From: Mark Rutland <mark.rutland@arm.com>
To: Will Deacon <will.deacon@arm.com>
Cc: linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org,
kernel-hardening@lists.openwall.com,
Catalin Marinas <catalin.marinas@arm.com>,
Kees Cook <keescook@chromium.org>,
Laura Abbott <labbott@redhat.com>
Subject: Re: [RFC PATCH 1/2] arm64: write __range_ok() in C
Date: Mon, 20 Nov 2017 12:22:35 +0000 [thread overview]
Message-ID: <20171120122235.ku6whdnpgatib6in@lakrids.cambridge.arm.com> (raw)
In-Reply-To: <20171116152818.GM9361@arm.com>
On Thu, Nov 16, 2017 at 03:28:19PM +0000, Will Deacon wrote:
> On Thu, Oct 26, 2017 at 10:09:41AM +0100, Mark Rutland wrote:
> > +static bool __range_ok_c(unsigned long addr, unsigned long size)
> > +{
> > + unsigned long result;
> > +
> > + if (__builtin_uaddl_overflow(addr, size, &result))
>
> I'm not sure if you're planning to revisit this series, but thought I'd
> give you a heads up that apparently GCC 4.x doesn't have support for this
> builtin, so we'll need to carry the asm at least for that toolchain.
Thanks for the heads-up. I see my Linaro 14.09 GCC 4.9 generates an
out-of-line call to a __builtin_uaddl_overflow helper.
We can avoid the builtin, and write the test in C instead, e.g.
static inline bool __range_ok_c(unsigned long addr, unsigned long size)
{
unsigned long end = addr + size;
if (end < addr)
return false;
return end <= current_thread_info()->addr_limit;
}
... in my standalone test-case, that generates code that's almost
identical to the builtin, except that the compiler chooses to look at a
different flag.
Thanks,
Mark.
next prev parent reply other threads:[~2017-11-20 12:22 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-26 9:09 [RFC PATCH 0/2] arm64: optional paranoid __{get,put}_user checks Mark Rutland
2017-10-26 9:09 ` [RFC PATCH 1/2] arm64: write __range_ok() in C Mark Rutland
2017-11-16 15:28 ` Will Deacon
2017-11-20 12:22 ` Mark Rutland [this message]
2017-10-26 9:09 ` [RFC PATCH 2/2] arm64: allow paranoid __{get,put}user Mark Rutland
2017-10-27 15:41 ` [RFC PATCH 0/2] arm64: optional paranoid __{get,put}_user checks Will Deacon
2017-10-27 20:44 ` Mark Rutland
2017-10-28 8:47 ` Russell King - ARM Linux
2017-10-31 23:56 ` Laura Abbott
2017-11-01 12:05 ` Mark Rutland
2017-11-01 21:13 ` Laura Abbott
2017-11-01 22:28 ` Kees Cook
2017-11-01 23:05 ` Laura Abbott
2017-11-01 23:29 ` Kees Cook
2017-11-02 1:25 ` Laura Abbott
2017-11-03 23:04 ` [RFC PATCH 1/2] x86: Avoid multiple evaluations in __{get,put}_user_size Laura Abbott
2017-11-03 23:04 ` [RFC PATCH 2/2] x86: Allow paranoid __{get,put}_user Laura Abbott
2017-11-04 0:14 ` Kees Cook
2017-11-04 0:24 ` Al Viro
2017-11-04 0:44 ` Al Viro
2017-11-04 1:39 ` Kees Cook
2017-11-04 1:41 ` Kees Cook
2017-11-04 1:58 ` Mark Rutland
2017-11-06 20:38 ` Laura Abbott
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