include/nolibc/arch-x86_64.h

0001 /* SPDX-License-Identifier: LGPL-2.1 OR MIT */
0002 /*
0003  * x86_64 specific definitions for NOLIBC
0004  * Copyright (C) 2017-2022 Willy Tarreau <w@1wt.eu>
0005  */
0006
0007 #ifndef _NOLIBC_ARCH_X86_64_H
0008 #define _NOLIBC_ARCH_X86_64_H
0009
0010 /* O_* macros for fcntl/open are architecture-specific */
0011 #define O_RDONLY            0
0012 #define O_WRONLY            1
0013 #define O_RDWR              2
0014 #define O_CREAT          0x40
0015 #define O_EXCL           0x80
0016 #define O_NOCTTY        0x100
0017 #define O_TRUNC         0x200
0018 #define O_APPEND        0x400
0019 #define O_NONBLOCK      0x800
0020 #define O_DIRECTORY   0x10000
0021
0022 /* The struct returned by the stat() syscall, equivalent to stat64(). The
0023  * syscall returns 116 bytes and stops in the middle of __unused.
0024  */
0025 struct sys_stat_struct {
0026     unsigned long st_dev;
0027     unsigned long st_ino;
0028     unsigned long st_nlink;
0029     unsigned int  st_mode;
0030     unsigned int  st_uid;
0031
0032     unsigned int  st_gid;
0033     unsigned int  __pad0;
0034     unsigned long st_rdev;
0035     long          st_size;
0036     long          st_blksize;
0037
0038     long          st_blocks;
0039     unsigned long st_atime;
0040     unsigned long st_atime_nsec;
0041     unsigned long st_mtime;
0042
0043     unsigned long st_mtime_nsec;
0044     unsigned long st_ctime;
0045     unsigned long st_ctime_nsec;
0046     long          __unused[3];
0047 };
0048
0049 /* Syscalls for x86_64 :
0050  *   - registers are 64-bit
0051  *   - syscall number is passed in rax
0052  *   - arguments are in rdi, rsi, rdx, r10, r8, r9 respectively
0053  *   - the system call is performed by calling the syscall instruction
0054  *   - syscall return comes in rax
0055  *   - rcx and r11 are clobbered, others are preserved.
0056  *   - the arguments are cast to long and assigned into the target registers
0057  *     which are then simply passed as registers to the asm code, so that we
0058  *     don't have to experience issues with register constraints.
0059  *   - the syscall number is always specified last in order to allow to force
0060  *     some registers before (gcc refuses a %-register at the last position).
0061  *   - see also x86-64 ABI section A.2 AMD64 Linux Kernel Conventions, A.2.1
0062  *     Calling Conventions.
0063  *
0064  * Link x86-64 ABI: https://gitlab.com/x86-psABIs/x86-64-ABI/-/wikis/home
0065  *
0066  */
0067
0068 #define my_syscall0(num)                                                      \
0069 ({                                                                            \
0070     long _ret;                                                            \
0071     register long _num  __asm__ ("rax") = (num);                          \
0072                                                                           \
0073     __asm__  volatile (                                                   \
0074         "syscall\n"                                                   \
0075         : "=a"(_ret)                                                  \
0076         : "0"(_num)                                                   \
0077         : "rcx", "r11", "memory", "cc"                                \
0078     );                                                                    \
0079     _ret;                                                                 \
0080 })
0081
0082 #define my_syscall1(num, arg1)                                                \
0083 ({                                                                            \
0084     long _ret;                                                            \
0085     register long _num  __asm__ ("rax") = (num);                          \
0086     register long _arg1 __asm__ ("rdi") = (long)(arg1);                   \
0087                                                                           \
0088     __asm__  volatile (                                                   \
0089         "syscall\n"                                                   \
0090         : "=a"(_ret)                                                  \
0091         : "r"(_arg1),                                                 \
0092           "0"(_num)                                                   \
0093         : "rcx", "r11", "memory", "cc"                                \
0094     );                                                                    \
0095     _ret;                                                                 \
0096 })
0097
0098 #define my_syscall2(num, arg1, arg2)                                          \
0099 ({                                                                            \
0100     long _ret;                                                            \
0101     register long _num  __asm__ ("rax") = (num);                          \
0102     register long _arg1 __asm__ ("rdi") = (long)(arg1);                   \
0103     register long _arg2 __asm__ ("rsi") = (long)(arg2);                   \
0104                                                                           \
0105     __asm__  volatile (                                                   \
0106         "syscall\n"                                                   \
0107         : "=a"(_ret)                                                  \
0108         : "r"(_arg1), "r"(_arg2),                                     \
0109           "0"(_num)                                                   \
0110         : "rcx", "r11", "memory", "cc"                                \
0111     );                                                                    \
0112     _ret;                                                                 \
0113 })
0114
0115 #define my_syscall3(num, arg1, arg2, arg3)                                    \
0116 ({                                                                            \
0117     long _ret;                                                            \
0118     register long _num  __asm__ ("rax") = (num);                          \
0119     register long _arg1 __asm__ ("rdi") = (long)(arg1);                   \
