linux-kernel - [PATCH 1/6] LoongArch: Get frame info in unwind

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Date:   Thu, 15 Dec 2022 12:01:36 +0800
From:   Jinyang He <hejinyang@...ngson.cn>
To:     Huacai Chen <chenhuacai@...nel.org>,
        WANG Xuerui <kernel@...0n.name>,
        Qing Zhang <zhangqing@...ngson.cn>
Cc:     loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Subject: [PATCH 1/6] LoongArch: Get frame info in unwind_start when regs is not supported

At unwind_start, it is better to try to get its frame info even we not
support regs rather than get them outside. So that we can simply use
unwind_{start, next_frame, done} outside.

Signed-off-by: Jinyang He <hejinyang@...ngson.cn>
---
 arch/loongarch/kernel/process.c         | 12 +++---------
 arch/loongarch/kernel/unwind_guess.c    |  6 ++++++
 arch/loongarch/kernel/unwind_prologue.c | 16 +++++++++++++---
 3 files changed, 22 insertions(+), 12 deletions(-)

diff --git a/arch/loongarch/kernel/process.c b/arch/loongarch/kernel/process.c
index 502b8b950057..6ef45174ad35 100644
--- a/arch/loongarch/kernel/process.c
+++ b/arch/loongarch/kernel/process.c
@@ -197,20 +197,14 @@ 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 e2d2e4f3001f..e03864511582 100644
--- a/arch/loongarch/kernel/unwind_guess.c
+++ b/arch/loongarch/kernel/unwind_guess.c
@@ -26,6 +26,12 @@ 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 == current) {
+		state->sp = (unsigned long)__builtin_frame_address(0);
+		state->pc = (unsigned long)__builtin_return_address(0);
+	} else {
+		state->sp = thread_saved_fp(task);
+		state->pc = thread_saved_ra(task);
 	}
 
 	state->task = task;
diff --git a/arch/loongarch/kernel/unwind_prologue.c b/arch/loongarch/kernel/unwind_prologue.c
index 0f8d1451ebb8..9d51ea37782e 100644
--- a/arch/loongarch/kernel/unwind_prologue.c
+++ b/arch/loongarch/kernel/unwind_prologue.c
@@ -141,12 +141,22 @@ 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 == current) {
+		state->sp = (unsigned long)__builtin_frame_address(0);
+		state->pc = (unsigned long)__builtin_return_address(0);
+		state->ra = 0;
+	} else {
+		state->sp = thread_saved_fp(task);
+		state->pc = thread_saved_ra(task);
+		state->ra = 0;
 	}
 
 	state->task = task;
-- 
2.34.3