From mboxrd@z Thu Jan 1 00:00:00 1970 From: "H. Peter Anvin" Date: Mon, 04 Jan 2016 18:13:46 +0000 Subject: Re: [PATCH 6/6] arm64: switch to relative exception tables Message-Id: <568AB65A.8030901@zytor.com> List-Id: References: <1451837157-447-1-git-send-email-ard.biesheuvel@linaro.org> <1451837157-447-7-git-send-email-ard.biesheuvel@linaro.org> <20160104144643.GE1616@arm.com> In-Reply-To: <20160104144643.GE1616@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Will Deacon , Ard Biesheuvel Cc: linux-alpha@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org, linux-s390@vger.kernel.org, x86@kernel.org, mingo@redhat.com, heiko.carstens@de.ibm.com, schwidefsky@de.ibm.com, mattst88@gmail.com, ink@jurassic.park.msu.ru, rth@twiddle.net, tony.luck@intel.com, fenghua.yu@intel.com, catalin.marinas@arm.com, arnd@arndb.de, akpm@linux-foundation.org, mark.rutland@arm.com, marc.zyngier@arm.com On 01/04/2016 06:46 AM, Will Deacon wrote: > On Sun, Jan 03, 2016 at 05:05:57PM +0100, Ard Biesheuvel wrote: >> Instead of using absolute addresses for both the exception location >> and the fixup, use offsets relative to the exception table entry values. >> Not only does this cut the size of the exception table in half, it is >> also a prerequisite for KASLR, since absolute exception table entries >> are subject to dynamic relocation, which is incompatible with the sorting >> of the exception table that occurs at build time. >> >> Cc: Catalin Marinas >> Cc: Will Deacon >> Signed-off-by: Ard Biesheuvel >> --- >> >> Note that this patch supersedes the version I sent as part of the series that >> implements KASLR for arm64: http://thread.gmane.org/gmane.linux.kernel/2116531 >> >> arch/arm64/include/asm/assembler.h | 2 +- >> arch/arm64/include/asm/futex.h | 4 ++-- >> arch/arm64/include/asm/uaccess.h | 18 ++++++++++-------- >> arch/arm64/kernel/armv8_deprecated.c | 4 ++-- >> arch/arm64/mm/extable.c | 2 +- >> scripts/sortextable.c | 2 +- >> 6 files changed, 17 insertions(+), 15 deletions(-) > > This looks good to me, so for the arm64 part (i.e. this patch): > > Acked-by: Will Deacon May I humbly ask why the [Finnish] you don't use the equivalent of the x86 _ASM_EXTABLE() macro? In fact, why don't we make that one generic, too? -hpa