From: Kees Cook <keescook@chromium.org>
To: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Cc: Miguel Ojeda <ojeda@kernel.org>,
Siddhesh Poyarekar <siddhesh@gotplt.org>,
Nick Desaulniers <ndesaulniers@google.com>,
Nathan Chancellor <nathan@kernel.org>, Tom Rix <trix@redhat.com>,
llvm@lists.linux.dev, linux-kernel@vger.kernel.org,
linux-hardening@vger.kernel.org
Subject: Re: [PATCH] Compiler Attributes: Introduce __access_*() function attribute
Date: Sat, 24 Sep 2022 07:58:54 -0700 [thread overview]
Message-ID: <202209240757.3AC47AC6@keescook> (raw)
In-Reply-To: <CANiq72n6zK=sXn2j71bAEUUYwRse2dT9f8kLrYzncnPjN1XTow@mail.gmail.com>
On Sat, Sep 24, 2022 at 12:06:31PM +0200, Miguel Ojeda wrote:
> On Sat, Sep 24, 2022 at 1:54 AM Kees Cook <keescook@chromium.org> wrote:
> >
> > are specified. While it is legal to provide only the pointer argument
> > position and access type, design the kernel macros to require also the
> > bounds (element count) argument position: if a function has no bounds
> > argument, refactor the code to include one.
>
> Should this bit be included in the comment of the attribute? (since it
> is specific to the kernel)
Sure; good idea!
>
> > These can be used multiple times. For example:
> >
> > __access_wo(2, 3) __access_ro(4, 5)
> > int copy_something(struct context *ctx, u32 *dst, size_t dst_count,
> > u8 *src, int src_len);
> >
> > (And if "dst" will also be read, it could use __access_rw(2, 3) instead.)
>
> Also maybe the example could be nice there too, since it uses the
> syntax for the kernel and you took the time to write it :)
>
> By the way, shouldn't `src` typically be `const u8 *`? Given it is an
> example, I would qualify it.
Yeah, I will update this.
>
> > +#if __has_attribute(__access__)
> > +#define __access_rw(ptr, count) __attribute__((__access__(read_write, ptr, count)))
> > +#define __access_ro(ptr, count) __attribute__((__access__(read_only, ptr, count)))
> > +#define __access_wo(ptr, count) __attribute__((__access__(write_only, ptr, count)))
> > +#else
> > +#define __access_rw(ptr, count)
> > +#define __access_ro(ptr, count)
> > +#define __access_wo(ptr, count)
> > +#endif
>
> If you do a v2 for the above, please take the chance to indent with a
> single space after the `#` (like `# define`) for consistency.
Fixed! I will send a v2.
--
Kees Cook
prev parent reply other threads:[~2022-09-24 14:58 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-23 23:54 [PATCH] Compiler Attributes: Introduce __access_*() function attribute Kees Cook
2022-09-24 0:17 ` Gustavo A. R. Silva
2022-09-24 10:06 ` Miguel Ojeda
2022-09-24 14:58 ` Kees Cook [this message]
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