linux/tools/include/nolibc/arch-s390.h

/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
/*
 * s390 specific definitions for NOLIBC
 */

#ifndef _NOLIBC_ARCH_S390_H
#define _NOLIBC_ARCH_S390_H
#include <asm/signal.h>
#include <asm/unistd.h>

#include "compiler.h"
#include "crt.h"

/* Syscalls for s390:
 *   - registers are 64-bit
 *   - syscall number is passed in r1
 *   - arguments are in r2-r7
 *   - the system call is performed by calling the svc instruction
 *   - syscall return value is in r2
 *   - r1 and r2 are clobbered, others are preserved.
 *
 * Link s390 ABI: https://github.com/IBM/s390x-abi
 *
 */

#define my_syscall0(num)						\
({									\
	register long _num __asm__ ("1") = (num);			\
	register long _rc __asm__ ("2");				\
									\
	__asm__ volatile (						\
		"svc 0\n"						\
		: "=d"(_rc)						\
		: "d"(_num)						\
		: "memory", "cc"					\
		);							\
	_rc;								\
})

#define my_syscall1(num, arg1)						\
({									\
	register long _num __asm__ ("1") = (num);			\
	register long _arg1 __asm__ ("2") = (long)(arg1);		\
									\
	__asm__ volatile (						\
		"svc 0\n"						\
		: "+d"(_arg1)						\
		: "d"(_num)						\
		: "memory", "cc"					\
		);							\
	_arg1;								\
})

#define my_syscall2(num, arg1, arg2)					\
({									\
	register long _num __asm__ ("1") = (num);			\
	register long _arg1 __asm__ ("2") = (long)(arg1);		\
	register long _arg2 __asm__ ("3") = (long)(arg2);		\
									\
	__asm__ volatile (						\
		"svc 0\n"						\
		: "+d"(_arg1)						\
		: "d"(_arg2), "d"(_num)					\
		: "memory", "cc"					\
		);							\
	_arg1;								\
})

#define my_syscall3(num, arg1, arg2, arg3)				\
({									\
	register long _num __asm__ ("1") = (num);			\
	register long _arg1 __asm__ ("2") = (long)(arg1);		\
	register long _arg2 __asm__ ("3") = (long)(arg2);		\
	register long _arg3 __asm__ ("4") = (long)(arg3);		\
									\
	__asm__ volatile (						\
		"svc 0\n"						\
		: "+d"(_arg1)						\
		: "d"(_arg2), "d"(_arg3), "d"(_num)			\
		: "memory", "cc"					\
		);							\
	_arg1;								\
})

#define my_syscall4(num, arg1, arg2, arg3, arg4)			\
({									\
	register long _num __asm__ ("1") = (num);			\
	register long _arg1 __asm__ ("2") = (long)(arg1);		\
	register long _arg2 __asm__ ("3") = (long)(arg2);		\
	register long _arg3 __asm__ ("4") = (long)(arg3);		\
	register long _arg4 __asm__ ("5") = (long)(arg4);		\
									\
	__asm__ volatile (						\
		"svc 0\n"						\
		: "+d"(_arg1)						\
		: "d"(_arg2), "d"(_arg3), "d"(_arg4), "d"(_num)		\
		: "memory", "cc"					\
		);							\
	_arg1;								\
})

#define my_syscall5(num, arg1, arg2, arg3, arg4, arg5)			\
({									\
	register long _num __asm__ ("1") = (num);			\
	register long _arg1 __asm__ ("2") = (long)(arg1);		\
	register long _arg2 __asm__ ("3") = (long)(arg2);		\
	register long _arg3 __asm__ ("4") = (long)(arg3);		\
	register long _arg4 __asm__ ("5") = (long)(arg4);		\
	register long _arg5 __asm__ ("6") = (long)(arg5);		\
									\
	__asm__ volatile (						\
		"svc 0\n"						\
		: "+d"(_arg1)						\
		: "d"(_arg2), "d"(_arg3), "d"(_arg4), "d"(_arg5),	\
		  "d"(_num)						\
		: "memory", "cc"					\
		);							\
	_arg1;								\
})

#define my_syscall6(num, arg1, arg2, arg3, arg4, arg5, arg6)		\
({									\
	register long _num __asm__ ("1") = (num);			\
	register long _arg1 __asm__ ("2") = (long)(arg1);		\
	register long _arg2 __asm__ ("3") = (long)(arg2);		\
	register long _arg3 __asm__ ("4") = (long)(arg3);		\
	register long _arg4 __asm__ ("5") = (long)(arg4);		\
	register long _arg5 __asm__ ("6") = (long)(arg5);		\
	register long _arg6 __asm__ ("7") = (long)(arg6);		\
									\
	__asm__ volatile (						\
		"svc 0\n"						\
		: "+d"(_arg1)						\
		: "d"(_arg2), "d"(_arg3), "d"(_arg4), "d"(_arg5),	\
		  "d"(_arg6), "d"(_num)					\
		: "memory", "cc"					\
		);							\
	_arg1;								\
})

/* startup code */
void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_stack_protector _start(void)
{
	__asm__ volatile (
		"lgr	%r2, %r15\n"          /* save stack pointer to %r2, as arg1 of _start_c */
		"aghi	%r15, -160\n"         /* allocate new stackframe                        */
		"xc	0(8,%r15), 0(%r15)\n" /* clear backchain                                */
		"brasl	%r14, _start_c\n"     /* transfer to c runtime                          */
	);
	__builtin_unreachable();
}

struct s390_mmap_arg_struct {
	unsigned long addr;
	unsigned long len;
	unsigned long prot;
	unsigned long flags;
	unsigned long fd;
	unsigned long offset;
};

static __attribute__((unused))
void *sys_mmap(void *addr, size_t length, int prot, int flags, int fd,
	       off_t offset)
{
	struct s390_mmap_arg_struct args = {
		.addr = (unsigned long)addr,
		.len = (unsigned long)length,
		.prot = prot,
		.flags = flags,
		.fd = fd,
		.offset = (unsigned long)offset
	};

	return (void *)my_syscall1(__NR_mmap, &args);
}
#define sys_mmap sys_mmap

static __attribute__((unused))
pid_t sys_fork(void)
{
	return my_syscall5(__NR_clone, 0, SIGCHLD, 0, 0, 0);
}
#define sys_fork sys_fork

#endif /* _NOLIBC_ARCH_S390_H */