Hi Jiri,
On Mon, Nov 09, 2020 at 10:53:54PM +0100, Jiri Olsa wrote:
> Adding support to carry build id data in mmap2 event.
>
> The build id data replaces maj/min/ino/ino_generation
> fields, whichc are also used to identify map's binary,
> so it's ok to replace them with build id data:
>
> union {
> struct {
> u32 maj;
> u32 min;
> u64 ino;
> u64 ino_generation;
> };
> struct {
> u8 build_id[20];
> u8 build_id_size;
> u8 __reserved_1;
> u16 __reserved_2;
> };
> };
>
> Replaced maj/min/ino/ino_generation fields give us size
> of 24 bytes. We use 20 bytes for build id data, 1 byte
> for size and rest is unused.
>
> There's new misc bit for mmap2 to signal there's build
> id data in it:
>
> #define PERF_RECORD_MISC_BUILD_ID (1 << 14)
>
> Signed-off-by: Jiri Olsa <jo...@kernel.org>
> ---
[SNIP]
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index da467e1dd49a..808473b6ce85 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -51,6 +51,7 @@
> #include <linux/proc_ns.h>
> #include <linux/mount.h>
> #include <linux/min_heap.h>
> +#include <linux/buildid.h>
>
> #include "internal.h"
>
> @@ -395,6 +396,7 @@ static atomic_t nr_ksymbol_events __read_mostly;
> static atomic_t nr_bpf_events __read_mostly;
> static atomic_t nr_cgroup_events __read_mostly;
> static atomic_t nr_text_poke_events __read_mostly;
> +static atomic_t nr_build_id_events __read_mostly;
>
> static LIST_HEAD(pmus);
> static DEFINE_MUTEX(pmus_lock);
> @@ -4672,6 +4674,8 @@ static void unaccount_event(struct perf_event *event)
> dec = true;
> if (event->attr.mmap || event->attr.mmap_data)
> atomic_dec(&nr_mmap_events);
> + if (event->attr.build_id)
> + atomic_dec(&nr_build_id_events);
> if (event->attr.comm)
> atomic_dec(&nr_comm_events);
> if (event->attr.namespaces)
> @@ -7942,6 +7946,8 @@ struct perf_mmap_event {
> u64 ino;
> u64 ino_generation;
> u32 prot, flags;
> + u8 build_id[BUILD_ID_SIZE];
> + u32 build_id_size;
>
> struct {
> struct perf_event_header header;
> @@ -7997,13 +8003,23 @@ static void perf_event_mmap_output(struct perf_event
> *event,
> mmap_event->event_id.pid = perf_event_pid(event, current);
> mmap_event->event_id.tid = perf_event_tid(event, current);
>
> + if (event->attr.mmap2 && event->attr.build_id)
> + mmap_event->event_id.header.misc |= PERF_RECORD_MISC_BUILD_ID;
> +
> perf_output_put(&handle, mmap_event->event_id);
>
> if (event->attr.mmap2) {
> - perf_output_put(&handle, mmap_event->maj);
> - perf_output_put(&handle, mmap_event->min);
> - perf_output_put(&handle, mmap_event->ino);
> - perf_output_put(&handle, mmap_event->ino_generation);
> + if (event->attr.build_id) {
> + u8 size[4] = { (u8) mmap_event->build_id_size, 0, 0, 0
> };
> +
> + __output_copy(&handle, mmap_event->build_id,
> BUILD_ID_SIZE);
> + __output_copy(&handle, size, 4);
> + } else {
> + perf_output_put(&handle, mmap_event->maj);
> + perf_output_put(&handle, mmap_event->min);
> + perf_output_put(&handle, mmap_event->ino);
> + perf_output_put(&handle, mmap_event->ino_generation);
> + }
> perf_output_put(&handle, mmap_event->prot);
> perf_output_put(&handle, mmap_event->flags);
> }
> @@ -8132,6 +8148,11 @@ static void perf_event_mmap_event(struct
> perf_mmap_event *mmap_event)
>
> mmap_event->event_id.header.size = sizeof(mmap_event->event_id) + size;
>
> + if (atomic_read(&nr_build_id_events)) {
> + build_id_parse_size(vma, mmap_event->build_id,
> + &mmap_event->build_id_size);
This can fail, right? Then we need to fallback to use dev/ino..
Thanks,
Namhyung
> + }
> +
> perf_iterate_sb(perf_event_mmap_output,
> mmap_event,
> NULL);
> @@ -11069,6 +11090,8 @@ static void account_event(struct perf_event *event)
> inc = true;
> if (event->attr.mmap || event->attr.mmap_data)
> atomic_inc(&nr_mmap_events);
> + if (event->attr.build_id)
> + atomic_inc(&nr_build_id_events);
> if (event->attr.comm)
> atomic_inc(&nr_comm_events);
> if (event->attr.namespaces)
> --
> 2.26.2
>
