diff options
Diffstat (limited to 'payloads/libpayload/arch/x86/head.S')
| -rw-r--r-- | payloads/libpayload/arch/x86/head.S | 43 |
1 files changed, 43 insertions, 0 deletions
diff --git a/payloads/libpayload/arch/x86/head.S b/payloads/libpayload/arch/x86/head.S index 94a4d41167..52504706db 100644 --- a/payloads/libpayload/arch/x86/head.S +++ b/payloads/libpayload/arch/x86/head.S @@ -2,6 +2,7 @@ * This file is part of the libpayload project. * * Copyright (C) 2008 Advanced Micro Devices, Inc. + * Copyright (C) 2017 Patrick Rudolph <siro@das-labor.org> * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions @@ -89,6 +90,48 @@ _init: movl $_stack, %esp pushl %eax + /* Enable special x86 functions if present. */ + pushl %eax + pushl %ebx + pushl %ecx + pushl %edx + + movl $0, %eax + cpuid + /* Test if CPUID(eax=1) is available. */ + test %eax, %eax + je cpuid_done + + /* Get CPU features. */ + movl $1, %eax + cpuid + +cpuid_fpu: + /* Test if x87 FPU is present */ + test $1, %edx + je cpuid_sse + + fninit + movl %cr0, %eax + andl $0xFFFFFFFB, %eax /* clear EM */ + orl $0x00000022, %eax /* set MP, NE */ + movl %eax, %cr0 + +cpuid_sse: + /* Test if SSE is available */ + test $0x02000000, %edx + je cpuid_done + + movl %cr4, %eax + orl $0x00000600, %eax /* set OSFXSR, OSXMMEXCPT */ + movl %eax, %cr4 + +cpuid_done: + popl %edx + popl %ecx + popl %ebx + popl %eax + /* Let's rock. */ call start_main |