arch/x86/kernel/verify_cpu.S

Source file repositories/reference/linux-study-clean/arch/x86/kernel/verify_cpu.S

File Facts

System
Linux kernel
Corpus path
arch/x86/kernel/verify_cpu.S
Extension
.S
Size
3879 bytes
Lines
145
Domain
Architecture Layer
Bucket
arch/x86
Inferred role
Architecture Layer: arch/x86
Status
atlas-only

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

#include <asm/cpufeatures.h>
#include <asm/cpufeaturemasks.h>
#include <asm/msr-index.h>

#define SSE_MASK	\
	(REQUIRED_MASK0 & ((1<<(X86_FEATURE_XMM & 31)) | (1<<(X86_FEATURE_XMM2 & 31))))

SYM_FUNC_START_LOCAL(verify_cpu)
	pushf				# Save caller passed flags
	push	$0			# Kill any dangerous flags
	popf

#ifndef __x86_64__
	pushfl				# standard way to check for cpuid
	popl	%eax
	movl	%eax,%ebx
	xorl	$0x200000,%eax
	pushl	%eax
	popfl
	pushfl
	popl	%eax
	cmpl	%eax,%ebx
	jz	.Lverify_cpu_no_longmode	# cpu has no cpuid
#endif

	movl	$0x0,%eax		# See if cpuid 1 is implemented
	cpuid
	cmpl	$0x1,%eax
	jb	.Lverify_cpu_no_longmode	# no cpuid 1

	xor	%di,%di
	cmpl	$0x68747541,%ebx	# AuthenticAMD
	jnz	.Lverify_cpu_noamd
	cmpl	$0x69746e65,%edx
	jnz	.Lverify_cpu_noamd
	cmpl	$0x444d4163,%ecx
	jnz	.Lverify_cpu_noamd
	mov	$1,%di			# cpu is from AMD
	jmp	.Lverify_cpu_check

.Lverify_cpu_noamd:
	cmpl	$0x756e6547,%ebx        # GenuineIntel?
	jnz	.Lverify_cpu_check
	cmpl	$0x49656e69,%edx
	jnz	.Lverify_cpu_check
	cmpl	$0x6c65746e,%ecx
	jnz	.Lverify_cpu_check

	# only call IA32_MISC_ENABLE when:
	# family > 6 || (family == 6 && model >= 0xd)
	movl	$0x1, %eax		# check CPU family and model
	cpuid
	movl	%eax, %ecx

	andl	$0x0ff00f00, %eax	# mask family and extended family
	shrl	$8, %eax
	cmpl	$6, %eax
	ja	.Lverify_cpu_clear_xd	# family > 6, ok
	jb	.Lverify_cpu_check	# family < 6, skip

	andl	$0x000f00f0, %ecx	# mask model and extended model
	shrl	$4, %ecx
	cmpl	$0xd, %ecx
	jb	.Lverify_cpu_check	# family == 6, model < 0xd, skip

.Lverify_cpu_clear_xd:
	movl	$MSR_IA32_MISC_ENABLE, %ecx
	rdmsr
	btrl	$2, %edx		# clear MSR_IA32_MISC_ENABLE_XD_DISABLE
	jnc	.Lverify_cpu_check	# only write MSR if bit was changed

Annotation

Implementation Notes