summaryrefslogtreecommitdiffstats
path: root/tools/include/nolibc/arch-x86_64.h
blob: 68609f42193485d015409b37af7ff91a53fc625d (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
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
/*
 * x86_64 specific definitions for NOLIBC
 * Copyright (C) 2017-2022 Willy Tarreau <w@1wt.eu>
 */

#ifndef _NOLIBC_ARCH_X86_64_H
#define _NOLIBC_ARCH_X86_64_H

#include "compiler.h"
#include "crt.h"

/* Syscalls for x86_64 :
 *   - registers are 64-bit
 *   - syscall number is passed in rax
 *   - arguments are in rdi, rsi, rdx, r10, r8, r9 respectively
 *   - the system call is performed by calling the syscall instruction
 *   - syscall return comes in rax
 *   - rcx and r11 are clobbered, others are preserved.
 *   - the arguments are cast to long and assigned into the target registers
 *     which are then simply passed as registers to the asm code, so that we
 *     don't have to experience issues with register constraints.
 *   - the syscall number is always specified last in order to allow to force
 *     some registers before (gcc refuses a %-register at the last position).
 *   - see also x86-64 ABI section A.2 AMD64 Linux Kernel Conventions, A.2.1
 *     Calling Conventions.
 *
 * Link x86-64 ABI: https://gitlab.com/x86-psABIs/x86-64-ABI/-/wikis/home
 *
 */

#define my_syscall0(num)                                                      \
({                                                                            \
	long _ret;                                                            \
	register long _num  __asm__ ("rax") = (num);                          \
									      \
	__asm__ volatile (                                                    \
		"syscall\n"                                                   \
		: "=a"(_ret)                                                  \
		: "0"(_num)                                                   \
		: "rcx", "r11", "memory", "cc"                                \
	);                                                                    \
	_ret;                                                                 \
})

#define my_syscall1(num, arg1)                                                \
({                                                                            \
	long _ret;                                                            \
	register long _num  __asm__ ("rax") = (num);                          \
	register long _arg1 __asm__ ("rdi") = (long)(arg1);                   \
									      \
	__asm__ volatile (                                                    \
		"syscall\n"                                                   \
		: "=a"(_ret)                                                  \
		: "r"(_arg1),                                                 \
		  "0"(_num)                                                   \
		: "rcx", "r11", "memory", "cc"                                \
	);                                                                    \
	_ret;                                                                 \
})

#define my_syscall2(num, arg1, arg2)                                          \
({                                                                            \
	long _ret;                                                            \
	register long _num  __asm__ ("rax") = (num);                          \
	register long _arg1 __asm__ ("rdi") = (long)(arg1);                   \
	register long _arg2 __asm__ ("rsi") = (long)(arg2);                   \
									      \
	__asm__ volatile (                                                    \
		"syscall\n"                                                   \
		: "=a"(_ret)                                                  \
		: "r"(_arg1), "r"(_arg2),                                     \
		  "0"(_num)                                                   \
		: "rcx", "r11", "memory", "cc"                                \
	);                                                                    \
	_ret;                                                                 \
})

#define my_syscall3(num, arg1, arg2, arg3)                                    \
({                                                                            \
	long _ret;                                                            \
	register long _num  __asm__ ("rax") = (num);                          \
	register long _arg1 __asm__ ("rdi") = (long)(arg1);                   \
	register long _arg2 __asm__ ("rsi") = (long)(arg2);                   \
	register long _arg3 __asm__ ("rdx") = (long)(arg3);                   \
									      \
	__asm__ volatile (                                                    \
		"syscall\n"                                                   \
		: "=a"(_ret)                                                  \
		: "r"(_arg1), "r"(_arg2), "r"(_arg3),                         \
		  "0"(_num)                                                   \
		: "rcx", "r11", "memory", "cc"                                \
	);                                                                    \
	_ret;                                                                 \
})

#define my_syscall4(num, arg1, arg2, arg3, arg4)                              \
({                                                                            \
	long _ret;                                                            \
	register long _num  __asm__ ("rax") = (num);                          \
	register long _arg1 __asm__ ("rdi") = (long)(arg1);                   \
	register long _arg2 __asm__ ("rsi") = (long)(arg2);                   \
	register long _arg3 __asm__ ("rdx") = (long)(arg3);                   \
	register long _arg4 __asm__ ("r10") = (long)(arg4);                   \
									      \
	__asm__ volatile (                                                    \
		"syscall\n"                                                   \
		: "=a"(_ret)                                                  \
		: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4),             \
		  "0"(_num)                                                   \
		: "rcx", "r11", "memory", "cc"                                \
	);                                                                    \
	_ret;                                                                 \
})

