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

PATCH Sergei Shtylyov 2 participants 2 messages Jul 5, 2004 – Jul 8, 2004 MIPS

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Sergei Shtylyov

author

2004-07-05 15:04 UTC #0 lore raw

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

arch/mips/kernel/gdb-low.S +1 -1

diff -a -u -r1.11.2.3 gdb-low.S
@@ -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)

Ralf Baechle

2004-07-08 11:43 UTC #1 lore raw

Quoted 5 lines · Sergei Shtylyov

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