To support livepatch, we need to add arch_stack_walk_reliable to support reliable stacktrace according to https://docs.kernel.org/livepatch/reliable-stacktrace.html#requirements report stacktrace is not reliable if we are not able to unwind the stack by sframe unwinder and fallback to FP based unwinder Signed-off-by: Weinan Liu <wnliu@xxxxxxxxxx> --- arch/arm64/include/asm/stacktrace/common.h | 2 + arch/arm64/kernel/stacktrace.c | 47 +++++++++++++++++++++- 2 files changed, 47 insertions(+), 2 deletions(-) diff --git a/arch/arm64/include/asm/stacktrace/common.h b/arch/arm64/include/asm/stacktrace/common.h index 19edae8a5b1a..26449cd402db 100644 --- a/arch/arm64/include/asm/stacktrace/common.h +++ b/arch/arm64/include/asm/stacktrace/common.h @@ -26,6 +26,7 @@ struct stack_info { * @stacks: An array of stacks which can be unwound. * @nr_stacks: The number of stacks in @stacks. * @cfa: The sp value at the call site of the current function. + * @unreliable: Stacktrace is unreliable. */ struct unwind_state { unsigned long fp; @@ -36,6 +37,7 @@ struct unwind_state { int nr_stacks; #ifdef CONFIG_SFRAME_UNWINDER unsigned long cfa; + bool unreliable; #endif }; diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c index c035adb8fe8a..eab16dc05bb5 100644 --- a/arch/arm64/kernel/stacktrace.c +++ b/arch/arm64/kernel/stacktrace.c @@ -310,11 +310,16 @@ kunwind_next(struct kunwind_state *state) case KUNWIND_SOURCE_TASK: case KUNWIND_SOURCE_REGS_PC: #ifdef CONFIG_SFRAME_UNWINDER - err = unwind_next_frame_sframe(&state->common); + if (!state->common.unreliable) + err = unwind_next_frame_sframe(&state->common); /* Fallback to FP based unwinder */ - if (err) + if (err || state->common.unreliable) { err = kunwind_next_frame_record(state); + /* Mark its stacktrace result as unreliable if it is unwindable via FP */ + if (!err) + state->common.unreliable = true; + } #else err = kunwind_next_frame_record(state); #endif @@ -446,6 +451,44 @@ noinline noinstr void arch_stack_walk(stack_trace_consume_fn consume_entry, kunwind_stack_walk(arch_kunwind_consume_entry, &data, task, regs); } +#ifdef CONFIG_SFRAME_UNWINDER +struct kunwind_reliable_consume_entry_data { + stack_trace_consume_fn consume_entry; + void *cookie; + bool unreliable; +}; + +static __always_inline bool +arch_kunwind_reliable_consume_entry(const struct kunwind_state *state, void *cookie) +{ + struct kunwind_reliable_consume_entry_data *data = cookie; + + if (state->common.unreliable) { + data->unreliable = true; + return false; + } + return data->consume_entry(data->cookie, state->common.pc); +} + +noinline notrace int arch_stack_walk_reliable( + stack_trace_consume_fn consume_entry, + void *cookie, struct task_struct *task) +{ + struct kunwind_reliable_consume_entry_data data = { + .consume_entry = consume_entry, + .cookie = cookie, + .unreliable = false, + }; + + kunwind_stack_walk(arch_kunwind_reliable_consume_entry, &data, task, NULL); + + if (data.unreliable) + return -EINVAL; + + return 0; +} +#endif + struct bpf_unwind_consume_entry_data { bool (*consume_entry)(void *cookie, u64 ip, u64 sp, u64 fp); void *cookie; -- 2.48.1.262.g85cc9f2d1e-goog
