diff options
Diffstat (limited to 'arch/x86/kernel/verify_cpu.S')
| -rw-r--r-- | arch/x86/kernel/verify_cpu.S | 140 |
1 files changed, 140 insertions, 0 deletions
diff --git a/arch/x86/kernel/verify_cpu.S b/arch/x86/kernel/verify_cpu.S new file mode 100644 index 000000000..1258a5872 --- /dev/null +++ b/arch/x86/kernel/verify_cpu.S @@ -0,0 +1,140 @@ +/* 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) |