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參數(shù)資料
| 型號： | 21086 |
| 英文描述： | SYSCALL and SYSRET Instruction Specification? 341KB (PDF) |
| 中文描述： | 系統(tǒng)調(diào)用和SYSRET指令規(guī)范？ 341KB（PDF格式） |
| 文件頁數(shù)： | 8/16頁 |
| 文件大?。?/td> | 341K |
| 代理商： | 21086 |
2
Feature Detection
SYSCALL and SYSRET Instruction Specification
21086C/0—May 1998
first test to see if the CPUID instruction is supported. For a
detailed description of the CPUID instruction, see the
AMD
Processor Recognition Application Note,
order# 20734.
The presence of the CPUID instruction is indicated by the ID
bit (21) in the EFLAGS register. If this bit is writeable, the
CPUID instruction is supported. The following code sample
shows how to test for the presence of the CPUID instruction.
pushfd
pop
mov
xor
push
popfd
pushfd
pop
cmp
jz
; save EFLAGS
; store EFLAGS in EAX
; save in EBX for later testing
; toggle bit 21
; put to stack
; save changed EAX to EFLAGS
; push EFLAGS to TOS
; store EFLAGS in EAX
; see if bit 21 has changed
; if no change, no CPUID
eax
ebx, eax
eax, 00200000h
eax
eax
eax, ebx
NO_CPUID
If the processor supports the CPUID instruction, the
programmer must execute the standard function, EAX=0. The
CPUID function returns a 12-character string that identifies the
processor’s vendor. For AMD processors, standard function 0
returns a vendor string of “AuthenticAMD”. This string
requires the software to follow the AMD definitions for
subsequent CPUID functions and the values returned for those
functions.
The next step for the programmer is to determine if the
SYSCALL/SYSRET instructions are supported. Extended
function 8000_0001h of the CPUID instruction provides this
information. Function 8000_0001h (EAX=8000_0001h) of the
AMD CPUID instruction returns the feature bits in the EDX
register. If bit 11 in the EDX register is set to 1,
SYSCALL/SYSRET is supported. The following code sample
shows how to test for SYSCALL/SYSRET support.
mov
CPUID
test
jnz
eax, 80000001h
; setup function 8000_0001h
; call the function
; test bit 11
edx, 800h
YES_SYSCALL/SYSRET
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