Re: [PATCH v1 0/3] perf trace: Augment struct pointer arguments

[Ian Rogers]

On Wed, Jul 31, 2024 at 12:49 PM Howard Chu <howardchu95@xxxxxxxxx> wrote:
>
> prerequisite: This series is built on top of the enum augmention series
> v5.
>
> This patch series adds augmentation feature to struct pointer, string
> and buffer arguments all-in-one. It also fixes 'perf trace -p <PID>',
> but unfortunately, it breaks perf trace <Workload>, this will be fixed
> in v2.
>
> With this patch series, perf trace will augment struct pointers well, it
> can be applied to syscalls such as clone3, epoll_wait, write, and so on.
> But unfortunately, it only collects the data once, when syscall enters.
> This makes syscalls that pass a pointer in order to let it get
> written, not to be augmented very well, I call them the read-like
> syscalls, because it reads from the kernel, using the syscall. This
> patch series only augments write-like syscalls well.
>
> Unfortunately, there are more read-like syscalls(such as read,
> readlinkat, even gettimeofday) than write-like syscalls(write, pwrite64,
> epoll_wait, clone3).
>
> Here are three test scripts that I find useful:
>
> pwrite64
> ```
>  #include <unistd.h>
>  #include <sys/syscall.h>
>
> int main()
> {
>         int i1 = 1, i2 = 2, i3 = 3, i4 = 4;
>         char s1[] = "DI\0NGZ\0HE\1N", s2[] = "XUEBAO";
>
>         while (1) {
>                 syscall(SYS_pwrite64, i1, s1, sizeof(s1), i2);
>                 sleep(1);
>         }
>
>         return 0;
> }
> ```
>
> epoll_wait
> ```
>  #include <unistd.h>
>  #include <sys/epoll.h>
>  #include <stdlib.h>
>  #include <string.h>
>
> #define MAXEVENTS 2
>
> int main()
> {
>         int i1 = 1, i2 = 2, i3 = 3, i4 = 4;
>         char s1[] = "DINGZHEN", s2[] = "XUEBAO";
>
>         struct epoll_event ee = {
>                 .events = 114,
>                 .data.ptr = NULL,
>         };
>
>         struct epoll_event *events = calloc(MAXEVENTS, sizeof(struct epoll_event));
>         memcpy(events, &ee, sizeof(ee));
>
>         while (1) {
>                 epoll_wait(i1, events, i2, i3);
>                 sleep(1);
>         }
>
>         return 0;
> }
> ```
>
> clone3
> ```
>  #include <unistd.h>
>  #include <sys/syscall.h>
>  #include <linux/sched.h>
>  #include <string.h>
>  #include <stdio.h>
>  #include <stdlib.h>
>
> int main()
> {
>         int i1 = 1, i2 = 2, i3 = 3, i4 = 4;
>         char s1[] = "DINGZHEN", s2[] = "XUEBAO";
>
>         struct clone_args cla = {
>                 .flags = 1,
>                 .pidfd = 1,
>                 .child_tid = 4,
>                 .parent_tid = 5,
>                 .exit_signal = 1,
>                 .stack = 4,
>                 .stack_size = 1,
>                 .tls = 9,
>                 .set_tid = 1,
>                 .set_tid_size = 9,
>                 .cgroup = 8,
>         };
>
>         while (1) {
>                 syscall(SYS_clone3, &cla, i1);
>                 sleep(1);
>         }
>
>         return 0;
> }
> ```
>
> Please save them, compile and run them, in a separate window, 'ps aux |
> grep a.out' to get the pid of them (I'm sorry, but the workload is
> broken after the pid fix), and trace them with -p, or, if you want, with
> extra -e <syscall-name>. Reminder: for the third script, you can't trace
> it with -e clone, you can only trace it with -e clone3.
>
> Although the read-like syscalls augmentation is not fully supported, I
> am making significant progress. After lots of debugging, I'm sure I can
> implement it in v2.
>
> Howard Chu (3):
>   perf trace: Set up beauty_map, load it to BPF
>   perf trace: Collect augmented data using BPF
>   perf trace: Fix perf trace -p <PID>

Series:
Acked-by: Ian Rogers <irogers@xxxxxxxxxx>

Thanks,
Ian

>  tools/perf/builtin-trace.c                    | 253 +++++++++++++++++-
>  .../bpf_skel/augmented_raw_syscalls.bpf.c     | 121 ++++++++-
>  tools/perf/util/evlist.c                      |  14 +-
>  tools/perf/util/evlist.h                      |   1 +
>  tools/perf/util/evsel.c                       |   3 +
>  5 files changed, 386 insertions(+), 6 deletions(-)
>
> --
> 2.45.2
>