Use __ehdr_start, if available, as fallback for AT_PHDR.

1 files changed, 18 insertions, 0 deletions

diff --git a/csu/libc-start.c b/csu/libc-start.c
index 9c4c01d..fa9085c 100644
--- a/csu/libc-start.c
+++ b/csu/libc-start.c
@@ -15,6 +15,7 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+#include <assert.h>
 #include <stdlib.h>
 #include <stdio.h>
 #include <unistd.h>
@@ -151,7 +152,24 @@ LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
   }
 #  endif
   _dl_aux_init (auxvec);
+  if (GL(dl_phdr) == NULL)
 # endif
+    {
+      /* Starting from binutils-2.23, the linker will define the
+         magic symbol __ehdr_start to point to our own ELF header
+         if it is visible in a segment that also includes the phdrs.
+         So we can set up _dl_phdr and _dl_phnum even without any
+         information from auxv.  */
+
+      extern const ElfW(Ehdr) __ehdr_start __attribute__ ((weak));
+      if (&__ehdr_start != NULL)
+        {
+          assert (__ehdr_start.e_phentsize == sizeof *GL(dl_phdr));
+          GL(dl_phdr) = (const void *) &__ehdr_start + __ehdr_start.e_phoff;
+          GL(dl_phnum) = __ehdr_start.e_phnum;
+        }
+    }
+
 # ifdef DL_SYSDEP_OSCHECK
   if (!__libc_multiple_libcs)
     {