clone-test.c

/*
 * Compile with a cross toolchain and run as shown below.
 * $ powerpc64le-linux-gnu-gcc clone-test.c -O0 -nostdlib -static -o clone-test
 * $ ./build/POWER/gem5.debug --debug-flags=ExecAll,Registers configs/example/se.py -n 2 -c ./clone-test
 */

#ifndef __powerpc64__
#error "unsupported architecture"
#endif

#define _GNU_SOURCE
#include <sched.h>
#include <sys/mman.h>
#include <sys/syscall.h>

#define STACK_SIZE	65536

int errno;

long __syscall(long syscall, long arg1, long arg2, long arg3, long arg4,
	       long arg5, long arg6, long arg7)
{
	long ret;
	int err;

	asm volatile(
		"mr	0, 3	\n\t"
		"mr	3, 4	\n\t"
		"mr	4, 5	\n\t"
		"mr	5, 6	\n\t"
		"mr	6, 7	\n\t"
		"mr	7, 8	\n\t"
		"mr	8, 9	\n\t"
		"mr	9, 10	\n\t"
		"sc		\n\t"
		"mr	%0, 3	\n\t"
		"mfcr	%1	\n\t"
		: "=r"(ret), "=r"(err)
		:
		: "cr0", "r0", "r3", "r4", "r5", "r6", "r7", "r8", "r9");

	if (err & 0x10000000) {
		errno = ret;
		ret = -1L;
	}

	return ret;
}

__attribute__ ((noreturn))
void __exit(int status)
{
	__syscall(__NR_exit, (long) status, 0, 0, 0, 0, 0, 0);
	while (1);
}

void *__mmap(void *addr, size_t length, int prot, int flags, int fd,
	   off_t offset)
{
	return (void *) __syscall(__NR_mmap, (long) addr, (long) length,
				  (long) prot, (long) flags, (long) fd,
				  (long) offset, 0);
}

int __munmap(void *addr, size_t length)
{
	return (int) __syscall(__NR_munmap, (long) addr, (long) length,
			       0, 0, 0, 0, 0);
}

int __clone(int flags, void *stack, int *ptid, unsigned long tls, int *ctid)
{
	return (int) __syscall(__NR_clone, (long) flags, (long) stack,
			       (long) ptid, (long) tls, (long) ctid, 0, 0);
}

long __write(int fd, const char *buf, size_t count)
{
	return (long) __syscall(__NR_write, (long) fd, (long) buf,
				(long) count, 0, 0, 0, 0);
}

const char pmsg[] = "exiting from parent\n";
const char cmsg[] = "exiting from child\n";

void _start(void)
{
	void *stack;
	int pid;

	stack = __mmap(NULL, STACK_SIZE, PROT_READ | PROT_WRITE,
		       MAP_ANONYMOUS | MAP_PRIVATE | MAP_STACK, -1, 0);
	if (stack == MAP_FAILED)
		__exit(1);

	pid = __clone(0, stack + STACK_SIZE, NULL, 0, NULL);
	if (pid < 0)
		__exit(1);

	if (!pid)
		/* exit path of child */
		__write(0, cmsg, sizeof(cmsg)), __exit(0);

	/* exit path of parent */
	__munmap(stack, STACK_SIZE);
	__write(0, pmsg, sizeof(pmsg));
	__exit(0);
}