arm64: allow vmalloc regions to be set with set_memory_*

The range of set_memory_* is currently restricted to the module address
range because of difficulties in breaking down larger block sizes.
vmalloc maps PAGE_SIZE pages so it is safe to use as well. Update the
function ranges and add a comment explaining why the range is restricted
the way it is.

Suggested-by: Laura Abbott <labbott@fedoraproject.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>

diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
index cf6240741134ecbeece606dade39dc90478a08b6..0795c3a36d8f0d140cf4952bd91b14962e7f81b4 100644 (file)
--- a/arch/arm64/mm/pageattr.c
+++ b/arch/arm64/mm/pageattr.c
@@ -14,6 +14,7 @@
 #include <linux/mm.h>
 #include <linux/module.h>
 #include <linux/sched.h>
+#include <linux/vmalloc.h>
 
 #include <asm/pgtable.h>
 #include <asm/tlbflush.h>
@@ -44,6 +45,7 @@ static int change_memory_common(unsigned long addr, int numpages,
        unsigned long end = start + size;
        int ret;
        struct page_change_data data;
+       struct vm_struct *area;
 
        if (!PAGE_ALIGNED(addr)) {
                start &= PAGE_MASK;
@@ -51,10 +53,23 @@ static int change_memory_common(unsigned long addr, int numpages,
                WARN_ON_ONCE(1);
        }
 
-       if (start < MODULES_VADDR || start >= MODULES_END)
-               return -EINVAL;
-
-       if (end < MODULES_VADDR || end >= MODULES_END)
+       /*
+        * Kernel VA mappings are always live, and splitting live section
+        * mappings into page mappings may cause TLB conflicts. This means
+        * we have to ensure that changing the permission bits of the range
+        * we are operating on does not result in such splitting.
+        *
+        * Let's restrict ourselves to mappings created by vmalloc (or vmap).
+        * Those are guaranteed to consist entirely of page mappings, and
+        * splitting is never needed.
+        *
+        * So check whether the [addr, addr + size) interval is entirely
+        * covered by precisely one VM area that has the VM_ALLOC flag set.
+        */
+       area = find_vm_area((void *)addr);
+       if (!area ||
+           end > (unsigned long)area->addr + area->size ||
+           !(area->flags & VM_ALLOC))
                return -EINVAL;
 
        if (!numpages)