[PATCH v1 3/4] arm/syscalls: Specific usage of verify_pre_usermode_state

[Thomas Garnier]

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
@@ -65,6 +68,7 @@ ret_fast_syscall:
  UNWIND(.fnstart       )
  UNWIND(.cantunwind    )
        str     r0, [sp, #S_R0 + S_OFF]!        @ save returned r0
+       bl      verify_pre_usermode_state
        disable_irq_notrace                     @ disable interrupts
        ldr     r1, [tsk, #TI_FLAGS]            @ re-check for syscall tracing
        tst     r1, #_TIF_SYSCALL_WORK | _TIF_WORK_MASK
@@ -263,6 +267,7 @@ __sys_trace:
 
 __sys_trace_return:
        str     r0, [sp, #S_R0 + S_OFF]!        @ save returned r0
+       bl      verify_pre_usermode_state
        mov     r0, sp
        bl      syscall_trace_exit
        b       ret_slow_syscall
-- 
2.12.0.246.ga2ecc84866-goog