add options when explicitly invoking dynamic loader

so far the options are --library-path and --preload which override the
corresponding environment variables, and --list which forces the
behavior of ldd even if the invocation name is not ldd. both the
two-arg form and the one-arg form using an equals sign are supported.

based loosely on a patch proposed by Rune.

diff --git a/src/ldso/dynlink.c b/src/ldso/dynlink.c
index 1517281a838be2ae2c835fc7d0769708eae215fc..1cb3fb4c436da28e6285fa78f738995318a3e802 100644 (file)
--- a/src/ldso/dynlink.c
+++ b/src/ldso/dynlink.c
@@ -1055,12 +1055,31 @@ void *__dynlink(int argc, char **argv)
                size_t l = strlen(ldname);
                if (l >= 3 && !strcmp(ldname+l-3, "ldd")) ldd_mode = 1;
                *argv++ = (void *)-1;
-               if (argv[0] && !strcmp(argv[0], "--")) *argv++ = (void *)-1;
+               while (argv[0] && argv[0][0]=='-' && argv[0][1]=='-') {
+                       char *opt = argv[0]+2;
+                       *argv++ = (void *)-1;
+                       if (!*opt) {
+                               break;
+                       } else if (!memcmp(opt, "list", 5)) {
+                               ldd_mode = 1;
+                       } else if (!memcmp(opt, "library-path", 12)) {
+                               if (opt[12]=='=') env_path = opt+13;
+                               else if (opt[12]) *argv = 0;
+                               else if (*argv) env_path = *argv++;
+                       } else if (!memcmp(opt, "preload", 7)) {
+                               if (opt[7]=='=') env_preload = opt+8;
+                               else if (opt[7]) *argv = 0;
+                               else if (*argv) env_preload = *argv++;
+                       } else {
+                               argv[0] = 0;
+                       }
+                       argv[-1] = (void *)-1;
+               }
                if (!argv[0]) {
                        dprintf(2, "musl libc\n"
                                "Version %s\n"
                                "Dynamic Program Loader\n"
-                               "Usage: %s [--] pathname%s\n",
+                               "Usage: %s [options] [--] pathname%s\n",
                                __libc_get_version(), ldname,
                                ldd_mode ? "" : " [args]");
                        _exit(1);