svn commit: r356300 - head/libexec/rtld-elf

[Konstantin Belousov]

Author: kib
Date: Thu Jan  2 22:48:08 2020
New Revision: 356300
URL: https://svnweb.freebsd.org/changeset/base/356300

Log:
  Fix AT_EXECPATH for direct exec mode.
  
  When activated in direct exec mode, kernel-provided AT_EXECPATH points
  to the interpreter.  We need to recalculate auxv to point to the
  string with the path to the executable which is actually executed.
  
  The somewhat problematic case is when the executable path is relative
  and either $PATH use is not enabled or it contains '/' so $PATH search
  is not performed. In this case resulting AT_EXECPATH is relative, I
  might fix this later.
  
  Reported and reviewed by:	rstone
  Sponsored by:	The FreeBSD Foundation
  MFC after:	1 week
  Differential revision:	https://reviews.freebsd.org/D22894

Modified:
  head/libexec/rtld-elf/rtld.c

Modified: head/libexec/rtld-elf/rtld.c
==============================================================================
--- head/libexec/rtld-elf/rtld.c	Thu Jan  2 22:47:10 2020	(r356299)
+++ head/libexec/rtld-elf/rtld.c	Thu Jan  2 22:48:08 2020	(r356300)
@@ -134,7 +134,8 @@ static void objlist_push_head(Objlist *, Obj_Entry *);
 static void objlist_push_tail(Objlist *, Obj_Entry *);
 static void objlist_put_after(Objlist *, Obj_Entry *, Obj_Entry *);
 static void objlist_remove(Objlist *, Obj_Entry *);
-static int open_binary_fd(const char *argv0, bool search_in_path);
+static int open_binary_fd(const char *argv0, bool search_in_path,
+    const char **binpath_res);
 static int parse_args(char* argv[], int argc, bool *use_pathp, int *fdp);
 static int parse_integer(const char *);
 static void *path_enumerate(const char *, path_enum_proc, const char *, void *);
@@ -378,7 +379,7 @@ _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entr
     struct stat st;
     Elf_Addr *argcp;
     char **argv, **env, **envp, *kexecpath, *library_path_rpath;
-    const char *argv0;
+    const char *argv0, *binpath;
     caddr_t imgentry;
     char buf[MAXPATHLEN];
     int argc, fd, i, phnum, rtld_argc;
@@ -464,8 +465,9 @@ _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entr
 		rtld_argc = parse_args(argv, argc, &search_in_path, &fd);
 		argv0 = argv[rtld_argc];
 		explicit_fd = (fd != -1);
+		binpath = NULL;
 		if (!explicit_fd)
-		    fd = open_binary_fd(argv0, search_in_path);
+		    fd = open_binary_fd(argv0, search_in_path, &binpath);
 		if (fstat(fd, &st) == -1) {
 		    _rtld_error("Failed to fstat FD %d (%s): %s", fd,
 		      explicit_fd ? "user-provided descriptor" : argv0,
@@ -518,6 +520,7 @@ _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entr
 		} while (*envp != NULL);
 		aux = auxp = (Elf_Auxinfo *)envp;
 		auxpf = (Elf_Auxinfo *)(envp + rtld_argc);
+		/* XXXKIB insert place for AT_EXECPATH if not present */
 		for (;; auxp++, auxpf++) {
 		    *auxp = *auxpf;
 		    if (auxp->a_type == AT_NULL)
@@ -530,6 +533,18 @@ _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entr
 		    if (auxp->a_type < AT_COUNT)
 			aux_info[auxp->a_type] = auxp;
 		}
+
+		/* Point AT_EXECPATH auxv and aux_info to the binary path. */
+		if (binpath == NULL) {
+		    aux_info[AT_EXECPATH] = NULL;
+		} else {
+		    if (aux_info[AT_EXECPATH] == NULL) {
+			aux_info[AT_EXECPATH] = xmalloc(sizeof(Elf_Auxinfo));
+			aux_info[AT_EXECPATH]->a_type = AT_EXECPATH;
+		    }
+		    aux_info[AT_EXECPATH]->a_un.a_ptr = __DECONST(void *,
+		      binpath);
+		}
 	    } else {
 		_rtld_error("No binary");
 		rtld_die();
@@ -5494,12 +5509,14 @@ symlook_init_from_req(SymLook *dst, const SymLook *src
 }
 
 static int
-open_binary_fd(const char *argv0, bool search_in_path)
+open_binary_fd(const char *argv0, bool search_in_path,
+    const char **binpath_res)
 {
-	char *pathenv, *pe, binpath[PATH_MAX];
+	char *pathenv, *pe, *binpath;
 	int fd;
 
 	if (search_in_path && strchr(argv0, '/') == NULL) {
+		binpath = xmalloc(PATH_MAX);
 		pathenv = getenv("PATH");
 		if (pathenv == NULL) {
 			_rtld_error("-p and no PATH environment variable");
@@ -5524,13 +5541,17 @@ open_binary_fd(const char *argv0, bool search_in_path)
 			    sizeof(binpath))
 				continue;
 			fd = open(binpath, O_RDONLY | O_CLOEXEC | O_VERIFY);
-			if (fd != -1 || errno != ENOENT)
+			if (fd != -1 || errno != ENOENT) {
+				*binpath_res = binpath;
 				break;
+			}
 		}
 		free(pathenv);
 	} else {
 		fd = open(argv0, O_RDONLY | O_CLOEXEC | O_VERIFY);
+		*binpath_res = argv0;
 	}
+	/* XXXKIB Use getcwd() to resolve relative binpath to absolute. */
 
 	if (fd == -1) {
 		_rtld_error("Cannot open %s: %s", argv0, rtld_strerror(errno));