[PATCH RFC] m68k/kernel: fix register dump for ColdFire format 4 exception frame

[Michael Schmitz <schmitzmic@gmail.com>]

On ColdFire, no extra processor state information is saved after an
exception frame. Take fault status and vector number from pt_regs.fmtvec
instead of from the longword following the exception frame (which would
be pt_regs.fmtvec from a prior exception on the stack).
Likewise, report the PC from pt_regs (redundant).

Untested ...

Signed-off-by: Michael Schmitz <schmitzmic@gmail.com>
---
 arch/m68k/kernel/traps.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/arch/m68k/kernel/traps.c b/arch/m68k/kernel/traps.c
index 60759ba3cbd4..ec5cf9703e15 100644
--- a/arch/m68k/kernel/traps.c
+++ b/arch/m68k/kernel/traps.c
@@ -868,6 +868,21 @@ void show_registers(struct pt_regs *regs)
 		addr += sizeof(fp->un.fmt3);
 		break;
 	case 0x4:
+#if defined(CONFIG_COLDFIRE) && defined(CONFIG_MMU)
+		/* ColdFire format 4 frame has all information in pt_regs */
+		if (CPU_IS_COLDFIRE) {
+			unsigned int fs = (regs->vector & 0x3) |
+					 ((regs->vector & 0xc00) >> 8);
+			int vector = (regs->vector >> 2) & 0xff;
+
+			pr_cont("fault status=%0x vector=%u pc=%08lx\n",
+				fs, vector, regs->pc);
+			/* Frame format 4 extra size on ColdFire is 0
+			 * so don't advance addr
+			 */
+			break;
+		}
+#endif /* CONFIG_COLDFIRE && CONFIG_MMU */
 		if (CPU_IS_060)
 			pr_cont("fault addr=%08lx fslw=%08lx\n",
 				fp->un.fmt4.effaddr, fp->un.fmt4.pc);
-- 
2.17.1