[Bug ld/418] New: ld builds shared library incorrectly for some eh_frame encodings

[mendell at ca dot ibm dot com]

Hardware Environment:
cpu     : POWER4+ (gq) 
clock   : 1453MHz      
revision: 2.1  

Firmware Environment:

Software Environment:
Linux version 2.4.21-9.0.1.EL (address@hidden) (gcc version 
3.2.3 20030502 (Red Hat Linux 3.2.3-26)) #1 SMP Mon Feb 9 22:10:20 EST 
2004      

Steps to Reproduce:
1. cc -m64 -shared t.s
2. objdump -s a.out | less +/eh_frame

Actual Results:
Contents of section .eh_frame:                                 
 12660 0000001c 00000000 017a504c 00047841  .........zPL..xA   
 12670 0a000000 00000000 0000130c 01000000  ................   
 12680 0000003c 00000024 00000000 00002250  ...<...$......"P   
 12690 00000000 0000013c 04effed9 d7429f01  .......<.....B..   

Expected Results:
Contents of section .eh_frame:                                 
 12660 0000001c 00000000 017a504c 00047841  .........zPL..xA   
 12670 0a000000 00000000 0000030c 01000000  ................   <<< 03, not 13
 12680 0000003c 00000024 00000000 00002250  ...<...$......"P   
 12690 00000000 0000013c 04effed9 d7429f01  .......<.....B..   
Additional Information:

The xlC C++ compiler generates eh_frame tables that use an LSDA encoding of 
DW_EH_PE_udata4 (value 0x03).  When linked to make a shared library, the 
linker rewrites the encoding to 0x13 (DW_EH_PE_udata4 | DW_EH_PE_pcrel).  
Unfortunately, this doesn't return the same information when 
_Unwind_GetLanguageSpecificData is invoked.

The problem code is in bfd/elf-eh-frame.c:
          if (info->shared                                        
              && (cie.lsda_encoding & 0xf0) == DW_EH_PE_absptr)   
            cie.make_lsda_relative = 1;                           
                                           
The problem is that the encoding is 0x3, and DW_EH_PE_absptr == 0.  
Unfortunately, the mask with 0xf0 makes 0x3 LOOK LIKE DW_EH_PE_absptr.
This causes cie.make_lsda_relative to be set to 1, when it shouldn't.

This affects all distributions, not just RedHat.  It is a problem for DB/2 
using xlC to improve performance on Linux/PPC.

-- 
           Summary: ld builds shared library incorrectly for some eh_frame
                    encodings
           Product: binutils
           Version: 2.15
            Status: NEW
          Severity: normal
          Priority: P2
         Component: ld
        AssignedTo: unassigned at sources dot redhat dot com
        ReportedBy: mendell at ca dot ibm dot com
                CC: bug-binutils at gnu dot org


http://sources.redhat.com/bugzilla/show_bug.cgi?id=418

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