[PATCH] powerpc: Fix 64 bits vDSO dwarf info for CR register

[Benjamin Herrenschmidt]

The current DWARF info for CR are incorrect causing the gcc unwinder to
go to lunch if taking a segfault in the vdso. This patch fixes it.

Problem identified by Andrew Haley, and fix provided by Jakub Jelinek
(thanks !).

Unfortunately, a bug in gcc cause it to not quite work either, but that
is being fixed separately with something around the lines of:

linux-unwind.h:

     fs->regs.reg[R_CR2].loc.offset = (long) &regs->ccr - new_cfa;
+    /* CR? regs are just 32-bit and PPC is big-endian.  */
+    fs->regs.reg[R_CR2].loc.offset += sizeof (long) - 4;

(According to Jakub)

Signed-off-by: Benjamin Herrenschmidt <benh at kernel.crashing.org>
---

Index: linux-work/arch/powerpc/kernel/vdso64/sigtramp.S
===================================================================
--- linux-work.orig/arch/powerpc/kernel/vdso64/sigtramp.S	2007-10-17 13:32:49.000000000 +1000
+++ linux-work/arch/powerpc/kernel/vdso64/sigtramp.S	2007-10-17 13:34:18.000000000 +1000
@@ -134,13 +134,16 @@ V_FUNCTION_END(__kernel_sigtramp_rt64)
 9:
 
 /* This is where the pt_regs pointer can be found on the stack.  */
-#define PTREGS 128+168+56
+#define PTREGS	128+168+56
 
 /* Size of regs.  */
-#define RSIZE 8
+#define RSIZE	8
+
+/* Size of CR reg in DWARF unwind info. */
+#define CRSIZE	4
 
 /* This is the offset of the VMX reg pointer.  */
-#define VREGS 48*RSIZE+33*8
+#define VREGS	48*RSIZE+33*8
 
 /* Describe where general purpose regs are saved.  */
 #define EH_FRAME_GEN \
@@ -178,7 +181,7 @@ V_FUNCTION_END(__kernel_sigtramp_rt64)
   rsave (31, 31*RSIZE);							\
   rsave (67, 32*RSIZE);		/* ap, used as temp for nip */		\
   rsave (65, 36*RSIZE);		/* lr */				\
-  rsave (70, 38*RSIZE)		/* cr */
+  rsave (70, 38*RSIZE + (RSIZE - CRSIZE)) /* cr */
 
 /* Describe where the FP regs are saved.  */
 #define EH_FRAME_FP \