[PATCH v12 04/10] arm64: Split unwind_init()

madvenka
2022-01-03T16:54:50Z

From: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com>

unwind_init() is currently a single function that initializes all of the
unwind state. Split it into the following functions and call them
appropriately:

- unwind_init_regs() - initialize from regs passed by caller.

- unwind_init_current() - initialize for the current task from the
caller of arch_stack_walk().

- unwind_init_from_task() - initialize from the saved state of a
task other than the current task. In this case, the other
task must not be running.

- unwind_init_common() - initialize fields that are common across
the above 3 cases.

This is done so that specialized initialization can be added to each case
in the future.

Signed-off-by: Madhavan T. Venkataraman <madvenka@linux.microsoft.com>
---
arch/arm64/kernel/stacktrace.c | 50 +++++++++++++++++++++++++++-------
1 file changed, 40 insertions(+), 10 deletions(-)

diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index a1a7ff93b84f..bd797e3f7789 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -33,11 +33,8 @@
*/

-static void unwind_init(struct unwind_state *state, unsigned long fp,
- unsigned long pc)
+static void unwind_init_common(struct unwind_state *state)
{
- state->fp = fp;
- state->pc = pc;
#ifdef CONFIG_KRETPROBES
state->kr_cur = NULL;
#endif
@@ -56,6 +53,40 @@ static void unwind_init(struct unwind_state *state, unsigned long fp,
state->prev_type = STACK_TYPE_UNKNOWN;
}

+/*
+ * TODO: document requirements here.
+ */
+static inline void unwind_init_regs(struct unwind_state *state,
+ struct pt_regs *regs)
+{
+ state->fp = regs->regs[29];
+ state->pc = regs->pc;
+}
+
+/*
+ * TODO: document requirements here.
+ *
+ * Note: this is always inlined, and we expect our caller to be a noinline
+ * function, such that this starts from our caller's caller.
+ */
+static __always_inline void unwind_init_current(struct unwind_state *state)
+{
+ state->fp = (unsigned long)__builtin_frame_address(1);
+ state->pc = (unsigned long)__builtin_return_address(0);
+}
+
+/*
+ * TODO: document requirements here.
+ *
+ * The caller guarantees that the task is not running.
+ */
+static inline void unwind_init_task(struct unwind_state *state,
+ struct task_struct *task)
+{
+ state->fp = thread_saved_fp(task);
+ state->pc = thread_saved_pc(task);
+}
+
/*
* Unwind from one frame record (A) to the next frame record (B).
*
@@ -194,15 +225,14 @@ noinline notrace void arch_stack_walk(stack_trace_consume_fn consume_entry,
{
struct unwind_state state;

+ unwind_init_common(&state);
+
if (regs)
- unwind_init(&state, regs->regs[29], regs->pc);
+ unwind_init_regs(&state, regs);
else if (task == current)
- unwind_init(&state,
- (unsigned long)__builtin_frame_address(1),
- (unsigned long)__builtin_return_address(0));
+ unwind_init_current(&state);
else
- unwind_init(&state, thread_saved_fp(task),
- thread_saved_pc(task));
+ unwind_init_task(&state, task);

unwind(task, &state, consume_entry, cookie);
}
--
2.25.1