svn commit: r318431 - head/libexec/rtld-elf
Jonathan Anderson
jonathan at FreeBSD.org
Wed May 17 22:51:30 UTC 2017
Author: jonathan
Date: Wed May 17 22:51:28 2017
New Revision: 318431
URL: https://svnweb.freebsd.org/changeset/base/318431
Log:
Allow rtld direct-exec to take a file descriptor.
When executing rtld directly, allow a file descriptor to be explicitly
specified rather than opened from the given path. This, together with the
LD_LIBRARY_PATH_FDS environment variable, allows dynamically-linked
applications to be executed from within capability mode.
Also add some rudimentary argument parsing (without pulling in getopt or
the like) to accept this file descriptor, a help (-h) option and a basic
usage string.
Reviewed by: kib
Sponsored by: NSERC, RDC
Differential Revision: https://reviews.freebsd.org/D10751
Modified:
head/libexec/rtld-elf/rtld.c
Modified: head/libexec/rtld-elf/rtld.c
==============================================================================
--- head/libexec/rtld-elf/rtld.c Wed May 17 22:29:25 2017 (r318430)
+++ head/libexec/rtld-elf/rtld.c Wed May 17 22:51:28 2017 (r318431)
@@ -115,8 +115,10 @@ static void objlist_push_head(Objlist *,
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 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, void *);
+static void print_usage(const char *argv0);
static void release_object(Obj_Entry *);
static int relocate_object_dag(Obj_Entry *root, bool bind_now,
Obj_Entry *rtldobj, int flags, RtldLockState *lockstate);
@@ -350,9 +352,9 @@ _rtld(Elf_Addr *sp, func_ptr_type *exit_
char **argv, *argv0, **env, **envp, *kexecpath, *library_path_rpath;
caddr_t imgentry;
char buf[MAXPATHLEN];
- int argc, fd, i, mib[2], phnum;
+ int argc, fd, i, mib[2], phnum, rtld_argc;
size_t len;
- bool dir_enable;
+ bool dir_enable, explicit_fd, search_in_path;
/*
* On entry, the dynamic linker itself has not been relocated yet.
@@ -428,15 +430,19 @@ _rtld(Elf_Addr *sp, func_ptr_type *exit_
}
dbg("opening main program in direct exec mode");
if (argc >= 2) {
- argv0 = argv[1];
- fd = open(argv0, O_RDONLY | O_CLOEXEC | O_VERIFY);
+ rtld_argc = parse_args(argv, argc, &search_in_path, &fd);
+ argv0 = argv[rtld_argc];
+ explicit_fd = (fd != -1);
+ if (!explicit_fd)
+ fd = open(argv0, O_RDONLY | O_CLOEXEC | O_VERIFY);
if (fd == -1) {
rtld_printf("Opening %s: %s\n", argv0,
rtld_strerror(errno));
rtld_die();
}
if (fstat(fd, &st) == -1) {
- rtld_printf("Stat %s: %s\n", argv0,
+ _rtld_error("failed to fstat FD %d (%s): %s", fd,
+ explicit_fd ? "user-provided descriptor" : argv0,
rtld_strerror(errno));
rtld_die();
}
@@ -469,26 +475,23 @@ _rtld(Elf_Addr *sp, func_ptr_type *exit_
/*
* For direct exec mode, argv[0] is the interpreter
- * name, we must remove it and shift arguments left by
- * 1 before invoking binary main. Since stack layout
+ * name, we must remove it and shift arguments left
+ * before invoking binary main. Since stack layout
* places environment pointers and aux vectors right
* after the terminating NULL, we must shift
* environment and aux as well.
- * XXX Shift will be > 1 when options are implemented.
*/
+ main_argc = argc - rtld_argc;
+ for (i = 0; i <= main_argc; i++)
+ argv[i] = argv[i + rtld_argc];
+ *argcp -= rtld_argc;
+ environ = env = envp = argv + main_argc + 1;
do {
- *argv = *(argv + 1);
- argv++;
- } while (*argv != NULL);
- *argcp -= 1;
- main_argc = argc - 1;
- environ = env = envp = argv;
- do {
- *envp = *(envp + 1);
+ *envp = *(envp + rtld_argc);
envp++;
} while (*envp != NULL);
aux = auxp = (Elf_Auxinfo *)envp;
- auxpf = (Elf_Auxinfo *)(envp + 1);
+ auxpf = (Elf_Auxinfo *)(envp + rtld_argc);
for (;; auxp++, auxpf++) {
*auxp = *auxpf;
if (auxp->a_type == AT_NULL)
@@ -5274,6 +5277,81 @@ symlook_init_from_req(SymLook *dst, cons
/*
+ * Parse a set of command-line arguments.
+ */
+static int
+parse_args(char* argv[], int argc, bool *use_pathp, int *fdp)
+{
+ const char *arg;
+ int fd, i, j, arglen;
+ char opt;
+
+ dbg("Parsing command-line arguments");
+ *use_pathp = false;
+ *fdp = -1;
+
+ for (i = 1; i < argc; i++ ) {
+ arg = argv[i];
+ dbg("argv[%d]: '%s'", i, arg);
+
+ /*
+ * rtld arguments end with an explicit "--" or with the first
+ * non-prefixed argument.
+ */
+ if (strcmp(arg, "--") == 0) {
+ i++;
+ break;
+ }
+ if (arg[0] != '-')
+ break;
+
+ /*
+ * All other arguments are single-character options that can
+ * be combined, so we need to search through `arg` for them.
+ */
+ arglen = strlen(arg);
+ for (j = 1; j < arglen; j++) {
+ opt = arg[j];
+ if (opt == 'h') {
+ print_usage(argv[0]);
+ rtld_die();
+ } else if (opt == 'f') {
+ /*
+ * -f XX can be used to specify a descriptor for the
+ * binary named at the command line (i.e., the later
+ * argument will specify the process name but the
+ * descriptor is what will actually be executed)
+ */
+ if (j != arglen - 1) {
+ /* -f must be the last option in, e.g., -abcf */
+ _rtld_error("invalid options: %s", arg);
+ rtld_die();
+ }
+ i++;
+ fd = parse_integer(argv[i]);
+ if (fd == -1) {
+ _rtld_error("invalid file descriptor: '%s'",
+ argv[i]);
+ rtld_die();
+ }
+ *fdp = fd;
+ break;
+ /* TODO:
+ } else if (opt == 'p') {
+ *use_pathp = true;
+ */
+ } else {
+ rtld_printf("invalid argument: '%s'\n", arg);
+ print_usage(argv[0]);
+ rtld_die();
+ }
+ }
+ }
+
+ return (i);
+}
+
+/*
* Parse a file descriptor number without pulling in more of libc (e.g. atoi).
*/
static int
@@ -5300,6 +5378,20 @@ parse_integer(const char *str)
return (n);
}
+void print_usage(const char *argv0)
+{
+
+ rtld_printf("Usage: %s [-h] [-f <FD>] [--] <binary> [<args>]\n"
+ "\n"
+ "Options:\n"
+ " -h Display this help message\n"
+ /* TODO: " -p Search in PATH for named binary\n" */
+ " -f <FD> Execute <FD> instead of searching for <binary>\n"
+ " -- End of RTLD options\n"
+ " <binary> Name of process to execute\n"
+ " <args> Arguments to the executed process\n", argv0);
+}
+
/*
* Overrides for libc_pic-provided functions.
*/
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