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![Christophe Leroy](/assets/img/avatar_default.png)
This patch adds the necessary glue to provide time namespaces. Things are mainly copied from ARM64. __arch_get_timens_vdso_data() calculates timens vdso data position based on the vdso data position, knowing it is the next page in vvar. This avoids having to redo the mflr/bcl/mflr/mtlr dance to locate the page relative to running code position. Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com> # vDSO parts Acked-by: Andrei Vagin <avagin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/1a15495f80ec19a87b16cf874dbf7c3fa5ec40fe.1617209142.git.christophe.leroy@csgroup.eu
410 lines
11 KiB
C
410 lines
11 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Copyright (C) 2004 Benjamin Herrenschmidt, IBM Corp.
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* <benh@kernel.crashing.org>
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*/
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#include <linux/errno.h>
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#include <linux/sched.h>
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#include <linux/kernel.h>
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#include <linux/mm.h>
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#include <linux/smp.h>
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#include <linux/stddef.h>
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#include <linux/unistd.h>
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#include <linux/slab.h>
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#include <linux/user.h>
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#include <linux/elf.h>
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#include <linux/security.h>
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#include <linux/memblock.h>
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#include <linux/syscalls.h>
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#include <linux/time_namespace.h>
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#include <vdso/datapage.h>
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#include <asm/syscall.h>
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#include <asm/processor.h>
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#include <asm/mmu.h>
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#include <asm/mmu_context.h>
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#include <asm/prom.h>
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#include <asm/machdep.h>
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#include <asm/cputable.h>
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#include <asm/sections.h>
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#include <asm/firmware.h>
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#include <asm/vdso.h>
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#include <asm/vdso_datapage.h>
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#include <asm/setup.h>
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/* The alignment of the vDSO */
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#define VDSO_ALIGNMENT (1 << 16)
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extern char vdso32_start, vdso32_end;
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extern char vdso64_start, vdso64_end;
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/*
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* The vdso data page (aka. systemcfg for old ppc64 fans) is here.
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* Once the early boot kernel code no longer needs to muck around
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* with it, it will become dynamically allocated
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*/
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static union {
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struct vdso_arch_data data;
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u8 page[PAGE_SIZE];
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} vdso_data_store __page_aligned_data;
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struct vdso_arch_data *vdso_data = &vdso_data_store.data;
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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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static int vdso_mremap(const struct vm_special_mapping *sm, struct vm_area_struct *new_vma,
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unsigned long text_size)
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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 != text_size)
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return -EINVAL;
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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 vdso32_mremap(const struct vm_special_mapping *sm, struct vm_area_struct *new_vma)
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{
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return vdso_mremap(sm, new_vma, &vdso32_end - &vdso32_start);
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}
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static int vdso64_mremap(const struct vm_special_mapping *sm, struct vm_area_struct *new_vma)
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{
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return vdso_mremap(sm, new_vma, &vdso64_end - &vdso64_start);
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}
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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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static struct vm_special_mapping vvar_spec __ro_after_init = {
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.name = "[vvar]",
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.fault = vvar_fault,
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};
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static struct vm_special_mapping vdso32_spec __ro_after_init = {
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.name = "[vdso]",
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.mremap = vdso32_mremap,
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};
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static struct vm_special_mapping vdso64_spec __ro_after_init = {
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.name = "[vdso]",
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.mremap = vdso64_mremap,
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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_arch_data *)vvar_page)->data;
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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, &vvar_spec))
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zap_page_range(vma, vma->vm_start, size);
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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 = virt_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 = virt_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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/*
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* This is called from binfmt_elf, we create the special vma for the
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* vDSO and insert it into the mm struct tree
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*/
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static int __arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
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{
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unsigned long vdso_size, vdso_base, mappings_size;
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struct vm_special_mapping *vdso_spec;
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unsigned long vvar_size = VVAR_NR_PAGES * PAGE_SIZE;
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struct mm_struct *mm = current->mm;
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struct vm_area_struct *vma;
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if (is_32bit_task()) {
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vdso_spec = &vdso32_spec;
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vdso_size = &vdso32_end - &vdso32_start;
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vdso_base = VDSO32_MBASE;
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} else {
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vdso_spec = &vdso64_spec;
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vdso_size = &vdso64_end - &vdso64_start;
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/*
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* On 64bit we don't have a preferred map address. This
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* allows get_unmapped_area to find an area near other mmaps
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* and most likely share a SLB entry.
