LO reg. gets trashed by kgdb in 2.4.x and older kernels

LO reg. gets trashed by kgdb in 2.4.x and older kernels

[Sergei Shtylyov]

Hi.

     I have discovered that the gdb-low.S trashes the LO reg. instead of 
restoring it. This was fixed for the 2.6 kernels but, as it seems, was left 
unfixed in the earlier ones (run into this on 2.4.18/2.4.20). Here's the patch
against the lastest 2.4.x revision of the file...

Index: linux/arch/mips/kernel/gdb-low.S
===================================================================
RCS file: /home/cvs/linux/arch/mips/kernel/gdb-low.S,v
retrieving revision 1.11.2.3
diff -a -u -r1.11.2.3 gdb-low.S
--- linux/arch/mips/kernel/gdb-low.S	20 Feb 2003 18:19:01 -0000	1.11.2.3
+++ linux/arch/mips/kernel/gdb-low.S	5 Jul 2004 14:48:08 -0000
@@ -283,7 +283,7 @@
  		lw	v0,GDB_FR_HI(sp)
  		lw	v1,GDB_FR_LO(sp)
  		mthi	v0
-		mtlo	v0
+		mtlo	v1
  		lw	ra,GDB_FR_REG31(sp)
  		lw	fp,GDB_FR_REG30(sp)
  		lw	gp,GDB_FR_REG28(sp)

Re: LO reg. gets trashed by kgdb in 2.4.x and older kernels

[Ralf Baechle]

On Mon, Jul 05, 2004 at 07:05:14PM +0400, Sergei Shtylyov wrote:

>     I have discovered that the gdb-low.S trashes the LO reg. instead of 
> restoring it. This was fixed for the 2.6 kernels but, as it seems, was left 
> unfixed in the earlier ones (run into this on 2.4.18/2.4.20). Here's the 
> patch
> against the lastest 2.4.x revision of the file...

Thanks.  This also was an ancient bug probably dating back to late '94 or
early '95 so all branches other than 2.6 were affected.

  Ralf