[PATCH][GOLD] Treat R_ARM_PREL31 as a function call in Target_arm::Scan::get_reference_flags

[Doug Kwan (關振德)]

Hi,

    This patch fixes a number of test breakage in which R_ARM_PREL31
relocations point to weak symbols of personality routines in ARM
unwind tables.  The existing code does not general PLTs for references
from R_ARM_PREL31 and ultimately it causes tests to crash on ARM.  The
patch was tested on armv7l-linux-gnueabi in qemu.

-Doug

2010-12-07  Doug Kwan  <dougkwan@google.com>

        * arm.cc (Target_arm::Scan::get_reference_flags): Treat R_ARM_PREL31
        like function call relocations.
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Index: gold/arm.cc
===================================================================
RCS file: /cvs/src/src/gold/arm.cc,v
retrieving revision 1.128
diff -u -u -p -r1.128 arm.cc
--- gold/arm.cc	11 Nov 2010 10:43:30 -0000	1.128
+++ gold/arm.cc	8 Dec 2010 02:07:24 -0000
@@ -7646,7 +7646,6 @@ Target_arm<big_endian>::Scan::get_refere
     case elfcpp::R_ARM_THM_MOVW_BREL:
     case elfcpp::R_ARM_GOTOFF32:
     case elfcpp::R_ARM_GOTOFF12:
-    case elfcpp::R_ARM_PREL31:
     case elfcpp::R_ARM_SBREL31:
       return Symbol::RELATIVE_REF;
 
@@ -7659,6 +7658,10 @@ Target_arm<big_endian>::Scan::get_refere
     case elfcpp::R_ARM_THM_JUMP6:
     case elfcpp::R_ARM_THM_JUMP11:
     case elfcpp::R_ARM_THM_JUMP8:
+    // R_ARM_PREL31 is not used to relocate call/jump instructions but
+    // in unwind tables. It may point to functions via PLTs.
+    // So we treat it like call/jump relocations above.
+    case elfcpp::R_ARM_PREL31:
       return Symbol::FUNCTION_CALL | Symbol::RELATIVE_REF;
 
     case elfcpp::R_ARM_GOT_BREL: