Commit 88b60426 authored by Vasily Gorbik's avatar Vasily Gorbik Committed by Heiko Carstens
Browse files

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: default avatarNathan Chancellor <nathan@kernel.org>
Suggested-by: default avatarMarco Elver <elver@google.com>
Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
Tested-by: default avatarMarco Elver <elver@google.com>
Tested-by: default avatarNathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/patch.git-04dd26be3043.your-ad-here.call-01630504868-ext-6188@work.hours


Signed-off-by: default avatarHeiko Carstens <hca@linux.ibm.com>
parent 81912856

arch/s390/include/asm/stacktrace.h

+10 −10
Original line number Diff line number Diff line
@@ -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.

arch/s390/include/asm/unwind.h

+4 −4
Original line number Diff line number Diff line
@@ -55,7 +55,7 @@ static inline bool unwind_error(struct unwind_state *state) 
	return state->error;

}



static inline void unwind_start(struct unwind_state *state,

static __always_inline void unwind_start(struct unwind_state *state,

					 struct task_struct *task,

					 struct pt_regs *regs,

					 unsigned long first_frame)