1 /* SPDX-License-Identifier: LGPL-2.1 OR MIT */ 2 /* 3 * x86_64 specific definitions for NOLIBC 4 * Copyright (C) 2017-2022 Willy Tarreau <w@1wt.eu> 5 */ 6 7 #ifndef _NOLIBC_ARCH_X86_64_H 8 #define _NOLIBC_ARCH_X86_64_H 9 10 /* O_* macros for fcntl/open are architecture-specific */ 11 #define O_RDONLY 0 12 #define O_WRONLY 1 13 #define O_RDWR 2 14 #define O_CREAT 0x40 15 #define O_EXCL 0x80 16 #define O_NOCTTY 0x100 17 #define O_TRUNC 0x200 18 #define O_APPEND 0x400 19 #define O_NONBLOCK 0x800 20 #define O_DIRECTORY 0x10000 21 22 /* The struct returned by the stat() syscall, equivalent to stat64(). The 23 * syscall returns 116 bytes and stops in the middle of __unused. 24 */ 25 struct sys_stat_struct { 26 unsigned long st_dev; 27 unsigned long st_ino; 28 unsigned long st_nlink; 29 unsigned int st_mode; 30 unsigned int st_uid; 31 32 unsigned int st_gid; 33 unsigned int __pad0; 34 unsigned long st_rdev; 35 long st_size; 36 long st_blksize; 37 38 long st_blocks; 39 unsigned long st_atime; 40 unsigned long st_atime_nsec; 41 unsigned long st_mtime; 42 43 unsigned long st_mtime_nsec; 44 unsigned long st_ctime; 45 unsigned long st_ctime_nsec; 46 long __unused[3]; 47 }; 48 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. 63 * 64 * Link x86-64 ABI: https://gitlab.com/x86-psABIs/x86-64-ABI/-/wikis/home 65 * 66 */ 67 68 #define my_syscall0(num) \ 69 ({ \ 70 long _ret; \ 71 register long _num __asm__ ("rax") = (num); \ 72 \ 73 __asm__ volatile ( \ 74 "syscall\n" \ 75 : "=a"(_ret) \ 76 : "0"(_num) \ 77 : "rcx", "r11", "memory", "cc" \ 78 ); \ 79 _ret; \ 80 }) 81 82 #define my_syscall1(num, arg1) \ 83 ({ \ 84 long _ret; \ 85 register long _num __asm__ ("rax") = (num); \ 86 register long _arg1 __asm__ ("rdi") = (long)(arg1); \ 87 \ 88 __asm__ volatile ( \ 89 "syscall\n" \ 90 : "=a"(_ret) \ 91 : "r"(_arg1), \ 92 "0"(_num) \ 93 : "rcx", "r11", "memory", "cc" \ 94 ); \ 95 _ret; \ 96 }) 97 98 #define my_syscall2(num, arg1, arg2) \ 99 ({ \ 100 long _ret; \ 101 register long _num __asm__ ("rax") = (num); \ 102 register long _arg1 __asm__ ("rdi") = (long)(arg1); \ 103 register long _arg2 __asm__ ("rsi") = (long)(arg2); \ 104 \ 105 __asm__ volatile ( \ 106 "syscall\n" \ 107 : "=a"(_ret) \ 108 : "r"(_arg1), "r"(_arg2), \ 109 "0"(_num) \ 110 : "rcx", "r11", "memory", "cc" \ 111 ); \ 112 _ret; \ 113 }) 114 115 #define my_syscall3(num, arg1, arg2, arg3) \ 116 ({ \ 117 long _ret; \ 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); \ 122 \ 123 __asm__ volatile ( \ 124 "syscall\n" \ 125 : "=a"(_ret) \ 126 : "r"(_arg1), "r"(_arg2), "r"(_arg3), \ 127 "0"(_num) \ 128 : "rcx", "r11", "memory", "cc" \ 129 ); \ 130 _ret; \ 131 }) 132 133 #define my_syscall4(num, arg1, arg2, arg3, arg4) \ 134 ({ \ 135 long _ret; \ 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); \ 141 \ 142 __asm__ volatile ( \ 143 "syscall\n" \ 144 : "=a"(_ret) \ 145 : "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), \ 146 "0"(_num) \ 147 : "rcx", "r11", "memory", "cc" \ 148 ); \ 149 _ret; \ 150 }) 151 152 #define my_syscall5(num, arg1, arg2, arg3, arg4, arg5) \ 153 ({ \ 154 long _ret; \ 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); \ 161 \ 162 __asm__ volatile ( \ 163 "syscall\n" \ 164 : "=a"(_ret) \ 165 : "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \ 166 "0"(_num) \ 167 : "rcx", "r11", "memory", "cc" \ 168 ); \ 169 _ret; \ 170 }) 171 172 #define my_syscall6(num, arg1, arg2, arg3, arg4, arg5, arg6) \ 173 ({ \ 174 long _ret; \ 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); \ 182 \ 183 __asm__ volatile ( \ 184 "syscall\n" \ 185 : "=a"(_ret) \ 186 : "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \ 187 "r"(_arg6), "0"(_num) \ 188 : "rcx", "r11", "memory", "cc" \ 189 ); \ 190 _ret; \ 191 }) 192 193 /* startup code */ 194 /* 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). 198 * 199 */ 200 __asm__ (".section .text\n" 201 ".weak _start\n" 202 "_start:\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 213 ""); 214 215 #endif // _NOLIBC_ARCH_X86_64_H 216