Patch "LoongArch: Get frame info in unwind_start() when regs is not available" has been added to the 6.1-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    LoongArch: Get frame info in unwind_start() when regs is not available

to the 6.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     loongarch-get-frame-info-in-unwind_start-when-regs-i.patch
and it can be found in the queue-6.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 4d0c27a7175599d5a02d0611f42c0aa72e06ccc3
Author: Jinyang He <hejinyang@xxxxxxxxxxx>
Date:   Tue Jan 17 11:42:16 2023 +0800

    LoongArch: Get frame info in unwind_start() when regs is not available
    
    [ Upstream commit 429a9671f235c94fc4b5d6687308714b74adc820 ]
    
    At unwind_start(), it is better to get its frame info here rather than
    get them outside, even we don't have 'regs'. In this way we can simply
    use unwind_{start, next_frame, done} outside.
    
    Signed-off-by: Jinyang He <hejinyang@xxxxxxxxxxx>
    Signed-off-by: Huacai Chen <chenhuacai@xxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/arch/loongarch/kernel/process.c b/arch/loongarch/kernel/process.c
index ddb8ba4eb399..90a5de746332 100644
--- a/arch/loongarch/kernel/process.c
+++ b/arch/loongarch/kernel/process.c
@@ -185,20 +185,14 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 
 unsigned long __get_wchan(struct task_struct *task)
 {
-	unsigned long pc;
+	unsigned long pc = 0;
 	struct unwind_state state;
 
 	if (!try_get_task_stack(task))
 		return 0;
 
-	unwind_start(&state, task, NULL);
-	state.sp = thread_saved_fp(task);
-	get_stack_info(state.sp, state.task, &state.stack_info);
-	state.pc = thread_saved_ra(task);
-#ifdef CONFIG_UNWINDER_PROLOGUE
-	state.type = UNWINDER_PROLOGUE;
-#endif
-	for (; !unwind_done(&state); unwind_next_frame(&state)) {
+	for (unwind_start(&state, task, NULL);
+	     !unwind_done(&state); unwind_next_frame(&state)) {
 		pc = unwind_get_return_address(&state);
 		if (!pc)
 			break;
diff --git a/arch/loongarch/kernel/unwind_guess.c b/arch/loongarch/kernel/unwind_guess.c
index 5afa6064d73e..0c20e5184de6 100644
--- a/arch/loongarch/kernel/unwind_guess.c
+++ b/arch/loongarch/kernel/unwind_guess.c
@@ -25,6 +25,12 @@ void unwind_start(struct unwind_state *state, struct task_struct *task,
 	if (regs) {
 		state->sp = regs->regs[3];
 		state->pc = regs->csr_era;
+	} else if (task && task != current) {
+		state->sp = thread_saved_fp(task);
+		state->pc = thread_saved_ra(task);
+	} else {
+		state->sp = (unsigned long)__builtin_frame_address(0);
+		state->pc = (unsigned long)__builtin_return_address(0);
 	}
 
 	state->task = task;
diff --git a/arch/loongarch/kernel/unwind_prologue.c b/arch/loongarch/kernel/unwind_prologue.c
index 4571c3c87cd4..1c5b65756144 100644
--- a/arch/loongarch/kernel/unwind_prologue.c
+++ b/arch/loongarch/kernel/unwind_prologue.c
@@ -111,12 +111,22 @@ void unwind_start(struct unwind_state *state, struct task_struct *task,
 		    struct pt_regs *regs)
 {
 	memset(state, 0, sizeof(*state));
+	state->type = UNWINDER_PROLOGUE;
 
-	if (regs &&  __kernel_text_address(regs->csr_era)) {
-		state->pc = regs->csr_era;
+	if (regs) {
 		state->sp = regs->regs[3];
+		state->pc = regs->csr_era;
 		state->ra = regs->regs[1];
-		state->type = UNWINDER_PROLOGUE;
+		if (!__kernel_text_address(state->pc))
+			state->type = UNWINDER_GUESS;
+	} else if (task && task != current) {
+		state->sp = thread_saved_fp(task);
+		state->pc = thread_saved_ra(task);
+		state->ra = 0;
+	} else {
+		state->sp = (unsigned long)__builtin_frame_address(0);
+		state->pc = (unsigned long)__builtin_return_address(0);
+		state->ra = 0;
 	}
 
 	state->task = task;