linux-kernel - [PATCH 2/3] LoongArch: Disable instrumentation for setup

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Message-ID: <20260127084619.1140692-2-chenhuacai@loongson.cn>
Date: Tue, 27 Jan 2026 16:46:18 +0800
From: Huacai Chen <chenhuacai@...ngson.cn>
To: Huacai Chen <chenhuacai@...nel.org>
Cc: loongarch@...ts.linux.dev,
	Xuefeng Li <lixuefeng@...ngson.cn>,
	Guo Ren <guoren@...nel.org>,
	Xuerui Wang <kernel@...0n.name>,
	Jiaxun Yang <jiaxun.yang@...goat.com>,
	linux-kernel@...r.kernel.org,
	Tiezhu Yang <yangtiezhu@...ngson.cn>,
	stable@...r.kernel.org,
	Huacai Chen <chenhuacai@...ngson.cn>
Subject: [PATCH 2/3] LoongArch: Disable instrumentation for setup_ptwalker()

From: Tiezhu Yang <yangtiezhu@...ngson.cn>

According to Documentation/dev-tools/kasan.rst, software KASAN modes use
compiler instrumentation to insert validity checks. Such instrumentation
might be incompatible with some parts of the kernel, and therefore needs
to be disabled, just use the attribute __no_sanitize_address to disable
instrumentation for the low level function setup_ptwalker().

Otherwise bringing up the secondary CPUs failed when CONFIG_KASAN is set
(especially when PTW is enabled), here are the call chains:

    smpboot_entry()
      start_secondary()
        cpu_probe()
          per_cpu_trap_init()
            tlb_init()
              setup_tlb_handler()
                setup_ptwalker()

The reason is the PGD registers are configured in setup_ptwalker(), but
KASAN instrumentation may cause TLB exceptions before that.

Cc: stable@...r.kernel.org
Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
Signed-off-by: Huacai Chen <chenhuacai@...ngson.cn>
---
 arch/loongarch/mm/tlb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/loongarch/mm/tlb.c b/arch/loongarch/mm/tlb.c
index 4014c4469587..aaf7d685cc2a 100644
--- a/arch/loongarch/mm/tlb.c
+++ b/arch/loongarch/mm/tlb.c
@@ -202,7 +202,7 @@ void __update_tlb(struct vm_area_struct *vma, unsigned long address, pte_t *ptep
 	local_irq_restore(flags);
 }
 
-static void setup_ptwalker(void)
+static void __no_sanitize_address setup_ptwalker(void)
 {
 	unsigned long pwctl0, pwctl1;
 	unsigned long pgd_i = 0, pgd_w = 0;
-- 
2.47.3