[RFC PATCH bpf-next 0/2] introduce bpf_strncmp() helper

[Hou Tao <houtao1@huawei.com>]

Hi,

The motivation for introducing bpf_strncmp() helper comes from
two aspects:

(1) clang doesn't always replace strncmp() automatically
    (and don't known why)
In tracing program, sometimes we need to using a home-made
strncmp() to check whether or not the file name is expected.

(2) the performance of home-made strncmp is not so good
As shown in the benchmark of patch #2, the performance of
bpf_strncmp helper is 80% better than home-made strncmp under
x86-64, and 600% better under arm64 thanks to its arch-optimized
strncmp().

But i'm concernt about whether the API of bpf_strncmp() is OK.
Now the first argument must be a read-only null-terminated
string, it is enough for our file-name comparsion case because
the target file name is const and read-only, but may be not
usable for comparsion of two strings stored in writable-maps.

Any comments are welcome.

Regards,
Tao

Hou Tao (2):
  bpf: add bpf_strncmp helper
  selftests/bpf: add benchmark bpf_strcmp

 include/linux/bpf.h                           |   1 +
 include/uapi/linux/bpf.h                      |  11 ++
 kernel/bpf/helpers.c                          |  14 +++
 kernel/trace/bpf_trace.c                      |   2 +
 tools/include/uapi/linux/bpf.h                |  11 ++
 .../bpf/prog_tests/test_strncmp_helper.c      |  75 ++++++++++++
 .../selftests/bpf/progs/strncmp_helper.c      | 109 ++++++++++++++++++
 7 files changed, 223 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/test_strncmp_helper.c
 create mode 100644 tools/testing/selftests/bpf/progs/strncmp_helper.c

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2.29.2