348 lines
8.5 KiB
C
348 lines
8.5 KiB
C
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/*
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* Copyright 2007 Andi Kleen, SUSE Labs.
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* Subject to the GPL, v.2
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*
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* This contains most of the x86 vDSO kernel-side code.
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*/
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#include <linux/mm.h>
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#include <linux/err.h>
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#include <linux/sched.h>
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#include <linux/sched/task_stack.h>
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#include <linux/slab.h>
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#include <linux/init.h>
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#include <linux/random.h>
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#include <linux/elf.h>
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#include <linux/cpu.h>
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#include <linux/ptrace.h>
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#include <asm/pvclock.h>
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#include <asm/vgtod.h>
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#include <asm/proto.h>
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#include <asm/vdso.h>
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#include <asm/vvar.h>
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#include <asm/page.h>
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#include <asm/desc.h>
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#include <asm/cpufeature.h>
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#include <asm/mshyperv.h>
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#if defined(CONFIG_X86_64)
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unsigned int __read_mostly vdso64_enabled = 1;
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#endif
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void __init init_vdso_image(const struct vdso_image *image)
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{
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BUG_ON(image->size % PAGE_SIZE != 0);
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apply_alternatives((struct alt_instr *)(image->data + image->alt),
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(struct alt_instr *)(image->data + image->alt +
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image->alt_len));
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}
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struct linux_binprm;
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static int vdso_fault(const struct vm_special_mapping *sm,
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struct vm_area_struct *vma, struct vm_fault *vmf)
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{
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const struct vdso_image *image = vma->vm_mm->context.vdso_image;
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if (!image || (vmf->pgoff << PAGE_SHIFT) >= image->size)
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return VM_FAULT_SIGBUS;
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vmf->page = virt_to_page(image->data + (vmf->pgoff << PAGE_SHIFT));
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get_page(vmf->page);
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return 0;
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}
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static void vdso_fix_landing(const struct vdso_image *image,
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struct vm_area_struct *new_vma)
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{
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#if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
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if (in_ia32_syscall() && image == &vdso_image_32) {
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struct pt_regs *regs = current_pt_regs();
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unsigned long vdso_land = image->sym_int80_landing_pad;
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unsigned long old_land_addr = vdso_land +
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(unsigned long)current->mm->context.vdso;
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/* Fixing userspace landing - look at do_fast_syscall_32 */
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if (regs->ip == old_land_addr)
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regs->ip = new_vma->vm_start + vdso_land;
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}
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#endif
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}
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static int vdso_mremap(const struct vm_special_mapping *sm,
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struct vm_area_struct *new_vma)
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{
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unsigned long new_size = new_vma->vm_end - new_vma->vm_start;
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const struct vdso_image *image = current->mm->context.vdso_image;
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if (image->size != new_size)
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return -EINVAL;
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vdso_fix_landing(image, new_vma);
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current->mm->context.vdso = (void __user *)new_vma->vm_start;
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return 0;
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}
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static int vvar_fault(const struct vm_special_mapping *sm,
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struct vm_area_struct *vma, struct vm_fault *vmf)
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{
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const struct vdso_image *image = vma->vm_mm->context.vdso_image;
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long sym_offset;
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int ret = -EFAULT;
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if (!image)
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return VM_FAULT_SIGBUS;
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sym_offset = (long)(vmf->pgoff << PAGE_SHIFT) +
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image->sym_vvar_start;
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/*
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* Sanity check: a symbol offset of zero means that the page
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* does not exist for this vdso image, not that the page is at
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* offset zero relative to the text mapping. This should be
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* impossible here, because sym_offset should only be zero for
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* the page past the end of the vvar mapping.
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*/
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if (sym_offset == 0)
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return VM_FAULT_SIGBUS;
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if (sym_offset == image->sym_vvar_page) {
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ret = vm_insert_pfn(vma, vmf->address,
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__pa_symbol(&__vvar_page) >> PAGE_SHIFT);
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} else if (sym_offset == image->sym_pvclock_page) {
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struct pvclock_vsyscall_time_info *pvti =
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pvclock_get_pvti_cpu0_va();
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if (pvti && vclock_was_used(VCLOCK_PVCLOCK)) {
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ret = vm_insert_pfn_prot(
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vma,
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vmf->address,
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__pa(pvti) >> PAGE_SHIFT,
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pgprot_decrypted(vma->vm_page_prot));
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}
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} else if (sym_offset == image->sym_hvclock_page) {
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struct ms_hyperv_tsc_page *tsc_pg = hv_get_tsc_page();
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if (tsc_pg && vclock_was_used(VCLOCK_HVCLOCK))
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ret = vm_insert_pfn(vma, vmf->address,
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vmalloc_to_pfn(tsc_pg));
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}
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if (ret == 0 || ret == -EBUSY)
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return VM_FAULT_NOPAGE;
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return VM_FAULT_SIGBUS;
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}
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static const struct vm_special_mapping vdso_mapping = {
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.name = "[vdso]",
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.fault = vdso_fault,
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.mremap = vdso_mremap,
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};
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static const struct vm_special_mapping vvar_mapping = {
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.name = "[vvar]",
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.fault = vvar_fault,
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};
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/*
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* Add vdso and vvar mappings to current process.
