On Wed, 05 Feb 2025 17:50:34 -0500
Steven Rostedt <rost...@goodmis.org> wrote:
> From: Steven Rostedt <rost...@goodmis.org>
>
> Now that there's one page at the start of the persistent memory used by
> the ring buffer, make the part of that page that is not used by the ring
> buffer available for the tracer to use. This will allow the tracer to
> store its own persistent data.
Looks good to me.
Reviewed-by: Masami Hiramatsu (Google) <mhira...@kernel.org>
Thanks,
>
> Signed-off-by: Steven Rostedt (Google) <rost...@goodmis.org>
> ---
> include/linux/ring_buffer.h | 1 +
> kernel/trace/ring_buffer.c | 13 +++++++++++++
> 2 files changed, 14 insertions(+)
>
> diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h
> index 8de035f4f0d9..b95f940fd07a 100644
> --- a/include/linux/ring_buffer.h
> +++ b/include/linux/ring_buffer.h
> @@ -95,6 +95,7 @@ struct trace_buffer *__ring_buffer_alloc_range(unsigned
> long size, unsigned flag
> struct lock_class_key *key);
>
> bool ring_buffer_last_boot_delta(struct trace_buffer *buffer, unsigned long
> *kaslr_addr);
> +void *ring_buffer_meta_scratch(struct trace_buffer *buffer, unsigned int
> *size);
>
> /*
> * Because the ring buffer is generic, if other users of the ring buffer get
> diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
> index 0446d053dbd6..5a81ff785665 100644
> --- a/kernel/trace/ring_buffer.c
> +++ b/kernel/trace/ring_buffer.c
> @@ -1730,6 +1730,9 @@ static bool rb_meta_init(struct trace_buffer *buffer)
> bmeta->total_size = total_size;
> bmeta->buffers_offset = (void *)ptr - (void *)bmeta;
>
> + /* Zero out the scatch pad */
> + memset((void *)bmeta + sizeof(*bmeta), 0, PAGE_SIZE - sizeof(*bmeta));
> +
> return false;
> }
>
> @@ -2532,6 +2535,16 @@ bool ring_buffer_last_boot_delta(struct trace_buffer
> *buffer, unsigned long *kas
> return true;
> }
>
> +void *ring_buffer_meta_scratch(struct trace_buffer *buffer, unsigned int
> *size)
> +{
> + if (!buffer || !buffer->meta)
> + return NULL;
> +
> + *size = PAGE_SIZE - sizeof(*buffer->meta);
> +
> + return (void *)buffer->meta + sizeof(*buffer->meta);
> +}
> +
> /**
> * ring_buffer_free - free a ring buffer.
> * @buffer: the buffer to free.
> --
> 2.45.2
>
>
--
Masami Hiramatsu (Google) <mhira...@kernel.org>
