From: Florent Revest <revest@chromium.org>
To: bpf@vger.kernel.org
Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org,
kpsingh@kernel.org, jackmanb@google.com,
linux@rasmusvillemoes.dk, rostedt@goodmis.org,
linux-kernel@vger.kernel.org,
Florent Revest <revest@chromium.org>
Subject: [PATCH bpf-next v2 0/2] Implement formatted output helpers with bstr_printf
Date: Tue, 27 Apr 2021 19:43:11 +0200 [thread overview]
Message-ID: <20210427174313.860948-1-revest@chromium.org> (raw)
BPF's formatted output helpers are currently implemented with
snprintf-like functions which use variadic arguments. The types of all
arguments need to be known at compilation time. BPF_CAST_FMT_ARG casts
all arguments to the size they should be (known at runtime), but the C
type promotion rules cast them back to u64s. On 32 bit architectures,
this can cause misaligned va_lists and generate mangled output.
This series refactors these helpers to avoid variadic arguments. It uses
a "binary printf" instead, where arguments are passed in a buffer
constructed at runtime.
---
Changes in v2:
- Reworded the second patch's description to better describe how
arguments get mangled on 32 bit architectures
Florent Revest (2):
seq_file: Add a seq_bprintf function
bpf: Implement formatted output helpers with bstr_printf
fs/seq_file.c | 18 ++++
include/linux/bpf.h | 22 +----
include/linux/seq_file.h | 4 +
init/Kconfig | 1 +
kernel/bpf/helpers.c | 188 +++++++++++++++++++++------------------
kernel/bpf/verifier.c | 2 +-
kernel/trace/bpf_trace.c | 34 +++----
7 files changed, 137 insertions(+), 132 deletions(-)
--
2.31.1.498.g6c1eba8ee3d-goog
next reply other threads:[~2021-04-27 17:43 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-27 17:43 Florent Revest [this message]
2021-04-27 17:43 ` [PATCH bpf-next v2 1/2] seq_file: Add a seq_bprintf function Florent Revest
2021-04-27 17:43 ` [PATCH bpf-next v2 2/2] bpf: Implement formatted output helpers with bstr_printf Florent Revest
2021-04-27 23:46 ` Alexei Starovoitov
2021-04-28 0:20 ` Florent Revest
2021-04-28 0:51 ` Alexei Starovoitov
2021-04-28 14:52 ` Florent Revest
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