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Commit 05ef76b2 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar
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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: default avatarAndy Lutomirski <luto@kernel.org>
Reviewed-by: default avatarKees 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: default avatarIngo Molnar <mingo@kernel.org>
parent 352b78c6

arch/x86/entry/vdso/vdso2c.h

+0 −7
Original line number Diff line number Diff line
@@ -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));

arch/x86/entry/vdso/vma.c

+19 −7
Original line number Diff line number Diff line
@@ -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);

arch/x86/include/asm/vdso.h

+0 −3
Original line number Diff line number Diff line
@@ -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 */