#define my_syscall5(num, arg1, arg2, arg3, arg4, arg5)                        \
({                                                                            \
	long _ret;                                                            \
	register long _num  __asm__ ("rax") = (num);                          \
	register long _arg1 __asm__ ("rdi") = (long)(arg1);                   \
	register long _arg2 __asm__ ("rsi") = (long)(arg2);                   \
	register long _arg3 __asm__ ("rdx") = (long)(arg3);                   \
	register long _arg4 __asm__ ("r10") = (long)(arg4);                   \
	register long _arg5 __asm__ ("r8")  = (long)(arg5);                   \
									      \
	__asm__ volatile (                                                    \
		"syscall\n"                                                   \
		: "=a"(_ret)                                                  \
		: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
		  "0"(_num)                                                   \
		: "rcx", "r11", "memory", "cc"                                \
	);                                                                    \
	_ret;                                                                 \
})

#define my_syscall6(num, arg1, arg2, arg3, arg4, arg5, arg6)                  \
({                                                                            \
	long _ret;                                                            \
	register long _num  __asm__ ("rax") = (num);                          \
	register long _arg1 __asm__ ("rdi") = (long)(arg1);                   \
	register long _arg2 __asm__ ("rsi") = (long)(arg2);                   \
	register long _arg3 __asm__ ("rdx") = (long)(arg3);                   \
	register long _arg4 __asm__ ("r10") = (long)(arg4);                   \
	register long _arg5 __asm__ ("r8")  = (long)(arg5);                   \
	register long _arg6 __asm__ ("r9")  = (long)(arg6);                   \
									      \
	__asm__ volatile (                                                    \
		"syscall\n"                                                   \
		: "=a"(_ret)                                                  \
		: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
		  "r"(_arg6), "0"(_num)                                       \
		: "rcx", "r11", "memory", "cc"                                \
	);                                                                    \
	_ret;                                                                 \
})

/* startup code */
/*
 * x86-64 System V ABI mandates:
 * 1) %rsp must be 16-byte aligned right before the function call.
 * 2) The deepest stack frame should be zero (the %rbp).
 *
 */
void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_stack_protector _start(void)
{
	__asm__ volatile (
		"xor  %ebp, %ebp\n"       /* zero the stack frame                            */
		"mov  %rsp, %rdi\n"       /* save stack pointer to %rdi, as arg1 of _start_c */
		"and  $-16, %rsp\n"       /* %rsp must be 16-byte aligned before call        */
		"call _start_c\n"         /* transfer to c runtime                           */
		"hlt\n"                   /* ensure it does not return                       */
	);
	__builtin_unreachable();
}

#define NOLIBC_ARCH_HAS_MEMMOVE
void *memmove(void *dst, const void *src, size_t len);

#define NOLIBC_ARCH_HAS_MEMCPY
void *memcpy(void *dst, const void *src, size_t len);

#define NOLIBC_ARCH_HAS_MEMSET
void *memset(void *dst, int c, size_t len);

__asm__ (
".section .text.nolibc_memmove_memcpy\n"
".weak memmove\n"
".weak memcpy\n"
"memmove:\n"
"memcpy:\n"
	"movq %rdx, %rcx\n\t"
	"movq %rdi, %rax\n\t"
	"movq %rdi, %rdx\n\t"
	"subq %rsi, %rdx\n\t"
	"cmpq %rcx, %rdx\n\t"
	"jb   .Lbackward_copy\n\t"
	"rep movsb\n\t"
	"retq\n"
".Lbackward_copy:"
	"leaq -1(%rdi, %rcx, 1), %rdi\n\t"
	"leaq -1(%rsi, %rcx, 1), %rsi\n\t"
	"std\n\t"
	"rep movsb\n\t"
	"cld\n\t"
	"retq\n"

".section .text.nolibc_memset\n"
".weak memset\n"
"memset:\n"
	"xchgl %eax, %esi\n\t"
	"movq  %rdx, %rcx\n\t"
	"pushq %rdi\n\t"
	"rep stosb\n\t"
	"popq  %rax\n\t"
	"retq\n"
);

#endif /* _NOLIBC_ARCH_X86_64_H */