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bcf9964342
Forbid splitting VVAR VMA resulting in a stricter ABI and reducing the amount of corner-cases to consider while working further on VDSO time namespace support. As the offset from timens to VVAR page is computed compile-time, the pages in VVAR should stay together and not being partically mremap()'ed. Signed-off-by: Andrei Vagin <avagin@gmail.com> Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com> Reviewed-by: Dmitry Safonov <dima@arista.com> Link: https://lore.kernel.org/r/20200624083321.144975-6-avagin@gmail.com Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
518 lines
12 KiB
C
518 lines
12 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* VDSO implementations.
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*
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* Copyright (C) 2012 ARM Limited
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*
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* Author: Will Deacon <will.deacon@arm.com>
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*/
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#include <linux/cache.h>
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#include <linux/clocksource.h>
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#include <linux/elf.h>
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#include <linux/err.h>
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#include <linux/errno.h>
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#include <linux/gfp.h>
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#include <linux/kernel.h>
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#include <linux/mm.h>
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#include <linux/sched.h>
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#include <linux/signal.h>
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#include <linux/slab.h>
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#include <linux/time_namespace.h>
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#include <linux/timekeeper_internal.h>
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#include <linux/vmalloc.h>
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#include <vdso/datapage.h>
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#include <vdso/helpers.h>
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#include <vdso/vsyscall.h>
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#include <asm/cacheflush.h>
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#include <asm/signal32.h>
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#include <asm/vdso.h>
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extern char vdso_start[], vdso_end[];
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#ifdef CONFIG_COMPAT_VDSO
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extern char vdso32_start[], vdso32_end[];
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#endif /* CONFIG_COMPAT_VDSO */
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enum vdso_abi {
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VDSO_ABI_AA64,
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#ifdef CONFIG_COMPAT_VDSO
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VDSO_ABI_AA32,
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#endif /* CONFIG_COMPAT_VDSO */
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};
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enum vvar_pages {
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VVAR_DATA_PAGE_OFFSET,
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VVAR_TIMENS_PAGE_OFFSET,
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VVAR_NR_PAGES,
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};
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struct vdso_abi_info {
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const char *name;
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const char *vdso_code_start;
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const char *vdso_code_end;
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unsigned long vdso_pages;
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/* Data Mapping */
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struct vm_special_mapping *dm;
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/* Code Mapping */
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struct vm_special_mapping *cm;
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};
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static struct vdso_abi_info vdso_info[] __ro_after_init = {
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[VDSO_ABI_AA64] = {
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.name = "vdso",
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.vdso_code_start = vdso_start,
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.vdso_code_end = vdso_end,
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},
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#ifdef CONFIG_COMPAT_VDSO
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[VDSO_ABI_AA32] = {
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.name = "vdso32",
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.vdso_code_start = vdso32_start,
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.vdso_code_end = vdso32_end,
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},
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#endif /* CONFIG_COMPAT_VDSO */
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};
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/*
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* The vDSO data page.
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*/
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static union {
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struct vdso_data data[CS_BASES];
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u8 page[PAGE_SIZE];
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} vdso_data_store __page_aligned_data;
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struct vdso_data *vdso_data = vdso_data_store.data;
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static int __vdso_remap(enum vdso_abi abi,
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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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unsigned long vdso_size = vdso_info[abi].vdso_code_end -
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vdso_info[abi].vdso_code_start;
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if (vdso_size != new_size)
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return -EINVAL;
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current->mm->context.vdso = (void *)new_vma->vm_start;
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return 0;
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}
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static int __vdso_init(enum vdso_abi abi)
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{
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int i;
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struct page **vdso_pagelist;
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unsigned long pfn;
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if (memcmp(vdso_info[abi].vdso_code_start, "\177ELF", 4)) {
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pr_err("vDSO is not a valid ELF object!\n");
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return -EINVAL;
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}
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vdso_info[abi].vdso_pages = (
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vdso_info[abi].vdso_code_end -
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vdso_info[abi].vdso_code_start) >>
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PAGE_SHIFT;
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vdso_pagelist = kcalloc(vdso_info[abi].vdso_pages,
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sizeof(struct page *),
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GFP_KERNEL);
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if (vdso_pagelist == NULL)
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return -ENOMEM;
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/* Grab the vDSO code pages. */
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pfn = sym_to_pfn(vdso_info[abi].vdso_code_start);
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for (i = 0; i < vdso_info[abi].vdso_pages; i++)
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vdso_pagelist[i] = pfn_to_page(pfn + i);
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vdso_info[abi].cm->pages = vdso_pagelist;
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return 0;
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}
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#ifdef CONFIG_TIME_NS
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struct vdso_data *arch_get_vdso_data(void *vvar_page)
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{
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return (struct vdso_data *)(vvar_page);
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}
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/*
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* The vvar mapping contains data for a specific time namespace, so when a task
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* changes namespace we must unmap its vvar data for the old namespace.
