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 <nathan@kernel.org> Suggested-by: Marco Elver <elver@google.com> Signed-off-by: Vasily Gorbik <gor@linux.ibm.com> Tested-by: Marco Elver <elver@google.com> Tested-by: Nathan 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: Heiko Carstens <hca@linux.ibm.com>
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@ -34,16 +34,6 @@ static inline bool on_stack(struct stack_info *info,
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return addr >= info->begin && addr + len <= info->end;
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}
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static __always_inline unsigned long get_stack_pointer(struct task_struct *task,
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struct pt_regs *regs)
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{
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if (regs)
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return (unsigned long) kernel_stack_pointer(regs);
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if (task == current)
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return current_stack_pointer();
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return (unsigned long) task->thread.ksp;
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}
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/*
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* Stack layout of a C stack frame.
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*/
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@ -74,6 +64,16 @@ struct stack_frame {
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((unsigned long)__builtin_frame_address(0) - \
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offsetof(struct stack_frame, back_chain))
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static __always_inline unsigned long get_stack_pointer(struct task_struct *task,
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struct pt_regs *regs)
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{
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if (regs)
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return (unsigned long)kernel_stack_pointer(regs);
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if (task == current)
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return current_frame_address();
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return (unsigned long)task->thread.ksp;
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}
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/*
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* To keep this simple mark register 2-6 as being changed (volatile)
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* by the called function, even though register 6 is saved/nonvolatile.
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@ -55,10 +55,10 @@ static inline bool unwind_error(struct unwind_state *state)
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return state->error;
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}
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static inline void unwind_start(struct unwind_state *state,
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struct task_struct *task,
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struct pt_regs *regs,
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unsigned long first_frame)
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static __always_inline void unwind_start(struct unwind_state *state,
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struct task_struct *task,
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struct pt_regs *regs,
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unsigned long first_frame)
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{
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task = task ?: current;
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first_frame = first_frame ?: get_stack_pointer(task, regs);
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