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203 lines
6.4 KiB
203 lines
6.4 KiB
2 years ago
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commit e0f1a58f3d1f4f55591b524e9dcff23cc98a509e
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Author: Florian Weimer <fweimer@redhat.com>
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Date: Thu Oct 8 10:57:10 2020 +0200
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elf: Implement ld.so --help
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--help processing is deferred to the point where the executable has
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been loaded, so that it is possible to eventually include information
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from the main executable in the help output.
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As suggested in the GNU command-line interface guidelines, the help
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message is printed to standard output, and the exit status is
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successful.
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Handle usage errors closer to the GNU command-line interface
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guidelines.
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Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
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diff --git a/elf/dl-main.h b/elf/dl-main.h
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index 79c9c40056504f80..ac7249a580214860 100644
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--- a/elf/dl-main.h
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+++ b/elf/dl-main.h
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@@ -63,6 +63,7 @@ struct audit_list
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enum rtld_mode
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{
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rtld_mode_normal, rtld_mode_list, rtld_mode_verify, rtld_mode_trace,
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+ rtld_mode_help,
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};
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/* Aggregated state information extracted from environment variables
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@@ -101,6 +102,11 @@ call_init_paths (const struct dl_main_state *state)
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}
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/* Print ld.so usage information and exit. */
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-_Noreturn void _dl_usage (void) attribute_hidden;
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+_Noreturn void _dl_usage (const char *argv0, const char *wrong_option)
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+ attribute_hidden;
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+
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+/* Print ld.so --help output and exit. */
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+_Noreturn void _dl_help (const char *argv0, struct dl_main_state *state)
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+ attribute_hidden;
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#endif /* _DL_MAIN */
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diff --git a/elf/dl-usage.c b/elf/dl-usage.c
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index f3d89d22b71d7d12..c1820dca2fa117ee 100644
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--- a/elf/dl-usage.c
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+++ b/elf/dl-usage.c
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@@ -19,12 +19,24 @@
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#include <dl-cache.h>
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#include <dl-main.h>
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#include <ldsodefs.h>
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+#include <unistd.h>
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void
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-_dl_usage (void)
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+_dl_usage (const char *argv0, const char *wrong_option)
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{
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- _dl_fatal_printf ("\
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-Usage: ld.so [OPTION]... EXECUTABLE-FILE [ARGS-FOR-PROGRAM...]\n\
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+ if (wrong_option != NULL)
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+ _dl_error_printf ("%s: unrecognized option '%s'\n", argv0, wrong_option);
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+ else
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+ _dl_error_printf ("%s: missing program name\n", argv0);
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+ _dl_error_printf ("Try '%s --help' for more information.\n", argv0);
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+ _exit (EXIT_FAILURE);
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+}
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+
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+void
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+_dl_help (const char *argv0, struct dl_main_state *state)
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+{
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+ _dl_printf ("\
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+Usage: %s [OPTION]... EXECUTABLE-FILE [ARGS-FOR-PROGRAM...]\n\
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You have invoked `ld.so', the helper program for shared library executables.\n\
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This program usually lives in the file `/lib/ld.so', and special directives\n\
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in executable files using ELF shared libraries tell the system's program\n\
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@@ -47,5 +59,9 @@ of this helper program; chances are you did not intend to run this program.\n\
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in LIST\n\
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--audit LIST use objects named in LIST as auditors\n\
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--preload LIST preload objects named in LIST\n\
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- --argv0 STRING set argv[0] to STRING before running\n");
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+ --argv0 STRING set argv[0] to STRING before running\n\
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+ --help display this help and exit\n\
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+",
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+ argv0);
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+ _exit (EXIT_SUCCESS);
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}
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diff --git a/elf/rtld.c b/elf/rtld.c
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index 8e91cee41b62b894..b92641cb1c2d99a6 100644
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--- a/elf/rtld.c
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+++ b/elf/rtld.c
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@@ -1145,6 +1145,7 @@ dl_main (const ElfW(Phdr) *phdr,
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/* Set up a flag which tells we are just starting. */
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_dl_starting_up = 1;
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+ const char *ld_so_name = _dl_argv[0];
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if (*user_entry == (ElfW(Addr)) ENTRY_POINT)
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{
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/* Ho ho. We are not the program interpreter! We are the program
