Blackfin arch: add supporting for double fault debug handling

Signed-off-by: Robin Getz <rgetz@blackfin.uclinux.org>
Signed-off-by: Mike Frysinger <vapier.adi@gmail.com>
Signed-off-by: Bryan Wu <cooloney@kernel.org>

2 files changed, 50 insertions, 14 deletions

diff --git a/arch/blackfin/kernel/setup.c b/arch/blackfin/kernel/setup.c
index 7a82d10b4eb..8e639dc886a 100644
--- a/arch/blackfin/kernel/setup.c
+++ b/arch/blackfin/kernel/setup.c
@@ -52,7 +52,8 @@ EXPORT_SYMBOL(mtd_size);
 #endif
 
 char __initdata command_line[COMMAND_LINE_SIZE];
-unsigned int __initdata *__retx;
+void __initdata *init_retx, *init_saved_retx, *init_saved_seqstat,
+	*init_saved_icplb_fault_addr, *init_saved_dcplb_fault_addr;
 
 /* boot memmap, for parsing "memmap=" */
 #define BFIN_MEMMAP_MAX		128 /* number of entries in bfin_memmap */
@@ -782,16 +783,25 @@ void __init setup_arch(char **cmdline_p)
 
 	_bfin_swrst = bfin_read_SWRST();
 
-	/* If we double fault, reset the system - otherwise we hang forever */
-	bfin_write_SWRST(DOUBLE_FAULT);
+#ifdef CONFIG_DEBUG_DOUBLEFAULT_PRINT
+	bfin_write_SWRST(_bfin_swrst & ~DOUBLE_FAULT);
+#endif
+#ifdef CONFIG_DEBUG_DOUBLEFAULT_RESET
+	bfin_write_SWRST(_bfin_swrst | DOUBLE_FAULT);
+#endif
 
-	if (_bfin_swrst & RESET_DOUBLE)
-		/*
-		 * don't decode the address, since you don't know if this
-		 * kernel's symbol map is the same as the crashing kernel
-		 */
-		printk(KERN_INFO "Recovering from Double Fault event at %pF\n", __retx);
-	else if (_bfin_swrst & RESET_WDOG)
+	if (_bfin_swrst & RESET_DOUBLE) {
+		printk(KERN_EMERG "Recovering from DOUBLE FAULT event\n");
+#ifdef CONFIG_DEBUG_DOUBLEFAULT
+		/* We assume the crashing kernel, and the current symbol table match */
+		printk(KERN_EMERG " While handling exception (EXCAUSE = 0x%x) at %pF\n",
+			(int)init_saved_seqstat & SEQSTAT_EXCAUSE, init_saved_retx);
+		printk(KERN_NOTICE "   DCPLB_FAULT_ADDR: %pF\n", init_saved_dcplb_fault_addr);
+		printk(KERN_NOTICE "   ICPLB_FAULT_ADDR: %pF\n", init_saved_icplb_fault_addr);
+#endif
+		printk(KERN_NOTICE " The instruction at %pF caused a double exception\n",
+			init_retx);
+	} else if (_bfin_swrst & RESET_WDOG)
 		printk(KERN_INFO "Recovering from Watchdog event\n");
 	else if (_bfin_swrst & RESET_SOFTWARE)
 		printk(KERN_NOTICE "Reset caused by Software reset\n");
diff --git a/arch/blackfin/kernel/traps.c b/arch/blackfin/kernel/traps.c
index fd24e04fc19..bd41fca315d 100644
--- a/arch/blackfin/kernel/traps.c
+++ b/arch/blackfin/kernel/traps.c
@@ -68,7 +68,15 @@ void __init trap_init(void)
 	CSYNC();
 }
 
-unsigned long saved_icplb_fault_addr, saved_dcplb_fault_addr;
+/*
+ * Used to save the RETX, SEQSTAT, I/D CPLB FAULT ADDR
+ * values across the transition from exception to IRQ5.
+ * We put these in L1, so they are going to be in a valid
+ * location during exception context
+ */
+__attribute__((l1_data))
+unsigned long saved_retx, saved_seqstat,
+	saved_icplb_fault_addr, saved_dcplb_fault_addr;
 
 static void decode_address(char *buf, unsigned long address)
 {
@@ -186,9 +194,27 @@ asmlinkage void double_fault_c(struct pt_regs *fp)
 	console_verbose();
 	oops_in_progress = 1;
 	printk(KERN_EMERG "\n" KERN_EMERG "Double Fault\n");
-	dump_bfin_process(fp);
-	dump_bfin_mem(fp);
-	show_regs(fp);
+#ifdef CONFIG_DEBUG_DOUBLEFAULT_PRINT
+	if (((long)fp->seqstat &  SEQSTAT_EXCAUSE) == VEC_UNCOV) {
+		char buf[150];
+		decode_address(buf, saved_retx);
+		printk(KERN_EMERG "While handling exception (EXCAUSE = 0x%x) at %s:\n",
+			(int)saved_seqstat & SEQSTAT_EXCAUSE, buf);
+		decode_address(buf, saved_dcplb_fault_addr);
+		printk(KERN_NOTICE "   DCPLB_FAULT_ADDR: %s\n", buf);
+		decode_address(buf, saved_icplb_fault_addr);
+		printk(KERN_NOTICE "   ICPLB_FAULT_ADDR: %s\n", buf);
+
+		decode_address(buf, fp->retx);
+		printk(KERN_NOTICE "The instruction at %s caused a double exception\n",
+			buf);
+	} else
+#endif
+	{
+		dump_bfin_process(fp);
+		dump_bfin_mem(fp);
+		show_regs(fp);
+	}
 	panic("Double Fault - unrecoverable event\n");
 
 }