dump_backtrace() has its own backtrace logic unlike perf callchain which
relies on walk_stackframe(). They behave differently when a symbol is
recorded. Perf writes it down *before* calling unwind_frame(), but
dump_backtrace() prints it out *after* unwind_frame(). As a result, the
last valid symbol is not added to a list in case of dump_backtrace().
This patch catches up the last symbol as synchronising dump_backtrace()
with perf callchain. However, the patch does not cover a case where MMU
is disabled. That is, a physical address can be stored in stack frame,
but it's not handled. For example, a swapper process falls into this case.
Unlike a swapper from a secondary core, a swapper on a boot cpu, which
starting from __mmap_switched(), can't be tracked down with a simple
conversion, phys_to_virt(), because PC is retrieved from LR - 4, not LR.
It is a big tradeoff to change both head.S and unwind_frame() structure
for a few of symbols in *.S, so this hunk does not take care of the case.
Cc: AKASHI Takahiro <takahiro.aka...@linaro.org>
Cc: James Morse <james.mo...@arm.com>
Cc: Mark Rutland <mark.rutl...@arm.com>
Signed-off-by: Jungseok Lee <jungseokle...@gmail.com>
---
arch/arm64/kernel/traps.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)
diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index f93aae5..4ddb928 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -103,12 +103,13 @@ static void dump_mem(const char *lvl, const char *str,
unsigned long bottom,
set_fs(fs);
}
-static void dump_backtrace_entry(unsigned long where, unsigned long stack)
+static void dump_backtrace_entry(unsigned long where)
{
+ /*
+ * The highest stack frame of a swapper process stores PC in a form
+ * of physical address, but this case is not handled.
+ */
print_ip_sym(where);
- if (in_exception_text(where))
- dump_mem("", "Exception stack", stack,
- stack + sizeof(struct pt_regs), false);
}
static void dump_instr(const char *lvl, struct pt_regs *regs)
@@ -172,12 +173,17 @@ static void dump_backtrace(struct pt_regs *regs, struct
task_struct *tsk)
pr_emerg("Call trace:\n");
while (1) {
unsigned long where = frame.pc;
+ unsigned long stack;
int ret;
+ dump_backtrace_entry(where);
ret = unwind_frame(&frame);
if (ret < 0)
break;
- dump_backtrace_entry(where, frame.sp);
+ stack = frame.sp;
+ if (in_exception_text(where))
+ dump_mem("", "Exception stack", stack,
+ stack + sizeof(struct pt_regs), false);
}
}
--
2.5.0
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
