From 280270828f108be56f0c486def58acabb070244f Mon Sep 17 00:00:00 2001 From: Ulrich Weigand Date: Thu, 21 Nov 2013 07:38:05 +1100 Subject: [PATCH] powerpc: Wrong DWARF CFI in the kernel vdso for little-endian / ELFv2 I've finally tracked down why my CR signal-unwind test case still fails on little-endian. The problem turned to be that the kernel installs a signal trampoline in the vDSO, and provides a DWARF CFI record for that trampoline. This CFI describes the save location for CR: rsave (70, 38*RSIZE + (RSIZE - CRSIZE)) which is correct for big-endian, but points to the wrong word on little-endian. This is wrong no matter which ABI. In addition, for the ELFv2 ABI, we should not only provide a CFI record for register 70 (cr2), but for all CR fields separately. Strictly speaking, I guess this would mean providing two separate vDSO images, one for ELFv1 processes and one for ELFv2 processes (or maybe playing some tricks with conditional DWARF expressions). However, having CFI records for the other CR fields in ELFv1 is not actually wrong, they just will be ignored. So it seems the simplest fix would be just to always provide CFI for all the fields. Signed-off-by: Ulrich Weigand Signed-off-by: Anton Blanchard Signed-off-by: Benjamin Herrenschmidt --- arch/powerpc/kernel/vdso64/sigtramp.S | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/kernel/vdso64/sigtramp.S b/arch/powerpc/kernel/vdso64/sigtramp.S index 45ea281e9a21..542c6f422e4d 100644 --- a/arch/powerpc/kernel/vdso64/sigtramp.S +++ b/arch/powerpc/kernel/vdso64/sigtramp.S @@ -142,6 +142,13 @@ V_FUNCTION_END(__kernel_sigtramp_rt64) /* Size of CR reg in DWARF unwind info. */ #define CRSIZE 4 +/* Offset of CR reg within a full word. */ +#ifdef __LITTLE_ENDIAN__ +#define CROFF 0 +#else +#define CROFF (RSIZE - CRSIZE) +#endif + /* This is the offset of the VMX reg pointer. */ #define VREGS 48*RSIZE+33*8 @@ -181,7 +188,14 @@ 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 + (RSIZE - CRSIZE)) /* cr */ + rsave (68, 38*RSIZE + CROFF); /* cr fields */ \ + rsave (69, 38*RSIZE + CROFF); \ + rsave (70, 38*RSIZE + CROFF); \ + rsave (71, 38*RSIZE + CROFF); \ + rsave (72, 38*RSIZE + CROFF); \ + rsave (73, 38*RSIZE + CROFF); \ + rsave (74, 38*RSIZE + CROFF); \ + rsave (75, 38*RSIZE + CROFF) /* Describe where the FP regs are saved. */ #define EH_FRAME_FP \