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@@ -1172,8 +1173,12 @@ dl_main (const ElfW(Phdr) *phdr,
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while (_dl_argc > 1)
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if (! strcmp (_dl_argv[1], "--list"))
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{
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- state.mode = rtld_mode_list;
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- GLRO(dl_lazy) = -1; /* This means do no dependency analysis. */
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+ if (state.mode != rtld_mode_help)
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+ {
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+ state.mode = rtld_mode_list;
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+ /* This means do no dependency analysis. */
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+ GLRO(dl_lazy) = -1;
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+ }
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++_dl_skip_args;
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--_dl_argc;
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@@ -1181,7 +1186,8 @@ dl_main (const ElfW(Phdr) *phdr,
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}
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else if (! strcmp (_dl_argv[1], "--verify"))
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{
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- state.mode = rtld_mode_verify;
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+ if (state.mode != rtld_mode_help)
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+ state.mode = rtld_mode_verify;
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++_dl_skip_args;
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--_dl_argc;
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@@ -1236,13 +1242,34 @@ dl_main (const ElfW(Phdr) *phdr,
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_dl_argc -= 2;
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_dl_argv += 2;
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}
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+ else if (strcmp (_dl_argv[1], "--help") == 0)
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+ {
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+ state.mode = rtld_mode_help;
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+ --_dl_argc;
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+ ++_dl_argv;
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+ }
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+ else if (_dl_argv[1][0] == '-' && _dl_argv[1][1] == '-')
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+ {
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+ if (_dl_argv[1][1] == '\0')
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+ /* End of option list. */
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+ break;
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+ else
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+ /* Unrecognized option. */
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+ _dl_usage (ld_so_name, _dl_argv[1]);
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+ }
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else
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break;
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/* If we have no further argument the program was called incorrectly.
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Grant the user some education. */
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if (_dl_argc < 2)
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- _dl_usage ();
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+ {
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+ if (state.mode == rtld_mode_help)
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+ /* --help without an executable is not an error. */
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+ _dl_help (ld_so_name, &state);
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+ else
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+ _dl_usage (ld_so_name, NULL);
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+ }
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++_dl_skip_args;
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--_dl_argc;
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@@ -1267,7 +1294,8 @@ dl_main (const ElfW(Phdr) *phdr,
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break;
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}
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- if (__glibc_unlikely (state.mode == rtld_mode_verify))
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+ if (__glibc_unlikely (state.mode == rtld_mode_verify
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+ || state.mode == rtld_mode_help))
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{
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const char *objname;
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const char *err_str = NULL;
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@@ -1280,9 +1308,16 @@ dl_main (const ElfW(Phdr) *phdr,
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(void) _dl_catch_error (&objname, &err_str, &malloced, map_doit,
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&args);
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if (__glibc_unlikely (err_str != NULL))
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- /* We don't free the returned string, the programs stops
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- anyway. */
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- _exit (EXIT_FAILURE);
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+ {
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+ /* We don't free the returned string, the programs stops
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+ anyway. */
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+ if (state.mode == rtld_mode_help)
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+ /* Mask the failure to load the main object. The help
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+ message contains less information in this case. */
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+ _dl_help (ld_so_name, &state);
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+ else
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+ _exit (EXIT_FAILURE);
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+ }
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}
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else
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{
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@@ -1632,6 +1667,11 @@ ERROR: '%s': cannot process note segment.\n", _dl_argv[0]);
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audit_list_add_dynamic_tag (&state.audit_list, main_map, DT_AUDIT);
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audit_list_add_dynamic_tag (&state.audit_list, main_map, DT_DEPAUDIT);
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+ /* At this point, all data has been obtained that is included in the
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+ --help output. */
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+ if (__glibc_unlikely (state.mode == rtld_mode_help))
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+ _dl_help (ld_so_name, &state);
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+
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/* If we have auditing DSOs to load, do it now. */
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bool need_security_init = true;
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if (state.audit_list.length > 0)
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