216 lines
11 KiB
C
216 lines
11 KiB
C
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/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
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/*
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* x86_64 specific definitions for NOLIBC
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* Copyright (C) 2017-2022 Willy Tarreau <w@1wt.eu>
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*/
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#ifndef _NOLIBC_ARCH_X86_64_H
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#define _NOLIBC_ARCH_X86_64_H
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/* The struct returned by the stat() syscall, equivalent to stat64(). The
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* syscall returns 116 bytes and stops in the middle of __unused.
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*/
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struct sys_stat_struct {
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unsigned long st_dev;
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unsigned long st_ino;
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unsigned long st_nlink;
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unsigned int st_mode;
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unsigned int st_uid;
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unsigned int st_gid;
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unsigned int __pad0;
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unsigned long st_rdev;
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long st_size;
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long st_blksize;
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long st_blocks;
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unsigned long st_atime;
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unsigned long st_atime_nsec;
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unsigned long st_mtime;
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unsigned long st_mtime_nsec;
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unsigned long st_ctime;
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unsigned long st_ctime_nsec;
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long __unused[3];
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};
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/* Syscalls for x86_64 :
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* - registers are 64-bit
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* - syscall number is passed in rax
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* - arguments are in rdi, rsi, rdx, r10, r8, r9 respectively
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* - the system call is performed by calling the syscall instruction
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* - syscall return comes in rax
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* - rcx and r11 are clobbered, others are preserved.
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* - the arguments are cast to long and assigned into the target registers
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* which are then simply passed as registers to the asm code, so that we
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* don't have to experience issues with register constraints.
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* - the syscall number is always specified last in order to allow to force
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* some registers before (gcc refuses a %-register at the last position).
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* - see also x86-64 ABI section A.2 AMD64 Linux Kernel Conventions, A.2.1
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* Calling Conventions.
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*
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* Link x86-64 ABI: https://gitlab.com/x86-psABIs/x86-64-ABI/-/wikis/home
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*
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*/
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#define my_syscall0(num) \
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({ \
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long _ret; \
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register long _num __asm__ ("rax") = (num); \
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\
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__asm__ volatile ( \
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"syscall\n" \
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: "=a"(_ret) \
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: "0"(_num) \
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: "rcx", "r11", "memory", "cc" \
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); \
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_ret; \
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})
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#define my_syscall1(num, arg1) \
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({ \
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long _ret; \
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register long _num __asm__ ("rax") = (num); \
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register long _arg1 __asm__ ("rdi") = (long)(arg1); \
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\
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__asm__ volatile ( \
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"syscall\n" \
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: "=a"(_ret) \
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: "r"(_arg1), \
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"0"(_num) \
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: "rcx", "r11", "memory", "cc" \
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); \
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_ret; \
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})
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#define my_syscall2(num, arg1, arg2) \
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({ \
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long _ret; \
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register long _num __asm__ ("rax") = (num); \
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register long _arg1 __asm__ ("rdi") = (long)(arg1); \
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register long _arg2 __asm__ ("rsi") = (long)(arg2); \
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\
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__asm__ volatile ( \
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"syscall\n" \
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: "=a"(_ret) \
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: "r"(_arg1), "r"(_arg2), \
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"0"(_num) \
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: "rcx", "r11", "memory", "cc" \
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); \
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_ret; \
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})
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#define my_syscall3(num, arg1, arg2, arg3) \
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({ \
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long _ret; \
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register long _num __asm__ ("rax") = (num); \
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register long _arg1 __asm__ ("rdi") = (long)(arg1); \
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register long _arg2 __asm__ ("rsi") = (long)(arg2); \
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register long _arg3 __asm__ ("rdx") = (long)(arg3); \
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\
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__asm__ volatile ( \
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"syscall\n" \
