[PATCH v3 06/37] s390/mm: add (non)secure page access exceptions handlers

Christian Borntraeger
2020-02-20T10:40:32Z

From: Vasily Gorbik <gor@linux.ibm.com>

Add exceptions handlers performing transparent transition of non-secure
pages to secure (import) upon guest access and secure pages to
non-secure (export) upon hypervisor access.

Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
[frankja@linux.ibm.com: adding checks for failures]
Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
[imbrenda@linux.ibm.com: adding a check for gmap fault]
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
[borntraeger@de.ibm.com: patch merging, splitting, fixing]
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
---
arch/s390/kernel/pgm_check.S | 4 +-
arch/s390/mm/fault.c | 78 ++++++++++++++++++++++++++++++++++++
2 files changed, 80 insertions(+), 2 deletions(-)

diff --git a/arch/s390/kernel/pgm_check.S b/arch/s390/kernel/pgm_check.S
index eee3a482195a..2c27907a5ffc 100644
--- a/arch/s390/kernel/pgm_check.S
+++ b/arch/s390/kernel/pgm_check.S
@@ -78,8 +78,8 @@ PGM_CHECK(do_dat_exception) /* 39 */
PGM_CHECK(do_dat_exception) /* 3a */
PGM_CHECK(do_dat_exception) /* 3b */
PGM_CHECK_DEFAULT /* 3c */
-PGM_CHECK_DEFAULT /* 3d */
-PGM_CHECK_DEFAULT /* 3e */
+PGM_CHECK(do_secure_storage_access) /* 3d */
+PGM_CHECK(do_non_secure_storage_access) /* 3e */
PGM_CHECK_DEFAULT /* 3f */
PGM_CHECK(monitor_event_exception) /* 40 */
PGM_CHECK_DEFAULT /* 41 */
diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index 7b0bb475c166..7bd86ebc882f 100644
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c
@@ -38,6 +38,7 @@
#include <asm/irq.h>
#include <asm/mmu_context.h>
#include <asm/facility.h>
+#include <asm/uv.h>
#include "../kernel/entry.h"

#define __FAIL_ADDR_MASK -4096L
@@ -816,3 +817,80 @@ static int __init pfault_irq_init(void)
early_initcall(pfault_irq_init);

#endif /* CONFIG_PFAULT */
+
+#if IS_ENABLED(CONFIG_PGSTE)
+void do_secure_storage_access(struct pt_regs *regs)
+{
+ unsigned long addr = regs->int_parm_long & __FAIL_ADDR_MASK;
+ struct vm_area_struct *vma;
+ struct mm_struct *mm;
+ struct page *page;
+ int rc;
+
+ switch (get_fault_type(regs)) {
+ case USER_FAULT:
+ mm = current->mm;
+ down_read(&mm->mmap_sem);
+ vma = find_vma(mm, addr);
+ if (!vma) {
+ up_read(&mm->mmap_sem);
+ do_fault_error(regs, VM_READ | VM_WRITE, VM_FAULT_BADMAP);
+ break;
+ }
+ page = follow_page(vma, addr, FOLL_WRITE | FOLL_GET);
+ if (IS_ERR_OR_NULL(page)) {
+ up_read(&mm->mmap_sem);
+ break;
+ }
+ if (arch_make_page_accessible(page))
+ send_sig(SIGSEGV, current, 0);
+ put_page(page);
+ up_read(&mm->mmap_sem);
+ break;
+ case KERNEL_FAULT:
+ page = phys_to_page(addr);
+ if (unlikely(!try_get_page(page)))
+ break;
+ rc = arch_make_page_accessible(page);
+ put_page(page);
+ if (rc)
+ BUG();
+ break;
+ case VDSO_FAULT:
+ /* fallthrough */
+ case GMAP_FAULT:
+ /* fallthrough */
+ default:
+ do_fault_error(regs, VM_READ | VM_WRITE, VM_FAULT_BADMAP);
+ WARN_ON_ONCE(1);
+ }
+}
+NOKPROBE_SYMBOL(do_secure_storage_access);
+
+void do_non_secure_storage_access(struct pt_regs *regs)
+{
+ unsigned long gaddr = regs->int_parm_long & __FAIL_ADDR_MASK;
+ struct gmap *gmap = (struct gmap *)S390_lowcore.gmap;
+
+ if (get_fault_type(regs) != GMAP_FAULT) {
+ do_fault_error(regs, VM_READ | VM_WRITE, VM_FAULT_BADMAP);
+ WARN_ON_ONCE(1);
+ return;
+ }
+
+ if (gmap_convert_to_secure(gmap, gaddr) == -EINVAL)
+ send_sig(SIGSEGV, current, 0);
+}
+NOKPROBE_SYMBOL(do_non_secure_storage_access);
+
+#else
+void do_secure_storage_access(struct pt_regs *regs)
+{
+ default_trap_handler(regs);
+}
+
+void do_non_secure_storage_access(struct pt_regs *regs)
+{
+ default_trap_handler(regs);
+}
+#endif
--
2.25.0