[PATCH v9 08/11] arm64: Rename unwinder functions, prevent them from being traced and kprobed

madvenka
2021-10-15T02:35:24Z

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

Rename unwinder functions for consistency and better naming.

- Rename start_backtrace() to unwind_start().
- Rename unwind_frame() to unwind_next().
- Rename walk_stackframe() to unwind().

Prevent the following unwinder functions from being traced:

- unwind_start()
- unwind_next()

unwind() is already prevented from being traced.

Prevent the following unwinder functions from being kprobed:

- unwind_start()

unwind_next() and unwind() are already prevented from being kprobed.

Signed-off-by: Madhavan T. Venkataraman <madvenka@linux.microsoft.com>
---
arch/arm64/kernel/stacktrace.c | 34 +++++++++++++++++++---------------
1 file changed, 19 insertions(+), 15 deletions(-)

diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index 7d32cee9ef4b..f4f3575f71fd 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -33,8 +33,8 @@
*/

-static void start_backtrace(struct stackframe *frame, unsigned long fp,
- unsigned long pc)
+static void notrace unwind_start(struct stackframe *frame, unsigned long fp,
+ unsigned long pc)
{
frame->fp = fp;
frame->pc = pc;
@@ -45,7 +45,7 @@ static void start_backtrace(struct stackframe *frame, unsigned long fp,
/*
* Prime the first unwind.
*
- * In unwind_frame() we'll check that the FP points to a valid stack,
+ * In unwind_next() we'll check that the FP points to a valid stack,
* which can't be STACK_TYPE_UNKNOWN, and the first unwind will be
* treated as a transition to whichever stack that happens to be. The
* prev_fp value won't be used, but we set it to 0 such that it is
@@ -56,6 +56,8 @@ static void start_backtrace(struct stackframe *frame, unsigned long fp,
frame->prev_type = STACK_TYPE_UNKNOWN;
}

+NOKPROBE_SYMBOL(unwind_start);
+
/*
* Unwind from one frame record (A) to the next frame record (B).
*
@@ -63,8 +65,8 @@ static void start_backtrace(struct stackframe *frame, unsigned long fp,
* 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_frame(struct task_struct *tsk,
- struct stackframe *frame)
+static int notrace unwind_next(struct task_struct *tsk,
+ struct stackframe *frame)
{
unsigned long fp = frame->fp;
struct stack_info info;
@@ -104,7 +106,7 @@ static int notrace unwind_frame(struct task_struct *tsk,

/*
* Record this frame record's values and location. The prev_fp and
- * prev_type are only meaningful to the next unwind_frame() invocation.
+ * prev_type are only meaningful to the next unwind_next() invocation.
*/
frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp));
frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8));
@@ -132,28 +134,30 @@ static int notrace unwind_frame(struct task_struct *tsk,

return 0;
}
-NOKPROBE_SYMBOL(unwind_frame);

-static void notrace walk_stackframe(struct task_struct *tsk,
- unsigned long fp, unsigned long pc,
- bool (*fn)(void *, unsigned long),
- void *data)
+NOKPROBE_SYMBOL(unwind_next);
+
+static void notrace unwind(struct task_struct *tsk,
+ unsigned long fp, unsigned long pc,
+ bool (*fn)(void *, unsigned long),
+ void *data)
{
struct stackframe frame;

- start_backtrace(&frame, fp, pc);
+ unwind_start(&frame, fp, pc);

while (1) {
int ret;

if (!fn(data, frame.pc))
break;
- ret = unwind_frame(tsk, &frame);
+ ret = unwind_next(tsk, &frame);
if (ret < 0)
break;
}
}
-NOKPROBE_SYMBOL(walk_stackframe);
+
+NOKPROBE_SYMBOL(unwind);

static bool dump_backtrace_entry(void *arg, unsigned long where)
{
@@ -208,7 +212,7 @@ noinline notrace void arch_stack_walk(stack_trace_consume_fn consume_entry,
fp = thread_saved_fp(task);
pc = thread_saved_pc(task);
}
- walk_stackframe(task, fp, pc, consume_entry, cookie);
+ unwind(task, fp, pc, consume_entry, cookie);

}

--
2.25.1