[PATCH v4 06/36] s390/mm: add (non)secure page access exceptions handlers

[Christian Borntraeger <borntraeger@de.ibm.com>]

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.

Acked-by: David Hildenbrand <david@redhat.com>
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>
Reviewed-by: Christian Borntraeger <borntraeger@de.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