linux-kernel - [PATCH 3/6] LoongArch: Adjust PC value when unwind next frame in prologue unwinder

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Date:   Thu, 15 Dec 2022 12:01:38 +0800
From:   Jinyang He <hejinyang@...ngson.cn>
To:     Huacai Chen <chenhuacai@...nel.org>,
        WANG Xuerui <kernel@...0n.name>,
        Qing Zhang <zhangqing@...ngson.cn>
Cc:     loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Subject: [PATCH 3/6] LoongArch: Adjust PC value when unwind next frame in prologue unwinder

When state->first is not set, the PC is a return address in the
previous frame. We need to adjust it value in case overflow to the
next symbol.

Signed-off-by: Jinyang He <hejinyang@...ngson.cn>
---
 arch/loongarch/kernel/unwind_prologue.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/loongarch/kernel/unwind_prologue.c b/arch/loongarch/kernel/unwind_prologue.c
index 35cab7f77c6b..d464c533c64f 100644
--- a/arch/loongarch/kernel/unwind_prologue.c
+++ b/arch/loongarch/kernel/unwind_prologue.c
@@ -48,7 +48,7 @@ static bool unwind_by_prologue(struct unwind_state *state)
 {
 	long frame_ra = -1;
 	unsigned long frame_size = 0;
-	unsigned long size, offset, pc = state->pc;
+	unsigned long size, offset, pc;
 	struct pt_regs *regs;
 	struct stack_info *info = &state->stack_info;
 	union loongarch_instruction *ip, *ip_end;
@@ -70,6 +70,10 @@ static bool unwind_by_prologue(struct unwind_state *state)
 		return true;
 	}
 
+	/* When first is not set, the PC is a return address in the previous frame.
+	 * We need to adjust it value in case overflow to the next symbol.
+	 */
+	pc = state->pc - (state->first ? 0 : LOONGARCH_INSN_SIZE);
 	if (!kallsyms_lookup_size_offset(pc, &size, &offset))
 		return false;
 
-- 
2.34.3