arch/sparc/vdso/vma.c

Source file repositories/reference/linux-study-clean/arch/sparc/vdso/vma.c

File Facts

System
Linux kernel
Corpus path
arch/sparc/vdso/vma.c
Extension
.c
Size
4420 bytes
Lines
212
Domain
Architecture Layer
Bucket
arch/sparc
Inferred role
Architecture Layer: exported/initcall integration point
Status
integration implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

subsys_initcall(init_vdso);

struct linux_binprm;

/* Shuffle the vdso up a bit, randomly. */
static unsigned long vdso_addr(unsigned long start, unsigned int len)
{
	unsigned int offset;

	/* This loses some more bits than a modulo, but is cheaper */
	offset = get_random_u32_below(PTRS_PER_PTE);
	return start + (offset << PAGE_SHIFT);
}

static_assert(VDSO_NR_PAGES == __VDSO_PAGES);

static int map_vdso(const struct vdso_image *image,
		struct vm_special_mapping *vdso_mapping)
{
	const size_t area_size = image->size + VDSO_NR_PAGES * PAGE_SIZE;
	struct mm_struct *mm = current->mm;
	struct vm_area_struct *vma;
	unsigned long text_start, addr = 0;
	int ret = 0;

	mmap_write_lock(mm);

	/*
	 * First, get an unmapped region: then randomize it, and make sure that
	 * region is free.
	 */
	if (current->flags & PF_RANDOMIZE) {
		addr = get_unmapped_area(NULL, 0, area_size, 0, 0);
		if (IS_ERR_VALUE(addr)) {
			ret = addr;
			goto up_fail;
		}
		addr = vdso_addr(addr, area_size);
	}
	addr = get_unmapped_area(NULL, addr, area_size, 0, 0);
	if (IS_ERR_VALUE(addr)) {
		ret = addr;
		goto up_fail;
	}

	text_start = addr + VDSO_NR_PAGES * PAGE_SIZE;
	current->mm->context.vdso = (void __user *)text_start;

	/*
	 * MAYWRITE to allow gdb to COW and set breakpoints
	 */
	vma = _install_special_mapping(mm,
				       text_start,
				       image->size,
				       VM_READ|VM_EXEC|
				       VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
				       vdso_mapping);

	if (IS_ERR(vma)) {
		ret = PTR_ERR(vma);
		goto up_fail;
	}

	vma = vdso_install_vvar_mapping(mm, addr);

	if (IS_ERR(vma)) {
		ret = PTR_ERR(vma);
		do_munmap(mm, text_start, image->size, NULL);
	}

up_fail:
	if (ret)
		current->mm->context.vdso = NULL;

	mmap_write_unlock(mm);
	return ret;
}

int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
{

	if (!vdso_enabled)
		return 0;

#if defined CONFIG_COMPAT
	if (!(is_32bit_task()))
		return map_vdso(&vdso_image_64_builtin, &vdso_mapping64);
	else
		return map_vdso(&vdso_image_32_builtin, &vdso_mapping32);
#else

Annotation

Implementation Notes