[Xen-changelog] [xen master] arm/mm: Introduce modify_xen_mappings

[patchbot@xxxxxxx]

commit 6559a686ae77bca2539d826120c9f3bd0d75cdf8
Author:     Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
AuthorDate: Mon Aug 8 23:14:33 2016 -0400
Commit:     Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
CommitDate: Fri Sep 16 11:36:35 2016 -0400

    arm/mm: Introduce modify_xen_mappings
    
    Which is only used by Livepatch code. The purpose behind
    this call is to modify the page table entries flags.
    
    Specifically the .ro and .nx flags. The current mechanism
    puts cache attributes in the flags and the .ro and .nx are
    locked down and assumed to be .ro=0, nx=1.
    
    Livepatch needs .nx=0 and also .ro to be set to 1.
    
    We introduce a new 'flags' where various bits determine
    whether .ro and .nx bits are set or cleared. We can't use
    an enum as the function prototype would diverge from x86.
    
    Reviewed-by: Julien Grall <julien.grall@xxxxxxx>
    Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 xen/arch/arm/mm.c          | 27 ++++++++++++++++++++++++---
 xen/include/asm-arm/page.h | 11 +++++++++++
 2 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
index 7ae9f63..07e2037 100644
--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -836,6 +836,7 @@ static int create_xen_table(lpae_t *entry)
 enum xenmap_operation {
     INSERT,
     REMOVE,
+    MODIFY,
     RESERVE
 };
 
@@ -881,14 +882,28 @@ static int create_xen_entries(enum xenmap_operation op,
                 pte.pt.table = 1;
                 write_pte(&third[third_table_offset(addr)], pte);
                 break;
+            case MODIFY:
             case REMOVE:
                 if ( !third[third_table_offset(addr)].pt.valid )
                 {
-                    printk("create_xen_entries: trying to remove a 
non-existing mapping addr=%lx\n",
-                           addr);
+                    printk("create_xen_entries: trying to %s a non-existing 
mapping addr=%lx\n",
+                           op == REMOVE ? "remove" : "modify", addr);
                     return -EINVAL;
                 }
-                pte.bits = 0;
+                if ( op == REMOVE )
+                    pte.bits = 0;
+                else
+                {
+                    pte = third[third_table_offset(addr)];
+                    pte.pt.ro = PTE_RO_MASK(ai);
+                    pte.pt.xn = PTE_NX_MASK(ai);
+                    if ( !pte.pt.ro && !pte.pt.xn )
+                    {
+                        printk("create_xen_entries: Incorrect combination for 
addr=%lx\n",
+                               addr);
+                        return -EINVAL;
+                    }
+                }
                 write_pte(&third[third_table_offset(addr)], pte);
                 break;
             default:
@@ -922,6 +937,12 @@ int destroy_xen_mappings(unsigned long v, unsigned long e)
     return create_xen_entries(REMOVE, v, 0, (e - v) >> PAGE_SHIFT, 0);
 }
 
+int modify_xen_mappings(unsigned long s, unsigned long e, unsigned int flags)
+{
+    ASSERT((flags & (PTE_NX | PTE_RO)) == flags);
+    return create_xen_entries(MODIFY, s, 0, (e - s) >> PAGE_SHIFT, flags);
+}
+
 enum mg { mg_clear, mg_ro, mg_rw, mg_rx };
 static void set_pte_flags_on_range(const char *p, unsigned long l, enum mg mg)
 {
diff --git a/xen/include/asm-arm/page.h b/xen/include/asm-arm/page.h
index 05d9f82..015ed63 100644
--- a/xen/include/asm-arm/page.h
+++ b/xen/include/asm-arm/page.h
@@ -66,6 +66,17 @@
 #define PAGE_HYPERVISOR_WC      (DEV_WC)
 
 /*
+ * Defines for changing the hypervisor PTE .ro and .nx bits. This is only to be
+ * used with modify_xen_mappings.
+ */
+#define _PTE_NX_BIT     0U
+#define _PTE_RO_BIT     1U
+#define PTE_NX          (1U << _PTE_NX_BIT)
+#define PTE_RO          (1U << _PTE_RO_BIT)
+#define PTE_NX_MASK(x)  (((x) >> _PTE_NX_BIT) & 0x1U)
+#define PTE_RO_MASK(x)  (((x) >> _PTE_RO_BIT) & 0x1U)
+
+/*
  * Stage 2 Memory Type.
  *
  * These are valid in the MemAttr[3:0] field of an LPAE stage 2 page
--
generated by git-patchbot for /home/xen/git/xen.git#master

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