@@ -103,12 +103,12 @@ 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)
{
+ /*
+ * Note that 'where' can have a physical address, but it's 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 +172,17 @@ 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);
}
}
Unlike perf callchain relying on walk_stackframe(), dump_backtrace() has its own backtrace logic. A major difference between them is the moment a symbol is recorded. Perf writes down a symobl *before* calling unwind_frame(), but dump_backtrace() prints it out *after* unwind_frame(). As a result, the last valid symbol cannot be hooked in case of dump_backtrace(). This patch addresses the issue as synchronising dump_backtrace() with perf callchain. A simple test and its results are as follows: - crash trigger $ sudo echo c > /proc/sysrq-trigger - current status Call trace: [<fffffe00003dc738>] sysrq_handle_crash+0x24/0x30 [<fffffe00003dd2ac>] __handle_sysrq+0x128/0x19c [<fffffe00003dd730>] write_sysrq_trigger+0x60/0x74 [<fffffe0000249fc4>] proc_reg_write+0x84/0xc0 [<fffffe00001f2638>] __vfs_write+0x44/0x104 [<fffffe00001f2e60>] vfs_write+0x98/0x1a8 [<fffffe00001fe730>] SyS_write+0x50/0xb0 - with this change Call trace: [<fffffe00003dc738>] sysrq_handle_crash+0x24/0x30 [<fffffe00003dd2ac>] __handle_sysrq+0x128/0x19c [<fffffe00003dd730>] write_sysrq_trigger+0x60/0x74 [<fffffe0000249fc4>] proc_reg_write+0x84/0xc0 [<fffffe00001f2638>] __vfs_write+0x44/0x104 [<fffffe00001f2e60>] vfs_write+0x98/0x1a8 [<fffffe00001fe730>] SyS_write+0x50/0xb0 [<fffffe00000939ec>] el0_svc_naked+0x20/0x28 Note that this patch does not cover a case where MMU is disabled. The last stack frame of swapper, for example, has PC in a form of physical address. Unfortunately, a simple conversion using phys_to_virt() cannot cover all scenarios since PC is retrieved from LR - 4, not LR. It is a big tradeoff to change both head.S and unwind_frame() for only a few of symbols in *.S. Thus, this hunk does not take care of the case. Cc: AKASHI Takahiro <takahiro.akashi@linaro.org> Cc: James Morse <james.morse@arm.com> Cc: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Jungseok Lee <jungseoklee85@gmail.com> --- Changes since v1: - Added an example to the commit msg, per Will - Modified a comment. arch/arm64/kernel/traps.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-)