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Date:   Thu, 14 Oct 2021 21:34:09 -0500
From:   madvenka@...ux.microsoft.com
To:     mark.rutland@....com, broonie@...nel.org, jpoimboe@...hat.com,
        ardb@...nel.org, nobuta.keiya@...itsu.com,
        sjitindarsingh@...il.com, catalin.marinas@....com, will@...nel.org,
        jmorris@...ei.org, linux-arm-kernel@...ts.infradead.org,
        live-patching@...r.kernel.org, linux-kernel@...r.kernel.org,
        madvenka@...ux.microsoft.com
Subject: [PATCH v9 05/11] arm64: Make dump_stacktrace() use arch_stack_walk()

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

Currently, dump_stacktrace() in ARM64 code walks the stack using
start_backtrace() and unwind_frame(). Make it use arch_stack_walk()
instead. This makes maintenance easier.

Signed-off-by: Madhavan T. Venkataraman <madvenka@...ux.microsoft.com>
---
 arch/arm64/kernel/stacktrace.c | 44 +++++-----------------------------
 1 file changed, 6 insertions(+), 38 deletions(-)

diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index 8982a2b78acf..776c4debb5a7 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -151,24 +151,20 @@ void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame,
 }
 NOKPROBE_SYMBOL(walk_stackframe);
 
-static void dump_backtrace_entry(unsigned long where, const char *loglvl)
+static bool dump_backtrace_entry(void *arg, unsigned long where)
 {
+	char *loglvl = arg;
 	printk("%s %pSb\n", loglvl, (void *)where);
+	return true;
 }
 
 void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk,
 		    const char *loglvl)
 {
-	struct stackframe frame;
-	int skip = 0;
-
 	pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
 
-	if (regs) {
-		if (user_mode(regs))
-			return;
-		skip = 1;
-	}
+	if (regs && user_mode(regs))
+		return;
 
 	if (!tsk)
 		tsk = current;
@@ -176,36 +172,8 @@ void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk,
 	if (!try_get_task_stack(tsk))
 		return;
 
-	if (tsk == current) {
-		start_backtrace(&frame,
-				(unsigned long)__builtin_frame_address(0),
-				(unsigned long)dump_backtrace);
-	} else {
-		/*
-		 * task blocked in __switch_to
-		 */
-		start_backtrace(&frame,
-				thread_saved_fp(tsk),
-				thread_saved_pc(tsk));
-	}
-
 	printk("%sCall trace:\n", loglvl);
-	do {
-		/* skip until specified stack frame */
-		if (!skip) {
-			dump_backtrace_entry(frame.pc, loglvl);
-		} else if (frame.fp == regs->regs[29]) {
-			skip = 0;
-			/*
-			 * Mostly, this is the case where this function is
-			 * called in panic/abort. As exception handler's
-			 * stack frame does not contain the corresponding pc
-			 * at which an exception has taken place, use regs->pc
-			 * instead.
-			 */
-			dump_backtrace_entry(regs->pc, loglvl);
-		}
-	} while (!unwind_frame(tsk, &frame));
+	arch_stack_walk(dump_backtrace_entry, (void *)loglvl, tsk, regs);
 
 	put_task_stack(tsk);
 }
-- 
2.25.1

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