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: "=a"(_ret) \
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: "r"(_arg1), "r"(_arg2), "r"(_arg3), \
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"0"(_num) \
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: "rcx", "r11", "memory", "cc" \
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); \
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_ret; \
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})
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#define my_syscall4(num, arg1, arg2, arg3, arg4) \
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({ \
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long _ret; \
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register long _num __asm__ ("rax") = (num); \
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register long _arg1 __asm__ ("rdi") = (long)(arg1); \
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register long _arg2 __asm__ ("rsi") = (long)(arg2); \
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register long _arg3 __asm__ ("rdx") = (long)(arg3); \
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register long _arg4 __asm__ ("r10") = (long)(arg4); \
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\
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__asm__ volatile ( \
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"syscall\n" \
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: "=a"(_ret) \
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: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), \
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"0"(_num) \
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: "rcx", "r11", "memory", "cc" \
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); \
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_ret; \
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})
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#define my_syscall5(num, arg1, arg2, arg3, arg4, arg5) \
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({ \
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long _ret; \
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register long _num __asm__ ("rax") = (num); \
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register long _arg1 __asm__ ("rdi") = (long)(arg1); \
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register long _arg2 __asm__ ("rsi") = (long)(arg2); \
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register long _arg3 __asm__ ("rdx") = (long)(arg3); \
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register long _arg4 __asm__ ("r10") = (long)(arg4); \
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register long _arg5 __asm__ ("r8") = (long)(arg5); \
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\
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__asm__ volatile ( \
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"syscall\n" \
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: "=a"(_ret) \
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: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
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"0"(_num) \
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: "rcx", "r11", "memory", "cc" \
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); \
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_ret; \
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})
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#define my_syscall6(num, arg1, arg2, arg3, arg4, arg5, arg6) \
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({ \
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long _ret; \
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register long _num __asm__ ("rax") = (num); \
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register long _arg1 __asm__ ("rdi") = (long)(arg1); \
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register long _arg2 __asm__ ("rsi") = (long)(arg2); \
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register long _arg3 __asm__ ("rdx") = (long)(arg3); \
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register long _arg4 __asm__ ("r10") = (long)(arg4); \
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register long _arg5 __asm__ ("r8") = (long)(arg5); \
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register long _arg6 __asm__ ("r9") = (long)(arg6); \
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\
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__asm__ volatile ( \
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"syscall\n" \
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: "=a"(_ret) \
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: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
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"r"(_arg6), "0"(_num) \
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: "rcx", "r11", "memory", "cc" \
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); \
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_ret; \
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})
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char **environ __attribute__((weak));
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const unsigned long *_auxv __attribute__((weak));
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/* startup code */
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/*
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* x86-64 System V ABI mandates:
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* 1) %rsp must be 16-byte aligned right before the function call.
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* 2) The deepest stack frame should be zero (the %rbp).
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*
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*/
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void __attribute__((weak,noreturn,optimize("omit-frame-pointer"))) _start(void)
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{
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__asm__ volatile (
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"pop %rdi\n" // argc (first arg, %rdi)
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"mov %rsp, %rsi\n" // argv[] (second arg, %rsi)
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"lea 8(%rsi,%rdi,8),%rdx\n" // then a NULL then envp (third arg, %rdx)
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"mov %rdx, environ\n" // save environ
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"xor %ebp, %ebp\n" // zero the stack frame
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"mov %rdx, %rax\n" // search for auxv (follows NULL after last env)
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"0:\n"
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"add $8, %rax\n" // search for auxv using rax, it follows the
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"cmp -8(%rax), %rbp\n" // ... NULL after last env (rbp is zero here)
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"jnz 0b\n"
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"mov %rax, _auxv\n" // save it into _auxv
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"and $-16, %rsp\n" // x86 ABI : esp must be 16-byte aligned before call
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"call main\n" // main() returns the status code, we'll exit with it.
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"mov %eax, %edi\n" // retrieve exit code (32 bit)
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"mov $60, %eax\n" // NR_exit == 60
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"syscall\n" // really exit
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"hlt\n" // ensure it does not return
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);
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__builtin_unreachable();
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}
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#endif // _NOLIBC_ARCH_X86_64_H
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