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/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
/*
* i386 specific definitions for NOLIBC
* Copyright (C) 2017-2022 Willy Tarreau <w@1wt.eu>
*/
#ifndef _NOLIBC_ARCH_I386_H
#define _NOLIBC_ARCH_I386_H
#include "compiler.h"
#include "crt.h"
/* 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; \
})
/* 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("Os", "omit-frame-pointer"))) __no_stack_protector _start(void)
{
__asm__ volatile (
"xor %ebp, %ebp\n" /* zero the stack frame */
"mov %esp, %eax\n" /* save stack pointer to %eax, as arg1 of _start_c */
"add $12, %esp\n" /* avoid over-estimating after the 'and' & 'sub' below */
"and $-16, %esp\n" /* the %esp must be 16-byte aligned on 'call' */
"sub $12, %esp\n" /* sub 12 to keep it aligned after the push %eax */
"push %eax\n" /* push arg1 on stack to support plain stack modes too */
"call _start_c\n" /* transfer to c runtime */
"hlt\n" /* ensure it does not return */
);
__builtin_unreachable();
}
#endif /* _NOLIBC_ARCH_I386_H */
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