tools/include/nolibc/arch-aarch64.h

/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
/*
 * AARCH64 specific definitions for NOLIBC
 * Copyright (C) 2017-2022 Willy Tarreau <w@1wt.eu>
 */

#ifndef _NOLIBC_ARCH_AARCH64_H
#define _NOLIBC_ARCH_AARCH64_H

/* The struct returned by the newfstatat() syscall. Differs slightly from the
 * x86_64's stat one by field ordering, so be careful.
 */
struct sys_stat_struct {
	unsigned long   st_dev;
	unsigned long   st_ino;
	unsigned int    st_mode;
	unsigned int    st_nlink;
	unsigned int    st_uid;
	unsigned int    st_gid;

	unsigned long   st_rdev;
	unsigned long   __pad1;
	long            st_size;
	int             st_blksize;
	int             __pad2;

	long            st_blocks;
	long            st_atime;
	unsigned long   st_atime_nsec;
	long            st_mtime;

	unsigned long   st_mtime_nsec;
	long            st_ctime;
	unsigned long   st_ctime_nsec;
	unsigned int    __unused[2];
};

/* Syscalls for AARCH64 :
 *   - registers are 64-bit
 *   - stack is 16-byte aligned
 *   - syscall number is passed in x8
 *   - arguments are in x0, x1, x2, x3, x4, x5
 *   - the system call is performed by calling svc 0
 *   - syscall return comes in x0.
 *   - 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.
 *
 * On aarch64, select() is not implemented so we have to use pselect6().
 */
#define __ARCH_WANT_SYS_PSELECT6

#define my_syscall0(num)                                                      \
({                                                                            \
	register long _num  __asm__ ("x8") = (num);                           \
	register long _arg1 __asm__ ("x0");                                   \
	                                                                      \
	__asm__  volatile (                                                   \
		"svc #0\n"                                                    \
		: "=r"(_arg1)                                                 \
		: "r"(_num)                                                   \
		: "memory", "cc"                                              \
	);                                                                    \
	_arg1;                                                                \
})

#define my_syscall1(num, arg1)                                                \
({                                                                            \
	register long _num  __asm__ ("x8") = (num);                           \
	register long _arg1 __asm__ ("x0") = (long)(arg1);                    \
	                                                                      \
	__asm__  volatile (                                                   \
		"svc #0\n"                                                    \
		: "=r"(_arg1)                                                 \
		: "r"(_arg1),                                                 \
		  "r"(_num)                                                   \
		: "memory", "cc"                                              \
	);                                                                    \
	_arg1;                                                                \
})

#define my_syscall2(num, arg1, arg2)                                          \
({                                                                            \
	register long _num  __asm__ ("x8") = (num);                           \
	register long _arg1 __asm__ ("x0") = (long)(arg1);                    \
	register long _arg2 __asm__ ("x1") = (long)(arg2);                    \
	                                                                      \
	__asm__  volatile (                                                   \
		"svc #0\n"                                                    \
		: "=r"(_arg1)                                                 \
		: "r"(_arg1), "r"(_arg2),                                     \
		  "r"(_num)                                                   \
		: "memory", "cc"                                              \
	);                                                                    \
	_arg1;                                                                \
})

#define my_syscall3(num, arg1, arg2, arg3)                                    \
({                                                                            \
	register long _num  __asm__ ("x8") = (num);                           \
	register long _arg1 __asm__ ("x0") = (long)(arg1);                    \
	register long _arg2 __asm__ ("x1") = (long)(arg2);                    \
	register long _arg3 __asm__ ("x2") = (long)(arg3);                    \
	                                                                      \
	__asm__  volatile (                                                   \
		"svc #0\n"                                                    \
		: "=r"(_arg1)                                                 \
		: "r"(_arg1), "r"(_arg2), "r"(_arg3),                         \
		  "r"(_num)                                                   \
		: "memory", "cc"                                              \
	);                                                                    \
	_arg1;                                                                \
})

