From c5cc3ca707bc916a3f326364751a41f25040aef3 Mon Sep 17 00:00:00 2001 From: Michael Ellerman Date: Fri, 22 Sep 2023 09:24:41 +1000 Subject: powerpc/stacktrace: Fix arch_stack_walk_reliable() The changes to copy_thread() made in commit eed7c420aac7 ("powerpc: copy_thread differentiate kthreads and user mode threads") inadvertently broke arch_stack_walk_reliable() because it has knowledge of the stack layout. Fix it by changing the condition to match the new logic in copy_thread(). The changes make the comments about the stack layout incorrect, rather than rephrasing them just refer the reader to copy_thread(). Also the comment about the stack backchain is no longer true, since commit edbd0387f324 ("powerpc: copy_thread add a back chain to the switch stack frame"), so remove that as well. Fixes: eed7c420aac7 ("powerpc: copy_thread differentiate kthreads and user mode threads") Reported-by: Joe Lawrence Reviewed-by: Petr Mladek Signed-off-by: Michael Ellerman Link: https://msgid.link/20230921232441.1181843-1-mpe@ellerman.id.au --- arch/powerpc/kernel/stacktrace.c | 27 +++++---------------------- 1 file changed, 5 insertions(+), 22 deletions(-) (limited to 'arch') diff --git a/arch/powerpc/kernel/stacktrace.c b/arch/powerpc/kernel/stacktrace.c index b15f15dcacb5..e6a958a5da27 100644 --- a/arch/powerpc/kernel/stacktrace.c +++ b/arch/powerpc/kernel/stacktrace.c @@ -73,29 +73,12 @@ int __no_sanitize_address arch_stack_walk_reliable(stack_trace_consume_fn consum bool firstframe; stack_end = stack_page + THREAD_SIZE; - if (!is_idle_task(task)) { - /* - * For user tasks, this is the SP value loaded on - * kernel entry, see "PACAKSAVE(r13)" in _switch() and - * system_call_common(). - * - * Likewise for non-swapper kernel threads, - * this also happens to be the top of the stack - * as setup by copy_thread(). - * - * Note that stack backlinks are not properly setup by - * copy_thread() and thus, a forked task() will have - * an unreliable stack trace until it's been - * _switch()'ed to for the first time. - */ - stack_end -= STACK_USER_INT_FRAME_SIZE; - } else { - /* - * idle tasks have a custom stack layout, - * c.f. cpu_idle_thread_init(). - */ + + // See copy_thread() for details. + if (task->flags & PF_KTHREAD) stack_end -= STACK_FRAME_MIN_SIZE; - } + else + stack_end -= STACK_USER_INT_FRAME_SIZE; if (task == current) sp = current_stack_frame(); -- cgit v1.2.3-58-ga151