0120     register long _arg2 __asm__ ("rsi") = (long)(arg2);                   \
0121     register long _arg3 __asm__ ("rdx") = (long)(arg3);                   \
0122                                                                           \
0123     __asm__  volatile (                                                   \
0124         "syscall\n"                                                   \
0125         : "=a"(_ret)                                                  \
0126         : "r"(_arg1), "r"(_arg2), "r"(_arg3),                         \
0127           "0"(_num)                                                   \
0128         : "rcx", "r11", "memory", "cc"                                \
0129     );                                                                    \
0130     _ret;                                                                 \
0131 })
0132
0133 #define my_syscall4(num, arg1, arg2, arg3, arg4)                              \
0134 ({                                                                            \
0135     long _ret;                                                            \
0136     register long _num  __asm__ ("rax") = (num);                          \
0137     register long _arg1 __asm__ ("rdi") = (long)(arg1);                   \
0138     register long _arg2 __asm__ ("rsi") = (long)(arg2);                   \
0139     register long _arg3 __asm__ ("rdx") = (long)(arg3);                   \
0140     register long _arg4 __asm__ ("r10") = (long)(arg4);                   \
0141                                                                           \
0142     __asm__  volatile (                                                   \
0143         "syscall\n"                                                   \
0144         : "=a"(_ret)                                                  \
0145         : "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4),             \
0146           "0"(_num)                                                   \
0147         : "rcx", "r11", "memory", "cc"                                \
0148     );                                                                    \
0149     _ret;                                                                 \
0150 })
0151
0152 #define my_syscall5(num, arg1, arg2, arg3, arg4, arg5)                        \
0153 ({                                                                            \
0154     long _ret;                                                            \
0155     register long _num  __asm__ ("rax") = (num);                          \
0156     register long _arg1 __asm__ ("rdi") = (long)(arg1);                   \
0157     register long _arg2 __asm__ ("rsi") = (long)(arg2);                   \
0158     register long _arg3 __asm__ ("rdx") = (long)(arg3);                   \
0159     register long _arg4 __asm__ ("r10") = (long)(arg4);                   \
0160     register long _arg5 __asm__ ("r8")  = (long)(arg5);                   \
0161                                                                           \
0162     __asm__  volatile (                                                   \
0163         "syscall\n"                                                   \
0164         : "=a"(_ret)                                                  \
0165         : "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
0166           "0"(_num)                                                   \
0167         : "rcx", "r11", "memory", "cc"                                \
0168     );                                                                    \
0169     _ret;                                                                 \
0170 })
0171
0172 #define my_syscall6(num, arg1, arg2, arg3, arg4, arg5, arg6)                  \
0173 ({                                                                            \
0174     long _ret;                                                            \
0175     register long _num  __asm__ ("rax") = (num);                          \
0176     register long _arg1 __asm__ ("rdi") = (long)(arg1);                   \
0177     register long _arg2 __asm__ ("rsi") = (long)(arg2);                   \
0178     register long _arg3 __asm__ ("rdx") = (long)(arg3);                   \
0179     register long _arg4 __asm__ ("r10") = (long)(arg4);                   \
0180     register long _arg5 __asm__ ("r8")  = (long)(arg5);                   \
0181     register long _arg6 __asm__ ("r9")  = (long)(arg6);                   \
0182                                                                           \
0183     __asm__  volatile (                                                   \
0184         "syscall\n"                                                   \
0185         : "=a"(_ret)                                                  \
0186         : "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
0187           "r"(_arg6), "0"(_num)                                       \
0188         : "rcx", "r11", "memory", "cc"                                \
0189     );                                                                    \
0190     _ret;                                                                 \
0191 })
0192
0193 /* startup code */
0194 /*
0195  * x86-64 System V ABI mandates:
0196  * 1) %rsp must be 16-byte aligned right before the function call.
0197  * 2) The deepest stack frame should be zero (the %rbp).
0198  *
0199  */
0200 __asm__ (".section .text\n"
0201     ".weak _start\n"
0202     "_start:\n"
0203     "pop %rdi\n"                // argc   (first arg, %rdi)
0204     "mov %rsp, %rsi\n"          // argv[] (second arg, %rsi)
0205     "lea 8(%rsi,%rdi,8),%rdx\n" // then a NULL then envp (third arg, %rdx)
0206     "xor %ebp, %ebp\n"          // zero the stack frame
0207     "and $-16, %rsp\n"          // x86 ABI : esp must be 16-byte aligned before call
0208     "call main\n"               // main() returns the status code, we'll exit with it.
0209     "mov %eax, %edi\n"          // retrieve exit code (32 bit)
0210     "mov $60, %eax\n"           // NR_exit == 60
0211     "syscall\n"                 // really exit
0212     "hlt\n"                     // ensure it does not return
0213     "");
0214
0215 #endif // _NOLIBC_ARCH_X86_64_H