Commit cb20311e authored by Will Deacon's avatar Will Deacon
Browse files

Merge branch 'for-next/stacktrace' into for-next/core 

* for-next/stacktrace:
  arm64: Copy the task argument to unwind_state
  arm64: Split unwind_init()
  arm64: stacktrace: use non-atomic __set_bit
  arm64: kasan: do not instrument stacktrace.c
parents 0f05dad9 82a592c1

arch/arm64/kernel/Makefile

+5 −0
Original line number Diff line number Diff line
@@ -14,6 +14,11 @@ CFLAGS_REMOVE_return_address.o = $(CC_FLAGS_FTRACE) 
CFLAGS_REMOVE_syscall.o	 = -fstack-protector -fstack-protector-strong

CFLAGS_syscall.o	+= -fno-stack-protector



# When KASAN is enabled, a stack trace is recorded for every alloc/free, which

# can significantly impact performance. Avoid instrumenting the stack trace

# collection code to minimize this impact.

KASAN_SANITIZE_stacktrace.o := n



# It's not safe to invoke KCOV when portions of the kernel environment aren't

# available or are out-of-sync with HW state. Since `noinstr` doesn't always

# inhibit KCOV instrumentation, disable it for the entire compilation unit.

arch/arm64/kernel/stacktrace.c

+75 −24
Original line number Diff line number Diff line
@@ -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;
@@ -48,13 +50,13 @@ struct unwind_state { 
#ifdef CONFIG_KRETPROBES

	struct llist_node *kr_cur;

#endif

	struct task_struct *task;

};



static notrace void unwind_init(struct unwind_state *state, unsigned long fp,

				unsigned long pc)

static void unwind_init_common(struct unwind_state *state,

			       struct task_struct *task)

{

	state->fp = fp;

	state->pc = pc;

	state->task = task;

#ifdef CONFIG_KRETPROBES

	state->kr_cur = NULL;

#endif
@@ -72,7 +74,57 @@ static notrace void unwind_init(struct unwind_state *state, unsigned long fp, 
	state->prev_fp = 0;

	state->prev_type = STACK_TYPE_UNKNOWN;

}

NOKPROBE_SYMBOL(unwind_init);



/*

 * Start an unwind from a pt_regs.

 *

 * The unwind will begin at the PC within the regs.

 *

 * The regs must be on a stack currently owned by the calling task.

 */

static inline void unwind_init_from_regs(struct unwind_state *state,

					 struct pt_regs *regs)

{

	unwind_init_common(state, current);



	state->fp = regs->regs[29];

	state->pc = regs->pc;

}



/*

 * Start an unwind from a caller.

 *

 * The unwind will begin at the caller of whichever function this is inlined

 * into.

 *

 * The function which invokes this must be noinline.

 */

static __always_inline void unwind_init_from_caller(struct unwind_state *state)

{

	unwind_init_common(state, current);



	state->fp = (unsigned long)__builtin_frame_address(1);

	state->pc = (unsigned long)__builtin_return_address(0);

}



/*

 * Start an unwind from a blocked task.

 *

 * The unwind will begin at the blocked tasks saved PC (i.e. the caller of

 * cpu_switch_to()).

 *

 * The caller should ensure the task is blocked in cpu_switch_to() for the

 * duration of the unwind, or the unwind will be bogus. It is never valid to

 * call this for the current task.

 */

static inline void unwind_init_from_task(struct unwind_state *state,

					 struct task_struct *task)

{

	unwind_init_common(state, 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).
@@ -81,9 +133,9 @@ NOKPROBE_SYMBOL(unwind_init); 
 * 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;
@@ -117,15 +169,15 @@ static int notrace unwind_next(struct task_struct *tsk, 
		if (fp <= state->prev_fp)

			return -EINVAL;

	} else {

		set_bit(state->prev_type, state->stacks_done);

		__set_bit(state->prev_type, state->stacks_done);

	}



	/*

	 * Record this frame record's values and location. The prev_fp and

	 * prev_type are only meaningful to the next unwind_next() invocation.

	 */

	state->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp));

	state->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8));

	state->fp = READ_ONCE(*(unsigned long *)(fp));

	state->pc = READ_ONCE(*(unsigned long *)(fp + 8));

	state->prev_fp = fp;

	state->prev_type = info.type;
@@ -157,8 +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) {
@@ -166,7 +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;

	}
@@ -212,15 +263,15 @@ noinline notrace void arch_stack_walk(stack_trace_consume_fn consume_entry, 
{

	struct unwind_state state;



	if (regs)

		unwind_init(&state, regs->regs[29], regs->pc);

	else if (task == current)

		unwind_init(&state,

				(unsigned long)__builtin_frame_address(1),

				(unsigned long)__builtin_return_address(0));

	else

		unwind_init(&state, thread_saved_fp(task),

				thread_saved_pc(task));



	unwind(task, &state, consume_entry, cookie);

	if (regs) {

		if (task != current)

			return;

		unwind_init_from_regs(&state, regs);

	} else if (task == current) {

		unwind_init_from_caller(&state);

	} else {

		unwind_init_from_task(&state, task);

	}



	unwind(&state, consume_entry, cookie);

}