From: Vasily Gorbik gor@linux.ibm.com
[ Upstream commit 88b604263f3d6eedae0b1c2c3bbd602d1e2e8775 ]
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-016305048... Signed-off-by: Heiko Carstens hca@linux.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/s390/include/asm/stacktrace.h | 20 ++++++++++---------- arch/s390/include/asm/unwind.h | 8 ++++---- 2 files changed, 14 insertions(+), 14 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. diff --git a/arch/s390/include/asm/unwind.h b/arch/s390/include/asm/unwind.h index de9006b0cfeb..5ebf534ef753 100644 --- a/arch/s390/include/asm/unwind.h +++ b/arch/s390/include/asm/unwind.h @@ -55,10 +55,10 @@ static inline bool unwind_error(struct unwind_state *state) return state->error; }
-static inline void unwind_start(struct unwind_state *state, - struct task_struct *task, - struct pt_regs *regs, - unsigned long first_frame) +static __always_inline void unwind_start(struct unwind_state *state, + struct task_struct *task, + struct pt_regs *regs, + unsigned long first_frame) { task = task ?: current; first_frame = first_frame ?: get_stack_pointer(task, regs);