linux-kernel - [PATCH v1 2/2] LoongArch: Enable BPF exception fixup for specific ADE subcode

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Message-Id: <20251209093405.1309253-3-duanchenghao@kylinos.cn>
Date: Tue,  9 Dec 2025 17:34:05 +0800
From: Chenghao Duan <duanchenghao@...inos.cn>
To: yangtiezhu@...ngson.cn,
	hengqi.chen@...il.com,
	chenhuacai@...nel.org
Cc: kernel@...0n.name,
	zhangtianyang@...ngson.cn,
	masahiroy@...nel.org,
	linux-kernel@...r.kernel.org,
	loongarch@...ts.linux.dev,
	bpf@...r.kernel.org,
	guodongtai@...inos.cn,
	duanchenghao@...inos.cn,
	youling.tang@...ux.dev,
	jianghaoran@...inos.cn,
	vincent.mc.li@...il.com
Subject: [PATCH v1 2/2] LoongArch: Enable BPF exception fixup for specific ADE subcode

This patch allows the LoongArch BPF JIT to handle recoverable memory
access errors generated by BPF_PROBE_MEM* instructions.

When a BPF program performs memory access operations, the instructions
it executes may trigger ADEM exceptions. The kernel’s built-in BPF
exception table mechanism (EX_TYPE_BPF) will generate corresponding
exception fixup entries in the JIT compilation phase; however, the
architecture-specific trap handling function needs to proactively call
the common fixup routine to achieve exception recovery.

do_ade(): fix EX_TYPE_BPF memory access exceptions for BPF programs,
ensure safe execution.

Signed-off-by: Chenghao Duan <duanchenghao@...inos.cn>
---
 arch/loongarch/kernel/traps.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/loongarch/kernel/traps.c b/arch/loongarch/kernel/traps.c
index da5926fead4a..9ca8aacc82b8 100644
--- a/arch/loongarch/kernel/traps.c
+++ b/arch/loongarch/kernel/traps.c
@@ -534,8 +534,13 @@ asmlinkage void noinstr do_fpe(struct pt_regs *regs, unsigned long fcsr)
 
 asmlinkage void noinstr do_ade(struct pt_regs *regs)
 {
-	irqentry_state_t state = irqentry_enter(regs);
+	irqentry_state_t state;
+	unsigned int esubcode = FIELD_GET(CSR_ESTAT_ESUBCODE, regs->csr_estat);
+
+	if ((esubcode == 1) && fixup_exception(regs))
+		return;
 
+	state = irqentry_enter(regs);
 	die_if_kernel("Kernel ade access", regs);
 	force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)regs->csr_badvaddr);
 
-- 
2.25.1