about summary refs log tree commit diff
path: root/sysdeps/i386/__longjmp.S
blob: 32c7e39dea2c8a5c0145f60908d86ae27d5efa68 (plain) (blame)
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
140
141
142
143
144
145
/* longjmp for i386.
   Copyright (C) 1995-2020 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <https://www.gnu.org/licenses/>.  */

#include <sysdep.h>
#include <jmpbuf-offsets.h>
#include <jmp_buf-ssp.h>
#include <asm-syntax.h>
#include <stap-probe.h>

/* Don't restore shadow stack register if
   1. Shadow stack isn't enabled.  Or
   2. __longjmp is defined for __longjmp_cancel.
 */
#if !SHSTK_ENABLED || defined __longjmp
# undef SHADOW_STACK_POINTER_OFFSET
#endif

	.text
ENTRY (__longjmp)
#ifdef PTR_DEMANGLE
	movl 4(%esp), %eax	/* User's jmp_buf in %eax.  */

# ifdef SHADOW_STACK_POINTER_OFFSET
#  if IS_IN (libc) && defined SHARED && defined FEATURE_1_OFFSET
	/* Check if Shadow Stack is enabled.  */
	testl $X86_FEATURE_1_SHSTK, %gs:FEATURE_1_OFFSET
	jz L(skip_ssp)
#  else
	xorl %edx, %edx
#  endif
	/* Check and adjust the Shadow-Stack-Pointer.  */
	rdsspd %edx
	/* And compare it with the saved ssp value.  */
	subl SHADOW_STACK_POINTER_OFFSET(%eax), %edx
	je L(skip_ssp)
	/* Count the number of frames to adjust and adjust it
	   with incssp instruction.  The instruction can adjust
	   the ssp by [0..255] value only thus use a loop if
	   the number of frames is bigger than 255.  */
	negl %edx
	shrl $2, %edx
	/* NB: We saved Shadow-Stack-Pointer of setjmp.  Since we are
	       restoring Shadow-Stack-Pointer of setjmp's caller, we
	       need to unwind shadow stack by one more frame.  */
	addl $1, %edx
	movl	$255, %ebx
L(loop):
	cmpl	%ebx, %edx
	cmovb	%edx, %ebx
	incsspd	%ebx
	subl	%ebx, %edx
	ja	L(loop)
L(skip_ssp):
# endif
	/* Save the return address now.  */
	movl (JB_PC*4)(%eax), %edx
	/* Get the stack pointer.  */
	movl (JB_SP*4)(%eax), %ecx
	PTR_DEMANGLE (%edx)
	PTR_DEMANGLE (%ecx)
	LIBC_PROBE (longjmp, 3, 4@%eax, -4@8(%esp), 4@%edx)
	cfi_def_cfa(%eax, 0)
	cfi_register(%eip, %edx)
	cfi_register(%esp, %ecx)
	cfi_offset(%ebx, JB_BX*4)
	cfi_offset(%esi, JB_SI*4)
	cfi_offset(%edi, JB_DI*4)
	cfi_offset(%ebp, JB_BP*4)
	/* Restore registers.  */
	movl (JB_BX*4)(%eax), %ebx
	movl (JB_SI*4)(%eax), %esi
	movl (JB_DI*4)(%eax), %edi
	movl (JB_BP*4)(%eax), %ebp
	cfi_restore(%ebx)
	cfi_restore(%esi)
	cfi_restore(%edi)
	cfi_restore(%ebp)

	LIBC_PROBE (longjmp_target, 3, 4@%eax, -4@8(%esp), 4@%edx)
	movl 8(%esp), %eax	/* Second argument is return value.  */
	movl %ecx, %esp
#else
	movl 4(%esp), %ecx	/* User's jmp_buf in %ecx.  */
	movl 8(%esp), %eax	/* Second argument is return value.  */
# ifdef SHADOW_STACK_POINTER_OFFSET
#  if IS_IN (libc) && defined SHARED
	/* Check if Shadow Stack is enabled.  */
	testl $X86_FEATURE_1_SHSTK, %gs:FEATURE_1_OFFSET
	jz L(skip_ssp)
#  endif
	/* Check and adjust the Shadow-Stack-Pointer.  */
	xorl %edx, %edx
	/* Get the current ssp.  */
	rdsspd	%edx
	/* And compare it with the saved ssp value.  */
	subl SHADOW_STACK_POINTER_OFFSET(%ecx), %edx
	je L(skip_ssp)
	/* Count the number of frames to adjust and adjust it
	   with incssp instruction.  The instruction can adjust
	   the ssp by [0..255] value only thus use a loop if
	   the number of frames is bigger than 255.  */
	negl %edx
	shrl $2, %edx
	/* NB: We saved Shadow-Stack-Pointer of setjmp.  Since we are
	       restoring Shadow-Stack-Pointer of setjmp's caller, we
	       need to unwind shadow stack by one more frame.  */
	addl $1, %edx
	movl	$255, %ebx
L(loop):
	cmpl	%ebx, %edx
	cmovb	%edx, %ebx
	incsspd	%ebx
	subl	%ebx, %edx
	ja	L(loop)
L(skip_ssp):
# endif
	/* Save the return address now.  */
	movl (JB_PC*4)(%ecx), %edx
	LIBC_PROBE (longjmp, 3, 4@%ecx, -4@%eax, 4@%edx)
	/* Restore registers.  */
	movl (JB_BX*4)(%ecx), %ebx
	movl (JB_SI*4)(%ecx), %esi
	movl (JB_DI*4)(%ecx), %edi
	movl (JB_BP*4)(%ecx), %ebp
	movl (JB_SP*4)(%ecx), %esp
	LIBC_PROBE (longjmp_target, 3, 4@%ecx, -4@%ecx, 4@%edx)
#endif
	/* Jump to saved PC.  */
	jmp *%edx
END (__longjmp)