On Thu, 5 Jun 2025 15:23:34 +0200
Jiri Olsa <jo...@kernel.org> wrote:
> Making update_ref_ctr call in uprobe_write conditional based
> on do_ref_ctr argument. This way we can use uprobe_write for
> instruction update without doing ref_ctr_offset update.
>
Can we just decouple this update from uprobe_write()?
If we do this exclusively, I think we can do something like;
lock()
update_ref_ctr(uprobe, mm, +1);
...
ret = uprobe_write();
...
if (ret < 0)
update_ref_ctr(uprobe, mm, -1);
unlock()
Thank you,
> Acked-by: Oleg Nesterov <o...@redhat.com>
> Signed-off-by: Jiri Olsa <jo...@kernel.org>
> ---
> include/linux/uprobes.h | 2 +-
> kernel/events/uprobes.c | 8 ++++----
> 2 files changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
> index 518b26756469..5080619560d4 100644
> --- a/include/linux/uprobes.h
> +++ b/include/linux/uprobes.h
> @@ -200,7 +200,7 @@ extern unsigned long uprobe_get_trap_addr(struct pt_regs
> *regs);
> extern int uprobe_write_opcode(struct arch_uprobe *auprobe, struct
> vm_area_struct *vma, unsigned long vaddr, uprobe_opcode_t,
> bool is_register);
> extern int uprobe_write(struct arch_uprobe *auprobe, struct vm_area_struct
> *vma, const unsigned long opcode_vaddr,
> - uprobe_opcode_t *insn, int nbytes,
> uprobe_write_verify_t verify, bool is_register);
> + uprobe_opcode_t *insn, int nbytes,
> uprobe_write_verify_t verify, bool is_register, bool do_update_ref_ctr);
> extern struct uprobe *uprobe_register(struct inode *inode, loff_t offset,
> loff_t ref_ctr_offset, struct uprobe_consumer *uc);
> extern int uprobe_apply(struct uprobe *uprobe, struct uprobe_consumer *uc,
> bool);
> extern void uprobe_unregister_nosync(struct uprobe *uprobe, struct
> uprobe_consumer *uc);
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index 1e5dc3b30707..6795b8d82b9c 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -492,12 +492,12 @@ int uprobe_write_opcode(struct arch_uprobe *auprobe,
> struct vm_area_struct *vma,
> bool is_register)
> {
> return uprobe_write(auprobe, vma, opcode_vaddr, &opcode,
> UPROBE_SWBP_INSN_SIZE,
> - verify_opcode, is_register);
> + verify_opcode, is_register, true /*
> do_update_ref_ctr */);
> }
>
> int uprobe_write(struct arch_uprobe *auprobe, struct vm_area_struct *vma,
> const unsigned long insn_vaddr, uprobe_opcode_t *insn, int
> nbytes,
> - uprobe_write_verify_t verify, bool is_register)
> + uprobe_write_verify_t verify, bool is_register, bool
> do_update_ref_ctr)
> {
> const unsigned long vaddr = insn_vaddr & PAGE_MASK;
> struct mm_struct *mm = vma->vm_mm;
> @@ -538,7 +538,7 @@ int uprobe_write(struct arch_uprobe *auprobe, struct
> vm_area_struct *vma,
> }
>
> /* We are going to replace instruction, update ref_ctr. */
> - if (!ref_ctr_updated && uprobe->ref_ctr_offset) {
> + if (do_update_ref_ctr && !ref_ctr_updated && uprobe->ref_ctr_offset) {
> ret = update_ref_ctr(uprobe, mm, is_register ? 1 : -1);
> if (ret) {
> folio_put(folio);
> @@ -590,7 +590,7 @@ int uprobe_write(struct arch_uprobe *auprobe, struct
> vm_area_struct *vma,
>
> out:
> /* Revert back reference counter if instruction update failed. */
> - if (ret < 0 && ref_ctr_updated)
> + if (do_update_ref_ctr && ret < 0 && ref_ctr_updated)
> update_ref_ctr(uprobe, mm, is_register ? -1 : 1);
>
> /* try collapse pmd for compound page */
> --
> 2.49.0
>
--
Masami Hiramatsu (Google) <mhira...@kernel.org>
