summaryrefslogtreecommitdiffstats
path: root/tools/include/nolibc/arch-arm.h
blob: cae4afa7c1c77ea29478484b80ff92aac5bcc4ca (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
/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
/*
 * ARM specific definitions for NOLIBC
 * Copyright (C) 2017-2022 Willy Tarreau <w@1wt.eu>
 */

#ifndef _NOLIBC_ARCH_ARM_H
#define _NOLIBC_ARCH_ARM_H

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

/* Syscalls for ARM in ARM or Thumb modes :
 *   - registers are 32-bit
 *   - stack is 8-byte aligned
 *     ( http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.faqs/ka4127.html)
 *   - syscall number is passed in r7
 *   - arguments are in r0, r1, r2, r3, r4, r5
 *   - the system call is performed by calling svc #0
 *   - syscall return comes in r0.
 *   - only lr is clobbered.
 *   - 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).
 *   - in thumb mode without -fomit-frame-pointer, r7 is also used to store the
 *     frame pointer, and we cannot directly assign it as a register variable,
 *     nor can we clobber it. Instead we assign the r6 register and swap it
 *     with r7 before calling svc, and r6 is marked as clobbered.
 *     We're just using any regular register which we assign to r7 after saving
 *     it.
 *
 * Also, ARM supports the old_select syscall if newselect is not available
 */
#define __ARCH_WANT_SYS_OLD_SELECT

#if (defined(__THUMBEB__) || defined(__THUMBEL__)) && \
    !defined(NOLIBC_OMIT_FRAME_POINTER)
/* swap r6,r7 needed in Thumb mode since we can't use nor clobber r7 */
#define _NOLIBC_SYSCALL_REG         "r6"
#define _NOLIBC_THUMB_SET_R7        "eor r7, r6\neor r6, r7\neor r7, r6\n"
#define _NOLIBC_THUMB_RESTORE_R7    "mov r7, r6\n"

#else  /* we're in ARM mode */
/* in Arm mode we can directly use r7 */
#define _NOLIBC_SYSCALL_REG         "r7"
#define _NOLIBC_THUMB_SET_R7        ""
#define _NOLIBC_THUMB_RESTORE_R7    ""

#endif /* end THUMB */

#define my_syscall0(num)                                                      \
({                                                                            \
	register long _num  __asm__(_NOLIBC_SYSCALL_REG) = (num);             \
	register long _arg1 __asm__ ("r0");                                   \
									      \
	__asm__ volatile (                                                    \
		_NOLIBC_THUMB_SET_R7                                          \
		"svc #0\n"                                                    \
		_NOLIBC_THUMB_RESTORE_R7                                      \
		: "=r"(_arg1), "=r"(_num)                                     \
		: "r"(_arg1),                                                 \
		  "r"(_num)                                                   \
		: "memory", "cc", "lr"                                        \
	);                                                                    \
	_arg1;                                                                \
})

#define my_syscall1(num, arg1)                                                \
({                                                                            \
	register long _num  __asm__(_NOLIBC_SYSCALL_REG) = (num);             \
	register long _arg1 __asm__ ("r0") = (long)(arg1);                    \
									      \
	__asm__ volatile (                                                    \
		_NOLIBC_THUMB_SET_R7                                          \
		"svc #0\n"                                                    \
		_NOLIBC_THUMB_RESTORE_R7                                      \
		: "=r"(_arg1), "=r" (_num)                                    \
		: "r"(_arg1),                                                 \
		  "r"(_num)                                                   \
		: "memory", "cc", "lr"                                        \
	);                                                                    \
	_arg1;                                                                \
})

#define my_syscall2(num, arg1, arg2)                                          \
({                                                                            \
	register long _num  __asm__(_NOLIBC_SYSCALL_REG) = (num);             \
	register long _arg1 __asm__ ("r0") = (long)(arg1);                    \
	register long _arg2 __asm__ ("r1") = (long)(arg2);                    \
									      \
	__asm__ volatile (                                                    \
		_NOLIBC_THUMB_SET_R7                                          \
		"svc #0\n"                                                    \
		_NOLIBC_THUMB_RESTORE_R7                                      \
		: "=r"(_arg1), "=r" (_num)                                    \
		: "r"(_arg1), "r"(_arg2),                                     \
		  "r"(_num)                                                   \
		: "memory", "cc", "lr"                                        \
	);                                                                    \
	_arg1;                                                                \
})

