/* 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/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
        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)