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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>
This commit is contained in:
Andy Lutomirski 2015-12-29 20:12:22 -08:00 committed by Ingo Molnar
parent 352b78c62f
commit 05ef76b20f
3 changed files with 19 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
arch/x86/entry/vdso/vdso2c.h
View File

@ -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));

26
arch/x86/entry/vdso/vma.c
View File

@ -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);

3
arch/x86/include/asm/vdso.h
View File

@ -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 */