linux-kernel - [PATCH v2 1/5] KVM: arm64: Factor out common stack unwinding logic

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Date:   Mon,  2 May 2022 12:12:01 -0700
From:   Kalesh Singh <kaleshsingh@...gle.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     mark.rutland@....com, broonie@...nel.org, will@...nel.org,
        maz@...nel.org, qperret@...gle.com, tabba@...gle.com,
        surenb@...gle.com, kernel-team@...roid.com,
        Kalesh Singh <kaleshsingh@...gle.com>,
        James Morse <james.morse@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Peter Collingbourne <pcc@...gle.com>,
        Alexei Starovoitov <ast@...nel.org>,
        "Madhavan T. Venkataraman" <madvenka@...ux.microsoft.com>,
        Andrew Jones <drjones@...hat.com>,
        Keir Fraser <keirf@...gle.com>, Marco Elver <elver@...gle.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        Zenghui Yu <yuzenghui@...wei.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 1/5] KVM: arm64: Factor out common stack unwinding logic

Factor out the stack unwinding logic common to both the host kernel and
the nVHE hypersivor into __unwind_next(). This allows for reuse in the
nVHE hypervisor stack unwinding (later in this series).

Signed-off-by: Kalesh Singh <kaleshsingh@...gle.com>
---
 arch/arm64/kernel/stacktrace.c | 36 +++++++++++++++++++++++-----------
 1 file changed, 25 insertions(+), 11 deletions(-)

diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index 0467cb79f080..ee60c279511c 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -81,23 +81,19 @@ 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 task_struct *tsk,
+				 struct unwind_state *state,
+				 struct stack_info *info)
 {
 	unsigned long fp = state->fp;
-	struct stack_info info;
-
-	/* Final frame; nothing to unwind */
-	if (fp == (unsigned long)task_pt_regs(tsk)->stackframe)
-		return -ENOENT;
 
 	if (fp & 0x7)
 		return -EINVAL;
 
-	if (!on_accessible_stack(tsk, fp, 16, &info))
+	if (!on_accessible_stack(tsk, fp, 16, info))
 		return -EINVAL;
 
-	if (test_bit(info.type, state->stacks_done))
+	if (test_bit(info->type, state->stacks_done))
 		return -EINVAL;
 
 	/*
@@ -113,7 +109,7 @@ static int notrace unwind_next(struct task_struct *tsk,
 	 * stack to another, it's never valid to unwind back to that first
 	 * stack.
 	 */
-	if (info.type == state->prev_type) {
+	if (info->type == state->prev_type) {
 		if (fp <= state->prev_fp)
 			return -EINVAL;
 	} else {
@@ -127,7 +123,25 @@ static int notrace unwind_next(struct task_struct *tsk,
 	state->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp));
 	state->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8));
 	state->prev_fp = fp;
-	state->prev_type = info.type;
+	state->prev_type = info->type;
+
+	return 0;
+}
+NOKPROBE_SYMBOL(__unwind_next);
+
+static int notrace unwind_next(struct task_struct *tsk,
+			       struct unwind_state *state)
+{
+	struct stack_info info;
+	int err;
+
+	/* Final frame; nothing to unwind */
+	if (state->fp == (unsigned long)task_pt_regs(tsk)->stackframe)
+		return -ENOENT;
+
+	err = __unwind_next(tsk, state, &info);
+	if (err)
+		return err;
 
 	state->pc = ptrauth_strip_insn_pac(state->pc);
 
-- 
2.36.0.464.gb9c8b46e94-goog