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| author |   Denys Vlasenko <dvlasenk@redhat.com> | 2015-02-12 20:06:57 +0100 |
|---|---|---|
| committer |   Ingo Molnar <mingo@kernel.org> | 2015-02-18 21:01:59 +0100 |
| commit | cbb53b9623a70f012e1fdfb6fc0af6878df4762b (patch) | |
| tree | c7cdaefe10cb242f20ee4c02da6bc36188740ca8 /arch | |
| parent | x86/asm/decoder: Create artificial 3rd byte for 2-byte VEX (diff) | |
| download | linux-dev-cbb53b9623a70f012e1fdfb6fc0af6878df4762b.tar.xz linux-dev-cbb53b9623a70f012e1fdfb6fc0af6878df4762b.zip | |
x86/asm/decoder: Explain CALLW discrepancy between Intel and AMD
In 64-bit mode, AMD and Intel CPUs treat 0x66 prefix before
branch insns differently. For near branches, it affects decode
too since immediate offset's width is different.
See these empirical tests:
http://marc.info/?l=linux-kernel&m=139714939728946&w=2
Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Link: http://lkml.kernel.org/r/1423768017-31766-1-git-send-email-dvlasenk@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/lib/x86-opcode-map.txt | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/arch/x86/lib/x86-opcode-map.txt b/arch/x86/lib/x86-opcode-map.txt index 1a2be7c6895d..816488c0b97e 100644 --- a/arch/x86/lib/x86-opcode-map.txt +++ b/arch/x86/lib/x86-opcode-map.txt @@ -273,6 +273,9 @@ dd: ESC de: ESC df: ESC # 0xe0 - 0xef +# Note: "forced64" is Intel CPU behavior: they ignore 0x66 prefix +# in 64-bit mode. AMD CPUs accept 0x66 prefix, it causes RIP truncation +# to 16 bits. In 32-bit mode, 0x66 is accepted by both Intel and AMD. e0: LOOPNE/LOOPNZ Jb (f64) e1: LOOPE/LOOPZ Jb (f64) e2: LOOP Jb (f64) @@ -281,6 +284,10 @@ e4: IN AL,Ib e5: IN eAX,Ib e6: OUT Ib,AL e7: OUT Ib,eAX +# With 0x66 prefix in 64-bit mode, for AMD CPUs immediate offset +# in "near" jumps and calls is 16-bit. For CALL, +# push of return address is 16-bit wide, RSP is decremented by 2 +# but is not truncated to 16 bits, unlike RIP. e8: CALL Jz (f64) e9: JMP-near Jz (f64) ea: JMP-far Ap (i64) @@ -456,6 +463,7 @@ AVXcode: 1 7e: movd/q Ey,Pd | vmovd/q Ey,Vy (66),(v1) | vmovq Vq,Wq (F3),(v1) 7f: movq Qq,Pq | vmovdqa Wx,Vx (66) | vmovdqu Wx,Vx (F3) # 0x0f 0x80-0x8f +# Note: "forced64" is Intel CPU behavior (see comment about CALL insn). 80: JO Jz (f64) 81: JNO Jz (f64) 82: JB/JC/JNAE Jz (f64) @@ -842,6 +850,7 @@ EndTable GrpTable: Grp5 0: INC Ev 1: DEC Ev +# Note: "forced64" is Intel CPU behavior (see comment about CALL insn). 2: CALLN Ev (f64) 3: CALLF Ep 4: JMPN Ev (f64) |