Mailing List Archive

commit 489a46c1775fdc0474261418dffef0e048848c82
Author: Andrew Cooper <andrew.cooper3@citrix.com>
AuthorDate: Thu Dec 28 18:41:30 2023 +0000
Commit: Andrew Cooper <andrew.cooper3@citrix.com>
CommitDate: Thu Apr 18 20:43:11 2024 +0100

x86/emul: Simplify segment override prefix decoding

x86_seg_* uses architectural encodings. Therefore, we can fold the prefix
handling cases together and derive the segment from the prefix byte itself.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
---
xen/arch/x86/x86_emulate/decode.c | 19 +++++--------------
1 file changed, 5 insertions(+), 14 deletions(-)

diff --git a/xen/arch/x86/x86_emulate/decode.c b/xen/arch/x86/x86_emulate/decode.c
index de836068fd..ee4cbdc000 100644
--- a/xen/arch/x86/x86_emulate/decode.c
+++ b/xen/arch/x86/x86_emulate/decode.c
@@ -1043,17 +1043,12 @@ int x86emul_decode(struct x86_emulate_state *s,
case 0x67: /* address-size override */
ad_bytes = def_ad_bytes ^ (mode_64bit() ? 12 : 6);
break;
- case 0x2e: /* CS override / ignored in 64-bit mode */
+ case 0x26: /* ES override */
+ case 0x2e: /* CS override */
+ case 0x36: /* SS override */
+ case 0x3e: /* DS override, all ignored in 64-bit mode */
if ( !mode_64bit() )
- override_seg = x86_seg_cs;
- break;
- case 0x3e: /* DS override / ignored in 64-bit mode */
- if ( !mode_64bit() )
- override_seg = x86_seg_ds;
- break;
- case 0x26: /* ES override / ignored in 64-bit mode */
- if ( !mode_64bit() )
- override_seg = x86_seg_es;
+ override_seg = (b >> 3) & 3;
break;
case 0x64: /* FS override */
override_seg = x86_seg_fs;
@@ -1061,10 +1056,6 @@ int x86emul_decode(struct x86_emulate_state *s,
case 0x65: /* GS override */
override_seg = x86_seg_gs;
break;
- case 0x36: /* SS override / ignored in 64-bit mode */
- if ( !mode_64bit() )
- override_seg = x86_seg_ss;
- break;
case 0xf0: /* LOCK */
s->lock_prefix = true;
break;
--
generated by git-patchbot for /home/xen/git/xen.git#staging