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* Subsequent faults will map in data for the new namespace.
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*
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* For more details see timens_setup_vdso_data().
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*/
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int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
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{
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struct mm_struct *mm = task->mm;
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struct vm_area_struct *vma;
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mmap_read_lock(mm);
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for (vma = mm->mmap; vma; vma = vma->vm_next) {
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unsigned long size = vma->vm_end - vma->vm_start;
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if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA64].dm))
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zap_page_range(vma, vma->vm_start, size);
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#ifdef CONFIG_COMPAT_VDSO
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if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA32].dm))
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zap_page_range(vma, vma->vm_start, size);
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#endif
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}
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mmap_read_unlock(mm);
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return 0;
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}
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static struct page *find_timens_vvar_page(struct vm_area_struct *vma)
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{
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if (likely(vma->vm_mm == current->mm))
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return current->nsproxy->time_ns->vvar_page;
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/*
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* VM_PFNMAP | VM_IO protect .fault() handler from being called
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* through interfaces like /proc/$pid/mem or
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* process_vm_{readv,writev}() as long as there's no .access()
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* in special_mapping_vmops.
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* For more details check_vma_flags() and __access_remote_vm()
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*/
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WARN(1, "vvar_page accessed remotely");
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return NULL;
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}
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#else
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static struct page *find_timens_vvar_page(struct vm_area_struct *vma)
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{
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return NULL;
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}
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#endif
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static vm_fault_t 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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struct page *timens_page = find_timens_vvar_page(vma);
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unsigned long pfn;
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switch (vmf->pgoff) {
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case VVAR_DATA_PAGE_OFFSET:
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if (timens_page)
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pfn = page_to_pfn(timens_page);
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else
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pfn = sym_to_pfn(vdso_data);
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break;
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#ifdef CONFIG_TIME_NS
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case VVAR_TIMENS_PAGE_OFFSET:
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/*
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* If a task belongs to a time namespace then a namespace
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* specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and
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* the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET
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* offset.
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* See also the comment near timens_setup_vdso_data().
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*/
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if (!timens_page)
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return VM_FAULT_SIGBUS;
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pfn = sym_to_pfn(vdso_data);
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break;
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#endif /* CONFIG_TIME_NS */
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default:
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return VM_FAULT_SIGBUS;
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}
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return vmf_insert_pfn(vma, vmf->address, pfn);
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}
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static int vvar_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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if (new_size != VVAR_NR_PAGES * PAGE_SIZE)
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return -EINVAL;
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return 0;
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}
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static int __setup_additional_pages(enum vdso_abi abi,
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struct mm_struct *mm,
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struct linux_binprm *bprm,
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int uses_interp)
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{
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unsigned long vdso_base, vdso_text_len, vdso_mapping_len;
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unsigned long gp_flags = 0;
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void *ret;
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BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES);
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vdso_text_len = vdso_info[abi].vdso_pages << PAGE_SHIFT;
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/* Be sure to map the data page */
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vdso_mapping_len = vdso_text_len + VVAR_NR_PAGES * PAGE_SIZE;
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vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0);
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if (IS_ERR_VALUE(vdso_base)) {
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ret = ERR_PTR(vdso_base);
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goto up_fail;
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}
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ret = _install_special_mapping(mm, vdso_base, VVAR_NR_PAGES * PAGE_SIZE,
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VM_READ|VM_MAYREAD|VM_PFNMAP,
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vdso_info[abi].dm);
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if (IS_ERR(ret))
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goto up_fail;
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if (IS_ENABLED(CONFIG_ARM64_BTI_KERNEL) && system_supports_bti())
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gp_flags = VM_ARM64_BTI;
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vdso_base += VVAR_NR_PAGES * PAGE_SIZE;
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mm->context.vdso = (void *)vdso_base;
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ret = _install_special_mapping(mm, vdso_base, vdso_text_len,
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VM_READ|VM_EXEC|gp_flags|
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VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
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vdso_info[abi].cm);
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if (IS_ERR(ret))
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goto up_fail;
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return 0;
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up_fail:
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mm->context.vdso = NULL;
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return PTR_ERR(ret);
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}
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#ifdef CONFIG_COMPAT
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/*
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* Create and map the vectors page for AArch32 tasks.
