summaryrefslogtreecommitdiff
path: root/arch/x86/kernel/verify_cpu.S
blob: 0edefc19a113290792667afe816bfdecaa0c8fc3 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
/*
 *
 *	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 source code is licensed under the GNU General Public License,
 * 	Version 2.  See the file COPYING for more details.
 *
 *	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 verfication
 *	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/cpufeature.h>
#include <asm/msr-index.h>

verify_cpu:
	pushfl				# Save caller passed flags
	pushl	$0			# Kill any dangerous flags
	popfl

	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	verify_cpu_no_longmode	# cpu has no cpuid

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

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

verify_cpu_noamd:
	cmpl	$0x756e6547,%ebx        # GenuineIntel?
	jnz	verify_cpu_check
	cmpl	$0x49656e69,%edx
	jnz	verify_cpu_check
	cmpl	$0x6c65746e,%ecx
	jnz	verify_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	verify_cpu_clear_xd	# family > 6, ok
	jb	verify_cpu_check	# family < 6, skip

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

verify_cpu_clear_xd:
	movl	$MSR_IA32_MISC_ENABLE, %ecx
	rdmsr
	btrl	$2, %edx		# clear MSR_IA32_MISC_ENABLE_XD_DISABLE
	jnc	verify_cpu_check	# only write MSR if bit was changed
	wrmsr

verify_cpu_check:
	movl    $0x1,%eax		# Does the cpu have what it takes
	cpuid
	andl	$REQUIRED_MASK0,%edx
	xorl	$REQUIRED_MASK0,%edx
	jnz	verify_cpu_no_longmode

	movl    $0x80000000,%eax	# See if extended cpuid is implemented
	cpuid
	cmpl    $0x80000001,%eax
	jb      verify_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     verify_cpu_no_longmode

verify_cpu_sse_test:
	movl	$1,%eax
	cpuid
	andl	$SSE_MASK,%edx
	cmpl	$SSE_MASK,%edx
	je	verify_cpu_sse_ok
	test	%di,%di
	jz	verify_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	verify_cpu_sse_test	# try again

verify_cpu_no_longmode:
	popfl				# Restore caller passed flags
	movl $1,%eax
	ret
verify_cpu_sse_ok:
	popfl				# Restore caller passed flags
	xorl %eax, %eax
	ret