[PATCH v3 09/10] lib: expose unwind_stack() and call it from panic()

[Casey Connolly]

unwind_stack() will walk the callstack and show the symbol names
if available by using the architecture-specific framepointer
implementation.

When available, call unwind_stack() during a panic to give more
information about what caused the panic and help with debugging.

Adjust the interrupt handlers to call panic_str() to avoid duplicating
the backtrace.

Signed-off-by: Casey Connolly <casey.connolly at linaro.org>
---
 arch/arm/lib/interrupts_64.c | 8 ++++----
 include/symbols.h            | 9 ++++++++-
 lib/panic.c                  | 7 +++++++
 3 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/arch/arm/lib/interrupts_64.c b/arch/arm/lib/interrupts_64.c
index 0f8ca7d343156bd53688bf4a0acd9437f041f8f5..dcba82b560d3be73233674d9b657767d8641a76e 100644
--- a/arch/arm/lib/interrupts_64.c
+++ b/arch/arm/lib/interrupts_64.c
@@ -114,10 +114,10 @@ static void print_sym(unsigned long lr)
 
 	symbol_lookup(lr, NULL, &offset, symname);
 
 	/* Print the symbol address and the offset to the LR */
-	printf("\t<%#016lx> %s+%#lx\n", lr - (gd->flags & GD_FLG_RELOC ? gd->reloc_off : 0),
-	       symname, offset);
+	printf("\t<%#016lx> %pS\n", lr - (gd->flags & GD_FLG_RELOC ? gd->reloc_off : 0),
+	       (void *)lr);
 }
 
 /**
  * show_backtrace - show backtrace using frame pointers
@@ -233,9 +233,9 @@ static void except_msg(const char *msg, struct pt_regs *pt_regs)
 	show_regs(pt_regs);
 	if (CONFIG_IS_ENABLED(FRAMEPOINTER))
 		show_backtrace(pt_regs->elr, pt_regs->regs[30], pt_regs->regs[29]);
 	show_efi_loaded_images(pt_regs);
-	panic("Resetting CPU ...\n");
+	panic_str("Resetting CPU ...\n");
 }
 
 /*
  * do_bad_sync handles the impossible case in the Synchronous Abort vector.
@@ -284,9 +284,9 @@ void do_sync(struct pt_regs *pt_regs)
 	show_regs(pt_regs);
 	if (CONFIG_IS_ENABLED(FRAMEPOINTER))
 		show_backtrace(pt_regs->elr, pt_regs->regs[30], pt_regs->regs[29]);
 	show_efi_loaded_images(pt_regs);
-	panic("Resetting CPU ...\n");
+	panic_str("Resetting CPU ...\n");
 }
 
 /*
  * do_irq handles the Irq exception.
diff --git a/include/symbols.h b/include/symbols.h
index c5267edbe768f304bc0f6235e71a39b6c3835a67..845f993060f042139df46bcc51a0180faadc35bc 100644
--- a/include/symbols.h
+++ b/include/symbols.h
@@ -4,9 +4,9 @@
 #include <string.h>
 
 #define KSYM_NAME_LEN 127
 
-#if IS_ENABLED(CONFIG_SYMBOL_LOOKUP)
+#if CONFIG_IS_ENABLED(SYMBOL_LOOKUP)
 const char * __attribute__((weak)) symbol_lookup(unsigned long addr, unsigned long *symaddr, unsigned long *offset,
 			   char *namebuf);
 #else
 static inline const char *symbol_lookup(unsigned long addr, unsigned long *symaddr, unsigned long *offset,
@@ -21,4 +21,11 @@ static inline const char *symbol_lookup(unsigned long addr, unsigned long *symad
 	namebuf[3] = '\0';
 	return namebuf;
 }
 #endif
+
+#if CONFIG_IS_ENABLED(FRAMEPOINTER)
+/**
+ * unwind_stack - unwind the callstack and print a backtrace.
+ */
+void unwind_stack(void);
+#endif
diff --git a/lib/panic.c b/lib/panic.c
index 0f578b5b5131589d215f5f4b16b95d9c9f3e8ce3..6f8bd7cc1eef7e5d97ba925bef65cc46924b4418 100644
--- a/lib/panic.c
+++ b/lib/panic.c
@@ -14,8 +14,9 @@
 #include <command.h>
 #endif
 #include <linux/delay.h>
 #include <stdio.h>
+#include <symbols.h>
 
 static void panic_finish(void) __attribute__ ((noreturn));
 
 static void panic_finish(void)
@@ -44,8 +45,14 @@ void panic(const char *fmt, ...)
 	va_list args;
 	va_start(args, fmt);
 	vprintf(fmt, args);
 	va_end(args);
+
+	if (CONFIG_IS_ENABLED(FRAMEPOINTER)) {
+		puts("\n");
+		unwind_stack();
+	}
+
 #endif
 	panic_finish();
 }
 

-- 
2.50.0