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 v3 0/6] Add a snprintf eBPF helper
Date: Mon, 12 Apr 2021 17:37:48 +0200 [thread overview]
Message-ID: <20210412153754.235500-1-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 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 | 7 +
include/uapi/linux/bpf.h | 28 +
kernel/bpf/helpers.c | 2 +
kernel/bpf/verifier.c | 82 +++
kernel/trace/bpf_trace.c | 579 +++++++++---------
tools/include/uapi/linux/bpf.h | 28 +
tools/lib/bpf/bpf_tracing.h | 58 +-
.../selftests/bpf/prog_tests/snprintf.c | 81 +++
.../selftests/bpf/progs/test_snprintf.c | 74 +++
9 files changed, 647 insertions(+), 292 deletions(-)
create mode 100644 tools/testing/selftests/bpf/prog_tests/snprintf.c
create mode 100644 tools/testing/selftests/bpf/progs/test_snprintf.c
--
2.31.1.295.g9ea45b61b8-goog
next reply other threads:[~2021-04-12 15:38 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-12 15:37 Florent Revest [this message]
2021-04-12 15:37 ` [PATCH bpf-next v3 1/6] bpf: Factorize bpf_trace_printk and bpf_seq_printf Florent Revest
2021-04-13 23:01 ` Andrii Nakryiko
2021-04-14 9:56 ` Florent Revest
2021-04-14 10:56 ` Florent Revest
2021-04-12 15:37 ` [PATCH bpf-next v3 2/6] bpf: Add a ARG_PTR_TO_CONST_STR argument type Florent Revest
2021-04-13 23:03 ` Andrii Nakryiko
2021-04-12 15:37 ` [PATCH bpf-next v3 3/6] bpf: Add a bpf_snprintf helper Florent Revest
2021-04-12 19:11 ` kernel test robot
2021-04-12 20:32 ` kernel test robot
2021-04-14 13:32 ` Florent Revest
2021-04-12 20:40 ` kernel test robot
2021-04-13 23:16 ` Andrii Nakryiko
2021-04-14 9:46 ` Florent Revest
2021-04-14 22:57 ` Andrii Nakryiko
2021-04-15 9:34 ` Florent Revest
2021-04-14 18:02 ` Geert Uytterhoeven
2021-04-14 18:30 ` Florent Revest
2021-04-14 22:58 ` Andrii Nakryiko
2021-04-15 7:18 ` Geert Uytterhoeven
2021-04-12 15:37 ` [PATCH bpf-next v3 4/6] libbpf: Initialize the bpf_seq_printf parameters array field by field Florent Revest
2021-04-13 23:18 ` Andrii Nakryiko
2021-04-12 15:37 ` [PATCH bpf-next v3 5/6] libbpf: Introduce a BPF_SNPRINTF helper macro Florent Revest
2021-04-13 23:18 ` Andrii Nakryiko
2021-04-12 15:37 ` [PATCH bpf-next v3 6/6] selftests/bpf: Add a series of tests for bpf_snprintf Florent Revest
2021-04-13 23:21 ` Andrii Nakryiko
2021-04-14 9:21 ` Florent Revest
2021-04-14 22:16 ` Andrii Nakryiko
2021-04-15 9:38 ` Florent Revest
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