/*
 * Copyright 2011 Gentoo Foundation
 * Distributed under the terms of the GNU General Public License v2
 * $Header: /var/cvsroot/gentoo-projects/portage-utils/libq/prelink.c,v 1.4 2012/08/13 22:23:35 robbat2 Exp $
 */

#include <signal.h>

static const char prelink_bin[] = "prelink";

static int prelink_in_current_path(bool quiet_missing)
{
	pid_t pid;

	switch ((pid = fork())) {
	case -1: errp("error forking process");
	case 0: {
		/* we are the child */
		int dev_null;
		close(STDOUT_FILENO);
		dev_null = open("/dev/null", O_WRONLY);
		if (dev_null == -1) {
			warnp("Error opening /dev/null");
			_exit(2);
		}
		if (dup2(dev_null, STDOUT_FILENO) == -1) {
			warnp("Error redirecting output");
			_exit(2);
		}
		execlp(prelink_bin, prelink_bin, "--version", NULL);
		if (!quiet_missing || errno != ENOENT)
			warnp("error executing %s", prelink_bin);
		_exit(errno == ENOENT ? 1 : 2);
	}
	default: {
		/* we are the parent */
		int status;
		waitpid(pid, &status, 0);
		if (WIFEXITED(status))
			return MIN(WEXITSTATUS(status), 2);
		else
			errp("%s freaked out %#x", prelink_bin, status);
	}
	}
}

static bool prelink_available(void)
{
	int status = prelink_in_current_path(true);

	if (status == 1) {
		/* extend path to include sbin and search again */
		static const char sbin_path[] = "/sbin:/usr/sbin:/usr/local/sbin";
		char *path;
		xasprintf(&path, "PATH=%s:%s", getenv("PATH") ? : "", sbin_path);
		putenv(path);
		status = prelink_in_current_path(0);
	}

	return status == 0 ? true : false;
}

#ifdef __linux__
#include <elf.h>
static bool is_prelink_elf(int fd, const char *filename)
{
	unsigned char header[EI_NIDENT + 2];
	ssize_t len;
	uint16_t e_type;

	len = read(fd, &header, sizeof(header));
	if (len == -1) {
		warnp("unable to read %s", filename);
		return false;
	}
	if (lseek(fd, 0, SEEK_SET) != 0)
		errp("unable to reset after ELF check %s\n", filename);
	if (len < (ssize_t)sizeof(header))
		return false;

	if (memcmp(header, ELFMAG, SELFMAG))
		return false;

	/* prelink only likes certain types of ELFs */
	switch (header[EI_DATA]) {
	case ELFDATA2LSB:
		e_type = header[EI_NIDENT] | (header[EI_NIDENT + 1] << 8);
		break;
	case ELFDATA2MSB:
		e_type = header[EI_NIDENT + 1] | (header[EI_NIDENT] << 8);
		break;
	default:
		return false;
	}
	switch (e_type) {
	case ET_EXEC:
	case ET_DYN:
		return true;
	default:
		return false;
	}

	/* XXX: should we also check OS's/arches that prelink supports ? */
}
#else
static bool is_prelink_elf(int fd, const char *filename)
{
	return false;
}
#endif

static int execvp_const(const char * const argv[])
{
	return execvp(argv[0], (void *)argv);
}

static int _hash_cb_prelink(int fd, const char *filename, const char * const argv[])
{
	int pipefd[2];

	if (!is_prelink_elf(fd, filename))
		return fd;

	if (pipe(pipefd))
		errp("unable to create pipe");

	switch (fork()) {
	case -1: errp("error forking process");
	case 0: {
		/* we are the child */
		static const char * const cat_argv[] = { "cat", NULL, };
		pid_t pid;

		/* make sure we get notified of the child exit */
		signal(SIGCHLD, SIG_DFL);

		/* connect up stdin/stdout for reading/writing the file */
		close(pipefd[0]);
		if (dup2(fd, STDIN_FILENO) == -1) {
			warnp("error redirecting input");
			_exit(EXIT_FAILURE);
		}
		if (dup2(pipefd[1], STDOUT_FILENO) == -1) {
			warnp("error redirecting output");
			_exit(EXIT_FAILURE);
		}

		/*
		 * fork a monitor process ... this way the main qcheck program
		 * can simply read their side of the pipe without having to wait
		 * for the whole prelink program to run.  gives a bit of speed
		 * up on multicore systems and doesn't need as much mem to hold
		 * all the data in the pipe before we read it.  this also makes
		 * it easy to fall back to `cat` when prelink skipped the file
		 * that we fed it (like the split debug files).
		 */
		switch ((pid = fork())) {
		case -1: errp("error forking process");
		case 0:
			/* we are the child */
			execvp_const(argv);
			warnp("error executing %s", prelink_bin);
			_exit(1);
		default: {
			int status;
			waitpid(pid, &status, 0);
			if (WIFEXITED(status)) {
				if (WEXITSTATUS(status) == EXIT_SUCCESS)
					_exit(0);
				/* assume prelink printed its own error message */
			} else
				warnp("%s freaked out %#x", argv[0], status);
			/* we've come too far!  try one last thing ... */
			execvp_const(cat_argv);
			_exit(1);
		}
		}
	}
	default:
		/* we are the parent */
		close(pipefd[1]);
		/* we don't need this anymore since we've got a pipe to read */
		close(fd);
		/* ignore the monitor process exit status to avoid ZOMBIES */
		signal(SIGCHLD, SIG_IGN);
		/* assume child worked ... if it didn't, it will warn for us */
		return pipefd[0];
	}

	return fd;
}

static int hash_cb_prelink_undo(int fd, const char *filename)
{
	static const char * const argv[] = {
		prelink_bin,
		"--undo",
		"--undo-output=-",
		"/dev/stdin",
		NULL,
	};
	return _hash_cb_prelink(fd, filename, argv);
}
