[PATCH v2 1/6] LoongArch: Get frame info in unwind_start when regs is not supported

From: Jinyang He
Date: Thu Dec 29 2022 - 01:16:36 EST


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@xxxxxxxxxxx>
---
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..a1bc7c852000 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 || task == NULL) {
+ 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..b8b830b69a48 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 || task == NULL) {
+ 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