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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2016-03-22 10:54:24 +0100
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2017-02-08 14:13:25 +0100
commit57d7f939e7bdd746992f5c318a78697ba837c523 (patch)
tree80c01c9c446fc190432798a6d1ecf0c8e5456b57 /arch/s390/mm/pgtable.c
parent2583b848cad049cf5f3f0a03af8b140668b376f3 (diff)
s390: add no-execute support
Bit 0x100 of a page table, segment table of region table entry can be used to disallow code execution for the virtual addresses associated with the entry. There is one tricky bit, the system call to return from a signal is part of the signal frame written to the user stack. With a non-executable stack this would stop working. To avoid breaking things the protection fault handler checks the opcode that caused the fault for 0x0a77 (sys_sigreturn) and 0x0aad (sys_rt_sigreturn) and injects a system call. This is preferable to the alternative solution with a stub function in the vdso because it works for vdso=off and statically linked binaries as well. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/mm/pgtable.c')
-rw-r--r--arch/s390/mm/pgtable.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
index 7a1897c51c54..190d0c65904a 100644
--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -274,6 +274,8 @@ void ptep_modify_prot_commit(struct mm_struct *mm, unsigned long addr,
{
pgste_t pgste;
+ if (!MACHINE_HAS_NX)
+ pte_val(pte) &= ~_PAGE_NOEXEC;
if (mm_has_pgste(mm)) {
pgste = pgste_get(ptep);
pgste_set_key(ptep, pgste, pte, mm);