s390/unwind: use current_frame_address() to unwind current task

current_stack_pointer() simply returns current value of %r15. If
current_stack_pointer() caller allocates stack (which is the case in
unwind code) %r15 points to a stack frame allocated for callees, meaning
current_stack_pointer() caller (e.g. stack_trace_save) will end up in
the stacktrace. This is not expected by stack_trace_save*() callers and
causes problems.

current_frame_address() on the other hand returns function stack frame
address, which matches %r15 upon function invocation. Using it in
get_stack_pointer() makes it more aligned with x86 implementation
(according to BACKTRACE_SELF_TEST output) and meets stack_trace_save*()
caller's expectations, notably KCSAN.

Also make sure unwind_start is always inlined.

Reported-by: Nathan Chancellor <[email protected]>
Suggested-by: Marco Elver <[email protected]>
Signed-off-by: Vasily Gorbik <[email protected]>
Tested-by: Marco Elver <[email protected]>
Tested-by: Nathan Chancellor <[email protected]>
Link: https://lore.kernel.org/r/patch.git-04dd26be3043.your-ad-here.call-01630504868-ext-6188@work.hours
Signed-off-by: Heiko Carstens <[email protected]>

1 files changed, 10 insertions, 10 deletions

diff --git a/arch/s390/include/asm/stacktrace.h b/arch/s390/include/asm/stacktrace.h
index 3d8a4b94c620..dd00d98804ec 100644
--- a/arch/s390/include/asm/stacktrace.h
+++ b/arch/s390/include/asm/stacktrace.h
@@ -34,16 +34,6 @@ static inline bool on_stack(struct stack_info *info,
 	return addr >= info->begin && addr + len <= info->end;
 }
 
-static __always_inline unsigned long get_stack_pointer(struct task_struct *task,
-						       struct pt_regs *regs)
-{
-	if (regs)
-		return (unsigned long) kernel_stack_pointer(regs);
-	if (task == current)
-		return current_stack_pointer();
-	return (unsigned long) task->thread.ksp;
-}
-
 /*
  * Stack layout of a C stack frame.
  */
@@ -74,6 +64,16 @@ struct stack_frame {
 	((unsigned long)__builtin_frame_address(0) -			\
 	 offsetof(struct stack_frame, back_chain))
 
+static __always_inline unsigned long get_stack_pointer(struct task_struct *task,
+						       struct pt_regs *regs)
+{
+	if (regs)
+		return (unsigned long)kernel_stack_pointer(regs);
+	if (task == current)
+		return current_frame_address();
+	return (unsigned long)task->thread.ksp;
+}
+
 /*
  * To keep this simple mark register 2-6 as being changed (volatile)
  * by the called function, even though register 6 is saved/nonvolatile.