1/* Copyright (C) 2001-2022 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
8
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <https://www.gnu.org/licenses/>. */
17
18#include <sysdep.h>
19#include <jmpbuf-offsets.h>
20#include <tcb-offsets.h>
21#include <asm-syntax.h>
22
23#include <signal-defines.h>
24/* #include <signal.h> */
25#define SS_ONSTACK 1
26
27
28 .section .rodata.str1.1,"aMS",@progbits,1
29 .type longjmp_msg,@object
30longjmp_msg:
31 .string "longjmp causes uninitialized stack frame"
32 .size longjmp_msg, .-longjmp_msg
33
34
35#ifdef PIC
36# define CALL_FAIL movl %ebx, %ecx; /* TODO: what's this mov good for? */ \
37 cfi_register(%ebx,%ecx); \
38 LOAD_PIC_REG (bx); \
39 leal longjmp_msg@GOTOFF(%ebx), %eax; \
40 movl %eax, (%esp); \
41 call HIDDEN_JUMPTARGET(__fortify_fail)
42#else
43# define CALL_FAIL movl $longjmp_msg, %eax; \
44 movl %eax, (%esp); \
45 call HIDDEN_JUMPTARGET(__fortify_fail)
46#endif
47
48
49 .text
50ENTRY (____longjmp_chk)
51 movl 4(%esp), %eax /* User's jmp_buf in %eax. */
52
53 /* Save the return address now. */
54 movl (JB_PC*4)(%eax), %edx
55 /* Get the stack pointer. */
56 movl (JB_SP*4)(%eax), %ecx
57 cfi_undefined(%ecx)
58#ifdef PTR_DEMANGLE
59 PTR_DEMANGLE (%edx)
60 PTR_DEMANGLE (%ecx)
61#endif
62
63 movw %ds, %si
64 movw %gs, %di
65 cmpw %si, %di
66 jz .Lok /* TLS not initialized yet */
67
68 movl %gs:SIGSTATE_OFFSET, %edi
69 testl %edi, %edi
70 jz .Lok /* sigstate not initialized yet */
71
72 testl $SS_ONSTACK, (HURD_SIGSTATE__SIGALTSTACK__OFFSET + SIGALTSTACK__SS_FLAGS__OFFSET)(%edi)
73 jnz .Lonstack
74
75 /* We were on the main stack */
76
77 cmpl %ecx, %esp
78 /* Jumping to a higher-address frame is always allowed. */
79 jbe .Lok
80
81 /* Otherwise it's not allowed. */
82 CALL_FAIL
83
84.Lonstack:
85 /* We were on the alternate stack, can't really easily check anything
86 since longjmp may get us out of the alternate stack. */
87
88 cmpl (HURD_SIGSTATE__SIGALTSTACK__OFFSET + SIGALTSTACK__SS_SP__OFFSET)(%edi), %ecx
89 jb .Loks /* We jump below the alternate stack, switch. */
90
91 movl (HURD_SIGSTATE__SIGALTSTACK__OFFSET + SIGALTSTACK__SS_SP__OFFSET)(%edi), %ebx
92 addl (HURD_SIGSTATE__SIGALTSTACK__OFFSET + SIGALTSTACK__SS_SIZE__OFFSET)(%edi), %ebx
93 cmpl %ebx, %ecx
94 jb .Lok /* We jump inside the alternate stack, do not switch. */
95
96 /* We jump above the alternate stack, switch. */
97
98.Loks: /* We jump out of the alternate stack, clear SS_ONSTACK flag. */
99 andl $~(SS_ONSTACK), (HURD_SIGSTATE__SIGALTSTACK__OFFSET + SIGALTSTACK__SS_FLAGS__OFFSET)(%edi)
100
101.Lok: /* We add unwind information for the target here. */
102 cfi_def_cfa(%eax, 0)
103 cfi_register(%eip, %edx)
104 cfi_register(%esp, %ecx)
105 cfi_offset(%ebx, JB_BX*4)
106 cfi_offset(%esi, JB_SI*4)
107 cfi_offset(%edi, JB_DI*4)
108 cfi_offset(%ebp, JB_BP*4)
109 /* Restore registers. */
110 movl (JB_BX*4)(%eax), %ebx
111 movl (JB_SI*4)(%eax), %esi
112 movl (JB_DI*4)(%eax), %edi
113 movl (JB_BP*4)(%eax), %ebp
114 cfi_restore(%ebx)
115 cfi_restore(%esi)
116 cfi_restore(%edi)
117 cfi_restore(%ebp)
118
119 movl 8(%esp), %eax /* Second argument is return value. */
120 movl %ecx, %esp
121
122 /* Jump to saved PC. */
123 jmp *%edx
124END (____longjmp_chk)
125

source code of glibc/sysdeps/mach/hurd/i386/____longjmp_chk.S