#define my_syscall4(num, arg1, arg2, arg3, arg4)                              \
({                                                                            \
	register long _num  __asm__ ("x8") = (num);                           \
	register long _arg1 __asm__ ("x0") = (long)(arg1);                    \
	register long _arg2 __asm__ ("x1") = (long)(arg2);                    \
	register long _arg3 __asm__ ("x2") = (long)(arg3);                    \
	register long _arg4 __asm__ ("x3") = (long)(arg4);                    \
	                                                                      \
	__asm__  volatile (                                                   \
		"svc #0\n"                                                    \
		: "=r"(_arg1)                                                 \
		: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4),             \
		  "r"(_num)                                                   \
		: "memory", "cc"                                              \
	);                                                                    \
	_arg1;                                                                \
})

#define my_syscall5(num, arg1, arg2, arg3, arg4, arg5)                        \
({                                                                            \
	register long _num  __asm__ ("x8") = (num);                           \
	register long _arg1 __asm__ ("x0") = (long)(arg1);                    \
	register long _arg2 __asm__ ("x1") = (long)(arg2);                    \
	register long _arg3 __asm__ ("x2") = (long)(arg3);                    \
	register long _arg4 __asm__ ("x3") = (long)(arg4);                    \
	register long _arg5 __asm__ ("x4") = (long)(arg5);                    \
	                                                                      \
	__asm__  volatile (                                                   \
		"svc #0\n"                                                    \
		: "=r" (_arg1)                                                \
		: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
		  "r"(_num)                                                   \
		: "memory", "cc"                                              \
	);                                                                    \
	_arg1;                                                                \
})

#define my_syscall6(num, arg1, arg2, arg3, arg4, arg5, arg6)                  \
({                                                                            \
	register long _num  __asm__ ("x8") = (num);                           \
	register long _arg1 __asm__ ("x0") = (long)(arg1);                    \
	register long _arg2 __asm__ ("x1") = (long)(arg2);                    \
	register long _arg3 __asm__ ("x2") = (long)(arg3);                    \
	register long _arg4 __asm__ ("x3") = (long)(arg4);                    \
	register long _arg5 __asm__ ("x4") = (long)(arg5);                    \
	register long _arg6 __asm__ ("x5") = (long)(arg6);                    \
	                                                                      \
	__asm__  volatile (                                                   \
		"svc #0\n"                                                    \
		: "=r" (_arg1)                                                \
		: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
		  "r"(_arg6), "r"(_num)                                       \
		: "memory", "cc"                                              \
	);                                                                    \
	_arg1;                                                                \
})

char **environ __attribute__((weak));
const unsigned long *_auxv __attribute__((weak));

/* startup code */
void __attribute__((weak,noreturn,optimize("omit-frame-pointer"))) _start(void)
{
	__asm__ volatile (
		"ldr x0, [sp]\n"     // argc (x0) was in the stack
		"add x1, sp, 8\n"    // argv (x1) = sp
		"lsl x2, x0, 3\n"    // envp (x2) = 8*argc ...
		"add x2, x2, 8\n"    //           + 8 (skip null)
		"add x2, x2, x1\n"   //           + argv
		"adrp x3, environ\n"          // x3 = &environ (high bits)
		"str x2, [x3, #:lo12:environ]\n" // store envp into environ
		"mov x4, x2\n"       // search for auxv (follows NULL after last env)
		"0:\n"
		"ldr x5, [x4], 8\n"  // x5 = *x4; x4 += 8
		"cbnz x5, 0b\n"      // and stop at NULL after last env
		"adrp x3, _auxv\n"   // x3 = &_auxv (high bits)
		"str x4, [x3, #:lo12:_auxv]\n" // store x4 into _auxv
		"and sp, x1, -16\n"  // sp must be 16-byte aligned in the callee
		"bl main\n"          // main() returns the status code, we'll exit with it.
		"mov x8, 93\n"       // NR_exit == 93
		"svc #0\n"
	);
	__builtin_unreachable();
}
#endif // _NOLIBC_ARCH_AARCH64_H