On Fri, May 9, 2025 at 9:52 AM Steven Rostedt <[email protected]> wrote:
>
> From: Josh Poimboeuf <[email protected]>
>
> get_perf_callchain() doesn't support cross-task unwinding for user space
> stacks, have it return NULL if both the crosstask and user arguments are
> set.
>
> Signed-off-by: Josh Poimboeuf <[email protected]>
> Signed-off-by: Steven Rostedt (Google) <[email protected]>
> ---
> kernel/events/callchain.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c
> index b0f5bd228cd8..abf258913ab6 100644
> --- a/kernel/events/callchain.c
> +++ b/kernel/events/callchain.c
> @@ -224,6 +224,10 @@ get_perf_callchain(struct pt_regs *regs, bool kernel,
> bool user,
> struct perf_callchain_entry_ctx ctx;
> int rctx, start_entry_idx;
>
> + /* crosstask is not supported for user stacks */
> + if (crosstask && user)
> + return NULL;
I think get_perf_callchain() supports requesting both user and kernel
stack traces, and if it's crosstask, you can still get kernel (but not
user) stack, if I'm reading the code correctly.
So by just returning NULL early you will change this behavior, no?
> +
> entry = get_callchain_entry(&rctx);
> if (!entry)
> return NULL;
> @@ -249,9 +253,6 @@ get_perf_callchain(struct pt_regs *regs, bool kernel,
> bool user,
> }
>
> if (regs) {
> - if (crosstask)
> - goto exit_put;
> -
> if (add_mark)
> perf_callchain_store_context(&ctx,
> PERF_CONTEXT_USER);
>
> @@ -261,7 +262,6 @@ get_perf_callchain(struct pt_regs *regs, bool kernel,
> bool user,
> }
> }
>
> -exit_put:
> put_callchain_entry(rctx);
>
> return entry;
> --
> 2.47.2
>
>
>
