From: H.J. Lu <hjl.tools@gmail.com>
Date: Thu, 28 Sep 2017 22:28:00 +0000 (-0700)
Subject: x86: Allow undefined _DYNAMIC in static executable
X-Git-Tag: glibc-2.27~843
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=4088d8dd29ce0629eeaa7cceca02414c85d98e05;p=thirdparty%2Fglibc.git

x86: Allow undefined _DYNAMIC in static executable

When --enable-static-pie is used to build static PIE, _DYNAMIC is used
to compute the load address of static PIE.  But _DYNAMIC is undefined
when creating static executable.  This patch makes _DYNAMIC weak in PIE
libc.a so that it can be undefined.

	* sysdeps/i386/dl-machine.h (elf_machine_load_address): Allow
	undefined _DYNAMIC in PIE libc.a.
	* sysdeps/x86_64/dl-machine.h (elf_machine_load_address):
	Likewse.
---

diff --git a/ChangeLog b/ChangeLog
index e4919f2f381..11719157387 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2017-09-28  H.J. Lu  <hongjiu.lu@intel.com>
+
+	* sysdeps/i386/dl-machine.h (elf_machine_load_address): Allow
+	undefined _DYNAMIC in PIE libc.a.
+	* sysdeps/x86_64/dl-machine.h (elf_machine_load_address):
+	Likewse.
+
 2017-09-28  Wilco Dijkstra  <wdijkstr@arm.com>
 
 	* sysdeps/alpha/fpu/bits/mathinline.h: Delete file.
diff --git a/sysdeps/i386/dl-machine.h b/sysdeps/i386/dl-machine.h
index 2e17eba5c08..242c692c17a 100644
--- a/sysdeps/i386/dl-machine.h
+++ b/sysdeps/i386/dl-machine.h
@@ -54,8 +54,15 @@ elf_machine_load_address (void)
   /* Compute the difference between the runtime address of _DYNAMIC as seen
      by a GOTOFF reference, and the link-time address found in the special
      unrelocated first GOT entry.  */
-  extern Elf32_Dyn bygotoff[] asm ("_DYNAMIC") attribute_hidden;
-  return (Elf32_Addr) &bygotoff - elf_machine_dynamic ();
+#ifndef SHARED
+  extern Elf32_Dyn _DYNAMIC[] __attribute__((weak, visibility ("hidden")));
+  if (!_DYNAMIC)
+    return 0;
+#endif
+  /* The address of dynamic must be taken as non-weak to avoid dynamic
+     relocation.  */
+  extern Elf32_Dyn dynamic[] asm ("_DYNAMIC") attribute_hidden;
+  return (Elf32_Addr) &dynamic - elf_machine_dynamic ();
 }
 
 /* Set up the loaded object described by L so its unrelocated PLT
diff --git a/sysdeps/x86_64/dl-machine.h b/sysdeps/x86_64/dl-machine.h
index 6a04cbcdc98..a79e5ca2f9e 100644
--- a/sysdeps/x86_64/dl-machine.h
+++ b/sysdeps/x86_64/dl-machine.h
@@ -55,8 +55,15 @@ elf_machine_load_address (void)
   /* Compute the difference between the runtime address of _DYNAMIC as seen
      by an IP-relative reference, and the link-time address found in the
      special unrelocated first GOT entry.  */
-  extern ElfW(Dyn) _DYNAMIC[] attribute_hidden;
-  return (ElfW(Addr)) &_DYNAMIC - elf_machine_dynamic ();
+#ifndef SHARED
+  extern ElfW(Dyn) _DYNAMIC[] __attribute__((weak, visibility ("hidden")));
+  if (!_DYNAMIC)
+    return 0;
+#endif
+  /* The address of dynamic must be taken as non-weak to avoid dynamic
+     relocation.  */
+  extern ElfW(Dyn) dynamic[] asm ("_DYNAMIC") attribute_hidden;
+  return (ElfW(Addr)) &dynamic - elf_machine_dynamic ();
 }
 
 /* Set up the loaded object described by L so its unrelocated PLT