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x86: Ignore CS/DS/ES/SS segment-override prefixes in 64-bit mode

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"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.
This commit is contained in:
Borislav Petkov
2020-11-14 06:16:26 -08:00
committed by H.J. Lu
parent e8b2f0d952
commit 0fa0fc8539
43 changed files with 467 additions and 401 deletions
Download Patch File Download Diff File Expand all files Collapse all files

7
opcodes/ChangeLog
View File

@@ -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.

25
opcodes/i386-dis.c
View File

@@ -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.