x86/vdso: Use .fault for the vDSO text mapping

The old scheme for mapping the vDSO text is rather complicated.
vdso2c generates a struct vm_special_mapping and a blank .pages
array of the correct size for each vdso image.  Init code in
vdso/vma.c populates the .pages array for each vDSO image, and
the mapping code selects the appropriate struct
vm_special_mapping.

With .fault, we can use a less roundabout approach: vdso_fault()
just returns the appropriate page for the selected vDSO image.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/f886954c186bafd74e1b967c8931d852ae199aa2.1451446564.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/entry/vdso/vdso2c.h b/arch/x86/entry/vdso/vdso2c.h
index 0224987556ce80bd606063b56ef124b0857a3f44..abe961c7c71c7464e9707afa01bfe14efc89ba5f 100644 (file)
--- a/arch/x86/entry/vdso/vdso2c.h
+++ b/arch/x86/entry/vdso/vdso2c.h
@@ -150,16 +150,9 @@ static void BITSFUNC(go)(void *raw_addr, size_t raw_len,
        }
        fprintf(outfile, "\n};\n\n");
 
-       fprintf(outfile, "static struct page *pages[%lu];\n\n",
-               mapping_size / 4096);
-
        fprintf(outfile, "const struct vdso_image %s = {\n", name);
        fprintf(outfile, "\t.data = raw_data,\n");
        fprintf(outfile, "\t.size = %lu,\n", mapping_size);
-       fprintf(outfile, "\t.text_mapping = {\n");
-       fprintf(outfile, "\t\t.name = \"[vdso]\",\n");
-       fprintf(outfile, "\t\t.pages = pages,\n");
-       fprintf(outfile, "\t},\n");
        if (alt_sec) {
                fprintf(outfile, "\t.alt = %lu,\n",
                        (unsigned long)GET_LE(&alt_sec->sh_offset));

diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
index 80b021067bd6ba4cb4d258cf5c3ba7b8e98b28f3..eb50d7c1f161460b20c12ecaff189bf654e61270 100644 (file)
--- a/arch/x86/entry/vdso/vma.c
+++ b/arch/x86/entry/vdso/vma.c
@@ -27,13 +27,7 @@ unsigned int __read_mostly vdso64_enabled = 1;
 
 void __init init_vdso_image(const struct vdso_image *image)
 {
-       int i;
-       int npages = (image->size) / PAGE_SIZE;
-
        BUG_ON(image->size % PAGE_SIZE != 0);
-       for (i = 0; i < npages; i++)
-               image->text_mapping.pages[i] =
-                       virt_to_page(image->data + i*PAGE_SIZE);
 
        apply_alternatives((struct alt_instr *)(image->data + image->alt),
                           (struct alt_instr *)(image->data + image->alt +
@@ -90,6 +84,24 @@ static unsigned long vdso_addr(unsigned long start, unsigned len)
 #endif
 }
 
+static int vdso_fault(const struct vm_special_mapping *sm,
+                     struct vm_area_struct *vma, struct vm_fault *vmf)
+{
+       const struct vdso_image *image = vma->vm_mm->context.vdso_image;
+
+       if (!image || (vmf->pgoff << PAGE_SHIFT) >= image->size)
+               return VM_FAULT_SIGBUS;
+
+       vmf->page = virt_to_page(image->data + (vmf->pgoff << PAGE_SHIFT));
+       get_page(vmf->page);
+       return 0;
+}
+
+static const struct vm_special_mapping text_mapping = {
+       .name = "[vdso]",
+       .fault = vdso_fault,
+};
+
 static int map_vdso(const struct vdso_image *image, bool calculate_addr)
 {
        struct mm_struct *mm = current->mm;
@@ -131,7 +143,7 @@ static int map_vdso(const struct vdso_image *image, bool calculate_addr)
                                       image->size,
                                       VM_READ|VM_EXEC|
                                       VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
-                                      &image->text_mapping);
+                                      &text_mapping);
 
        if (IS_ERR(vma)) {
                ret = PTR_ERR(vma);

diff --git a/arch/x86/include/asm/vdso.h b/arch/x86/include/asm/vdso.h
index deabaf9759b640d5cd93f50f9db67ef2dc60a807..43dc55be524e7fdc8e5150f87b02a8639b20b3f3 100644 (file)
--- a/arch/x86/include/asm/vdso.h
+++ b/arch/x86/include/asm/vdso.h
@@ -13,9 +13,6 @@ struct vdso_image {
        void *data;
        unsigned long size;   /* Always a multiple of PAGE_SIZE */
 
-       /* text_mapping.pages is big enough for data/size page pointers */
-       struct vm_special_mapping text_mapping;
-
        unsigned long alt, alt_len;
 
        long sym_vvar_start;  /* Negative offset to the vvar area */