.c @@ -9141,22 +9141,34 @@ ckprefix (void) case 0x2e: prefixes |= PREFIX_CS; last_seg_prefix = i; - active_seg_prefix = PREFIX_CS; + + if (address_mode != mode_64bit) + active_seg_prefix = PREFIX_CS; + break; case 0x36: prefixes |= PREFIX_SS; last_seg_prefix = i; - active_seg_prefix = PREFIX_SS; + + if (address_mode != mode_64bit) + active_seg_prefix = PREFIX_SS; + break; case 0x3e: prefixes |= PREFIX_DS; last_seg_prefix = i; - active_seg_prefix = PREFIX_DS; + + if (address_mode != mode_64bit) + active_seg_prefix = PREFIX_DS; + break; case 0x26: prefixes |= PREFIX_ES; last_seg_prefix = i; - active_seg_prefix = PREFIX_ES; + + if (address_mode != mode_64bit) + active_seg_prefix = PREFIX_ES; + break; case 0x64: prefixes |= PREFIX_FS; @@ -13656,7 +13668,10 @@ static void NOTRACK_Fixup (int bytemode ATTRIBUTE_UNUSED, int sizeflag ATTRIBUTE_UNUSED) { - if (active_seg_prefix == PREFIX_DS + + /* Since active_seg_prefix is not set in 64-bit mode, check whether + we've seen a PREFIX_DS. */ + if ((prefixes & PREFIX_DS) != 0 && (address_mode != mode_64bit || last_data_prefix < 0)) { /* NOTRACK prefix is only valid on indirect branch instructions. |