| Message ID | 20220223022428.58385-1-haibo.li@mediatek.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | ARM:Fix incomplete stacktrace when unwind ftrace_regs_caller | expand |
diff --git a/arch/arm/kernel/entry-ftrace.S b/arch/arm/kernel/entry-ftrace.S index a74289ebc803..eafa0c9b8992 100644 --- a/arch/arm/kernel/entry-ftrace.S +++ b/arch/arm/kernel/entry-ftrace.S @@ -75,15 +75,18 @@ add ip, sp, #12 @ move in IP the value of SP as it was @ before the push {lr} of the mcount mechanism - + UNWIND(.movsp ip) str lr, [sp, #0] @ store LR instead of PC + UNWIND(.save{pc}) @it is the caller of ftrace_regs_caller ldr lr, [sp, #8] @ get previous LR str r0, [sp, #8] @ write r0 as OLD_R0 over previous LR stmdb sp!, {ip, lr} + UNWIND(.save{ip,lr}) stmdb sp!, {r0-r11, lr} + UNWIND(.save{r0-r11,lr}) @ stack content at this point: @ 0 4 48 52 56 60 64 68 72
We can use register_ftrace_function(&ops) to register a function callback. if we set FTRACE_OPS_FL_SAVE_REGS in ftrace flags(flags in ops), then do stack unwind like dump_stack or WARN in the callback,we get incomplete stacktrace. The stack unwind ends in ftrace_regs_caller. Below is the output from test code. The test code do register_ftrace_function with FTRACE_OPS_FL_SAVE_REGS set, and set sysrq_handle_loglevel as filter,then do dump_stack in callback.It can not continue to unwind the stack from ftrace_regs_call echo 7 >/proc/sysrq-trigger sysrq: Changing Loglevel CPU: 1 PID: 145 Comm: sh Not tainted 5.17.0-rc4-00002-gb0dc07624ccd-dirty #2 [ 9.023226][ T145] Hardware name: Generic DT based system [ 9.023670][ T145] unwind_backtrace from show_stack+0x28/0x2c [ 9.024070][ T145] show_stack from dump_stack_lvl+0x48/0x54 [ 9.024298][ T145] dump_stack_lvl from ftrace_regs_call+0x4/0x18 [ 9.024650][ T145] sysrq: Loglevel set to 7 Fix it by adding unwind directives in ftrace_regs_caller. Signed-off-by: Haibo Li <haibo.li@mediatek.com> --- arch/arm/kernel/entry-ftrace.S | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)