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Message-Id: <20210324022211.1718762-1-revest@chromium.org>
Date: Wed, 24 Mar 2021 03:22:05 +0100
From: Florent Revest <revest@...omium.org>
To: bpf@...r.kernel.org
Cc: ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
yhs@...com, kpsingh@...nel.org, jackmanb@...omium.org,
linux-kernel@...r.kernel.org, Florent Revest <revest@...omium.org>
Subject: [PATCH bpf-next v2 0/6] Add a snprintf eBPF helper
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 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 | 79 +++
kernel/trace/bpf_trace.c | 581 +++++++++---------
tools/include/uapi/linux/bpf.h | 28 +
tools/lib/bpf/bpf_tracing.h | 44 +-
.../selftests/bpf/prog_tests/snprintf.c | 65 ++
.../selftests/bpf/progs/test_snprintf.c | 59 ++
9 files changed, 604 insertions(+), 289 deletions(-)
create mode 100644 tools/testing/selftests/bpf/prog_tests/snprintf.c
create mode 100644 tools/testing/selftests/bpf/progs/test_snprintf.c
--
2.31.0.291.g576ba9dcdaf-goog
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