[yocto] [prelink-cross][PATCH] Always create a conflict for R_ARM_TLS_DESC relocs

[Maciej W. Rozycki]

Hi,

 This is a bit obscure.  In my testing, for the purpose of upstreaming, of 
the glibc change to support ARM TLS descriptors in prelinked binaries (cf 
upstream BZ #17078, https://sourceware.org/bugzilla/show_bug.cgi?id=17078) 
I have come across a problem where all programs prelinked against glibc 
binaries using ARM TLS descriptors themselves segfaulted in the normal 
exit path, where libc.so's own TLS destructors are called.  I have tracked 
it down to the GOT entry (pointed to by the DT_TLSDESC_GOT dynamic tag) 
meant to point to the lazy TLS descriptor resolver (pointed to by the 
DT_TLSDESC_PLT dynamic tag) being left uninitialised and therefore NULL.  
An attempt to call that resolver caused therefore a segfault.

 The cause of this lack of initialisation turned out to be an omission in 
the original fix (dated 2011-04-13 in ChangeLog.cross), that didn't ensure 
that a conflict entry is created even for these R_ARM_TLS_DESC relocations 
that refer to a local symbol.  Somehow it didn't trigger in testing back 
when implemented, perhaps glibc didn't require or access the missing entry 
in code handling TLS destructors then.  Such an entry is needed, because 
for prelinked binaries the DT_TLSDESC_GOT GOT entry is only initialised by 
the dynamic linker when a conflict is resolved.  The change below enforces 
this conflict entry creation.

 This fix removes 33 failures in prelink testing with glibc built using 
ARM TLS descriptors, that is with the `-mtls-dialect=gnu2' GCC option in 
effect (that is not the default unless explicitly requested at GCC build 
time):

FAIL -> PASS: default/prelink.sum:cxx1.sh
FAIL -> PASS: default/prelink.sum:cxx2.sh
FAIL -> PASS: default/prelink.sum:cxx3.sh
FAIL -> PASS: default/prelink.sum:layout1.sh
FAIL -> PASS: default/prelink.sum:layout2.sh
FAIL -> PASS: default/prelink.sum:reloc1.sh
FAIL -> PASS: default/prelink.sum:reloc10.sh
FAIL -> PASS: default/prelink.sum:reloc11.sh
FAIL -> PASS: default/prelink.sum:reloc2.sh
FAIL -> PASS: default/prelink.sum:reloc3.sh
FAIL -> PASS: default/prelink.sum:reloc4.sh
FAIL -> PASS: default/prelink.sum:reloc5.sh
FAIL -> PASS: default/prelink.sum:reloc6.sh
FAIL -> PASS: default/prelink.sum:reloc7.sh
FAIL -> PASS: default/prelink.sum:reloc8.sh
FAIL -> PASS: default/prelink.sum:reloc9.sh
FAIL -> PASS: default/prelink.sum:shuffle1.sh
FAIL -> PASS: default/prelink.sum:shuffle2.sh
FAIL -> PASS: default/prelink.sum:shuffle3.sh
FAIL -> PASS: default/prelink.sum:shuffle4.sh
FAIL -> PASS: default/prelink.sum:shuffle5.sh
FAIL -> PASS: default/prelink.sum:shuffle6.sh
FAIL -> PASS: default/prelink.sum:shuffle7.sh
FAIL -> PASS: default/prelink.sum:shuffle8.sh
FAIL -> PASS: default/prelink.sum:shuffle9.sh
FAIL -> PASS: default/prelink.sum:tls1.sh
FAIL -> PASS: default/prelink.sum:tls2.sh
FAIL -> PASS: default/prelink.sum:tls3.sh
FAIL -> PASS: default/prelink.sum:tls4.sh
FAIL -> PASS: default/prelink.sum:tls5.sh
FAIL -> PASS: default/prelink.sum:tls6.sh
FAIL -> PASS: default/prelink.sum:tls7.sh
FAIL -> PASS: default/prelink.sum:undo1.sh

 Please apply.

2014-07-22  Maciej W. Rozycki  <macro at codesourcery.com>

	* src/arch-arm.c (arm_prelink_conflict_rel): Always create a 
	conflict for R_ARM_TLS_DESC relocs.
	(arm_prelink_conflict_rela): Likewise.

  Maciej

prelink-arm-tlsdesc-conflict-always.diff
Index: trunk/src/arch-arm.c
===================================================================
--- trunk.orig/src/arch-arm.c	2014-07-17 23:26:08.000000000 +0100
+++ trunk/src/arch-arm.c	2014-07-18 04:18:53.790564615 +0100
@@ -416,7 +416,9 @@ arm_prelink_conflict_rel (DSO *dso, stru
 	case R_ARM_TLS_DTPMOD32:
 	case R_ARM_TLS_TPOFF32:
 	  break;
-
+	/* Likewise TLS_DESC.  */
+	case R_ARM_TLS_DESC:
+	  break;
 	default:
 	  return 0;
 	}
@@ -526,7 +528,9 @@ arm_prelink_conflict_rela (DSO *dso, str
 	case R_ARM_TLS_DTPMOD32:
 	case R_ARM_TLS_TPOFF32:
 	  break;
-
+	/* Likewise TLS_DESC.  */
+	case R_ARM_TLS_DESC:
+	  break;
 	default:
 	  return 0;
 	}