#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#include <errno.h>
#include <unistd.h>
#include <sys/time.h>
#include <sys/syscall.h>

#undef SYS_stacktrace_setup
#define SYS_stacktrace_setup		472

enum {
	STACKTRACE_REGISTER_SFRAME = 1,
	STACKTRACE_UNREGISTER_SFRAME,
};

#define stacktrace_setup(op, start_addr, length, text_addr, text_length)\
	syscall(SYS_stacktrace_setup, op, start_addr, length, text_addr, text_length)

static void usage(const char *name)
{
	printf("usage: %s sframe-offset sframe-length\n"
	       "\n",name);
	exit(-1);
}

static unsigned long long get_time(void)
{
	struct timeval tv;
	unsigned long long time;

	gettimeofday(&tv, NULL);

	time = tv.tv_sec * 1000000ULL;
	time += tv.tv_usec;

	return time;
}

void do_spin(void)
{
	unsigned long long start = get_time();

	/* 2 seconds */
	start += 2 * 1000 * 1000;

	while (get_time() < start)
		;
}

static int dump_self(unsigned long idx, unsigned long *sframe,
		     unsigned long *text, unsigned long *text_len)
{
	FILE *fp;
	char *line = NULL;
	size_t size;
	unsigned long ptr = 0;

	*text = 0;

	fp = fopen("/proc/self/maps", "r");
	if (!fp) {
		perror("self");
		exit(-1);
	}

	while ((!ptr || !*text) && getline(&line, &size, fp) > 0) {
		unsigned long start, end;
		char *file;
		char *perm;
		int r;
		int l;

		r = sscanf(line, "%lx-%lx %ms %*x %*s %*d %ms\n",
			   &start, &end, &perm, &file);
		if (r != 4)
			continue;
		printf("%s", line);
//		printf("file=%s\n", file);
		l = strlen(file);
		for (l--; l > 0; l--) {
			if (file[l] == '/') {
				l++;
				break;
			}
		}
		// r-xp	
		if (!strncmp(file + l, "libc.so", 7)) {
			if (!ptr) {
				ptr = start + idx;
				printf("found sframe libc.so %lx-%lx (%lx)\n", start, end, ptr);
				printf("VAL=%lx\n", *(unsigned long*)ptr);
			}
			if (!*text && !strcmp(perm, "r-xp")) {
				*text = start;
				*text_len = end - start;
				printf("found text libc.so %lx-%lx (%lx)\n", start, end, ptr);
			}
		}
		free(file);
		free(perm);
	}
	free(line);

	*sframe = ptr;
	return ptr && *text;
}

int main (int argc, char **argv)
{
	unsigned long idx; // 0x001d3fc0;
	unsigned long len; // 0x303f9;
	unsigned long ptr;
	unsigned long text;
	unsigned long text_len;
	int ret = 0;

	if (argc < 3)
		usage(argv[0]);


	idx = strtoul(argv[1], NULL, 0);
	len = strtoul(argv[2], NULL, 0);

	if (!dump_self(idx, &ptr, &text, &text_len)) {
		fprintf(stderr, "Could not find data");
		exit(-1);
	}
	ret = stacktrace_setup(STACKTRACE_REGISTER_SFRAME, ptr, len, text, text_len);
	if (ret < 0) {
		perror("Registering stacktrace");
		exit(-1);
	}

	do_spin();

	stacktrace_setup(STACKTRACE_UNREGISTER_SFRAME, ptr, len, text, text_len);

	do_spin();
	
	return 0;
}