From: arnd@arndb.de (Arnd Bergmann)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v5 3/4] arm64: mm: support ARCH_MMAP_RND_BITS.
Date: Tue, 08 Dec 2015 11:03:51 +0100 [thread overview]
Message-ID: <7610963.Sys3aageLY@wuerfel> (raw)
In-Reply-To: <5665CF5A.1090207@android.com>
On Monday 07 December 2015 10:26:34 Daniel Cashman wrote:
> > Ideally we'd remove the #ifdef around the mmap_rnd_compat_bits declaration
> > and change this code to use
> >
> > if (IS_ENABLED(CONFIG_COMPAT) && test_thread_flag(TIF_32BIT))
> >
> That would result in "undefined reference to mmap_rnd_compat_bits" in
> the not-defined case, no?
No. The compiler eliminates all code paths that it knows are unused.
The IS_ENABLED() macro is designed to let the compiler figure this out.
Arnd
WARNING: multiple messages have this Message-ID (diff)
From: Arnd Bergmann <arnd@arndb.de>
To: linux-arm-kernel@lists.infradead.org
Cc: Daniel Cashman <dcashman@android.com>,
Jon Hunter <jonathanh@nvidia.com>,
linux-doc@vger.kernel.org, catalin.marinas@arm.com,
will.deacon@arm.com, linux-mm@kvack.org, hpa@zytor.com,
mingo@kernel.org, aarcange@redhat.com, linux@arm.linux.org.uk,
kirill.shutemov@linux.intel.com, corbet@lwn.net,
xypron.glpk@gmx.de, x86@kernel.org, hecmargi@upv.es,
mgorman@suse.de, rientjes@google.com, bp@suse.de, nnk@google.com,
dzickus@redhat.com, keescook@chromium.org, jpoimboe@redhat.com,
tglx@linutronix.de, akpm@linux-foundation.org,
linux-kernel@vger.kernel.org, salyzyn@android.com,
ebiederm@xmission.com, jeffv@google.com,
n-horiguchi@ah.jp.nec.com, dcashman@google.com
Subject: Re: [PATCH v5 3/4] arm64: mm: support ARCH_MMAP_RND_BITS.
Date: Tue, 08 Dec 2015 11:03:51 +0100 [thread overview]
Message-ID: <7610963.Sys3aageLY@wuerfel> (raw)
In-Reply-To: <5665CF5A.1090207@android.com>
On Monday 07 December 2015 10:26:34 Daniel Cashman wrote:
> > Ideally we'd remove the #ifdef around the mmap_rnd_compat_bits declaration
> > and change this code to use
> >
> > if (IS_ENABLED(CONFIG_COMPAT) && test_thread_flag(TIF_32BIT))
> >
> That would result in "undefined reference to mmap_rnd_compat_bits" in
> the not-defined case, no?
No. The compiler eliminates all code paths that it knows are unused.
The IS_ENABLED() macro is designed to let the compiler figure this out.
Arnd
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WARNING: multiple messages have this Message-ID (diff)
From: Arnd Bergmann <arnd@arndb.de>
To: linux-arm-kernel@lists.infradead.org
Cc: Daniel Cashman <dcashman@android.com>,
Jon Hunter <jonathanh@nvidia.com>,
linux-doc@vger.kernel.org, catalin.marinas@arm.com,
will.deacon@arm.com, linux-mm@kvack.org, hpa@zytor.com,
mingo@kernel.org, aarcange@redhat.com, linux@arm.linux.org.uk,
kirill.shutemov@linux.intel.com, corbet@lwn.net,
xypron.glpk@gmx.de, x86@kernel.org, hecmargi@upv.es,
mgorman@suse.de, rientjes@google.com, bp@suse.de, nnk@google.com,
dzickus@redhat.com, keescook@chromium.org, jpoimboe@redhat.com,
tglx@linutronix.de, akpm@linux-foundation.org,
linux-kernel@vger.kernel.org, salyzyn@android.com,
ebiederm@xmission.com, jeffv@google.com,
n-horiguchi@ah.jp.nec.com, dcashman@google.com
Subject: Re: [PATCH v5 3/4] arm64: mm: support ARCH_MMAP_RND_BITS.
Date: Tue, 08 Dec 2015 11:03:51 +0100 [thread overview]
Message-ID: <7610963.Sys3aageLY@wuerfel> (raw)
In-Reply-To: <5665CF5A.1090207@android.com>
On Monday 07 December 2015 10:26:34 Daniel Cashman wrote:
> > Ideally we'd remove the #ifdef around the mmap_rnd_compat_bits declaration
> > and change this code to use
> >
> > if (IS_ENABLED(CONFIG_COMPAT) && test_thread_flag(TIF_32BIT))
> >
> That would result in "undefined reference to mmap_rnd_compat_bits" in
> the not-defined case, no?
No. The compiler eliminates all code paths that it knows are unused.
The IS_ENABLED() macro is designed to let the compiler figure this out.
Arnd
next prev parent reply other threads:[~2015-12-08 10:03 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-01 20:10 [PATCH v5 0/4] Allow customizable random offset to mmap_base address Daniel Cashman
2015-12-01 20:10 ` Daniel Cashman
2015-12-01 20:10 ` Daniel Cashman
2015-12-01 20:10 ` [PATCH v5 1/4] mm: mmap: Add new /proc tunable for mmap_base ASLR Daniel Cashman
2015-12-01 20:10 ` Daniel Cashman
2015-12-01 20:10 ` Daniel Cashman
2015-12-01 20:10 ` [PATCH v5 2/4] arm: mm: support ARCH_MMAP_RND_BITS Daniel Cashman
2015-12-01 20:10 ` Daniel Cashman
2015-12-01 20:10 ` Daniel Cashman
2015-12-01 20:10 ` [PATCH v5 3/4] arm64: " Daniel Cashman
2015-12-01 20:10 ` Daniel Cashman
2015-12-01 20:10 ` Daniel Cashman
2015-12-01 20:10 ` [PATCH v5 4/4] x86: " Daniel Cashman
2015-12-01 20:10 ` Daniel Cashman
2015-12-01 20:10 ` Daniel Cashman
2015-12-03 12:17 ` [PATCH v5 3/4] arm64: " Will Deacon
2015-12-03 12:17 ` Will Deacon
2015-12-03 12:17 ` Will Deacon
2015-12-03 16:12 ` Daniel Cashman
2015-12-03 16:12 ` Daniel Cashman
2015-12-03 16:12 ` Daniel Cashman
2015-12-07 10:26 ` Jon Hunter
2015-12-07 10:26 ` Jon Hunter
2015-12-07 10:26 ` Jon Hunter
2015-12-07 11:13 ` Arnd Bergmann
2015-12-07 11:13 ` Arnd Bergmann
2015-12-07 11:13 ` Arnd Bergmann
2015-12-07 18:26 ` Daniel Cashman
2015-12-07 18:26 ` Daniel Cashman
2015-12-07 18:26 ` Daniel Cashman
2015-12-08 10:03 ` Arnd Bergmann [this message]
2015-12-08 10:03 ` Arnd Bergmann
2015-12-08 10:03 ` Arnd Bergmann
2015-12-01 22:39 ` [PATCH v5 0/4] Allow customizable random offset to mmap_base address Kees Cook
2015-12-01 22:39 ` Kees Cook
2015-12-01 22:39 ` Kees Cook
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