linux-kernel - [PATCH v2 2/4] LoongArch: Handle percpu handler address for ORC unwinder

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Message-ID: <20260121095911.20868-3-yangtiezhu@loongson.cn>
Date: Wed, 21 Jan 2026 17:59:09 +0800
From: Tiezhu Yang <yangtiezhu@...ngson.cn>
To: Huacai Chen <chenhuacai@...nel.org>
Cc: loongarch@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/4] LoongArch: Handle percpu handler address for ORC unwinder

After commit 4cd641a79e69 ("LoongArch: Remove unnecessary checks for
ORC unwinder"), the system can not boot normally under some configs,
there are many error messages "cannot find unwind pc".

The kernel boots normally with the defconfig, so no problem found out
at the first time. Here is one way to reproduce:

  cd linux
  make mrproper defconfig -j"$(nproc)"
  scripts/config -e KASAN
  make olddefconfig all -j"$(nproc)"
  sudo make modules_install
  sudo make install
  sudo reboot

The address that can not unwind is not a valid kernel address which is
between "pcpu_handlers[cpu]" and "pcpu_handlers[cpu] + vec_sz" due to
the code of eentry was copied to the new area of pcpu_handlers[cpu] in
setup_tlb_handler(), handle this special case to get the valid address
to unwind normally.

Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
---
 arch/loongarch/include/asm/setup.h |  2 ++
 arch/loongarch/kernel/unwind_orc.c | 15 +++++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/arch/loongarch/include/asm/setup.h b/arch/loongarch/include/asm/setup.h
index 3c2fb16b11b6..79eb63e749f9 100644
--- a/arch/loongarch/include/asm/setup.h
+++ b/arch/loongarch/include/asm/setup.h
@@ -14,6 +14,8 @@
 
 extern unsigned long eentry;
 extern unsigned long tlbrentry;
+extern unsigned long pcpu_handlers[NR_CPUS];
+extern long exception_handlers[VECSIZE * 128 / sizeof(long)];
 extern char init_command_line[COMMAND_LINE_SIZE];
 extern void tlb_init(int cpu);
 extern void cpu_cache_init(void);
diff --git a/arch/loongarch/kernel/unwind_orc.c b/arch/loongarch/kernel/unwind_orc.c
index d6b3688a1ce9..e0c0dc22eb08 100644
--- a/arch/loongarch/kernel/unwind_orc.c
+++ b/arch/loongarch/kernel/unwind_orc.c
@@ -351,6 +351,21 @@ EXPORT_SYMBOL_GPL(unwind_start);
 static inline unsigned long bt_address(unsigned long ra)
 {
 	extern unsigned long eentry;
+#if defined(CONFIG_NUMA) && !defined(CONFIG_PREEMPT_RT)
+	int cpu;
+	int vec_sz = sizeof(exception_handlers);
+
+	for_each_possible_cpu(cpu) {
+		if (!pcpu_handlers[cpu])
+			continue;
+
+		if (ra >= pcpu_handlers[cpu] &&
+		    ra < pcpu_handlers[cpu] + vec_sz) {
+			ra = eentry + (ra - pcpu_handlers[cpu]);
+			break;
+		}
+	}
+#endif
 
 	if (ra >= eentry && ra < eentry +  EXCCODE_INT_END * VECSIZE) {
 		unsigned long func;
-- 
2.42.0