/* SPDX-License-Identifier: LGPL-2.1 OR MIT */ /* * x86_64 specific definitions for NOLIBC * Copyright (C) 2017-2022 Willy Tarreau */ #ifndef _NOLIBC_ARCH_X86_64_H #define _NOLIBC_ARCH_X86_64_H /* The struct returned by the stat() syscall, equivalent to stat64(). The * syscall returns 116 bytes and stops in the middle of __unused. */ struct sys_stat_struct { unsigned long st_dev; unsigned long st_ino; unsigned long st_nlink; unsigned int st_mode; unsigned int st_uid; unsigned int st_gid; unsigned int __pad0; unsigned long st_rdev; long st_size; long st_blksize; long st_blocks; unsigned long st_atime; unsigned long st_atime_nsec; unsigned long st_mtime; unsigned long st_mtime_nsec; unsigned long st_ctime; unsigned long st_ctime_nsec; long __unused[3]; }; /* 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; \ }) char **environ __attribute__((weak)); const unsigned long *_auxv __attribute__((weak)); #define __ARCH_SUPPORTS_STACK_PROTECTOR /* 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("omit-frame-pointer"))) _start(void) { __asm__ volatile ( #ifdef NOLIBC_STACKPROTECTOR "call __stack_chk_init\n" /* initialize stack protector */ #endif "pop %rdi\n" /* argc (first arg, %rdi) */ "mov %rsp, %rsi\n" /* argv[] (second arg, %rsi) */ "lea 8(%rsi,%rdi,8),%rdx\n" /* then a NULL then envp (third arg, %rdx) */ "mov %rdx, environ\n" /* save environ */ "xor %ebp, %ebp\n" /* zero the stack frame */ "mov %rdx, %rax\n" /* search for auxv (follows NULL after last env) */ "0:\n" "add $8, %rax\n" /* search for auxv using rax, it follows the */ "cmp -8(%rax), %rbp\n" /* ... NULL after last env (rbp is zero here) */ "jnz 0b\n" "mov %rax, _auxv\n" /* save it into _auxv */ "and $-16, %rsp\n" /* x86 ABI : esp must be 16-byte aligned before call */ "call main\n" /* main() returns the status code, we'll exit with it. */ "mov %eax, %edi\n" /* retrieve exit code (32 bit) */ "mov $60, %eax\n" /* NR_exit == 60 */ "syscall\n" /* really exit */ "hlt\n" /* ensure it does not return */ ); __builtin_unreachable(); } #endif /* _NOLIBC_ARCH_X86_64_H */