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.
Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Jiri Olsa <jolsa@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 */
--
2.49.0On Thu, 5 Jun 2025 15:23:34 +0200
Jiri Olsa <jolsa@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 <oleg@redhat.com>
> Signed-off-by: Jiri Olsa <jolsa@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) <mhiramat@kernel.org>
On Wed, Jun 25, 2025 at 03:42:59PM +0900, Masami Hiramatsu wrote:
> On Thu, 5 Jun 2025 15:23:34 +0200
> Jiri Olsa <jolsa@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,
it was the intention in the v1 but as Oleg pointed out [1] it won't
work, because the set_orig_refctr part of this change does not know
if the refctr should be really updated or not
while inside uprobe_write it happens right after verify callback and
we make sure to update refctr only if the instruction was updated
thanks,
jirka
[1] https://lore.kernel.org/bpf/20250427141335.GA9350@redhat.com/
>
>
> > Acked-by: Oleg Nesterov <oleg@redhat.com>
> > Signed-off-by: Jiri Olsa <jolsa@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) <mhiramat@kernel.org>
On Wed, 25 Jun 2025 17:11:09 +0200
Jiri Olsa <olsajiri@gmail.com> wrote:
> On Wed, Jun 25, 2025 at 03:42:59PM +0900, Masami Hiramatsu wrote:
> > On Thu, 5 Jun 2025 15:23:34 +0200
> > Jiri Olsa <jolsa@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,
>
> it was the intention in the v1 but as Oleg pointed out [1] it won't
> work, because the set_orig_refctr part of this change does not know
> if the refctr should be really updated or not
Ah, uprobe_unregister() can not check the given uprobe failed to
update the code for each mm....
>
> while inside uprobe_write it happens right after verify callback and
> we make sure to update refctr only if the instruction was updated
OK. But this is very complicated. Eventually I think uprobe should
have a list of mm(or refcnt) to manage whether it is updated the
refcounter.
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Thanks,
>
> thanks,
> jirka
>
>
> [1] https://lore.kernel.org/bpf/20250427141335.GA9350@redhat.com/
>
> >
> >
> > > Acked-by: Oleg Nesterov <oleg@redhat.com>
> > > Signed-off-by: Jiri Olsa <jolsa@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) <mhiramat@kernel.org>
--
Masami Hiramatsu (Google) <mhiramat@kernel.org>
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