Re: [PATCH v15 2/6] arm64: Copy the task argument to unwind_state

Mark Rutland
2022-06-26T07:41:04Z

On Fri, Jun 17, 2022 at 04:07:13PM -0500, madvenka@linux.microsoft.com wrote:
> From: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com>
>
> 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 <madvenka@linux.microsoft.com>
> Reviewed-by: Mark Brown <broonie@kernel.org>

Acked-by: Mark Rutland <mark.rutland@arm.com>

Mark.

> ---
> arch/arm64/kernel/stacktrace.c | 33 ++++++++++++++++++++-------------
> 1 file changed, 20 insertions(+), 13 deletions(-)
>
> diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
> index e44f93ff25f0..8e43444d50e2 100644
> --- a/arch/arm64/kernel/stacktrace.c
> +++ b/arch/arm64/kernel/stacktrace.c
> @@ -38,6 +38,8 @@
> * @kr_cur: When KRETPROBES is selected, holds the kretprobe instance
> * associated with the most recently encountered replacement lr
> * value.
> + *
> + * @task: The task being unwound.
> */
> struct unwind_state {
> unsigned long fp;
> @@ -48,10 +50,13 @@ struct unwind_state {
> #ifdef CONFIG_KRETPROBES
> struct llist_node *kr_cur;
> #endif
> + struct task_struct *task;
> };
>
> -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
> @@ -80,7 +85,7 @@ static void unwind_init_common(struct unwind_state *state)
> static inline void unwind_init_from_regs(struct unwind_state *state,
> struct pt_regs *regs)
> {
> - unwind_init_common(state);
> + unwind_init_common(state, current);
>
> state->fp = regs->regs[29];
> state->pc = regs->pc;
> @@ -96,7 +101,7 @@ static inline void unwind_init_from_regs(struct unwind_state *state,
> */
> static __always_inline void unwind_init_from_caller(struct unwind_state *state)
> {
> - unwind_init_common(state);
> + unwind_init_common(state, current);
>
> state->fp = (unsigned long)__builtin_frame_address(1);
> state->pc = (unsigned long)__builtin_return_address(0);
> @@ -115,7 +120,7 @@ static __always_inline void unwind_init_from_caller(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);
> @@ -128,9 +133,9 @@ 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)
> {
> + struct task_struct *tsk = state->task;
> unsigned long fp = state->fp;
> struct stack_info info;
>
> @@ -204,8 +209,7 @@ 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,
> stack_trace_consume_fn consume_entry, void *cookie)
> {
> while (1) {
> @@ -213,7 +217,7 @@ static void notrace unwind(struct task_struct *tsk,
>
> if (!consume_entry(cookie, state->pc))
> break;
> - ret = unwind_next(tsk, state);
> + ret = unwind_next(state);
> if (ret < 0)
> break;
> }
> @@ -259,12 +263,15 @@ noinline notrace void arch_stack_walk(stack_trace_consume_fn consume_entry,
> {
> struct unwind_state state;
>
> - if (regs)
> + if (regs) {
> + if (task != current)
> + return;
> unwind_init_from_regs(&state, regs);
> - else if (task == current)
> + } else if (task == current) {
> unwind_init_from_caller(&state);
> - else
> + } else {
> unwind_init_from_task(&state, task);
> + }
>
> - unwind(task, &state, consume_entry, cookie);
> + unwind(&state, consume_entry, cookie);
> }
> --
> 2.25.1