[glibc/release/2.33/master] elf: ld.so --help calls _dl_init_paths without a main map [BZ #27577]

[glibc/release/2.33/master] elf: ld.so --help calls _dl_init_paths without a main map [BZ #27577]

[Florian Weimer]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=dd8023c2ac0af28a6e391a2eb5038bb351694243

commit dd8023c2ac0af28a6e391a2eb5038bb351694243
Author: Florian Weimer <fweimer@redhat.com>
Date:   Mon Mar 15 10:33:43 2021 +0100

    elf: ld.so --help calls _dl_init_paths without a main map [BZ #27577]
    
    In this case, use the link map of the dynamic loader itself as
    a replacement.  This is more than just a hack: if we ever support
    DT_RUNPATH/DT_RPATH for the dynamic loader, reporting it for
    ld.so --help (without further command line arguments) would be the
    right thing to do.
    
    Fixes commit 332421312576bd7095e70589154af99b124dd2d1 ("elf: Always
    set l in _dl_init_paths (bug 23462)").
    
    (cherry picked from commit 4e6db99c665d3b82a70a3e218860ef087b1555b4)

Diff:
---
 NEWS          |  1 +
 elf/Makefile  | 18 ++++++++++++++++--
 elf/dl-load.c |  8 +++++++-
 3 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/NEWS b/NEWS
index abc4206f58..55eed26d15 100644
--- a/NEWS
+++ b/NEWS
@@ -17,6 +17,7 @@ The following bugs are resolved with this release:
 
   [23462] Static binary with dynamic string tokens ($LIB, $PLATFORM, $ORIGIN)
     crashes
+  [27577] elf/ld.so --help doesn't work
 \f
 Version 2.33
 
diff --git a/elf/Makefile b/elf/Makefile
index 63da0ed64f..4b92f8b305 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -245,7 +245,7 @@ tests += $(tests-execstack-$(have-z-execstack))
 ifeq ($(run-built-tests),yes)
 tests-special += $(objpfx)tst-leaks1-mem.out \
 		 $(objpfx)tst-leaks1-static-mem.out $(objpfx)noload-mem.out \
-		 $(objpfx)tst-ldconfig-X.out
+		 $(objpfx)tst-ldconfig-X.out $(objpfx)tst-rtld-help.out
 endif
 tlsmod17a-suffixes = 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
 tlsmod18a-suffixes = 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
@@ -433,7 +433,8 @@ endif
 ifeq (yes,$(build-shared))
 ifeq ($(run-built-tests),yes)
 tests-special += $(objpfx)tst-pathopt.out $(objpfx)tst-rtld-load-self.out \
-		 $(objpfx)tst-rtld-preload.out $(objpfx)argv0test.out
+		 $(objpfx)tst-rtld-preload.out $(objpfx)argv0test.out \
+		 $(objpfx)tst-rtld-help.out
 endif
 tests-special += $(objpfx)check-textrel.out $(objpfx)check-execstack.out \
 		 $(objpfx)check-wx-segment.out \
@@ -1908,3 +1909,16 @@ $(objpfx)list-tunables.out: tst-rtld-list-tunables.sh $(objpfx)ld.so
 	$(evaluate-test)
 
 tst-dst-static-ENV = LD_LIBRARY_PATH='$$ORIGIN'
+
+$(objpfx)tst-rtld-help.out: $(objpfx)ld.so
+	$(test-wrapper) $(rtld-prefix) --help > $@; \
+	status=$$?; \
+	echo "info: ld.so exit status: $$status" >> $@; \
+	if ! grep -q 'Legacy HWCAP subdirectories under library search path directories' $@; then \
+	  echo "error: missing subdirectory pattern" >> $@; \
+	  if test $$status -eq 0; then \
+	    status=1; \
+	  fi; \
+	fi; \
+	(exit $$status); \
+	$(evaluate-test)
diff --git a/elf/dl-load.c b/elf/dl-load.c
index 376a2e64d6..2f760503c5 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -758,8 +758,14 @@ _dl_init_paths (const char *llp, const char *source,
   max_dirnamelen = SYSTEM_DIRS_MAX_LEN;
   *aelem = NULL;
 
-  /* This points to the map of the main object.  */
+  /* This points to the map of the main object.  If there is no main
+     object (e.g., under --help, use the dynamic loader itself as a
+     stand-in.  */
   l = GL(dl_ns)[LM_ID_BASE]._ns_loaded;
+#ifdef SHARED
+  if (l == NULL)
+    l = &GL (dl_rtld_map);
+#endif
   assert (l->l_type != lt_loaded);
 
   if (l->l_info[DT_RUNPATH])