| /* |
| * Set up the VMAs to tell the VM about the vDSO. |
| * Copyright 2007 Andi Kleen, SUSE Labs. |
| * Subject to the GPL, v.2 |
| */ |
| #include <linux/mm.h> |
| #include <linux/err.h> |
| #include <linux/sched.h> |
| #include <linux/slab.h> |
| #include <linux/init.h> |
| #include <linux/random.h> |
| #include <linux/elf.h> |
| #include <asm/vsyscall.h> |
| #include <asm/vgtod.h> |
| #include <asm/proto.h> |
| #include <asm/vdso.h> |
| #include <asm/page.h> |
| |
| #if defined(CONFIG_X86_64) |
| unsigned int __read_mostly vdso64_enabled = 1; |
| |
| extern unsigned short vdso_sync_cpuid; |
| #endif |
| |
| 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->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 + |
| image->alt_len)); |
| } |
| |
| |
| #if defined(CONFIG_X86_64) |
| static int __init init_vdso(void) |
| { |
| init_vdso_image(&vdso_image_64); |
| |
| #ifdef CONFIG_X86_X32_ABI |
| init_vdso_image(&vdso_image_x32); |
| #endif |
| |
| return 0; |
| } |
| subsys_initcall(init_vdso); |
| |
| struct linux_binprm; |
| |
| /* Put the vdso above the (randomized) stack with another randomized offset. |
| This way there is no hole in the middle of address space. |
| To save memory make sure it is still in the same PTE as the stack top. |
| This doesn't give that many random bits */ |
| static unsigned long vdso_addr(unsigned long start, unsigned len) |
| { |
| unsigned long addr, end; |
| unsigned offset; |
| end = (start + PMD_SIZE - 1) & PMD_MASK; |
| if (end >= TASK_SIZE_MAX) |
| end = TASK_SIZE_MAX; |
| end -= len; |
| /* This loses some more bits than a modulo, but is cheaper */ |
| offset = get_random_int() & (PTRS_PER_PTE - 1); |
| addr = start + (offset << PAGE_SHIFT); |
| if (addr >= end) |
| addr = end; |
| |
| /* |
| * page-align it here so that get_unmapped_area doesn't |
| * align it wrongfully again to the next page. addr can come in 4K |
| * unaligned here as a result of stack start randomization. |
| */ |
| addr = PAGE_ALIGN(addr); |
| addr = align_vdso_addr(addr); |
| |
| return addr; |
| } |
| |
| /* Setup a VMA at program startup for the vsyscall page. |
| Not called for compat tasks */ |
| static int setup_additional_pages(struct linux_binprm *bprm, |
| int uses_interp, |
| struct page **pages, |
| unsigned size) |
| { |
| struct mm_struct *mm = current->mm; |
| unsigned long addr; |
| int ret; |
| |
| if (!vdso64_enabled) |
| return 0; |
| |
| down_write(&mm->mmap_sem); |
| addr = vdso_addr(mm->start_stack, size); |
| addr = get_unmapped_area(NULL, addr, size, 0, 0); |
| if (IS_ERR_VALUE(addr)) { |
| ret = addr; |
| goto up_fail; |
| } |
| |
| current->mm->context.vdso = (void __user *)addr; |
| |
| ret = install_special_mapping(mm, addr, size, |
| VM_READ|VM_EXEC| |
| VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC, |
| pages); |
| if (ret) { |
| current->mm->context.vdso = NULL; |
| goto up_fail; |
| } |
| |
| up_fail: |
| up_write(&mm->mmap_sem); |
| return ret; |
| } |
| |
| int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) |
| { |
| return setup_additional_pages(bprm, uses_interp, vdso_image_64.pages, |
| vdso_image_64.size); |
| } |
| |
| #ifdef CONFIG_X86_X32_ABI |
| int x32_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) |
| { |
| return setup_additional_pages(bprm, uses_interp, vdso_image_x32.pages, |
| vdso_image_x32.size); |
| } |
| #endif |
| |
| static __init int vdso_setup(char *s) |
| { |
| vdso64_enabled = simple_strtoul(s, NULL, 0); |
| return 0; |
| } |
| __setup("vdso=", vdso_setup); |
| #endif |