On Wed, Dec 22, 2021 at 2:17 PM Andrii Nakryiko
[off-list ref] wrote:

On Wed, Dec 22, 2021 at 5:44 AM Jiri Olsa [off-list ref] wrote:

quoted

On Tue, Dec 21, 2021 at 01:58:14PM -0800, Andrii Nakryiko wrote:

quoted

On Tue, Dec 21, 2021 at 12:23 AM Jiri Olsa [off-list ref] wrote:

quoted

On Thu, Dec 16, 2021 at 02:21:08PM -0800, Christy Lee wrote:

quoted

bpf__object_next is deprecated, track bpf_objects directly in
perf instead.

Signed-off-by: Christy Lee <redacted>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
---
 tools/perf/util/bpf-loader.c | 72 +++++++++++++++++++++++++++---------
 tools/perf/util/bpf-loader.h |  1 +
 2 files changed, 55 insertions(+), 18 deletions(-)

diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
index 528aeb0ab79d..9e3988fd719a 100644
--- a/tools/perf/util/bpf-loader.c
+++ b/tools/perf/util/bpf-loader.c

@@ -29,9 +29,6 @@

 #include <internal/xyarray.h>

-/* temporarily disable libbpf deprecation warnings */
-#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
-
 static int libbpf_perf_print(enum libbpf_print_level level __attribute__((unused)),
                            const char *fmt, va_list args)
 {

@@ -49,6 +46,36 @@ struct bpf_prog_priv {
      int *type_mapping;
 };

+struct bpf_perf_object {
+     struct bpf_object *obj;
+     struct list_head list;
+};
+
+static LIST_HEAD(bpf_objects_list);

hum, so this duplicates libbpf's bpf_objects_list,
how do objects get on this list?

yep, this list needs to be updated on perf side each time
bpf_object__open() (and any variant of open) is called.

quoted

could you please put more comments in changelog
and share how you tested this?

I actually have no idea how to test this as well, can you please share
some ideas?

I don't use it, I just know it's there.. that's why I asked ;-)

it's possible to specify bpf program on the perf command line
to be attached to event, like:

      # cat tools/perf/examples/bpf/hello.c
      #include <stdio.h>

      int syscall_enter(openat)(void *args)
      {
              puts("Hello, world\n");
              return 0;
      }

      license(GPL);
      #
      # perf trace -e openat,tools/perf/examples/bpf/hello.c cat /etc/passwd > /dev/null
         0.016 (         ): __bpf_stdout__:Hello, world
         0.018 ( 0.010 ms): cat/9079 openat(dfd: CWD, filename: /etc/ld.so.cache, flags: CLOEXEC) = 3
         0.057 (         ): __bpf_stdout__:Hello, world
         0.059 ( 0.011 ms): cat/9079 openat(dfd: CWD, filename: /lib64/libc.so.6, flags: CLOEXEC) = 3
         0.417 (         ): __bpf_stdout__:Hello, world
         0.419 ( 0.009 ms): cat/9079 openat(dfd: CWD, filename: /etc/passwd) = 3
      #

I took that example from commit message

[...]

I found the original commit aa3abf30bb28addcf593578d37447d42e3f65fc3
that included a test case, but I'm having trouble reproducing it due to syntax
error. I am running this on bpf-next master without my patches.

I ran 'perf test -v LLVM' and used it's output to generate a script for
compiling the perf test object:

--------------------------------------------------
$ cat ~/bin/hello-ebpf
INPUT_FILE=/tmp/test.c
OUTPUT_FILE=/tmp/test.o

export KBUILD_DIR=/lib/modules/5.12.0-0_fbk2_3390_g7ecb4ac46d7f/build
export NR_CPUS=56
export LINUX_VERSION_CODE=0x50c00
export CLANG_EXEC=/data/users/christylee/devtools/llvm/latest/bin/clang
export CLANG_OPTIONS=-xc
export KERNEL_INC_OPTIONS="-nostdinc -isystem
/data/users/christylee/devtools/gcc/10.3.0/lib/gcc/x86_64-pc-linux-gnu/10.3.0/include
-I./arch/\
x86/include -I./arch/x86/include/generated  -I./include
-I./arch/x86/include/uapi -I./arch/x86/include/generated/uapi
-I./include/uapi -I./in\
clude/generated/uapi -include ./include/linux/compiler-version.h
-include ./include/linux/kconfig.h"
export PERF_BPF_INC_OPTIONS=-I/home/christylee/lib/perf/include/bpf
export WORKING_DIR=/lib/modules/5.12.0-0_fbk2_3390_g7ecb4ac46d7f/build
export CLANG_SOURCE=-

