| Message ID | 20220103165212.9303-8-madvenka@linux.microsoft.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: Reorganize the unwinder and implement stack trace reliability checks | expand |
On Mon, Jan 03, 2022 at 10:52:09AM -0600, madvenka@linux.microsoft.com wrote: > From: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com> > > There are some kernel features and conditions that make a stack trace > unreliable. Callers may require the unwinder to detect these cases. > E.g., livepatch. Reviwed-by: Mark Brown <broonie@kernel.org>
Thanks for the review. Do you have any comments on: [PATCH v12 04/10] arm64: Split unwind_init() [PATCH v12 10/10] arm64: Select HAVE_RELIABLE_STACKTRACE Madhavan On 1/5/22 10:58 AM, Mark Brown wrote: > On Mon, Jan 03, 2022 at 10:52:09AM -0600, madvenka@linux.microsoft.com wrote: >> From: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com> >> >> There are some kernel features and conditions that make a stack trace >> unreliable. Callers may require the unwinder to detect these cases. >> E.g., livepatch. > > Reviwed-by: Mark Brown <broonie@kernel.org> > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >
On Wed, Jan 05, 2022 at 05:58:59PM -0600, Madhavan T. Venkataraman wrote: > Thanks for the review. Do you have any comments on: > > [PATCH v12 04/10] arm64: Split unwind_init() > [PATCH v12 10/10] arm64: Select HAVE_RELIABLE_STACKTRACE Not yet.
diff --git a/arch/arm64/include/asm/stacktrace.h b/arch/arm64/include/asm/stacktrace.h index 9d1fddc26586..47d4be69799a 100644 --- a/arch/arm64/include/asm/stacktrace.h +++ b/arch/arm64/include/asm/stacktrace.h @@ -63,6 +63,8 @@ struct stack_info { * @final_fp Pointer to the final frame. * * @failed: Unwind failed. + * + * @reliable: Stack trace is reliable. */ struct unwind_state { unsigned long fp; @@ -79,6 +81,7 @@ struct unwind_state { void *cookie; unsigned long final_fp; bool failed; + bool reliable; }; extern void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk, diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c index af0949f028c9..54c3396a65c3 100644 --- a/arch/arm64/kernel/stacktrace.c +++ b/arch/arm64/kernel/stacktrace.c @@ -18,6 +18,25 @@ #include <asm/stack_pointer.h> #include <asm/stacktrace.h> +/* + * Check the stack frame for conditions that make further unwinding unreliable. + */ +static void unwind_check_reliability(struct unwind_state *state) +{ + if (state->fp == state->final_fp) { + /* Final frame; no more unwind, no need to check reliability */ + return; + } + + /* + * If the PC is not a known kernel text address, then we cannot + * be sure that a subsequent unwind will be reliable, as we + * don't know that the code follows our unwind requirements. + */ + if (!__kernel_text_address(state->pc)) + state->reliable = false; +} + /* * AArch64 PCS assigns the frame pointer to x29. * @@ -64,6 +83,8 @@ static void unwind_init_common(struct unwind_state *state, /* Stack trace terminates here. */ state->final_fp = (unsigned long)task_pt_regs(task)->stackframe; + + state->reliable = true; } /* @@ -202,10 +223,14 @@ static void notrace unwind_next(struct unwind_state *state) } NOKPROBE_SYMBOL(unwind_next); -static void notrace unwind(struct unwind_state *state) +static bool notrace unwind(struct unwind_state *state) { - while (unwind_continue(state)) + unwind_check_reliability(state); + while (unwind_continue(state)) { unwind_next(state); + unwind_check_reliability(state); + } + return !state->failed && state->reliable; } NOKPROBE_SYMBOL(unwind);