xref: /freebsd-14.2/libexec/rtld-elf/libmap.c (revision 68f1db20)

/*
 * $FreeBSD$
 */

#include <sys/param.h>
#include <sys/fcntl.h>
#include <sys/mman.h>
#include <sys/queue.h>
#include <sys/stat.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>

#include "debug.h"
#include "rtld.h"
#include "libmap.h"

#ifndef _PATH_LIBMAP_CONF
#define	_PATH_LIBMAP_CONF	"/etc/libmap.conf"
#endif

#ifdef COMPAT_32BIT
#undef _PATH_LIBMAP_CONF
#define	_PATH_LIBMAP_CONF	"/etc/libmap32.conf"
#endif

TAILQ_HEAD(lm_list, lm);
struct lm {
	char *f;
	char *t;
	TAILQ_ENTRY(lm)	lm_link;
};

TAILQ_HEAD(lmp_list, lmp) lmp_head = TAILQ_HEAD_INITIALIZER(lmp_head);
struct lmp {
	char *p;
	enum { T_EXACT=0, T_BASENAME, T_DIRECTORY } type;
	struct lm_list lml;
	TAILQ_ENTRY(lmp) lmp_link;
};

static int lm_count;

static void lmc_parse(char *, size_t);
static void lm_add(const char *, const char *, const char *);
static void lm_free(struct lm_list *);
static char *lml_find(struct lm_list *, const char *);
static struct lm_list *lmp_find(const char *);
static struct lm_list *lmp_init(char *);
static const char *quickbasename(const char *);

#define	iseol(c)	(((c) == '#') || ((c) == '\0') || \
			 ((c) == '\n') || ((c) == '\r'))

/*
 * Do not use ctype.h macros, which rely on working TLS.  It is
 * too early to have thread-local variables functional.
 */
#define	rtld_isspace(c)	((c) == ' ' || (c) == '\t')

int
lm_init(char *libmap_override)
{
	struct stat st;
	char *lm_map, *p;
	int fd;

	dbg("lm_init(\"%s\")", libmap_override);
	TAILQ_INIT(&lmp_head);

	fd = open(_PATH_LIBMAP_CONF, O_RDONLY);
	if (fd == -1) {
		dbg("lm_init: open(\"%s\") failed, %s", _PATH_LIBMAP_CONF,
		    strerror(errno));
		goto override;
	}
	if (fstat(fd, &st) == -1) {
		close(fd);
		dbg("lm_init: fstat(\"%s\") failed, %s", _PATH_LIBMAP_CONF,
		    strerror(errno));
		goto override;
	}
	lm_map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
	if (lm_map == (const char *)MAP_FAILED) {
		close(fd);
		dbg("lm_init: mmap(\"%s\") failed, %s", _PATH_LIBMAP_CONF,
		    strerror(errno));
		goto override;
	}
	close(fd);
	lmc_parse(lm_map, st.st_size);
	munmap(lm_map, st.st_size);

override:
	if (libmap_override) {
		/*
		 * Do some character replacement to make $LIBMAP look
		 * like a text file, then parse it.
		 */
		libmap_override = xstrdup(libmap_override);
		for (p = libmap_override; *p; p++) {
			switch (*p) {
			case '=':
				*p = ' ';
				break;
			case ',':
				*p = '\n';
				break;
			}
		}
		lmc_parse(p, strlen(p));
		free(p);
	}

	return (lm_count == 0);
}

static void
lmc_parse(char *lm_p, size_t lm_len)
{
	char *cp, *f, *t, *c, *p;
	char prog[MAXPATHLEN];
	char line[MAXPATHLEN + 2];
	size_t cnt;
	int i;

	cnt = 0;
	p = NULL;
	while (cnt < lm_len) {
		i = 0;
		while (lm_p[cnt] != '\n' && cnt < lm_len &&
		    i < sizeof(line) - 1) {
			line[i] = lm_p[cnt];
			cnt++;
			i++;
		}
		line[i] = '\0';
		while (lm_p[cnt] != '\n' && cnt < lm_len)
			cnt++;
		/* skip over nl */
		cnt++;

		cp = &line[0];
		t = f = c = NULL;

		/* Skip over leading space */
		while (rtld_isspace(*cp)) cp++;

		/* Found a comment or EOL */
		if (iseol(*cp)) continue;

		/* Found a constraint selector */
		if (*cp == '[') {
			cp++;

			/* Skip leading space */
			while (rtld_isspace(*cp)) cp++;

			/* Found comment, EOL or end of selector */
			if  (iseol(*cp) || *cp == ']')
				continue;

			c = cp++;
			/* Skip to end of word */
			while (!rtld_isspace(*cp) && !iseol(*cp) && *cp != ']')
				cp++;

			/* Skip and zero out trailing space */
			while (rtld_isspace(*cp)) *cp++ = '\0';

			/* Check if there is a closing brace */
			if (*cp != ']') continue;

			/* Terminate string if there was no trailing space */
			*cp++ = '\0';

			/*
			 * There should be nothing except whitespace or comment
			  from this point to the end of the line.
			 */
			while(rtld_isspace(*cp)) cp++;
			if (!iseol(*cp)) continue;

			strcpy(prog, c);
			p = prog;
			continue;
		}

		/* Parse the 'from' candidate. */
		f = cp++;
		while (!rtld_isspace(*cp) && !iseol(*cp)) cp++;

