lkml.org 
[lkml]   [2021]   [Mar]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Subject[PATCH bpf-next 0/5] Add a snprintf eBPF helper
Date
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

Florent Revest (5):
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 | 5 +
include/uapi/linux/bpf.h | 28 +++
kernel/bpf/verifier.c | 178 ++++++++++++++++++
kernel/trace/bpf_trace.c | 110 +++++++++++
tools/include/uapi/linux/bpf.h | 28 +++
tools/lib/bpf/bpf_tracing.h | 45 ++++-
.../selftests/bpf/prog_tests/snprintf.c | 71 +++++++
.../selftests/bpf/progs/test_snprintf.c | 71 +++++++
8 files changed, 535 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/selftests/bpf/prog_tests/snprintf.c
create mode 100644 tools/testing/selftests/bpf/progs/test_snprintf.c

--
2.30.1.766.gb4fecdf3b7-goog

\
 
 \ /
  Last update: 2021-03-10 23:05    [W:0.137 / U:0.328 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site