1/*
2 Copyright Oliver Kowalke 2009.
3 Distributed under the Boost Software License, Version 1.0.
4 (See accompanying file LICENSE_1_0.txt or copy at
5 http://www.boost.org/LICENSE_1_0.txt)
6*/
7
8/****************************************************************************************
9 * *
10 * ---------------------------------------------------------------------------------- *
11 * | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | *
12 * ---------------------------------------------------------------------------------- *
13 * | 0x0 | 0x4 | 0x8 | 0xc | 0x10 | 0x14 | 0x18 | 0x1c | *
14 * ---------------------------------------------------------------------------------- *
15 * | fc_mxcsr|fc_x87_cw| guard | R12 | R13 | *
16 * ---------------------------------------------------------------------------------- *
17 * ---------------------------------------------------------------------------------- *
18 * | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | *
19 * ---------------------------------------------------------------------------------- *
20 * | 0x20 | 0x24 | 0x28 | 0x2c | 0x30 | 0x34 | 0x38 | 0x3c | *
21 * ---------------------------------------------------------------------------------- *
22 * | R14 | R15 | RBX | RBP | *
23 * ---------------------------------------------------------------------------------- *
24 * ---------------------------------------------------------------------------------- *
25 * | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | *
26 * ---------------------------------------------------------------------------------- *
27 * | 0x40 | 0x44 | | *
28 * ---------------------------------------------------------------------------------- *
29 * | RIP | | *
30 * ---------------------------------------------------------------------------------- *
31 * *
32 ****************************************************************************************/
33
34# ifdef __i386__
35# include "make_i386_sysv_elf_gas.S"
36# else
37# if defined __CET__
38# include <cet.h>
39# define SHSTK_ENABLED (__CET__ & 0x2)
40# define BOOST_CONTEXT_SHADOW_STACK (SHSTK_ENABLED && SHADOW_STACK_SYSCALL)
41# else
42# define _CET_ENDBR
43# endif
44.file "make_x86_64_sysv_elf_gas.S"
45.text
46.globl make_fcontext
47.type make_fcontext,@function
48.align 16
49make_fcontext:
50 _CET_ENDBR
51
52#if BOOST_CONTEXT_SHADOW_STACK
53 /* the new shadow stack pointer (SSP) */
54 movq -0x8(%rdi), %r9
55#endif
56
57 /* first arg of make_fcontext() == top of context-stack */
58 movq %rdi, %rax
59
60 /* shift address in RAX to lower 16 byte boundary */
61 andq $-16, %rax
62
63 /* reserve space for context-data on context-stack */
64 /* on context-function entry: (RSP -0x8) % 16 == 0 */
65 leaq -0x48(%rax), %rax
66
67 /* third arg of make_fcontext() == address of context-function */
68 /* stored in RBX */
69 movq %rdx, 0x30(%rax)
70
71 /* save MMX control- and status-word */
72 stmxcsr (%rax)
73 /* save x87 control-word */
74 fnstcw 0x4(%rax)
75
76#if defined(BOOST_CONTEXT_TLS_STACK_PROTECTOR)
77 /* save stack guard */
78 movq %fs:0x28, %rcx /* read stack guard from TLS record */
79 movq %rcx, 0x8(%rsp) /* save stack guard */
80#endif
81
82 /* compute abs address of label trampoline */
83 leaq trampoline(%rip), %rcx
84 /* save address of trampoline as return-address for context-function */
85 /* will be entered after calling jump_fcontext() first time */
86 movq %rcx, 0x40(%rax)
87
88 /* compute abs address of label finish */
89 leaq finish(%rip), %rcx
90 /* save address of finish as return-address for context-function */
91 /* will be entered after context-function returns */
92 movq %rcx, 0x38(%rax)
93
94#if BOOST_CONTEXT_SHADOW_STACK
95 /* Populate the shadow stack and normal stack */
96 /* get original SSP */
97 rdsspq %r8
98 /* restore new shadow stack */
99 rstorssp -0x8(%r9)
100 /* save the restore token on the original shadow stack */
101 saveprevssp
102 /* push the address of "jmp trampoline" to the new shadow stack */
103 /* as well as the stack */
104 call 1f
105 jmp trampoline
1061:
107 /* save address of "jmp trampoline" as return-address */
108 /* for context-function */
109 pop 0x38(%rax)
110 /* Get the new SSP. */
111 rdsspq %r9
112 /* restore original shadow stack */
113 rstorssp -0x8(%r8)
114 /* save the restore token on the new shadow stack. */
115 saveprevssp
116
117 /* reserve space for the new SSP */
118 leaq -0x8(%rax), %rax
119 /* save the new SSP to this fcontext */
120 movq %r9, (%rax)
121#endif
122
123#if BOOST_CONTEXT_SHADOW_STACK
124 /* Populate the shadow stack */
125
126 /* get original SSP */
127 rdsspq %r8
128 /* restore new shadow stack */
129 rstorssp -0x8(%r9)
130 /* save the restore token on the original shadow stack */
131 saveprevssp
132 /* push the address of "jmp trampoline" to the new shadow stack */
133 /* as well as the stack */
134 call 1f
135 jmp trampoline
1361:
137 /* save address of "jmp trampoline" as return-address */
138 /* for context-function */
139 pop 0x38(%rax)
140 /* Get the new SSP. */
141 rdsspq %r9
142 /* restore original shadow stack */
143 rstorssp -0x8(%r8)
144 /* save the restore token on the new shadow stack. */
145 saveprevssp
146
147 /* now the new shadow stack looks like:
148 base-> +------------------------------+
149 | address of "jmp trampoline" |
150 SSP-> +------------------------------+
151 | restore token |
152 +------------------------------+
153 */
154
155 /* reserve space for the new SSP */
156 leaq -0x8(%rax), %rax
157 /* save the new SSP to this fcontext */
158 movq %r9, (%rax)
159#endif
160
161 ret /* return pointer to context-data */
162
163trampoline:
164 /* store return address on stack */
165 /* fix stack alignment */
166 _CET_ENDBR
167#if BOOST_CONTEXT_SHADOW_STACK
168 /* save address of "jmp *%rbp" as return-address */
169 /* on stack and shadow stack */
170 call 2f
171 jmp *%rbp
1722:
173#else
174 push %rbp
175#endif
176 /* jump to context-function */
177 jmp *%rbx
178
179finish:
180 _CET_ENDBR
181 /* exit code is zero */
182 xorq %rdi, %rdi
183 /* exit application */
184 call _exit@PLT
185 hlt
186.size make_fcontext,.-make_fcontext
187
188/* Mark that we don't need executable stack. */
189.section .note.GNU-stack,"",%progbits
190# endif
191

source code of boost/libs/context/src/asm/make_x86_64_sysv_elf_gas.S