rm -f $OUTPUT_FILE
cat $INPUT_FILE |
/data/users/christylee/devtools/llvm/latest/bin/clang -D__KERNEL__
-D__NR_CPUS__=56 -DLINUX_VERSION_CODE=0x50c00 -xc  -I/ho\
me/christylee/lib/perf/include/bpf  -nostdinc -isystem
/data/users/christylee/devtools/gcc/10.3.0/lib/gcc/x86_64-pc-linux-gnu/10.3.0/include
\
-I./arch/x86/include -I./arch/x86/include/generated  -I./include
-I./arch/x86/include/uapi -I./arch/x86/include/generated/uapi
-I./include/ua\
pi -I./include/generated/uapi -include
./include/linux/compiler-version.h -include ./include/linux/kconfig.h
-Wno-unused-value -Wno-pointer-\
sign -working-directory
/lib/modules/5.12.0-0_fbk2_3390_g7ecb4ac46d7f/build -c - -target bpf
-O2 -o $OUTPUT_FILE
--------------------------------------------------

I then wrote and compiled a script that ask to get asks to put a probe
at a function that
does not exists in the kernel, it errors out as expected:

$ cat /tmp/test.c
__attribute__((section("fork=does_not_exist"), used)) int fork(void *ctx) {
    return 0;
}

char _license[] __attribute__((section("license"), used)) = "GPL";
int _version __attribute__((section("version"), used)) = 0x40100;
$ cd ~/bin && ./hello-ebpf
$ perf record --event /tmp/test.o sleep 1
Using perf wrapper that supports hot-text. Try perf.real if you
encounter any issues.
Probe point 'does_not_exist' not found.
event syntax error: '/tmp/test.o'
                     \___ You need to check probing points in BPF file

(add -v to see detail)
Run 'perf list' for a list of valid events

 Usage: perf record [<options>] [<command>]
    or: perf record [<options>] -- <command> [<options>]

    -e, --event <event>   event selector. use 'perf list' to list
available events

---------------------------------------------------

Next I changed the attribute to something that exists in the kernel.
As expected, it errors out
with permission problem:
$ cat /tmp/test.c
__attribute__((section("fork=fork_init"), used)) int fork(void *ctx) {
    return 0;
}
char _license[] __attribute__((section("license"), used)) = "GPL";
int _version __attribute__((section("version"), used)) = 0x40100;
$ grep fork_init /proc/kallsyms
ffffffff8146e250 T xfs_ifork_init_cow
ffffffff83980481 T fork_init
$ cd ~/bin && ./hello-ebpf
$ perf record --event /tmp/test.o sleep 1
Using perf wrapper that supports hot-text. Try perf.real if you
encounter any issues.
Failed to open kprobe_events: Permission denied
event syntax error: '/tmp/test.o'
                     \___ You need to be root

(add -v to see detail)
Run 'perf list' for a list of valid events

 Usage: perf record [<options>] [<command>]
    or: perf record [<options>] -- <command> [<options>]

    -e, --event <event>   event selector. use 'perf list' to list
available events

---------------------------------------------------

So I reran as root, but this time I get an invalid syntax error:

# perf record --event /tmp/test.o -v sleep 1
Using perf wrapper that supports hot-text. Try perf.real if you
encounter any issues.
Failed to write event: Invalid argument
event syntax error: '/tmp/test.o'
                     \___ Invalid argument

(add -v to see detail)
Run 'perf list' for a list of valid events

 Usage: perf record [<options>] [<command>]
    or: perf record [<options>] -- <command> [<options>]

    -e, --event <event>   event selector. use 'perf list' to list
available events
---------------------------------------------------

Is there a different way to attach a custom event probe point?