From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Kees Cook <keescook@chromium.org>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>,
linux-kernel@vger.kernel.org, patches@lists.linux.dev,
dri-devel@lists.freedesktop.org, kasan-dev@googlegroups.com,
kernel-janitors@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-block@vger.kernel.org, linux-crypto@vger.kernel.org,
linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-media@vger.kernel.org, linux-mips@vger.kernel.org,
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linux-s390@vger.kernel.org, linux-um@lists.infradead.org,
linux-usb@vger.kernel.org, linux-wireless@vger.kernel.org,
linuxppc-dev@lists.ozlabs.org, loongarch@lists.linux.dev,
netdev@vger.kernel.org, sparclinux@vger.kernel.org,
x86@kernel.org, Jan Kara <jack@suse.cz>
Subject: Re: [PATCH v4 2/6] treewide: use prandom_u32_max() when possible
Date: Sat, 8 Oct 2022 21:16:20 +0300 [thread overview]
Message-ID: <Y0G+dP9uGaYHSa9y@smile.fi.intel.com> (raw)
In-Reply-To: <53DD0148-ED15-4294-8496-9E4B4C7AD061@chromium.org>
On Fri, Oct 07, 2022 at 08:50:43PM -0700, Kees Cook wrote:
> On October 7, 2022 7:21:28 PM PDT, "Jason A. Donenfeld" <Jason@zx2c4.com> wrote:
> >On Fri, Oct 07, 2022 at 03:47:44PM -0700, Kees Cook wrote:
> >> On Fri, Oct 07, 2022 at 12:01:03PM -0600, Jason A. Donenfeld wrote:
...
> >> These are more fun, but Coccinelle can still do them with a little
> >> Pythonic help:
> >>
> >> // Find a potential literal
> >> @literal_mask@
> >> expression LITERAL;
> >> identifier randfunc =~ "get_random_int|prandom_u32|get_random_u32";
> >> position p;
> >> @@
> >>
> >> (randfunc()@p & (LITERAL))
> >>
> >> // Add one to the literal.
> >> @script:python add_one@
> >> literal << literal_mask.LITERAL;
> >> RESULT;
> >> @@
> >>
> >> if literal.startswith('0x'):
> >> value = int(literal, 16) + 1
> >> coccinelle.RESULT = cocci.make_expr("0x%x" % (value))
> >> elif literal[0] in '123456789':
> >> value = int(literal, 10) + 1
> >> coccinelle.RESULT = cocci.make_expr("%d" % (value))
> >> else:
> >> print("I don't know how to handle: %s" % (literal))
Wouldn't Python take care about (known) prefixes itself?
try:
x = int(literal)
except ValueError as ex:
print(..., ex.error)
> >> // Replace the literal mask with the calculated result.
> >> @plus_one@
> >> expression literal_mask.LITERAL;
> >> position literal_mask.p;
> >> expression add_one.RESULT;
> >> identifier FUNC;
> >> @@
> >>
> >> - (FUNC()@p & (LITERAL))
> >> + prandom_u32_max(RESULT)
> >
> >Oh that's pretty cool. I can do the saturation check in python, since
> >`value` holds the parsed result. Neat.
>
> It is (at least how I have it here) just the string, so YMMV.
...
> >Thanks a bunch for the guidance.
>
> Sure thing! I was pleased to figure out how to do the python bit.
I believe it can be optimized
--
With Best Regards,
Andy Shevchenko
next prev parent reply other threads:[~2022-10-08 18:16 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-08 3:50 [PATCH v4 2/6] treewide: use prandom_u32_max() when possible Kees Cook
2022-10-08 7:33 ` Julia Lawall
2022-10-08 18:16 ` Andy Shevchenko [this message]
-- strict thread matches above, loose matches on Subject: below --
2022-10-07 18:01 [PATCH v4 0/6] treewide cleanup of random integer usage Jason A. Donenfeld
2022-10-07 18:01 ` [PATCH v4 2/6] treewide: use prandom_u32_max() when possible Jason A. Donenfeld
2022-10-07 21:17 ` Darrick J. Wong
2022-10-08 1:28 ` Jason A. Donenfeld
2022-10-07 22:47 ` Kees Cook
2022-10-08 2:21 ` Jason A. Donenfeld
2022-10-08 3:21 ` Jason A. Donenfeld
2022-10-08 22:08 ` David Laight
2022-10-08 22:19 ` Jason A. Donenfeld
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