Subject: [PATCH v13 05/11] arm64: Copy the task argument to unwind_state

From: [email-masked]
Date: Mon, 17 Jan 2022 08:56:02 -0600

From: "Madhavan T. Venkataraman" <[email-masked]>

Copy the task argument passed to arch_stack_walk() to unwind_state so that
it can be passed to unwind functions via unwind_state rather than as a
separate argument. The task is a fundamental part of the unwind state.

Signed-off-by: Madhavan T. Venkataraman <[email-masked]>
---
 arch/arm64/include/asm/stacktrace.h |  3 +++
 arch/arm64/kernel/stacktrace.c      | 29 ++++++++++++++++-------------
 2 files changed, 19 insertions(+), 13 deletions(-)

diff --git a/arch/arm64/include/asm/stacktrace.h b/arch/arm64/include/asm/stacktrace.h
index 41ec360515f6..af423f5d7ad8 100644
--- a/arch/arm64/include/asm/stacktrace.h
+++ b/arch/arm64/include/asm/stacktrace.h
@@ -51,6 +51,8 @@ struct stack_info {
  * @kr_cur:      When KRETPROBES is selected, holds the kretprobe instance
  *               associated with the most recently encountered replacement lr
  *               value.
+ *
+ * @task:        Pointer to the task structure.
  */
 struct unwind_state {
 	unsigned long fp;
@@ -61,6 +63,7 @@ struct unwind_state {
 #ifdef CONFIG_KRETPROBES
 	struct llist_node *kr_cur;
 #endif
+	struct task_struct *task;
 };
 
 extern void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk,
diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index b2b568e5deba..1b32e55735aa 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -33,8 +33,10 @@
  */

-static void unwind_init_common(struct unwind_state *state)
+static void unwind_init_common(struct unwind_state *state,
+			       struct task_struct *task)
 {
+	state->task = task;
 #ifdef CONFIG_KRETPROBES
 	state->kr_cur = NULL;
 #endif
@@ -57,9 +59,10 @@ static void unwind_init_common(struct unwind_state *state)
  * TODO: document requirements here.
  */
 static inline void unwind_init_from_regs(struct unwind_state *state,
+					 struct task_struct *task,
 					 struct pt_regs *regs)
 {
-	unwind_init_common(state);
+	unwind_init_common(state, task);
 
 	state->fp = regs->regs[29];
 	state->pc = regs->pc;
@@ -71,9 +74,10 @@ static inline void unwind_init_from_regs(struct unwind_state *state,
  * 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_from_current(struct unwind_state *state)
+static __always_inline void unwind_init_from_current(struct unwind_state *state,
+						     struct task_struct *task)
 {
-	unwind_init_common(state);
+	unwind_init_common(state, task);
 
 	state->fp = (unsigned long)__builtin_frame_address(1);
 	state->pc = (unsigned long)__builtin_return_address(0);
@@ -87,7 +91,7 @@ static __always_inline void unwind_init_from_current(struct unwind_state *state)
 static inline void unwind_init_from_task(struct unwind_state *state,
 					 struct task_struct *task)
 {
-	unwind_init_common(state);
+	unwind_init_common(state, task);
 
 	state->fp = thread_saved_fp(task);
 	state->pc = thread_saved_pc(task);
@@ -100,11 +104,11 @@ static inline void unwind_init_from_task(struct unwind_state *state,
  * records (e.g. a cycle), determined based on the location and fp value of A
  * and the location (but not the fp value) of B.
  */
-static int notrace unwind_next(struct task_struct *tsk,
-			       struct unwind_state *state)
+static int notrace unwind_next(struct unwind_state *state)
 {
 	unsigned long fp = state->fp;
 	struct stack_info info;
+	struct task_struct *tsk = state->task;
 
 	/* Final frame; nothing to unwind */
 	if (fp == (unsigned long)task_pt_regs(tsk)->stackframe)
@@ -176,8 +180,7 @@ static int notrace unwind_next(struct task_struct *tsk,
 }
 NOKPROBE_SYMBOL(unwind_next);
 
-static void notrace unwind(struct task_struct *tsk,
-			   struct unwind_state *state,
+static void notrace unwind(struct unwind_state *state,
 			   bool (*fn)(void *, unsigned long), void *data)
 {
 	while (1) {
@@ -185,7 +188,7 @@ static void notrace unwind(struct task_struct *tsk,
 
 		if (!fn(data, state->pc))
 			break;
-		ret = unwind_next(tsk, state);
+		ret = unwind_next(state);
 		if (ret < 0)
 			break;
 	}
@@ -232,11 +235,11 @@ noinline notrace void arch_stack_walk(stack_trace_consume_fn consume_entry,
 	struct unwind_state state;
 
 	if (regs)
-		unwind_init_from_regs(&state, regs);
+		unwind_init_from_regs(&state, task, regs);
 	else if (task == current)
-		unwind_init_from_current(&state);
+		unwind_init_from_current(&state, task);
 	else
 		unwind_init_from_task(&state, task);
 
-	unwind(task, &state, consume_entry, cookie);
+	unwind(&state, consume_entry, cookie);
 }
-- 
2.25.1

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