[PATCH v1 3/4] arm/syscalls: Specific usage of verify_pre_usermode_state
From: Nicolas Pitre <hidden>
Date: 2017-03-08 22:42:48
Also in:
linux-api, lkml
On Wed, 8 Mar 2017, Thomas Garnier wrote:
quoted hunk ↗ jump to hunk
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_RMWdiff --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