LoongArch: Enable exception fixup for specific ADE subcode

[ Upstream commit 9bdc1ab5e4ce6f066119018d8f69631a46f9c5a0 ]

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.

Relevant test cases: illegal address access tests in module_attach and
subprogs_extable of selftests/bpf.

Signed-off-by: Chenghao Duan <duanchenghao@kylinos.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Sasha Levin <sashal@kernel.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/arch/loongarch/kernel/traps.c b/arch/loongarch/kernel/traps.c
index 12c726482d15..cad1e08ca3fb 100644
--- a/arch/loongarch/kernel/traps.c
+++ b/arch/loongarch/kernel/traps.c
@@ -361,10 +361,15 @@ out:
 asmlinkage void noinstr do_ade(struct pt_regs *regs)
 {
 	irqentry_state_t state = irqentry_enter(regs);
+	unsigned int esubcode = FIELD_GET(CSR_ESTAT_ESUBCODE, regs->csr_estat);
+
+	if ((esubcode == EXSUBCODE_ADEM) && fixup_exception(regs))
+		goto out;
 
 	die_if_kernel("Kernel ade access", regs);
 	force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)regs->csr_badvaddr);
 
+out:
 	irqentry_exit(regs, state);
 }