Re: [PATCH v16 10/13] arch/arm: enable task isolation functionality

From: Chris Metcalf
Date: Fri Nov 03 2017 - 13:28:12 EST


On 11/3/2017 1:23 PM, Russell King - ARM Linux wrote:
On Fri, Nov 03, 2017 at 01:04:49PM -0400, Chris Metcalf wrote:
From: Francis Giraldeau <francis.giraldeau@xxxxxxxxx>

This patch is a port of the task isolation functionality to the arm 32-bit
architecture. The task isolation needs an additional thread flag that
requires to change the entry assembly code to accept a bitfield larger than
one byte. The constants _TIF_SYSCALL_WORK and _TIF_WORK_MASK are now
defined in the literal pool. The rest of the patch is straightforward and
reflects what is done on other architectures.

To avoid problems with the tst instruction in the v7m build, we renumber
TIF_SECCOMP to bit 8 and let TIF_TASK_ISOLATION use bit 7.
After a bit of digging (which could've been saved if our patch format
contained information about what kernel version this patch was
generated against) it turns out that this patch will not apply since
commit 73ac5d6a2b6ac ("arm/syscalls: Check address limit on user-mode
return") has been applied, which means the TIF numbers have changed
as well as the assembly code that your patch touches.

My guess is that this patch was generated from a 4.13 kernel, so
misses the 4.14-rc1 changes. Since we're potentially about to start
the merge window for 4.15 this weekend, the timing of this doesn't
work well either.

What patch failure did you see? The patch is based against 4.14-rc4, so while
it's a few weeks out of date, it does include the commit you reference.

Once 4.15-rc1 has been published, please rebase against that version
and resend.

Sure. I was hoping to eke out a little bit of attention from kernel developers
before the merge window actually opens :)

--
Chris Metcalf, Mellanox Technologies
http://www.mellanox.com