[patch 2.6.6] Workaround linker bug

[patch 2.6.6] Workaround linker bug

[Keith Owens]

Building 2.6.6-ia64-040521, using GNU ld version 2.14.90.0.4 20030523.
__gp is sometimes set incorrectly.  Instead of being .got + 0x2000000,
it is set to .data + 0x2000000, which breaks some LTOFF22 and GPREL22
entries.

This is non-deterministic, changing the path name to the kernel tree
which changes the size of some messages in .data is enough to make the
linker get it right.  Force __gp to be based on .got.

Index: linux/arch/ia64/kernel/vmlinux.lds.S
=================================--- linux.orig/arch/ia64/kernel/vmlinux.lds.S	Thu May 27 15:08:02 2004
+++ linux/arch/ia64/kernel/vmlinux.lds.S	Thu May 27 15:16:11 2004
@@ -202,11 +202,10 @@ SECTIONS
   .data : AT(ADDR(.data) - LOAD_OFFSET)
 	{ *(.data) *(.data1) *(.gnu.linkonce.d*) CONSTRUCTORS }
 
-  . = ALIGN(16);
-  __gp = . + 0x200000;	/* gp must be 16-byte aligned for exc. table */
-
+  . = ALIGN(16);	/* gp must be 16-byte aligned for exc. table */
   .got : AT(ADDR(.got) - LOAD_OFFSET)
 	{ *(.got.plt) *(.got) }
+  __gp = ADDR(.got) + 0x200000;
   /* We want the small data sections together, so single-instruction offsets
      can access them all, and initialized data all before uninitialized, so
      we can shorten the on-disk segment size.  */

Re: [patch 2.6.6] Workaround linker bug

[H. J. Lu]

On Thu, May 27, 2004 at 03:39:41PM +1000, Keith Owens wrote:
> Building 2.6.6-ia64-040521, using GNU ld version 2.14.90.0.4 20030523.
> __gp is sometimes set incorrectly.  Instead of being .got + 0x2000000,
> it is set to .data + 0x2000000, which breaks some LTOFF22 and GPREL22
> entries.
> 

There are a few ia64 linker fixes since 2.14.90.0.4. One of them is

http://sources.redhat.com/ml/binutils/2003-11/msg00000.html

among many others. May I suggest you try 2.15.90.0.3?


H.J.

Re: [patch 2.6.6] Workaround linker bug

[David Mosberger]

>>>>> On Thu, 27 May 2004 15:39:41 +1000, Keith Owens <kaos@sgi.com> said:

  Keith> Building 2.6.6-ia64-040521, using GNU ld version 2.14.90.0.4
  Keith> 20030523.  __gp is sometimes set incorrectly.  Instead of
  Keith> being .got + 0x2000000, it is set to .data + 0x2000000, which
  Keith> breaks some LTOFF22 and GPREL22 entries.

  Keith> This is non-deterministic, changing the path name to the
  Keith> kernel tree which changes the size of some messages in .data
  Keith> is enough to make the linker get it right.  Force __gp to be
  Keith> based on .got.

I can't say I have seen this myself, but the workaround is sensible enough,
so I applied the patch.

Thanks, and sorry for the delay (still working through my backlog...).

	--david