[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, 3 insertions, 8 deletions

diff --git a/arch/s390/include/asm/tlbflush.h b/arch/s390/include/asm/tlbflush.h
index 29d5d6d4becc..4fdcefc1a98d 100644
--- a/arch/s390/include/asm/tlbflush.h
+++ b/arch/s390/include/asm/tlbflush.h
@@ -80,16 +80,11 @@ static inline void __tlb_flush_mm(struct mm_struct * mm)
 	 * on all cpus instead of doing a local flush if the mm
 	 * only ran on the local cpu.
 	 */
-	if (MACHINE_HAS_IDTE) {
-		if (mm->context.noexec)
-			__tlb_flush_idte((unsigned long)
-					 get_shadow_table(mm->pgd) |
-					 mm->context.asce_bits);
+	if (MACHINE_HAS_IDTE)
 		__tlb_flush_idte((unsigned long) mm->pgd |
 				 mm->context.asce_bits);
-		return;
-	}
-	__tlb_flush_full(mm);
+	else
+		__tlb_flush_full(mm);
 }
 
 static inline void __tlb_flush_mm_cond(struct mm_struct * mm)