/* SPDX-License-Identifier: LGPL-2.1 OR MIT */ /* * i386 specific definitions for NOLIBC * Copyright (C) 2017-2022 Willy Tarreau */ #ifndef _NOLIBC_ARCH_I386_H #define _NOLIBC_ARCH_I386_H #include "compiler.h" /* The struct returned by the stat() syscall, 32-bit only, the syscall returns * exactly 56 bytes (stops before the unused array). */ struct sys_stat_struct { unsigned long st_dev; unsigned long st_ino; unsigned short st_mode; unsigned short st_nlink; unsigned short st_uid; unsigned short st_gid; unsigned long st_rdev; unsigned long st_size; unsigned long st_blksize; unsigned 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; unsigned long __unused[2]; }; /* Syscalls for i386 : * - mostly similar to x86_64 * - registers are 32-bit * - syscall number is passed in eax * - arguments are in ebx, ecx, edx, esi, edi, ebp respectively * - all registers are preserved (except eax of course) * - the system call is performed by calling int $0x80 * - syscall return comes in eax * - 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). * * Also, i386 supports the old_select syscall if newselect is not available */ #define __ARCH_WANT_SYS_OLD_SELECT #define my_syscall0(num) \ ({ \ long _ret; \ register long _num __asm__ ("eax") = (num); \ \ __asm__ volatile ( \ "int $0x80\n" \ : "=a" (_ret) \ : "0"(_num) \ : "memory", "cc" \ ); \ _ret; \ }) #define my_syscall1(num, arg1) \ ({ \ long _ret; \ register long _num __asm__ ("eax") = (num); \ register long _arg1 __asm__ ("ebx") = (long)(arg1); \ \ __asm__ volatile ( \ "int $0x80\n" \ : "=a" (_ret) \ : "r"(_arg1), \ "0"(_num) \ : "memory", "cc" \ ); \ _ret; \ }) #define my_syscall2(num, arg1, arg2) \ ({ \ long _ret; \ register long _num __asm__ ("eax") = (num); \ register long _arg1 __asm__ ("ebx") = (long)(arg1); \ register long _arg2 __asm__ ("ecx") = (long)(arg2); \ \ __asm__ volatile ( \ "int $0x80\n" \ : "=a" (_ret) \ : "r"(_arg1), "r"(_arg2), \ "0"(_num) \ : "memory", "cc" \ ); \ _ret; \ }) #define my_syscall3(num, arg1, arg2, arg3) \ ({ \ long _ret; \ register long _num __asm__ ("eax") = (num); \ register long _arg1 __asm__ ("ebx") = (long)(arg1); \ register long _arg2 __asm__ ("ecx") = (long)(arg2); \ register long _arg3 __asm__ ("edx") = (long)(arg3); \ \ __asm__ volatile ( \ "int $0x80\n" \ : "=a" (_ret) \ : "r"(_arg1), "r"(_arg2), "r"(_arg3), \ "0"(_num) \ : "memory", "cc" \ ); \ _ret; \ }) #define my_syscall4(num, arg1, arg2, arg3, arg4) \ ({ \ long _ret; \ register long _num __asm__ ("eax") = (num); \ register long _arg1 __asm__ ("ebx") = (long)(arg1); \ register long _arg2 __asm__ ("ecx") = (long)(arg2); \ register long _arg3 __asm__ ("edx") = (long)(arg3); \ register long _arg4 __asm__ ("esi") = (long)(arg4); \ \ __asm__ volatile ( \ "int $0x80\n" \ : "=a" (_ret) \ : "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), \ "0"(_num) \ : "memory", "cc" \ ); \ _ret; \ }) #define my_syscall5(num, arg1, arg2, arg3, arg4, arg5) \ ({ \ long _ret; \ register long _num __asm__ ("eax") = (num); \ register long _arg1 __asm__ ("ebx") = (long)(arg1); \ register long _arg2 __asm__ ("ecx") = (long)(arg2); \ register long _arg3 __asm__ ("edx") = (long)(arg3); \ register long _arg4 __asm__ ("esi") = (long)(arg4); \ register long _arg5 __asm__ ("edi") = (long)(arg5); \ \ __asm__ volatile ( \ "int $0x80\n" \ : "=a" (_ret) \ : "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \ "0"(_num) \ : "memory", "cc" \ ); \ _ret; \ }) #define my_syscall6(num, arg1, arg2, arg3, arg4, arg5, arg6) \ ({ \ long _eax = (long)(num); \ long _arg6 = (long)(arg6); /* Always in memory */ \ __asm__ volatile ( \ "pushl %[_arg6]\n\t" \ "pushl %%ebp\n\t" \ "movl 4(%%esp),%%ebp\n\t" \ "int $0x80\n\t" \ "popl %%ebp\n\t" \ "addl $4,%%esp\n\t" \ : "+a"(_eax) /* %eax */ \ : "b"(arg1), /* %ebx */ \ "c"(arg2), /* %ecx */ \ "d"(arg3), /* %edx */ \ "S"(arg4), /* %esi */ \ "D"(arg5), /* %edi */ \ [_arg6]"m"(_arg6) /* memory */ \ : "memory", "cc" \ ); \ _eax; \ }) char **environ __attribute__((weak)); const unsigned long *_auxv __attribute__((weak)); /* startup code */ /* * i386 System V ABI mandates: * 1) last pushed argument must be 16-byte aligned. * 2) The deepest stack frame should be set to zero * */ void __attribute__((weak,noreturn,optimize("omit-frame-pointer"))) __no_stack_protector _start(void) { __asm__ volatile ( #ifdef _NOLIBC_STACKPROTECTOR "call __stack_chk_init\n" /* initialize stack protector */ #endif "pop %eax\n" /* argc (first arg, %eax) */ "mov %esp, %ebx\n" /* argv[] (second arg, %ebx) */ "lea 4(%ebx,%eax,4),%ecx\n" /* then a NULL then envp (third arg, %ecx) */ "mov %ecx, environ\n" /* save environ */ "xor %ebp, %ebp\n" /* zero the stack frame */ "mov %ecx, %edx\n" /* search for auxv (follows NULL after last env) */ "0:\n" "add $4, %edx\n" /* search for auxv using edx, it follows the */ "cmp -4(%edx), %ebp\n" /* ... NULL after last env (ebp is zero here) */ "jnz 0b\n" "mov %edx, _auxv\n" /* save it into _auxv */ "and $-16, %esp\n" /* x86 ABI : esp must be 16-byte aligned before */ "sub $4, %esp\n" /* the call instruction (args are aligned) */ "push %ecx\n" /* push all registers on the stack so that we */ "push %ebx\n" /* support both regparm and plain stack modes */ "push %eax\n" "call main\n" /* main() returns the status code in %eax */ "mov %eax, %ebx\n" /* retrieve exit code (32-bit int) */ "movl $1, %eax\n" /* NR_exit == 1 */ "int $0x80\n" /* exit now */ "hlt\n" /* ensure it does not */ ); __builtin_unreachable(); } #endif /* _NOLIBC_ARCH_I386_H */