linux-kernel - [RFC PATCH v2 3/8] arm64: Terminate the stack trace at TASK_FRAME and EL0

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Date:   Mon, 15 Mar 2021 11:57:55 -0500
From:   madvenka@...ux.microsoft.com
To:     broonie@...nel.org, mark.rutland@....com, jpoimboe@...hat.com,
        jthierry@...hat.com, catalin.marinas@....com, will@...nel.org,
        linux-arm-kernel@...ts.infradead.org,
        live-patching@...r.kernel.org, linux-kernel@...r.kernel.org,
        madvenka@...ux.microsoft.com
Subject: [RFC PATCH v2 3/8] arm64: Terminate the stack trace at TASK_FRAME and EL0_FRAME

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

Implement the following checks in the unwinder to detect the terminating
frame reliably:

	- The frame must end in task_pt_regs(task)->stackframe.

	- The frame type must be either TASK_FRAME or EL0_FRAME.

Signed-off-by: Madhavan T. Venkataraman <madvenka@...ux.microsoft.com>
---
 arch/arm64/kernel/stacktrace.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index ad20981dfda4..504cd161339d 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -43,16 +43,22 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
 {
 	unsigned long fp = frame->fp;
 	struct stack_info info;
+	struct pt_regs *regs;
 
-	/* Terminal record; nothing to unwind */
-	if (!fp)
-		return -ENOENT;
+	if (!tsk)
+		tsk = current;
+	regs = task_pt_regs(tsk);
 
-	if (fp & 0xf)
+	/* Terminal record, nothing to unwind */
+	if (fp == (unsigned long) regs->stackframe) {
+		if (regs->frame_type == TASK_FRAME ||
+		    regs->frame_type == EL0_FRAME)
+			return -ENOENT;
 		return -EINVAL;
+	}
 
-	if (!tsk)
-		tsk = current;
+	if (!fp || fp & 0xf)
+		return -EINVAL;
 
 	if (!on_accessible_stack(tsk, fp, &info))
 		return -EINVAL;
-- 
2.25.1