		/* Skip and zero out the trailing whitespace */
		while (rtld_isspace(*cp)) *cp++ = '\0';

		/* Found a comment or EOL */
		if (iseol(*cp)) continue;

		/* Parse 'to' mapping */
		t = cp++;
		while (!rtld_isspace(*cp) && !iseol(*cp)) cp++;

		/* Skip and zero out the trailing whitespace */
		while (rtld_isspace(*cp)) *cp++ = '\0';

		/* Should be no extra tokens at this point */
		if (!iseol(*cp)) continue;

		*cp = '\0';
		lm_add(p, f, t);
	}
}

static void
lm_free (struct lm_list *lml)
{
	struct lm *lm;

	dbg("%s(%p)", __func__, lml);

	while (!TAILQ_EMPTY(lml)) {
		lm = TAILQ_FIRST(lml);
		TAILQ_REMOVE(lml, lm, lm_link);
		free(lm->f);
		free(lm->t);
		free(lm);
	}
	return;
}

void
lm_fini (void)
{
	struct lmp *lmp;

	dbg("%s()", __func__);

	while (!TAILQ_EMPTY(&lmp_head)) {
		lmp = TAILQ_FIRST(&lmp_head);
		TAILQ_REMOVE(&lmp_head, lmp, lmp_link);
		free(lmp->p);
		lm_free(&lmp->lml);
		free(lmp);
	}
	return;
}

static void
lm_add (const char *p, const char *f, const char *t)
{
	struct lm_list *lml;
	struct lm *lm;

	if (p == NULL)
		p = "$DEFAULT$";

	dbg("%s(\"%s\", \"%s\", \"%s\")", __func__, p, f, t);

	if ((lml = lmp_find(p)) == NULL)
		lml = lmp_init(xstrdup(p));

	lm = xmalloc(sizeof(struct lm));
	lm->f = xstrdup(f);
	lm->t = xstrdup(t);
	TAILQ_INSERT_HEAD(lml, lm, lm_link);
	lm_count++;
}

char *
lm_find (const char *p, const char *f)
{
	struct lm_list *lml;
	char *t;

	dbg("%s(\"%s\", \"%s\")", __func__, p, f);

	if (p != NULL && (lml = lmp_find(p)) != NULL) {
		t = lml_find(lml, f);
		if (t != NULL) {
			/*
			 * Add a global mapping if we have
			 * a successful constrained match.
			 */
			lm_add(NULL, f, t);
			return (t);
		}
	}
	lml = lmp_find("$DEFAULT$");
	if (lml != NULL)
		return (lml_find(lml, f));
	else
		return (NULL);
}

/* Given a libmap translation list and a library name, return the
   replacement library, or NULL */
#ifdef COMPAT_32BIT
char *
lm_findn (const char *p, const char *f, const int n)
{
	char pathbuf[64], *s, *t;

	if (n < sizeof(pathbuf) - 1)
		s = pathbuf;
	else
		s = xmalloc(n + 1);
	memcpy(s, f, n);
	s[n] = '\0';
	t = lm_find(p, s);
	if (s != pathbuf)
		free(s);
	return (t);
}
#endif

static char *
lml_find (struct lm_list *lmh, const char *f)
{
	struct lm *lm;

	dbg("%s(%p, \"%s\")", __func__, lmh, f);

	TAILQ_FOREACH(lm, lmh, lm_link)
		if (strcmp(f, lm->f) == 0)
			return (lm->t);
	return (NULL);
}

/* Given an executable name, return a pointer to the translation list or
   NULL if no matches */
static struct lm_list *
lmp_find (const char *n)
{
	struct lmp *lmp;

	dbg("%s(\"%s\")", __func__, n);

	TAILQ_FOREACH(lmp, &lmp_head, lmp_link)
		if ((lmp->type == T_EXACT && strcmp(n, lmp->p) == 0) ||
		    (lmp->type == T_DIRECTORY && strncmp(n, lmp->p, strlen(lmp->p)) == 0) ||
		    (lmp->type == T_BASENAME && strcmp(quickbasename(n), lmp->p) == 0))
			return (&lmp->lml);
	return (NULL);
}

static struct lm_list *
lmp_init (char *n)
{
	struct lmp *lmp;

	dbg("%s(\"%s\")", __func__, n);

	lmp = xmalloc(sizeof(struct lmp));
	lmp->p = n;
	if (n[strlen(n)-1] == '/')
		lmp->type = T_DIRECTORY;
	else if (strchr(n,'/') == NULL)
		lmp->type = T_BASENAME;
	else
		lmp->type = T_EXACT;
	TAILQ_INIT(&lmp->lml);
	TAILQ_INSERT_HEAD(&lmp_head, lmp, lmp_link);

	return (&lmp->lml);
}

/* libc basename is overkill.  Return a pointer to the character after the
   last /, or the original string if there are no slashes. */
static const char *
quickbasename (const char *path)
{
	const char *p = path;
	for (; *path; path++) {
		if (*path == '/')
			p = path+1;
	}
	return (p);
}