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*/
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#ifdef CONFIG_COMPAT_VDSO
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static int aarch32_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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return __vdso_remap(VDSO_ABI_AA32, sm, new_vma);
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}
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#endif /* CONFIG_COMPAT_VDSO */
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enum aarch32_map {
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AA32_MAP_VECTORS, /* kuser helpers */
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#ifdef CONFIG_COMPAT_VDSO
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AA32_MAP_VVAR,
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AA32_MAP_VDSO,
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#endif
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AA32_MAP_SIGPAGE
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};
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static struct page *aarch32_vectors_page __ro_after_init;
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static struct page *aarch32_sig_page __ro_after_init;
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static struct vm_special_mapping aarch32_vdso_maps[] = {
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[AA32_MAP_VECTORS] = {
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.name = "[vectors]", /* ABI */
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.pages = &aarch32_vectors_page,
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},
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#ifdef CONFIG_COMPAT_VDSO
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[AA32_MAP_VVAR] = {
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.name = "[vvar]",
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.fault = vvar_fault,
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.mremap = vvar_mremap,
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},
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[AA32_MAP_VDSO] = {
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.name = "[vdso]",
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.mremap = aarch32_vdso_mremap,
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},
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#endif /* CONFIG_COMPAT_VDSO */
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[AA32_MAP_SIGPAGE] = {
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.name = "[sigpage]", /* ABI */
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.pages = &aarch32_sig_page,
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},
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};
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static int aarch32_alloc_kuser_vdso_page(void)
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{
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extern char __kuser_helper_start[], __kuser_helper_end[];
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int kuser_sz = __kuser_helper_end - __kuser_helper_start;
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unsigned long vdso_page;
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if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
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return 0;
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vdso_page = get_zeroed_page(GFP_ATOMIC);
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if (!vdso_page)
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return -ENOMEM;
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memcpy((void *)(vdso_page + 0x1000 - kuser_sz), __kuser_helper_start,
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kuser_sz);
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aarch32_vectors_page = virt_to_page(vdso_page);
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flush_dcache_page(aarch32_vectors_page);
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return 0;
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}
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static int aarch32_alloc_sigpage(void)
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{
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extern char __aarch32_sigret_code_start[], __aarch32_sigret_code_end[];
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int sigret_sz = __aarch32_sigret_code_end - __aarch32_sigret_code_start;
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unsigned long sigpage;
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sigpage = get_zeroed_page(GFP_ATOMIC);
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if (!sigpage)
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return -ENOMEM;
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memcpy((void *)sigpage, __aarch32_sigret_code_start, sigret_sz);
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aarch32_sig_page = virt_to_page(sigpage);
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flush_dcache_page(aarch32_sig_page);
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return 0;
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}
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#ifdef CONFIG_COMPAT_VDSO
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static int __aarch32_alloc_vdso_pages(void)
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{
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vdso_info[VDSO_ABI_AA32].dm = &aarch32_vdso_maps[AA32_MAP_VVAR];
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vdso_info[VDSO_ABI_AA32].cm = &aarch32_vdso_maps[AA32_MAP_VDSO];
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return __vdso_init(VDSO_ABI_AA32);
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}
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#endif /* CONFIG_COMPAT_VDSO */
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static int __init aarch32_alloc_vdso_pages(void)
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{
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int ret;
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#ifdef CONFIG_COMPAT_VDSO
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ret = __aarch32_alloc_vdso_pages();
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if (ret)
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return ret;
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#endif
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ret = aarch32_alloc_sigpage();
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if (ret)
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return ret;
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return aarch32_alloc_kuser_vdso_page();
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}
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arch_initcall(aarch32_alloc_vdso_pages);
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static int aarch32_kuser_helpers_setup(struct mm_struct *mm)
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{
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void *ret;
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if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
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return 0;
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/*
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* Avoid VM_MAYWRITE for compatibility with arch/arm/, where it's
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* not safe to CoW the page containing the CPU exception vectors.