#define my_syscall3(num, arg1, arg2, arg3)                                    \
({                                                                            \
	register long _num  __asm__(_NOLIBC_SYSCALL_REG) = (num);             \
	register long _arg1 __asm__ ("r0") = (long)(arg1);                    \
	register long _arg2 __asm__ ("r1") = (long)(arg2);                    \
	register long _arg3 __asm__ ("r2") = (long)(arg3);                    \
									      \
	__asm__ volatile (                                                    \
		_NOLIBC_THUMB_SET_R7                                          \
		"svc #0\n"                                                    \
		_NOLIBC_THUMB_RESTORE_R7                                      \
		: "=r"(_arg1), "=r" (_num)                                    \
		: "r"(_arg1), "r"(_arg2), "r"(_arg3),                         \
		  "r"(_num)                                                   \
		: "memory", "cc", "lr"                                        \
	);                                                                    \
	_arg1;                                                                \
})

#define my_syscall4(num, arg1, arg2, arg3, arg4)                              \
({                                                                            \
	register long _num  __asm__(_NOLIBC_SYSCALL_REG) = (num);             \
	register long _arg1 __asm__ ("r0") = (long)(arg1);                    \
	register long _arg2 __asm__ ("r1") = (long)(arg2);                    \
	register long _arg3 __asm__ ("r2") = (long)(arg3);                    \
	register long _arg4 __asm__ ("r3") = (long)(arg4);                    \
									      \
	__asm__ volatile (                                                    \
		_NOLIBC_THUMB_SET_R7                                          \
		"svc #0\n"                                                    \
		_NOLIBC_THUMB_RESTORE_R7                                      \
		: "=r"(_arg1), "=r" (_num)                                    \
		: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4),             \
		  "r"(_num)                                                   \
		: "memory", "cc", "lr"                                        \
	);                                                                    \
	_arg1;                                                                \
})

#define my_syscall5(num, arg1, arg2, arg3, arg4, arg5)                        \
({                                                                            \
	register long _num  __asm__(_NOLIBC_SYSCALL_REG) = (num);             \
	register long _arg1 __asm__ ("r0") = (long)(arg1);                    \
	register long _arg2 __asm__ ("r1") = (long)(arg2);                    \
	register long _arg3 __asm__ ("r2") = (long)(arg3);                    \
	register long _arg4 __asm__ ("r3") = (long)(arg4);                    \
	register long _arg5 __asm__ ("r4") = (long)(arg5);                    \
									      \
	__asm__ volatile (                                                    \
		_NOLIBC_THUMB_SET_R7                                          \
		"svc #0\n"                                                    \
		_NOLIBC_THUMB_RESTORE_R7                                      \
		: "=r"(_arg1), "=r" (_num)                                    \
		: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
		  "r"(_num)                                                   \
		: "memory", "cc", "lr"                                        \
	);                                                                    \
	_arg1;                                                                \
})

#define my_syscall6(num, arg1, arg2, arg3, arg4, arg5, arg6)                  \
({                                                                            \
	register long _num  __asm__(_NOLIBC_SYSCALL_REG) = (num);             \
	register long _arg1 __asm__ ("r0") = (long)(arg1);                    \
	register long _arg2 __asm__ ("r1") = (long)(arg2);                    \
	register long _arg3 __asm__ ("r2") = (long)(arg3);                    \
	register long _arg4 __asm__ ("r3") = (long)(arg4);                    \
	register long _arg5 __asm__ ("r4") = (long)(arg5);                    \
	register long _arg6 __asm__ ("r5") = (long)(arg6);                    \
									      \
	__asm__ volatile (                                                    \
		_NOLIBC_THUMB_SET_R7                                          \
		"svc #0\n"                                                    \
		_NOLIBC_THUMB_RESTORE_R7                                      \
		: "=r"(_arg1), "=r" (_num)                                    \
		: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
		  "r"(_arg6), "r"(_num)                                       \
		: "memory", "cc", "lr"                                        \
	);                                                                    \
	_arg1;                                                                \
})

/* startup code */
void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_stack_protector _start(void)
{
	__asm__ volatile (
		"mov %r0, sp\n"         /* save stack pointer to %r0, as arg1 of _start_c */
		"and ip, %r0, #-8\n"    /* sp must be 8-byte aligned in the callee        */
		"mov sp, ip\n"
		"bl  _start_c\n"        /* transfer to c runtime                          */
	);
	__builtin_unreachable();
}

#endif /* _NOLIBC_ARCH_ARM_H */