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/* SPDX-License-Identifier: GPL-2.0-only */
/*
*
* verify_cpu.S - Code for cpu long mode and SSE verification. This
* code has been borrowed from boot/setup.S and was introduced by
* Andi Kleen.
*
* Copyright (c) 2007 Andi Kleen (ak@suse.de)
* Copyright (c) 2007 Eric Biederman (ebiederm@xmission.com)
* Copyright (c) 2007 Vivek Goyal (vgoyal@in.ibm.com)
* Copyright (c) 2010 Kees Cook (kees.cook@canonical.com)
*
* This is a common code for verification whether CPU supports
* long mode and SSE or not. It is not called directly instead this
* file is included at various places and compiled in that context.
* This file is expected to run in 32bit code. Currently:
*
* arch/x86/boot/compressed/head_64.S: Boot cpu verification
* arch/x86/kernel/trampoline_64.S: secondary processor verification
* arch/x86/kernel/head_32.S: processor startup
*
* verify_cpu, returns the status of longmode and SSE in register %eax.
* 0: Success 1: Failure
*
* On Intel, the XD_DISABLE flag will be cleared as a side-effect.
*
* The caller needs to check for the error code and take the action
* appropriately. Either display a message or halt.
*/
#include <asm/cpufeatures.h>
#include <asm/msr-index.h>
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
wrmsr
.Lverify_cpu_check:
movl $0x1,%eax # Does the cpu have what it takes
cpuid
andl $REQUIRED_MASK0,%edx
xorl $REQUIRED_MASK0,%edx
jnz .Lverify_cpu_no_longmode
movl $0x80000000,%eax # See if extended cpuid is implemented
cpuid
cmpl $0x80000001,%eax
jb .Lverify_cpu_no_longmode # no extended cpuid
movl $0x80000001,%eax # Does the cpu have what it takes
cpuid
andl $REQUIRED_MASK1,%edx
xorl $REQUIRED_MASK1,%edx
jnz .Lverify_cpu_no_longmode
.Lverify_cpu_sse_test:
movl $1,%eax
cpuid
andl $SSE_MASK,%edx
cmpl $SSE_MASK,%edx
je .Lverify_cpu_sse_ok
test %di,%di
jz .Lverify_cpu_no_longmode # only try to force SSE on AMD
movl $MSR_K7_HWCR,%ecx
rdmsr
btr $15,%eax # enable SSE
wrmsr
xor %di,%di # don't loop
jmp .Lverify_cpu_sse_test # try again
.Lverify_cpu_no_longmode:
popf # Restore caller passed flags
movl $1,%eax
ret
.Lverify_cpu_sse_ok:
popf # Restore caller passed flags
xorl %eax, %eax
ret
SYM_FUNC_END(verify_cpu)
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