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*/
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ret = _install_special_mapping(mm, AARCH32_VECTORS_BASE, PAGE_SIZE,
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VM_READ | VM_EXEC |
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VM_MAYREAD | VM_MAYEXEC,
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&aarch32_vdso_maps[AA32_MAP_VECTORS]);
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return PTR_ERR_OR_ZERO(ret);
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}
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static int aarch32_sigreturn_setup(struct mm_struct *mm)
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{
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unsigned long addr;
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void *ret;
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addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
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if (IS_ERR_VALUE(addr)) {
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ret = ERR_PTR(addr);
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goto out;
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}
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/*
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* VM_MAYWRITE is required to allow gdb to Copy-on-Write and
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* set breakpoints.
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*/
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ret = _install_special_mapping(mm, addr, PAGE_SIZE,
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VM_READ | VM_EXEC | VM_MAYREAD |
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VM_MAYWRITE | VM_MAYEXEC,
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&aarch32_vdso_maps[AA32_MAP_SIGPAGE]);
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if (IS_ERR(ret))
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goto out;
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mm->context.sigpage = (void *)addr;
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out:
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return PTR_ERR_OR_ZERO(ret);
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}
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int aarch32_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
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{
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struct mm_struct *mm = current->mm;
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int ret;
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if (mmap_write_lock_killable(mm))
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return -EINTR;
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ret = aarch32_kuser_helpers_setup(mm);
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if (ret)
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goto out;
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#ifdef CONFIG_COMPAT_VDSO
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ret = __setup_additional_pages(VDSO_ABI_AA32,
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mm,
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bprm,
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uses_interp);
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if (ret)
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goto out;
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#endif /* CONFIG_COMPAT_VDSO */
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ret = aarch32_sigreturn_setup(mm);
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out:
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mmap_write_unlock(mm);
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return ret;
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}
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#endif /* CONFIG_COMPAT */
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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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return __vdso_remap(VDSO_ABI_AA64, sm, new_vma);
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}
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enum aarch64_map {
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AA64_MAP_VVAR,
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AA64_MAP_VDSO,
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};
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static struct vm_special_mapping aarch64_vdso_maps[] __ro_after_init = {
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[AA64_MAP_VVAR] = {
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.name = "[vvar]",
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.fault = vvar_fault,
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.mremap = vvar_mremap,
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},
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[AA64_MAP_VDSO] = {
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.name = "[vdso]",
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.mremap = vdso_mremap,
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},
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};
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static int __init vdso_init(void)
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{
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vdso_info[VDSO_ABI_AA64].dm = &aarch64_vdso_maps[AA64_MAP_VVAR];
|
|
vdso_info[VDSO_ABI_AA64].cm = &aarch64_vdso_maps[AA64_MAP_VDSO];
|
|
|
|
return __vdso_init(VDSO_ABI_AA64);
|
|
}
|
|
arch_initcall(vdso_init);
|
|
|
|
int arch_setup_additional_pages(struct linux_binprm *bprm,
|
|
int uses_interp)
|
|
{
|
|
struct mm_struct *mm = current->mm;
|
|
int ret;
|
|
|
|
if (mmap_write_lock_killable(mm))
|
|
return -EINTR;
|
|
|
|
ret = __setup_additional_pages(VDSO_ABI_AA64,
|
|
mm,
|
|
bprm,
|
|
uses_interp);
|
|
|
|
mmap_write_unlock(mm);
|
|
|
|
return ret;
|
|
}
|