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x86: Allow undefined _DYNAMIC in static executable

Message ID 20170928122207.GA25931@gmail.com
State New, archived
Headers show

Commit Message

H.J. Lu Sept. 28, 2017, 12:22 p.m. UTC
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.

Any comments?


H.J.
---
	* 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.
---
 sysdeps/i386/dl-machine.h   | 17 +++++++++++++++--
 sysdeps/x86_64/dl-machine.h | 13 +++++++++++++
 2 files changed, 28 insertions(+), 2 deletions(-)
diff mbox

Patch

diff --git a/sysdeps/i386/dl-machine.h b/sysdeps/i386/dl-machine.h
index 2e17eba5c0..0a5c83398f 100644
--- a/sysdeps/i386/dl-machine.h
+++ b/sysdeps/i386/dl-machine.h
@@ -54,8 +54,21 @@  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 ();
+#ifdef SHARED
+  extern Elf32_Dyn _DYNAMIC[] attribute_hidden;
+  return (Elf32_Addr) &_DYNAMIC - elf_machine_dynamic ();
+#else
+  extern Elf32_Dyn _DYNAMIC[] __attribute__((weak, visibility ("hidden")));
+  if (_DYNAMIC)
+    {
+      /* 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 ();
+    }
+  else
+    return 0;
+#endif
 }
 
 /* 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 6a04cbcdc9..4114c798f0 100644
--- a/sysdeps/x86_64/dl-machine.h
+++ b/sysdeps/x86_64/dl-machine.h
@@ -55,8 +55,21 @@  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.  */
+#ifdef SHARED
   extern ElfW(Dyn) _DYNAMIC[] attribute_hidden;
   return (ElfW(Addr)) &_DYNAMIC - elf_machine_dynamic ();
+#else
+  extern ElfW(Dyn) _DYNAMIC[] __attribute__((weak, visibility ("hidden")));
+  if (_DYNAMIC)
+    {
+      /* 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 ();
+    }
+  else
+    return 0;
+#endif
 }
 
 /* Set up the loaded object described by L so its unrelocated PLT