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-rw-r--r--arch/s390/mm/dump_pagetables.c14
-rw-r--r--arch/s390/mm/vmem.c10
2 files changed, 19 insertions, 5 deletions
diff --git a/arch/s390/mm/dump_pagetables.c b/arch/s390/mm/dump_pagetables.c
index 0b0c8c284953..9f9af5298dd6 100644
--- a/arch/s390/mm/dump_pagetables.c
+++ b/arch/s390/mm/dump_pagetables.c
@@ -8,6 +8,7 @@
#include <linux/kasan.h>
#include <asm/ptdump.h>
#include <asm/kasan.h>
+#include <asm/nospec-branch.h>
#include <asm/sections.h>
static unsigned long max_addr;
@@ -116,8 +117,13 @@ static void note_prot_wx(struct pg_state *st, unsigned long addr)
return;
if (st->current_prot & _PAGE_NOEXEC)
return;
- /* The first lowcore page is currently still W+X. */
- if (addr == PAGE_SIZE)
+ /*
+ * The first lowcore page is W+X if spectre mitigations are using
+ * trampolines or the BEAR enhancements facility is not installed,
+ * in which case we have two lpswe instructions in lowcore that need
+ * to be executable.
+ */
+ if (addr == PAGE_SIZE && (nospec_uses_trampoline() || !static_key_enabled(&cpu_has_bear)))
return;
WARN_ONCE(1, "s390/mm: Found insecure W+X mapping at address %pS\n",
(void *)st->start_address);
@@ -203,7 +209,9 @@ void ptdump_check_wx(void)
if (st.wx_pages)
pr_warn("Checked W+X mappings: FAILED, %lu W+X pages found\n", st.wx_pages);
else
- pr_info("Checked W+X mappings: passed, no unexpected W+X pages found\n");
+ pr_info("Checked W+X mappings: passed, no %sW+X pages found\n",
+ (nospec_uses_trampoline() || !static_key_enabled(&cpu_has_bear)) ?
+ "unexpected " : "");
}
#endif /* CONFIG_DEBUG_WX */
diff --git a/arch/s390/mm/vmem.c b/arch/s390/mm/vmem.c
index 2b1c6d916cf9..7d9705eeb02f 100644
--- a/arch/s390/mm/vmem.c
+++ b/arch/s390/mm/vmem.c
@@ -13,6 +13,7 @@
#include <linux/hugetlb.h>
#include <linux/slab.h>
#include <asm/cacheflush.h>
+#include <asm/nospec-branch.h>
#include <asm/pgalloc.h>
#include <asm/setup.h>
#include <asm/tlbflush.h>
@@ -584,8 +585,13 @@ void __init vmem_map_init(void)
__set_memory(__stext_amode31, (__etext_amode31 - __stext_amode31) >> PAGE_SHIFT,
SET_MEMORY_RO | SET_MEMORY_X);
- /* we need lowcore executable for our LPSWE instructions */
- set_memory_x(0, 1);
+ if (nospec_uses_trampoline() || !static_key_enabled(&cpu_has_bear)) {
+ /*
+ * Lowcore must be executable for LPSWE
+ * and expoline trampoline branch instructions.
+ */
+ set_memory_x(0, 1);
+ }
pr_info("Write protected kernel read-only data: %luk\n",
(unsigned long)(__end_rodata - _stext) >> 10);