Hi, Chenghao,
On Fri, Dec 12, 2025 at 5:11 PM Chenghao Duan <duanchenghao@kylinos.cn> wrote:
>
> 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@kylinos.cn>
> ---
> arch/loongarch/kernel/traps.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/arch/loongarch/kernel/traps.c b/arch/loongarch/kernel/traps.c
> index da5926fead4a..4cf72e0af6a3 100644
> --- a/arch/loongarch/kernel/traps.c
> +++ b/arch/loongarch/kernel/traps.c
> @@ -534,7 +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 == EXSUBCODE_ADEM) && fixup_exception(regs))
> + return;
No chance for ADEF? And I don't think ixup_exception() can be done out
of irqentry_enter().
This patch is needed by BPF but not part of BPF, so I think the
subject should be:
LoongArch: Enable exception fixup for specific ADE subcode
Huacai
> +
> + 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
>