[PATCH v6 10/18] perf: Have get_perf_callchain() return NULL if crosstask and user are set

Steven Rostedt
2025-04-25T14:56:15Z

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 <jpoimboe@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
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;
+
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