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1/* SPDX-License-Identifier: LGPL-2.1 OR MIT */2/*3 * i386 specific definitions for NOLIBC4 * Copyright (C) 2017-2022 Willy Tarreau <w@1wt.eu>5 */6 7#ifndef _NOLIBC_ARCH_I386_H8#define _NOLIBC_ARCH_I386_H9 10#include "compiler.h"11#include "crt.h"12 13/* Syscalls for i386 :14 * - mostly similar to x86_6415 * - registers are 32-bit16 * - syscall number is passed in eax17 * - arguments are in ebx, ecx, edx, esi, edi, ebp respectively18 * - all registers are preserved (except eax of course)19 * - the system call is performed by calling int $0x8020 * - syscall return comes in eax21 * - the arguments are cast to long and assigned into the target registers22 * which are then simply passed as registers to the asm code, so that we23 * don't have to experience issues with register constraints.24 * - the syscall number is always specified last in order to allow to force25 * some registers before (gcc refuses a %-register at the last position).26 *27 * Also, i386 supports the old_select syscall if newselect is not available28 */29#define __ARCH_WANT_SYS_OLD_SELECT30 31#define my_syscall0(num) \32({ \33 long _ret; \34 register long _num __asm__ ("eax") = (num); \35 \36 __asm__ volatile ( \37 "int $0x80\n" \38 : "=a" (_ret) \39 : "0"(_num) \40 : "memory", "cc" \41 ); \42 _ret; \43})44 45#define my_syscall1(num, arg1) \46({ \47 long _ret; \48 register long _num __asm__ ("eax") = (num); \49 register long _arg1 __asm__ ("ebx") = (long)(arg1); \50 \51 __asm__ volatile ( \52 "int $0x80\n" \53 : "=a" (_ret) \54 : "r"(_arg1), \55 "0"(_num) \56 : "memory", "cc" \57 ); \58 _ret; \59})60 61#define my_syscall2(num, arg1, arg2) \62({ \63 long _ret; \64 register long _num __asm__ ("eax") = (num); \65 register long _arg1 __asm__ ("ebx") = (long)(arg1); \66 register long _arg2 __asm__ ("ecx") = (long)(arg2); \67 \68 __asm__ volatile ( \69 "int $0x80\n" \70 : "=a" (_ret) \71 : "r"(_arg1), "r"(_arg2), \72 "0"(_num) \73 : "memory", "cc" \74 ); \75 _ret; \76})77 78#define my_syscall3(num, arg1, arg2, arg3) \79({ \80 long _ret; \81 register long _num __asm__ ("eax") = (num); \82 register long _arg1 __asm__ ("ebx") = (long)(arg1); \83 register long _arg2 __asm__ ("ecx") = (long)(arg2); \84 register long _arg3 __asm__ ("edx") = (long)(arg3); \85 \86 __asm__ volatile ( \87 "int $0x80\n" \88 : "=a" (_ret) \89 : "r"(_arg1), "r"(_arg2), "r"(_arg3), \90 "0"(_num) \91 : "memory", "cc" \92 ); \93 _ret; \94})95 96#define my_syscall4(num, arg1, arg2, arg3, arg4) \97({ \98 long _ret; \99 register long _num __asm__ ("eax") = (num); \100 register long _arg1 __asm__ ("ebx") = (long)(arg1); \101 register long _arg2 __asm__ ("ecx") = (long)(arg2); \102 register long _arg3 __asm__ ("edx") = (long)(arg3); \103 register long _arg4 __asm__ ("esi") = (long)(arg4); \104 \105 __asm__ volatile ( \106 "int $0x80\n" \107 : "=a" (_ret) \108 : "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), \109 "0"(_num) \110 : "memory", "cc" \111 ); \112 _ret; \113})114 115#define my_syscall5(num, arg1, arg2, arg3, arg4, arg5) \116({ \117 long _ret; \118 register long _num __asm__ ("eax") = (num); \119 register long _arg1 __asm__ ("ebx") = (long)(arg1); \120 register long _arg2 __asm__ ("ecx") = (long)(arg2); \121 register long _arg3 __asm__ ("edx") = (long)(arg3); \122 register long _arg4 __asm__ ("esi") = (long)(arg4); \123 register long _arg5 __asm__ ("edi") = (long)(arg5); \124 \125 __asm__ volatile ( \126 "int $0x80\n" \127 : "=a" (_ret) \128 : "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \129 "0"(_num) \130 : "memory", "cc" \131 ); \132 _ret; \133})134 135#define my_syscall6(num, arg1, arg2, arg3, arg4, arg5, arg6) \136({ \137 long _eax = (long)(num); \138 long _arg6 = (long)(arg6); /* Always in memory */ \139 __asm__ volatile ( \140 "pushl %[_arg6]\n\t" \141 "pushl %%ebp\n\t" \142 "movl 4(%%esp),%%ebp\n\t" \143 "int $0x80\n\t" \144 "popl %%ebp\n\t" \145 "addl $4,%%esp\n\t" \146 : "+a"(_eax) /* %eax */ \147 : "b"(arg1), /* %ebx */ \148 "c"(arg2), /* %ecx */ \149 "d"(arg3), /* %edx */ \150 "S"(arg4), /* %esi */ \151 "D"(arg5), /* %edi */ \152 [_arg6]"m"(_arg6) /* memory */ \153 : "memory", "cc" \154 ); \155 _eax; \156})157 158/* startup code */159/*160 * i386 System V ABI mandates:161 * 1) last pushed argument must be 16-byte aligned.162 * 2) The deepest stack frame should be set to zero163 *164 */165void __attribute__((weak, noreturn)) __nolibc_entrypoint __no_stack_protector _start(void)166{167 __asm__ volatile (168 "xor %ebp, %ebp\n" /* zero the stack frame */169 "mov %esp, %eax\n" /* save stack pointer to %eax, as arg1 of _start_c */170 "add $12, %esp\n" /* avoid over-estimating after the 'and' & 'sub' below */171 "and $-16, %esp\n" /* the %esp must be 16-byte aligned on 'call' */172 "sub $12, %esp\n" /* sub 12 to keep it aligned after the push %eax */173 "push %eax\n" /* push arg1 on stack to support plain stack modes too */174 "call _start_c\n" /* transfer to c runtime */175 "hlt\n" /* ensure it does not return */176 );177 __nolibc_entrypoint_epilogue();178}179 180#endif /* _NOLIBC_ARCH_I386_H */181