1 /* SPDX-License-Identifier: LGPL-2.1 OR MIT */
3 * x86_64 specific definitions for NOLIBC
4 * Copyright (C) 2017-2022 Willy Tarreau <w@1wt.eu>
7 #ifndef _NOLIBC_ARCH_X86_64_H
8 #define _NOLIBC_ARCH_X86_64_H
10 /* O_* macros for fcntl/open are architecture-specific */
16 #define O_NOCTTY 0x100
18 #define O_APPEND 0x400
19 #define O_NONBLOCK 0x800
20 #define O_DIRECTORY 0x10000
22 /* The struct returned by the stat() syscall, equivalent to stat64(). The
23 * syscall returns 116 bytes and stops in the middle of __unused.
25 struct sys_stat_struct {
28 unsigned long st_nlink;
34 unsigned long st_rdev;
39 unsigned long st_atime;
40 unsigned long st_atime_nsec;
41 unsigned long st_mtime;
43 unsigned long st_mtime_nsec;
44 unsigned long st_ctime;
45 unsigned long st_ctime_nsec;
49 /* Syscalls for x86_64 :
50 * - registers are 64-bit
51 * - syscall number is passed in rax
52 * - arguments are in rdi, rsi, rdx, r10, r8, r9 respectively
53 * - the system call is performed by calling the syscall instruction
54 * - syscall return comes in rax
55 * - rcx and r11 are clobbered, others are preserved.
56 * - the arguments are cast to long and assigned into the target registers
57 * which are then simply passed as registers to the asm code, so that we
58 * don't have to experience issues with register constraints.
59 * - the syscall number is always specified last in order to allow to force
60 * some registers before (gcc refuses a %-register at the last position).
61 * - see also x86-64 ABI section A.2 AMD64 Linux Kernel Conventions, A.2.1
62 * Calling Conventions.
64 * Link x86-64 ABI: https://gitlab.com/x86-psABIs/x86-64-ABI/-/wikis/home
68 #define my_syscall0(num) \
71 register long _num __asm__ ("rax") = (num); \
77 : "rcx", "r11", "memory", "cc" \
82 #define my_syscall1(num, arg1) \
85 register long _num __asm__ ("rax") = (num); \
86 register long _arg1 __asm__ ("rdi") = (long)(arg1); \
93 : "rcx", "r11", "memory", "cc" \
98 #define my_syscall2(num, arg1, arg2) \
101 register long _num __asm__ ("rax") = (num); \
102 register long _arg1 __asm__ ("rdi") = (long)(arg1); \
103 register long _arg2 __asm__ ("rsi") = (long)(arg2); \
108 : "r"(_arg1), "r"(_arg2), \
110 : "rcx", "r11", "memory", "cc" \
115 #define my_syscall3(num, arg1, arg2, arg3) \
118 register long _num __asm__ ("rax") = (num); \
119 register long _arg1 __asm__ ("rdi") = (long)(arg1); \
120 register long _arg2 __asm__ ("rsi") = (long)(arg2); \
121 register long _arg3 __asm__ ("rdx") = (long)(arg3); \
126 : "r"(_arg1), "r"(_arg2), "r"(_arg3), \
128 : "rcx", "r11", "memory", "cc" \
133 #define my_syscall4(num, arg1, arg2, arg3, arg4) \
136 register long _num __asm__ ("rax") = (num); \
137 register long _arg1 __asm__ ("rdi") = (long)(arg1); \
138 register long _arg2 __asm__ ("rsi") = (long)(arg2); \
139 register long _arg3 __asm__ ("rdx") = (long)(arg3); \
140 register long _arg4 __asm__ ("r10") = (long)(arg4); \
145 : "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), \
147 : "rcx", "r11", "memory", "cc" \
152 #define my_syscall5(num, arg1, arg2, arg3, arg4, arg5) \
155 register long _num __asm__ ("rax") = (num); \
156 register long _arg1 __asm__ ("rdi") = (long)(arg1); \
157 register long _arg2 __asm__ ("rsi") = (long)(arg2); \
158 register long _arg3 __asm__ ("rdx") = (long)(arg3); \
159 register long _arg4 __asm__ ("r10") = (long)(arg4); \
160 register long _arg5 __asm__ ("r8") = (long)(arg5); \
165 : "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
167 : "rcx", "r11", "memory", "cc" \
172 #define my_syscall6(num, arg1, arg2, arg3, arg4, arg5, arg6) \
175 register long _num __asm__ ("rax") = (num); \
176 register long _arg1 __asm__ ("rdi") = (long)(arg1); \
177 register long _arg2 __asm__ ("rsi") = (long)(arg2); \
178 register long _arg3 __asm__ ("rdx") = (long)(arg3); \
179 register long _arg4 __asm__ ("r10") = (long)(arg4); \
180 register long _arg5 __asm__ ("r8") = (long)(arg5); \
181 register long _arg6 __asm__ ("r9") = (long)(arg6); \
186 : "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
187 "r"(_arg6), "0"(_num) \
188 : "rcx", "r11", "memory", "cc" \
195 * x86-64 System V ABI mandates:
196 * 1) %rsp must be 16-byte aligned right before the function call.
197 * 2) The deepest stack frame should be zero (the %rbp).
200 __asm__ (".section .text\n"
203 "pop %rdi\n" // argc (first arg, %rdi)
204 "mov %rsp, %rsi\n" // argv[] (second arg, %rsi)
205 "lea 8(%rsi,%rdi,8),%rdx\n" // then a NULL then envp (third arg, %rdx)
206 "xor %ebp, %ebp\n" // zero the stack frame
207 "and $-16, %rsp\n" // x86 ABI : esp must be 16-byte aligned before call
208 "call main\n" // main() returns the status code, we'll exit with it.
209 "mov %eax, %edi\n" // retrieve exit code (32 bit)
210 "mov $60, %eax\n" // NR_exit == 60
211 "syscall\n" // really exit
212 "hlt\n" // ensure it does not return
215 #endif // _NOLIBC_ARCH_X86_64_H