[S390] Remove data execution protection

The noexec support on s390 does not rely on a bit in the page table
entry but utilizes the secondary space mode to distinguish between
memory accesses for instructions vs. data. The noexec code relies
on the assumption that the cpu will always use the secondary space
page table for data accesses while it is running in the secondary
space mode. Up to the z9-109 class machines this has been the case.
Unfortunately this is not true anymore with z10 and later machines.
The load-relative-long instructions lrl, lgrl and lgfrl access the
memory operand using the same addressing-space mode that has been
used to fetch the instruction.
This breaks the noexec mode for all user space binaries compiled
with march=z10 or later. The only option is to remove the current
noexec support.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 0 insertions, 11 deletions

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 4a7f14079e03..ff2d2371b2e9 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -230,17 +230,6 @@ config SYSVIPC_COMPAT
 config AUDIT_ARCH
         def_bool y
 
-config S390_EXEC_PROTECT
-        def_bool y
-        prompt "Data execute protection"
-        help
-          This option allows to enable a buffer overflow protection for user
-          space programs and it also selects the addressing mode option above.
-          The kernel parameter noexec=on will enable this feature and also
-          switch the addressing modes, default is disabled. Enabling this (via
-          kernel parameter) on machines earlier than IBM System z9 this will
-          reduce system performance.
-
 comment "Code generation options"
 
 choice