1 files changed, 34 insertions, 0 deletions

diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
index 6cacdc8dd654..db5c2cab8fda 100644
--- a/arch/arm/mm/Kconfig
+++ b/arch/arm/mm/Kconfig
@@ -421,24 +421,28 @@ config CPU_32v3
         select CPU_USE_DOMAINS if MMU
         select NEEDS_SYSCALL_FOR_CMPXCHG if SMP
         select TLS_REG_EMUL if SMP || !MMU
+        select NEED_KUSER_HELPERS
 
 config CPU_32v4
         bool
         select CPU_USE_DOMAINS if MMU
         select NEEDS_SYSCALL_FOR_CMPXCHG if SMP
         select TLS_REG_EMUL if SMP || !MMU
+        select NEED_KUSER_HELPERS
 
 config CPU_32v4T
         bool
         select CPU_USE_DOMAINS if MMU
         select NEEDS_SYSCALL_FOR_CMPXCHG if SMP
         select TLS_REG_EMUL if SMP || !MMU
+        select NEED_KUSER_HELPERS
 
 config CPU_32v5
         bool
         select CPU_USE_DOMAINS if MMU
         select NEEDS_SYSCALL_FOR_CMPXCHG if SMP
         select TLS_REG_EMUL if SMP || !MMU
+        select NEED_KUSER_HELPERS
 
 config CPU_32v6
         bool
@@ -776,6 +780,7 @@ config CPU_BPREDICT_DISABLE
 
 config TLS_REG_EMUL
         bool
+        select NEED_KUSER_HELPERS
         help
           An SMP system using a pre-ARMv6 processor (there are apparently
           a few prototypes like that in existence) and therefore access to
@@ -783,11 +788,40 @@ config TLS_REG_EMUL
 
 config NEEDS_SYSCALL_FOR_CMPXCHG
         bool
+        select NEED_KUSER_HELPERS
         help
           SMP on a pre-ARMv6 processor?  Well OK then.
           Forget about fast user space cmpxchg support.
           It is just not possible.
 
+config NEED_KUSER_HELPERS
+        bool
+
+config KUSER_HELPERS
+        bool "Enable kuser helpers in vector page" if !NEED_KUSER_HELPERS
+        default y
+        help
+          Warning: disabling this option may break user programs.
+
+          Provide kuser helpers in the vector page.  The kernel provides
+          helper code to userspace in read only form at a fixed location
+          in the high vector page to allow userspace to be independent of
+          the CPU type fitted to the system.  This permits binaries to be
+          run on ARMv4 through to ARMv7 without modification.
+
+          However, the fixed address nature of these helpers can be used
+          by ROP (return orientated programming) authors when creating
+          exploits.
+
+          If all of the binaries and libraries which run on your platform
+          are built specifically for your platform, and make no use of
+          these helpers, then you can turn this option off.  However,
+          when such an binary or library is run, it will receive a SIGILL
+          signal, which will terminate the program.
+
+          Say N here only if you are absolutely certain that you do not
+          need these helpers; otherwise, the safe option is to say Y.
+
 config DMA_CACHE_RWFO
         bool "Enable read/write for ownership DMA cache maintenance"
         depends on CPU_V6K && SMP