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Message-ID: <f954c330-fb58-5f8f-1d66-5bbcd0d9dadb@redhat.com>
Date: Tue, 20 Sep 2016 18:26:54 -0700
From: Laura Abbott <labbott@...hat.com>
To: Mark Rutland <mark.rutland@....com>, linux-arm-kernel@...ts.infradead.org
Cc: akpm@...ux-foundation.org, ard.biesheuvel@...aro.org,
catalin.marinas@....com, james.morse@....com, keescook@...omium.org,
linux-kernel@...r.kernel.org, lorenzo.pieralisi@....com, luto@...nel.org,
suzuki.poulose@....com, takahiro.akashi@...aro.org, will.deacon@....com,
kernel-hardening@...ts.openwall.com
Subject: Re: [RFC PATCH 0/8] arm64: move thread_info off of the task stack
On 09/15/2016 06:49 AM, Mark Rutland wrote:
> Building atop of Andy's work on x86 and generic code, these patches move
> arm64's thread_info off of the stack and into task_struct. This protects
> thread_info from corruption in the face of stack overflow, and serves as
> a step towards fully robust stack overflow handling will be addressed by
> subsequent patches.
>
> In contrast to x86, we can't place some critical data such as
> preempt_count in percpu variables, and we must store these in some
> per-task location. This, compounded with the way headers are organised
> conspires to require us to still define our own thread_info. I
> understand that the longer term plan is to kill off thread_info
> entirely, hence I'm sending this as an RFC so we can figure out if/how
> we can achieve that.
>
> These patches are based on Andy's x86/vmap_stack branch [1,2], and I've
> pushed a copy to me arm64/ti-stack-split branch [3,4]. The result of
> these patches boots happily on platforms within reach of my desk, but
> has not seen much stressing so far.
>
FWIW, I used your ti-stack-split branch while running some kernel builds
and it seems to work well enough. You can take that as a Tested-by or I
can re-test with a non-RFC version.
> Thanks,
> Mark.
>
> [1] git://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git x86/vmap_stack
> [2] https://git.kernel.org/cgit/linux/kernel/git/luto/linux.git/log/?h=x86/vmap_stack
> [3] git://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git arm64/ti-stack-split
> [4] https://git.kernel.org/cgit/linux/kernel/git/mark/linux.git/log/?h=arm64/ti-stack-split
>
> Mark Rutland (8):
> thread_info: include <current.h> for THREAD_INFO_IN_TASK
> thread_info: allow custom in-task thread_info
> arm64: thread_info remove stale items
> arm64: asm-offsets: remove unused definitions
> arm64: assembler: introduce ldr_this_cpu
> arm64: traps: use task_struct instead of thread_info
> arm64: move sp_el0 and tpidr_el1 into cpu_suspend_ctx
> arm64: split thread_info from task stack
>
> arch/arm64/Kconfig | 2 ++
> arch/arm64/include/asm/Kbuild | 1 -
> arch/arm64/include/asm/assembler.h | 19 +++++++++++++++----
> arch/arm64/include/asm/current.h | 22 ++++++++++++++++++++++
> arch/arm64/include/asm/smp.h | 1 +
> arch/arm64/include/asm/suspend.h | 2 +-
> arch/arm64/include/asm/thread_info.h | 21 ---------------------
> arch/arm64/kernel/asm-offsets.c | 3 +--
> arch/arm64/kernel/entry.S | 6 +++---
> arch/arm64/kernel/head.S | 11 +++++------
> arch/arm64/kernel/process.c | 31 ++++++++++++++++++++++++++-----
> arch/arm64/kernel/sleep.S | 3 ---
> arch/arm64/kernel/smp.c | 2 ++
> arch/arm64/kernel/stacktrace.c | 5 +++++
> arch/arm64/kernel/suspend.c | 6 ------
> arch/arm64/kernel/traps.c | 12 ++++++------
> arch/arm64/mm/proc.S | 6 ++++++
> include/linux/thread_info.h | 4 +++-
> init/Kconfig | 3 +++
> 19 files changed, 101 insertions(+), 59 deletions(-)
> create mode 100644 arch/arm64/include/asm/current.h
>
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