On 7/23/26 08:31, Masami Hiramatsu (Google) wrote:
> On Fri, 17 Jul 2026 16:23:31 +0800
> daichengrong <[email protected]> wrote:
>
>> uretprobe replaces the original return address of a probed function with
>> a trampoline address to capture function return events.
>>
>> After the trampoline is entered and the uretprobe handler completes, the
>> original return address needs to be restored in the user register context
>> to keep the register state consistent with the state before probing.
>>
>> Add an architecture-specific hook for restoring the original return
>> address during uretprobe handling.
>>
>> The initial implementation adds support for RISC-V. Other architectures
>> keep the default empty implementation until their corresponding restore
>> logic is implemented.
>>
>> Signed-off-by: daichengrong <[email protected]>
>> ---
>> arch/riscv/kernel/probes/uprobes.c | 7 +++++++
>> include/linux/uprobes.h | 1 +
>> kernel/events/uprobes.c | 5 +++++
>> 3 files changed, 13 insertions(+)
>>
>> diff --git a/arch/riscv/kernel/probes/uprobes.c
>> b/arch/riscv/kernel/probes/uprobes.c
>> index eb177d0ce8ab..0b1b94d9683e 100644
>> --- a/arch/riscv/kernel/probes/uprobes.c
>> +++ b/arch/riscv/kernel/probes/uprobes.c
>> @@ -139,6 +139,13 @@ arch_uretprobe_hijack_return_addr(unsigned long
>> trampoline_vaddr,
>> return ra;
>> }
>>
>> +void
>> +arch_uretprobe_hijack_set_addr(unsigned long orig_ret_vaddr,
>> + struct pt_regs *regs)
>
> OK, but hijack may not be a good naming, what about
> "arch_uretprobe_restore_return_address()"?
Thanks for the suggestion.
I’ve renamed the function in v2 as suggested:
https://lore.kernel.org/all/[email protected]/
Thanks,
>
> And I need RISC-V maintainer's review.
>
> Thank you,
>
>> +{
>> + regs->ra = orig_ret_vaddr;
>> +}
>> +
>> int arch_uprobe_exception_notify(struct notifier_block *self,
>> unsigned long val, void *data)
>> {
>> diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
>> index f548fea2adec..2d0dc919845d 100644
>> --- a/include/linux/uprobes.h
>> +++ b/include/linux/uprobes.h
>> @@ -230,6 +230,7 @@ extern bool arch_uprobe_xol_was_trapped(struct
>> task_struct *tsk);
>> extern int arch_uprobe_exception_notify(struct notifier_block *self,
>> unsigned long val, void *data);
>> extern void arch_uprobe_abort_xol(struct arch_uprobe *aup, struct pt_regs
>> *regs);
>> extern unsigned long arch_uretprobe_hijack_return_addr(unsigned long
>> trampoline_vaddr, struct pt_regs *regs);
>> +extern void arch_uretprobe_hijack_set_addr(unsigned long orig_ret_vaddr,
>> struct pt_regs *regs);
>> extern bool arch_uretprobe_is_alive(struct return_instance *ret, enum
>> rp_check ctx, struct pt_regs *regs);
>> extern bool arch_uprobe_ignore(struct arch_uprobe *aup, struct pt_regs
>> *regs);
>> extern void arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr,
>> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
>> index 4084e926e284..deecaae01ab7 100644
>> --- a/kernel/events/uprobes.c
>> +++ b/kernel/events/uprobes.c
>> @@ -1748,6 +1748,10 @@ void * __weak arch_uretprobe_trampoline(unsigned long
>> *psize)
>> return &insn;
>> }
>>
>> +void __weak arch_uretprobe_hijack_set_addr(unsigned long orig_ret_vaddr,
>> struct pt_regs *regs)
>> +{
>> +}
>> +
>> static struct xol_area *__create_xol_area(unsigned long vaddr)
>> {
>> struct mm_struct *mm = current->mm;
>> @@ -2659,6 +2663,7 @@ void uprobe_handle_trampoline(struct pt_regs *regs)
>> valid = !next_chain || arch_uretprobe_is_alive(next_chain,
>> RP_CHECK_RET, regs);
>>
>> instruction_pointer_set(regs, ri->orig_ret_vaddr);
>> + arch_uretprobe_hijack_set_addr(ri->orig_ret_vaddr, regs);
>> do {
>> /* pop current instance from the stack of pending
>> return instances,
>> * as it's not pending anymore: we just fixed up
>> original
>> --
>> 2.25.1
>>
>>
>
>
--
Chengrong
