* [PATCH bpf v2] ftrace: fix incorrect hash size in register_ftrace_direct()
@ 2025-04-13 1:44 Menglong Dong
2025-04-14 7:05 ` Masami Hiramatsu
0 siblings, 1 reply; 5+ messages in thread
From: Menglong Dong @ 2025-04-13 1:44 UTC (permalink / raw)
To: rostedt
Cc: mhiramat, mark.rutland, mathieu.desnoyers, linux-kernel,
linux-trace-kernel, bpf, Menglong Dong
The maximum of the ftrace hash bits is made fls(32) in
register_ftrace_direct(), which seems illogical. So, we fix it by making
the max hash bits FTRACE_HASH_MAX_BITS instead.
Fixes: d05cb470663a ("ftrace: Fix modification of direct_function hash while in use")
Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
---
v2:
- thanks for Steven's advice, we fix the problem by making the max hash
bits FTRACE_HASH_MAX_BITS instead.
---
kernel/trace/ftrace.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 1a48aedb5255..d153ad13e0e0 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -5914,9 +5914,10 @@ int register_ftrace_direct(struct ftrace_ops *ops, unsigned long addr)
/* Make a copy hash to place the new and the old entries in */
size = hash->count + direct_functions->count;
- if (size > 32)
- size = 32;
- new_hash = alloc_ftrace_hash(fls(size));
+ size = fls(size);
+ if (size > FTRACE_HASH_MAX_BITS)
+ size = FTRACE_HASH_MAX_BITS;
+ new_hash = alloc_ftrace_hash(size);
if (!new_hash)
goto out_unlock;
--
2.39.5
^ permalink raw reply related [flat|nested] 5+ messages in thread* Re: [PATCH bpf v2] ftrace: fix incorrect hash size in register_ftrace_direct()
2025-04-13 1:44 [PATCH bpf v2] ftrace: fix incorrect hash size in register_ftrace_direct() Menglong Dong
@ 2025-04-14 7:05 ` Masami Hiramatsu
2025-04-15 23:14 ` Andrii Nakryiko
0 siblings, 1 reply; 5+ messages in thread
From: Masami Hiramatsu @ 2025-04-14 7:05 UTC (permalink / raw)
To: Menglong Dong
Cc: rostedt, mhiramat, mark.rutland, mathieu.desnoyers, linux-kernel,
linux-trace-kernel, bpf, Menglong Dong
On Sun, 13 Apr 2025 09:44:44 +0800
Menglong Dong <menglong8.dong@gmail.com> wrote:
> The maximum of the ftrace hash bits is made fls(32) in
> register_ftrace_direct(), which seems illogical. So, we fix it by making
> the max hash bits FTRACE_HASH_MAX_BITS instead.
>
Loogs good to me.
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Thanks!
> Fixes: d05cb470663a ("ftrace: Fix modification of direct_function hash while in use")
> Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
> ---
> v2:
> - thanks for Steven's advice, we fix the problem by making the max hash
> bits FTRACE_HASH_MAX_BITS instead.
> ---
> kernel/trace/ftrace.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 1a48aedb5255..d153ad13e0e0 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -5914,9 +5914,10 @@ int register_ftrace_direct(struct ftrace_ops *ops, unsigned long addr)
>
> /* Make a copy hash to place the new and the old entries in */
> size = hash->count + direct_functions->count;
> - if (size > 32)
> - size = 32;
> - new_hash = alloc_ftrace_hash(fls(size));
> + size = fls(size);
> + if (size > FTRACE_HASH_MAX_BITS)
> + size = FTRACE_HASH_MAX_BITS;
> + new_hash = alloc_ftrace_hash(size);
> if (!new_hash)
> goto out_unlock;
>
> --
> 2.39.5
>
>
--
Masami Hiramatsu (Google) <mhiramat@kernel.org>
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH bpf v2] ftrace: fix incorrect hash size in register_ftrace_direct()
2025-04-14 7:05 ` Masami Hiramatsu
@ 2025-04-15 23:14 ` Andrii Nakryiko
2025-04-16 0:55 ` Steven Rostedt
2025-04-16 1:06 ` Menglong Dong
0 siblings, 2 replies; 5+ messages in thread
From: Andrii Nakryiko @ 2025-04-15 23:14 UTC (permalink / raw)
To: Masami Hiramatsu
Cc: Menglong Dong, rostedt, mark.rutland, mathieu.desnoyers,
linux-kernel, linux-trace-kernel, bpf, Menglong Dong
On Mon, Apr 14, 2025 at 12:05 AM Masami Hiramatsu <mhiramat@kernel.org> wrote:
>
> On Sun, 13 Apr 2025 09:44:44 +0800
> Menglong Dong <menglong8.dong@gmail.com> wrote:
>
> > The maximum of the ftrace hash bits is made fls(32) in
> > register_ftrace_direct(), which seems illogical. So, we fix it by making
> > the max hash bits FTRACE_HASH_MAX_BITS instead.
> >
>
> Loogs good to me.
>
> Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
>
> Thanks!
>
I'm a bit confused by the "[PATCH bpf]" prefix... This fix doesn't
seem to be BPF-related, so I'm not sure why it would go through the
bpf tree. I presume Masami or Steven will route it through their tree,
is that right?
> > Fixes: d05cb470663a ("ftrace: Fix modification of direct_function hash while in use")
> > Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
> > ---
> > v2:
> > - thanks for Steven's advice, we fix the problem by making the max hash
> > bits FTRACE_HASH_MAX_BITS instead.
