From: Nicolas Pitre <nicolas.pitre@linaro.org>
To: Thomas Garnier <thgarnie@google.com>
Cc: "Arnd Bergmann" <arnd@arndb.de>,
"David Howells" <dhowells@redhat.com>,
"Al Viro" <viro@zeniv.linux.org.uk>,
"Dave Hansen" <dave.hansen@intel.com>,
"René Nyffenegger" <mail@renenyffenegger.ch>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Kees Cook" <keescook@chromium.org>,
"Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
"Petr Mladek" <pmladek@suse.com>,
"Andy Lutomirski" <luto@kernel.org>,
"Ard Biesheuvel" <ard.biesheuvel@linaro.org>,
"Sebastian Andrzej Siewior" <bigeasy@linutronix.de>,
"Sergey Senozhatsky" <sergey.senozhatsky@gmail.com>,
"Helge Deller" <deller@gmx.de>, "Rik van Riel" <riel@redhat.com>,
"Ingo Molnar" <mingo@kernel.org>,
"John Stultz" <john.stultz@linaro.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Oleg Nesterov" <oleg@redhat.com>,
"Stanislav Kinsburskiy" <skinsbursky@virtuozzo.com>
Subject: Re: [PATCH v1 3/4] arm/syscalls: Specific usage of verify_pre_usermode_state
Date: Wed, 8 Mar 2017 23:05:46 +0100 (CET) [thread overview]
Message-ID: <alpine.LFD.2.20.1703082256480.23532@knanqh.ubzr> (raw)
In-Reply-To: <20170308213844.131877-3-thgarnie@google.com>
On Wed, 8 Mar 2017, Thomas Garnier wrote:
> Implement specific usage of verify_pre_usermode_state for user-mode
> returns for arm.
> ---
> Based on next-20170308
> ---
> arch/arm/Kconfig | 1 +
> arch/arm/kernel/entry-common.S | 5 +++++
> 2 files changed, 6 insertions(+)
>
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index 0d4e71b42c77..704fd8f197fa 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -12,6 +12,7 @@ config ARM
> select ARCH_HAVE_CUSTOM_GPIO_H
> select ARCH_HAS_GCOV_PROFILE_ALL
> select ARCH_MIGHT_HAVE_PC_PARPORT
> + select ARCH_NO_SYSCALL_VERIFY_PRE_USERMODE_STATE
> select ARCH_OPTIONAL_KERNEL_RWX if ARCH_HAS_STRICT_KERNEL_RWX
> select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT if CPU_V7
> select ARCH_SUPPORTS_ATOMIC_RMW
> diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
> index eb5cd77bf1d8..80cfdc7fabde 100644
> --- a/arch/arm/kernel/entry-common.S
> +++ b/arch/arm/kernel/entry-common.S
> @@ -39,6 +39,9 @@
> ret_fast_syscall:
> UNWIND(.fnstart )
> UNWIND(.cantunwind )
> + push {r0} @ save returned r0
> + bl verify_pre_usermode_state
> + pop {r0} @ restore r0
> disable_irq_notrace @ disable interrupts
> ldr r1, [tsk, #TI_FLAGS] @ re-check for syscall tracing
> tst r1, #_TIF_SYSCALL_WORK | _TIF_WORK_MASK
This feature is configurable, right?
Here the branch overhead is imposed even if the feature is configured
out. You should consider conditionally defining a macro like some other
features do.
Furthermore I think we still support old toolchains that don't know what
push and pop mean. You should use the legacy syntax instead.
Nicolas
next prev parent reply other threads:[~2017-03-08 22:05 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-08 21:38 [PATCH v1 1/4] syscalls: Restore address limit after a syscall Thomas Garnier
2017-03-08 21:38 ` [PATCH v1 2/4] x86/syscalls: Specific usage of verify_pre_usermode_state Thomas Garnier
2017-03-08 21:38 ` [PATCH v1 3/4] arm/syscalls: " Thomas Garnier
2017-03-08 21:49 ` Russell King - ARM Linux
2017-03-08 22:05 ` Nicolas Pitre [this message]
2017-03-08 22:33 ` Thomas Garnier
2017-03-08 21:38 ` [PATCH v1 4/4] arm64/syscalls: " Thomas Garnier
2017-03-08 21:57 ` [PATCH v1 1/4] syscalls: Restore address limit after a syscall Kees Cook
2017-03-09 1:13 ` Thomas Garnier
2017-03-08 21:58 ` Russell King - ARM Linux
2017-03-08 22:20 ` Andy Lutomirski
2017-03-08 22:27 ` Thomas Garnier
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