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/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
/*
* x86_64 specific definitions for NOLIBC
* Copyright (C) 2017-2022 Willy Tarreau <w@1wt.eu>
*/
#ifndef _NOLIBC_ARCH_X86_64_H
#define _NOLIBC_ARCH_X86_64_H
/* O_* macros for fcntl/open are architecture-specific */
#define O_RDONLY 0
#define O_WRONLY 1
#define O_RDWR 2
#define O_CREAT 0x40
#define O_EXCL 0x80
#define O_NOCTTY 0x100
#define O_TRUNC 0x200
#define O_APPEND 0x400
#define O_NONBLOCK 0x800
#define O_DIRECTORY 0x10000
/* 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; \
})
/* 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).
*
*/
__asm__ (".section .text\n"
".weak _start\n"
".global _start\n"
"_start:\n"
"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)
"xor %ebp, %ebp\n" // zero the stack frame
"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
"");
#endif // _NOLIBC_ARCH_X86_64_H
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