> > ---
> > kernel/trace/ftrace.c | 7 ++++---
> > 1 file changed, 4 insertions(+), 3 deletions(-)
> >
> > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> > index 1a48aedb5255..d153ad13e0e0 100644
> > --- a/kernel/trace/ftrace.c
> > +++ b/kernel/trace/ftrace.c
> > @@ -5914,9 +5914,10 @@ int register_ftrace_direct(struct ftrace_ops *ops, unsigned long addr)
> >
> > /* Make a copy hash to place the new and the old entries in */
> > size = hash->count + direct_functions->count;
> > - if (size > 32)
> > - size = 32;
> > - new_hash = alloc_ftrace_hash(fls(size));
> > + size = fls(size);
> > + if (size > FTRACE_HASH_MAX_BITS)
> > + size = FTRACE_HASH_MAX_BITS;
> > + new_hash = alloc_ftrace_hash(size);
> > if (!new_hash)
> > goto out_unlock;
> >
> > --
> > 2.39.5
> >
> >
>
>
> --
> Masami Hiramatsu (Google) <mhiramat@kernel.org>
>
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH bpf v2] ftrace: fix incorrect hash size in register_ftrace_direct()
2025-04-15 23:14 ` Andrii Nakryiko
@ 2025-04-16 0:55 ` Steven Rostedt
2025-04-16 1:06 ` Menglong Dong
1 sibling, 0 replies; 5+ messages in thread
From: Steven Rostedt @ 2025-04-16 0:55 UTC (permalink / raw)
To: Andrii Nakryiko
Cc: Masami Hiramatsu, Menglong Dong, mark.rutland, mathieu.desnoyers,
linux-kernel, linux-trace-kernel, bpf, Menglong Dong
On Tue, 15 Apr 2025 16:14:01 -0700
Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote:
> I'm a bit confused by the "[PATCH bpf]" prefix... This fix doesn't
> seem to be BPF-related, so I'm not sure why it would go through the
> bpf tree. I presume Masami or Steven will route it through their tree,
> is that right?
I can take this in my tree.
-- Steve
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH bpf v2] ftrace: fix incorrect hash size in register_ftrace_direct()
2025-04-15 23:14 ` Andrii Nakryiko
2025-04-16 0:55 ` Steven Rostedt
@ 2025-04-16 1:06 ` Menglong Dong
1 sibling, 0 replies; 5+ messages in thread
From: Menglong Dong @ 2025-04-16 1:06 UTC (permalink / raw)
To: Andrii Nakryiko
Cc: Masami Hiramatsu, rostedt, mark.rutland, mathieu.desnoyers,
linux-kernel, linux-trace-kernel, bpf, Menglong Dong
On Wed, Apr 16, 2025 at 7:14 AM Andrii Nakryiko
<andrii.nakryiko@gmail.com> wrote:
>
> On Mon, Apr 14, 2025 at 12:05 AM Masami Hiramatsu <mhiramat@kernel.org> wrote:
> >
> > On Sun, 13 Apr 2025 09:44:44 +0800
> > Menglong Dong <menglong8.dong@gmail.com> wrote:
> >
> > > The maximum of the ftrace hash bits is made fls(32) in
> > > register_ftrace_direct(), which seems illogical. So, we fix it by making
> > > the max hash bits FTRACE_HASH_MAX_BITS instead.
> > >
> >
> > Loogs good to me.
> >
> > Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> >
> > Thanks!
> >
>
> I'm a bit confused by the "[PATCH bpf]" prefix... This fix doesn't
> seem to be BPF-related, so I'm not sure why it would go through the
> bpf tree. I presume Masami or Steven will route it through their tree,
> is that right?
>
Sorry about the confusing......I throught the register_ftrace_direct()
is mainly used by BPF, and it should go to the ftrace tree :/
Thanks!
Menglong Dong
>
> > > Fixes: d05cb470663a ("ftrace: Fix modification of direct_function hash while in use")
> > > Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
> > > ---
> > > v2:
> > > - thanks for Steven's advice, we fix the problem by making the max hash
> > > bits FTRACE_HASH_MAX_BITS instead.
> > > ---
> > > kernel/trace/ftrace.c | 7 ++++---
> > > 1 file changed, 4 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> > > index 1a48aedb5255..d153ad13e0e0 100644
> > > --- a/kernel/trace/ftrace.c
> > > +++ b/kernel/trace/ftrace.c
> > > @@ -5914,9 +5914,10 @@ int register_ftrace_direct(struct ftrace_ops *ops, unsigned long addr)
> > >
> > > /* Make a copy hash to place the new and the old entries in */
> > > size = hash->count + direct_functions->count;
> > > - if (size > 32)
> > > - size = 32;
> > > - new_hash = alloc_ftrace_hash(fls(size));
> > > + size = fls(size);
> > > + if (size > FTRACE_HASH_MAX_BITS)
> > > + size = FTRACE_HASH_MAX_BITS;
> > > + new_hash = alloc_ftrace_hash(size);
> > > if (!new_hash)
> > > goto out_unlock;
> > >
> > > --
> > > 2.39.5
> > >
> > >
> >
> >
> > --
> > Masami Hiramatsu (Google) <mhiramat@kernel.org>
> >
^ permalink raw reply [flat|nested] 5+ messages in thread
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2025-04-13 1:44 [PATCH bpf v2] ftrace: fix incorrect hash size in register_ftrace_direct() Menglong Dong
2025-04-14 7:05 ` Masami Hiramatsu
2025-04-15 23:14 ` Andrii Nakryiko
2025-04-16 0:55 ` Steven Rostedt
2025-04-16 1:06 ` Menglong Dong
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