From: Florent Revest <revest@chromium.org>
To: bpf@vger.kernel.org
Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org,
yhs@fb.com, kpsingh@kernel.org, jackmanb@chromium.org,
linux-kernel@vger.kernel.org,
Florent Revest <revest@chromium.org>
Subject: [PATCH bpf-next v5 0/6] Add a snprintf eBPF helper
Date: Mon, 19 Apr 2021 17:52:37 +0200 [thread overview]
Message-ID: <20210419155243.1632274-1-revest@chromium.org> (raw)
We have a usecase where we want to audit symbol names (if available) in
callback registration hooks. (ex: fentry/nf_register_net_hook)
A few months back, I proposed a bpf_kallsyms_lookup series but it was
decided in the reviews that a more generic helper, bpf_snprintf, would
be more useful.
This series implements the helper according to the feedback received in
https://lore.kernel.org/bpf/20201126165748.1748417-1-revest@google.com/T/#u
- A new arg type guarantees the NULL-termination of string arguments and
lets us pass format strings in only one arg
- A new helper is implemented using that guarantee. Because the format
string is known at verification time, the format string validation is
done by the verifier
- To implement a series of tests for bpf_snprintf, the logic for
marshalling variadic args in a fixed-size array is reworked as per:
https://lore.kernel.org/bpf/20210310015455.1095207-1-revest@chromium.org/T/#u
---
Changes in v5:
- Fixed the bpf_printf_buf_used counter logic in try_get_fmt_tmp_buf
- Added a couple of extra incorrect specifiers tests
- Call test_snprintf_single__destroy unconditionally
- Fixed a C++-style comment
---
Changes in v4:
- Moved bpf_snprintf, bpf_printf_prepare and bpf_printf_cleanup to
kernel/bpf/helpers.c so that they get built without CONFIG_BPF_EVENTS
- Added negative test cases (various invalid format strings)
- Renamed put_fmt_tmp_buf() as bpf_printf_cleanup()
- Fixed a mistake that caused temporary buffers to be unconditionally
freed in bpf_printf_prepare
- Fixed a mistake that caused missing 0 character to be ignored
- Fixed a warning about integer to pointer conversion
- Misc cleanups
---
Changes in v3:
- Simplified temporary buffer acquisition with try_get_fmt_tmp_buf()
- Made zero-termination check more consistent
- Allowed NULL output_buffer
- Simplified the BPF_CAST_FMT_ARG macro
- Three new test cases: number padding, simple string with no arg and
string length extraction only with a NULL output buffer
- Clarified helper's description for edge cases (eg: str_size == 0)
- Lots of cosmetic changes
---
Changes in v2:
- Extracted the format validation/argument sanitization in a generic way
for all printf-like helpers.
- bpf_snprintf's str_size can now be 0
- bpf_snprintf is now exposed to all BPF program types
- We now preempt_disable when using a per-cpu temporary buffer
- Addressed a few cosmetic changes
Florent Revest (6):
bpf: Factorize bpf_trace_printk and bpf_seq_printf
bpf: Add a ARG_PTR_TO_CONST_STR argument type
bpf: Add a bpf_snprintf helper
libbpf: Initialize the bpf_seq_printf parameters array field by field
libbpf: Introduce a BPF_SNPRINTF helper macro
selftests/bpf: Add a series of tests for bpf_snprintf
include/linux/bpf.h | 22 ++
include/uapi/linux/bpf.h | 28 ++
kernel/bpf/helpers.c | 306 ++++++++++++++
kernel/bpf/verifier.c | 82 ++++
kernel/trace/bpf_trace.c | 373 ++----------------
tools/include/uapi/linux/bpf.h | 28 ++
tools/lib/bpf/bpf_tracing.h | 58 ++-
.../selftests/bpf/prog_tests/snprintf.c | 125 ++++++
.../selftests/bpf/progs/test_snprintf.c | 73 ++++
.../bpf/progs/test_snprintf_single.c | 20 +
10 files changed, 770 insertions(+), 345 deletions(-)
create mode 100644 tools/testing/selftests/bpf/prog_tests/snprintf.c
create mode 100644 tools/testing/selftests/bpf/progs/test_snprintf.c
create mode 100644 tools/testing/selftests/bpf/progs/test_snprintf_single.c
--
2.31.1.368.gbe11c130af-goog
next reply other threads:[~2021-04-19 15:52 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-19 15:52 Florent Revest [this message]
2021-04-19 15:52 ` [PATCH bpf-next v5 1/6] bpf: Factorize bpf_trace_printk and bpf_seq_printf Florent Revest
2021-04-19 15:52 ` [PATCH bpf-next v5 2/6] bpf: Add a ARG_PTR_TO_CONST_STR argument type Florent Revest
2021-04-19 22:54 ` Alexei Starovoitov
2021-04-20 12:35 ` Florent Revest
2021-04-20 15:23 ` Alexei Starovoitov
2021-04-22 8:41 ` Florent Revest
2021-04-19 15:52 ` [PATCH bpf-next v5 3/6] bpf: Add a bpf_snprintf helper Florent Revest
2021-04-19 15:52 ` [PATCH bpf-next v5 4/6] libbpf: Initialize the bpf_seq_printf parameters array field by field Florent Revest
2021-04-19 15:52 ` [PATCH bpf-next v5 5/6] libbpf: Introduce a BPF_SNPRINTF helper macro Florent Revest
2021-04-19 15:52 ` [PATCH bpf-next v5 6/6] selftests/bpf: Add a series of tests for bpf_snprintf Florent Revest
2021-04-23 22:38 ` Andrii Nakryiko
2021-04-26 10:10 ` Florent Revest
2021-04-26 16:19 ` Andrii Nakryiko
2021-04-26 21:08 ` Florent Revest
2021-04-27 6:35 ` Rasmus Villemoes
2021-04-27 9:50 ` Florent Revest
2021-04-27 18:03 ` Andrii Nakryiko
2021-04-28 14:59 ` Florent Revest
2021-05-05 6:55 ` Rasmus Villemoes
2021-05-05 14:25 ` Florent Revest
2021-04-19 19:33 ` [PATCH bpf-next v5 0/6] Add a snprintf eBPF helper Andrii Nakryiko
2021-04-20 12:02 ` Florent Revest
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