Blackfin: improve double fault debug handling

Since the hardware only provides reporting for the last exception handled,
and the values are valid only when executing the exception handler, we
need to save the context for reporting at a later point.  While we do this
for one exception, it doesn't work properly when handling a second one as
the original exception is clobbered by the double fault.  So when double
fault debugging is enabled, create a dedicated shadow of these values and
save/restore out of there.  Now the crash report properly displays the
first exception as well as the second one.

Signed-off-by: Graf Yang <graf.yang@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>

2 files changed, 10 insertions, 4 deletions

diff --git a/arch/blackfin/kernel/asm-offsets.c b/arch/blackfin/kernel/asm-offsets.c
index 8ad4f2c69961..f05d1b99b0ef 100644
--- a/arch/blackfin/kernel/asm-offsets.c
+++ b/arch/blackfin/kernel/asm-offsets.c
@@ -153,6 +153,12 @@ int main(void)
         DEFINE(PDA_ICPLB, offsetof(struct blackfin_pda, icplb_fault_addr));
         DEFINE(PDA_RETX, offsetof(struct blackfin_pda, retx));
         DEFINE(PDA_SEQSTAT, offsetof(struct blackfin_pda, seqstat));
+#ifdef CONFIG_DEBUG_DOUBLEFAULT
+        DEFINE(PDA_DF_DCPLB, offsetof(struct blackfin_pda, dcplb_doublefault_addr));
+        DEFINE(PDA_DF_ICPLB, offsetof(struct blackfin_pda, icplb_doublefault_addr));
+        DEFINE(PDA_DF_SEQSTAT, offsetof(struct blackfin_pda, seqstat_doublefault));
+        DEFINE(PDA_DF_RETX, offsetof(struct blackfin_pda, retx_doublefault));
+#endif
 #ifdef CONFIG_SMP
         /* Inter-core lock (in L2 SRAM) */
         DEFINE(SIZEOF_CORELOCK, sizeof(struct corelock_slot));
diff --git a/arch/blackfin/kernel/traps.c b/arch/blackfin/kernel/traps.c
index 644e35e33553..0904430d4137 100644
--- a/arch/blackfin/kernel/traps.c
+++ b/arch/blackfin/kernel/traps.c
@@ -229,12 +229,12 @@ asmlinkage void double_fault_c(struct pt_regs *fp)
         if (((long)fp->seqstat &  SEQSTAT_EXCAUSE) == VEC_UNCOV) {
                 unsigned int cpu = smp_processor_id();
                 char buf[150];
-                decode_address(buf, cpu_pda[cpu].retx);
+                decode_address(buf, cpu_pda[cpu].retx_doublefault);
                 printk(KERN_EMERG "While handling exception (EXCAUSE = 0x%x) at %s:\n",
-                        (unsigned int)cpu_pda[cpu].seqstat & SEQSTAT_EXCAUSE, buf);
-                decode_address(buf, cpu_pda[cpu].dcplb_fault_addr);
+                        (unsigned int)cpu_pda[cpu].seqstat_doublefault & SEQSTAT_EXCAUSE, buf);
+                decode_address(buf, cpu_pda[cpu].dcplb_doublefault_addr);
                 printk(KERN_NOTICE "   DCPLB_FAULT_ADDR: %s\n", buf);
-                decode_address(buf, cpu_pda[cpu].icplb_fault_addr);
+                decode_address(buf, cpu_pda[cpu].icplb_doublefault_addr);
                 printk(KERN_NOTICE "   ICPLB_FAULT_ADDR: %s\n", buf);
 
                 decode_address(buf, fp->retx);