diff mbox series

[v5,2/3] arm64: stacktrace: Relax frame record alignment requirement to 8 bytes

Message ID 20210513165427.1133795-2-pcc@google.com (mailing list archive)
State New, archived
Headers show
Series [v5,1/3] arm64: Change the on_*stack functions to take a size argument | expand

Commit Message

Peter Collingbourne May 13, 2021, 4:54 p.m. UTC 
The AAPCS places no requirements on the alignment of the frame
record. In theory it could be placed anywhere, although it seems
sensible to require it to be aligned to 8 bytes. With an upcoming
enhancement to tag-based KASAN Clang will begin creating frame records
located at an address that is only aligned to 8 bytes. Accommodate
such frame records in the stack unwinding code.

As pointed out by Mark Rutland, the userspace stack unwinding code
has the same problem, so fix it there as well.

Signed-off-by: Peter Collingbourne <pcc@google.com>
Link: https://linux-review.googlesource.com/id/Ia22c375230e67ca055e9e4bb639383567f7ad268
Acked-by: Andrey Konovalov <andreyknvl@gmail.com>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>
---
v5:
- fix rebase

v4:
- rebase to 5.13rc1

v2:
- fix it in the userspace unwinding code as well

 arch/arm64/kernel/perf_callchain.c | 2 +-
 arch/arm64/kernel/stacktrace.c     | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

Comments

Mark Brown May 13, 2021, 5:06 p.m. UTC | #1 
On Thu, May 13, 2021 at 09:54:26AM -0700, Peter Collingbourne wrote:
> The AAPCS places no requirements on the alignment of the frame
> record. In theory it could be placed anywhere, although it seems
> sensible to require it to be aligned to 8 bytes. With an upcoming
> enhancement to tag-based KASAN Clang will begin creating frame records
> located at an address that is only aligned to 8 bytes. Accommodate
> such frame records in the stack unwinding code.

Reviewed-by: Mark Brown <broonie@kernel.org>
diff mbox series

Patch

diff --git a/arch/arm64/kernel/perf_callchain.c b/arch/arm64/kernel/perf_callchain.c
index 88ff471b0bce..4a72c2727309 100644
--- a/arch/arm64/kernel/perf_callchain.c
+++ b/arch/arm64/kernel/perf_callchain.c
@@ -116,7 +116,7 @@  void perf_callchain_user(struct perf_callchain_entry_ctx *entry,
 		tail = (struct frame_tail __user *)regs->regs[29];
 
 		while (entry->nr < entry->max_stack &&
-		       tail && !((unsigned long)tail & 0xf))
+		       tail && !((unsigned long)tail & 0x7))
 			tail = user_backtrace(tail, entry);
 	} else {
 #ifdef CONFIG_COMPAT
diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index 2fecbf152e80..bc672bfd7ac7 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -68,7 +68,7 @@  int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
 	unsigned long fp = frame->fp;
 	struct stack_info info;
 
-	if (fp & 0xf)
+	if (fp & 0x7)
 		return -EINVAL;
 
 	if (!tsk)