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* @image - blob to map
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* @addr - request a specific address (zero to map at free addr)
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*/
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static int map_vdso(const struct vdso_image *image, unsigned long addr)
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{
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struct mm_struct *mm = current->mm;
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struct vm_area_struct *vma;
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unsigned long text_start;
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int ret = 0;
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if (down_write_killable(&mm->mmap_sem))
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return -EINTR;
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addr = get_unmapped_area(NULL, addr,
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image->size - image->sym_vvar_start, 0, 0);
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if (IS_ERR_VALUE(addr)) {
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ret = addr;
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goto up_fail;
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}
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text_start = addr - image->sym_vvar_start;
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/*
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* MAYWRITE to allow gdb to COW and set breakpoints
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*/
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vma = _install_special_mapping(mm,
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text_start,
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image->size,
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VM_READ|VM_EXEC|
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VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
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&vdso_mapping);
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if (IS_ERR(vma)) {
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ret = PTR_ERR(vma);
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goto up_fail;
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}
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vma = _install_special_mapping(mm,
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addr,
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-image->sym_vvar_start,
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VM_READ|VM_MAYREAD|VM_IO|VM_DONTDUMP|
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VM_PFNMAP,
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&vvar_mapping);
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if (IS_ERR(vma)) {
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ret = PTR_ERR(vma);
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do_munmap(mm, text_start, image->size, NULL);
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} else {
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current->mm->context.vdso = (void __user *)text_start;
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current->mm->context.vdso_image = image;
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}
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up_fail:
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up_write(&mm->mmap_sem);
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return ret;
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}
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#ifdef CONFIG_X86_64
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/*
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* Put the vdso above the (randomized) stack with another randomized
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* offset. This way there is no hole in the middle of address space.
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* To save memory make sure it is still in the same PTE as the stack
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* top. This doesn't give that many random bits.
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*
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* Note that this algorithm is imperfect: the distribution of the vdso
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* start address within a PMD is biased toward the end.
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*
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* Only used for the 64-bit and x32 vdsos.
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*/
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static unsigned long vdso_addr(unsigned long start, unsigned len)
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{
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unsigned long addr, end;
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unsigned offset;
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/*
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* Round up the start address. It can start out unaligned as a result
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* of stack start randomization.
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*/
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start = PAGE_ALIGN(start);
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/* Round the lowest possible end address up to a PMD boundary. */
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end = (start + len + PMD_SIZE - 1) & PMD_MASK;
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if (end >= TASK_SIZE_MAX)
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end = TASK_SIZE_MAX;
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end -= len;
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if (end > start) {
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offset = get_random_int() % (((end - start) >> PAGE_SHIFT) + 1);
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addr = start + (offset << PAGE_SHIFT);
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} else {
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addr = start;
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}
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/*
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* Forcibly align the final address in case we have a hardware
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* issue that requires alignment for performance reasons.
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*/
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addr = align_vdso_addr(addr);
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return addr;
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}
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static int map_vdso_randomized(const struct vdso_image *image)
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{
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unsigned long addr = vdso_addr(current->mm->start_stack, image->size-image->sym_vvar_start);
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return map_vdso(image, addr);
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}
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#endif
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int map_vdso_once(const struct vdso_image *image, unsigned long addr)
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{
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struct mm_struct *mm = current->mm;
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struct vm_area_struct *vma;
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down_write(&mm->mmap_sem);
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/*
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* Check if we have already mapped vdso blob - fail to prevent
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* abusing from userspace install_speciall_mapping, which may
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* not do accounting and rlimit right.
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* We could search vma near context.vdso, but it's a slowpath,
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* so let's explicitely check all VMAs to be completely sure.
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*/
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for (vma = mm->mmap; vma; vma = vma->vm_next) {
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if (vma_is_special_mapping(vma, &vdso_mapping) ||
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vma_is_special_mapping(vma, &vvar_mapping)) {
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up_write(&mm->mmap_sem);
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return -EEXIST;
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}
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}
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up_write(&mm->mmap_sem);
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return map_vdso(image, addr);
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}
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#if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
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static int load_vdso32(void)
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{
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if (vdso32_enabled != 1) /* Other values all mean "disabled" */
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return 0;
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return map_vdso(&vdso_image_32, 0);
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}
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#endif
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#ifdef CONFIG_X86_64
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int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
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{
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if (!vdso64_enabled)
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return 0;
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return map_vdso_randomized(&vdso_image_64);
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}
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#ifdef CONFIG_COMPAT
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int compat_arch_setup_additional_pages(struct linux_binprm *bprm,
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int uses_interp)
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{
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#ifdef CONFIG_X86_X32_ABI
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if (test_thread_flag(TIF_X32)) {
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if (!vdso64_enabled)
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return 0;
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return map_vdso_randomized(&vdso_image_x32);
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}
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#endif
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#ifdef CONFIG_IA32_EMULATION
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return load_vdso32();
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#else
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return 0;
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#endif
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}
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#endif
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#else
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int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
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{
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return load_vdso32();
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}
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#endif
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#ifdef CONFIG_X86_64
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static __init int vdso_setup(char *s)
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{
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vdso64_enabled = simple_strtoul(s, NULL, 0);
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return 0;
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}
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__setup("vdso=", vdso_setup);
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static int __init init_vdso(void)
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{
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init_vdso_image(&vdso_image_64);
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#ifdef CONFIG_X86_X32_ABI
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init_vdso_image(&vdso_image_x32);
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#endif
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return 0;
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}
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subsys_initcall(init_vdso);
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#endif /* CONFIG_X86_64 */
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