From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Florent Revest <revest@chromium.org>, bpf <bpf@vger.kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>, Yonghong Song <yhs@fb.com>,
KP Singh <kpsingh@kernel.org>,
Brendan Jackman <jackmanb@chromium.org>,
open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH bpf-next v3 3/6] bpf: Add a bpf_snprintf helper
Date: Wed, 14 Apr 2021 20:02:15 +0200 [thread overview]
Message-ID: <CAMuHMdUQOi8h31D_Qtnv_E1vsEu6RO8sHy-DArQ0jQt5v_JoVA@mail.gmail.com> (raw)
In-Reply-To: <CAEf4BzZCR2JMXwNvJikfWYnZa-CyCQTQsW+Xs_5w9zOT3kbVSA@mail.gmail.com>
Hi Andrii,
On Wed, Apr 14, 2021 at 9:41 AM Andrii Nakryiko
<andrii.nakryiko@gmail.com> wrote:
> On Mon, Apr 12, 2021 at 8:38 AM Florent Revest <revest@chromium.org> wrote:
> > The implementation takes inspiration from the existing bpf_trace_printk
> > helper but there are a few differences:
> >
> > To allow for a large number of format-specifiers, parameters are
> > provided in an array, like in bpf_seq_printf.
> >
> > Because the output string takes two arguments and the array of
> > parameters also takes two arguments, the format string needs to fit in
> > one argument. Thankfully, ARG_PTR_TO_CONST_STR is guaranteed to point to
> > a zero-terminated read-only map so we don't need a format string length
> > arg.
> >
> > Because the format-string is known at verification time, we also do
> > a first pass of format string validation in the verifier logic. This
> > makes debugging easier.
> >
> > Signed-off-by: Florent Revest <revest@chromium.org>
> > ---
> > include/linux/bpf.h | 6 ++++
> > include/uapi/linux/bpf.h | 28 +++++++++++++++++++
> > kernel/bpf/helpers.c | 2 ++
> > kernel/bpf/verifier.c | 41 ++++++++++++++++++++++++++++
> > kernel/trace/bpf_trace.c | 50 ++++++++++++++++++++++++++++++++++
> > tools/include/uapi/linux/bpf.h | 28 +++++++++++++++++++
> > 6 files changed, 155 insertions(+)
> >
>
> [...]
>
> > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> > index 5f46dd6f3383..d4020e5f91ee 100644
> > --- a/kernel/bpf/verifier.c
> > +++ b/kernel/bpf/verifier.c
> > @@ -5918,6 +5918,41 @@ static int check_reference_leak(struct bpf_verifier_env *env)
> > return state->acquired_refs ? -EINVAL : 0;
> > }
> >
> > +static int check_bpf_snprintf_call(struct bpf_verifier_env *env,
> > + struct bpf_reg_state *regs)
> > +{
> > + struct bpf_reg_state *fmt_reg = ®s[BPF_REG_3];
> > + struct bpf_reg_state *data_len_reg = ®s[BPF_REG_5];
> > + struct bpf_map *fmt_map = fmt_reg->map_ptr;
> > + int err, fmt_map_off, num_args;
> > + u64 fmt_addr;
> > + char *fmt;
> > +
> > + /* data must be an array of u64 */
> > + if (data_len_reg->var_off.value % 8)
> > + return -EINVAL;
> > + num_args = data_len_reg->var_off.value / 8;
> > +
> > + /* fmt being ARG_PTR_TO_CONST_STR guarantees that var_off is const
> > + * and map_direct_value_addr is set.
> > + */
> > + fmt_map_off = fmt_reg->off + fmt_reg->var_off.value;
> > + err = fmt_map->ops->map_direct_value_addr(fmt_map, &fmt_addr,
> > + fmt_map_off);
> > + if (err)
> > + return err;
> > + fmt = (char *)fmt_addr + fmt_map_off;
> > +
>
> bot complained about lack of (long) cast before fmt_addr, please address
(uintptr_t), I assume?
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
next prev parent reply other threads:[~2021-04-14 18:02 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-12 15:37 [PATCH bpf-next v3 0/6] Add a snprintf eBPF helper Florent Revest
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 [this message]
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAMuHMdUQOi8h31D_Qtnv_E1vsEu6RO8sHy-DArQ0jQt5v_JoVA@mail.gmail.com \
--to=geert@linux-m68k.org \
--cc=andrii.nakryiko@gmail.com \
--cc=andrii@kernel.org \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=jackmanb@chromium.org \
--cc=kpsingh@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=revest@chromium.org \
--cc=yhs@fb.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).