kprobe has been broken on riscv for quite some time. There is an attempt [1] to fix that which actually works. This patch works because it enables ARCH_HAVE_NMI_SAFE_CMPXCHG and that makes the ring buffer allocation succeed when handling a kprobe because we handle *all* kprobes in nmi context. We do so because Peter advised us to treat all kernel traps as nmi [2].
But that does not seem right for kprobe handling, so instead, treat break traps from kernel as non-nmi.
Link: https://lore.kernel.org/linux-riscv/20250711090443.1688404-1-pulehui@huaweic... [1] Link: https://lore.kernel.org/linux-riscv/20250422094419.GC14170@noisy.programming... [2] Fixes: f0bddf50586d ("riscv: entry: Convert to generic entry") Cc: stable@vger.kernel.org Signed-off-by: Alexandre Ghiti alexghiti@rivosinc.com --- This is clearly an RFC and this is likely not the right way to go, it is just a way to trigger a discussion about if handling kprobes in an nmi context is the right way or not. --- arch/riscv/kernel/traps.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c index 80230de167def3c33db5bc190347ec5f87dbb6e3..90f36bb9b12d4ba0db0f084f87899156e3c7dc6f 100644 --- a/arch/riscv/kernel/traps.c +++ b/arch/riscv/kernel/traps.c @@ -315,11 +315,11 @@ asmlinkage __visible __trap_section void do_trap_break(struct pt_regs *regs) local_irq_disable(); irqentry_exit_to_user_mode(regs); } else { - irqentry_state_t state = irqentry_nmi_enter(regs); + irqentry_state_t state = irqentry_enter(regs);
handle_break(regs);
- irqentry_nmi_exit(regs, state); + irqentry_exit(regs, state); } }
--- base-commit: ae9a687664d965b13eeab276111b2f97dd02e090 change-id: 20250903-dev-alex-break_nmi_v1-57c5321f3e80
Best regards,