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

[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:


Signed-off-by: Benjamin Herrenschmidt <benh@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 \

[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@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 \

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

[Jakub Jelinek]

On Wed, Oct 17, 2007 at 02:26:50PM +1000, Benjamin Herrenschmidt wrote:
> 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;

Small correction.  If vdso is present, then fixing the vdso is all that is
needed, the above mentioned code is used only if the vdso is not present
(or if glibc doesn't support the vdso).

	Jakub

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

[Andrew Haley]

Jakub Jelinek writes:
 > On Wed, Oct 17, 2007 at 02:26:50PM +1000, Benjamin Herrenschmidt wrote:
 > > 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;
 > 
 > Small correction.  If vdso is present, then fixing the vdso is all that is
 > needed, the above mentioned code is used only if the vdso is not present
 > (or if glibc doesn't support the vdso).

Perhaps we should test this change with a hacked libgcc, just to make
sure it fixes the bug.

Andrew.

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