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*/
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vdso_base = 0;
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}
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mappings_size = vdso_size + vvar_size;
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mappings_size += (VDSO_ALIGNMENT - 1) & PAGE_MASK;
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/*
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* pick a base address for the vDSO in process space. We try to put it
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* at vdso_base which is the "natural" base for it, but we might fail
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* and end up putting it elsewhere.
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* Add enough to the size so that the result can be aligned.
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*/
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vdso_base = get_unmapped_area(NULL, vdso_base, mappings_size, 0, 0);
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if (IS_ERR_VALUE(vdso_base))
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return vdso_base;
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/* Add required alignment. */
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vdso_base = ALIGN(vdso_base, VDSO_ALIGNMENT);
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/*
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* Put vDSO base into mm struct. We need to do this before calling
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* install_special_mapping or the perf counter mmap tracking code
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* will fail to recognise it as a vDSO.
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*/
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mm->context.vdso = (void __user *)vdso_base + vvar_size;
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vma = _install_special_mapping(mm, vdso_base, vvar_size,
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VM_READ | VM_MAYREAD | VM_IO |
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VM_DONTDUMP | VM_PFNMAP, &vvar_spec);
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if (IS_ERR(vma))
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return PTR_ERR(vma);
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/*
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* our vma flags don't have VM_WRITE so by default, the process isn't
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* allowed to write those pages.
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* gdb can break that with ptrace interface, and thus trigger COW on
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* those pages but it's then your responsibility to never do that on
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* the "data" page of the vDSO or you'll stop getting kernel updates
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* and your nice userland gettimeofday will be totally dead.
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* It's fine to use that for setting breakpoints in the vDSO code
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* pages though.
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*/
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vma = _install_special_mapping(mm, vdso_base + vvar_size, vdso_size,
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VM_READ | VM_EXEC | VM_MAYREAD |
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VM_MAYWRITE | VM_MAYEXEC, vdso_spec);
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if (IS_ERR(vma))
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do_munmap(mm, vdso_base, vvar_size, NULL);
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return PTR_ERR_OR_ZERO(vma);
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}
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int arch_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 rc;
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mm->context.vdso = NULL;
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if (mmap_write_lock_killable(mm))
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return -EINTR;
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rc = __arch_setup_additional_pages(bprm, uses_interp);
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if (rc)
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mm->context.vdso = NULL;
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mmap_write_unlock(mm);
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return rc;
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}
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#define VDSO_DO_FIXUPS(type, value, bits, sec) do { \
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void *__start = (void *)VDSO##bits##_SYMBOL(&vdso##bits##_start, sec##_start); \
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void *__end = (void *)VDSO##bits##_SYMBOL(&vdso##bits##_start, sec##_end); \
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\
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do_##type##_fixups((value), __start, __end); \
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} while (0)
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static void __init vdso_fixup_features(void)
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{
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#ifdef CONFIG_PPC64
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VDSO_DO_FIXUPS(feature, cur_cpu_spec->cpu_features, 64, ftr_fixup);
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VDSO_DO_FIXUPS(feature, cur_cpu_spec->mmu_features, 64, mmu_ftr_fixup);
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VDSO_DO_FIXUPS(feature, powerpc_firmware_features, 64, fw_ftr_fixup);
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VDSO_DO_FIXUPS(lwsync, cur_cpu_spec->cpu_features, 64, lwsync_fixup);
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#endif /* CONFIG_PPC64 */
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#ifdef CONFIG_VDSO32
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VDSO_DO_FIXUPS(feature, cur_cpu_spec->cpu_features, 32, ftr_fixup);
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VDSO_DO_FIXUPS(feature, cur_cpu_spec->mmu_features, 32, mmu_ftr_fixup);
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#ifdef CONFIG_PPC64
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VDSO_DO_FIXUPS(feature, powerpc_firmware_features, 32, fw_ftr_fixup);
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#endif /* CONFIG_PPC64 */
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VDSO_DO_FIXUPS(lwsync, cur_cpu_spec->cpu_features, 32, lwsync_fixup);
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#endif
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}
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/*
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* Called from setup_arch to initialize the bitmap of available
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* syscalls in the systemcfg page
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*/
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static void __init vdso_setup_syscall_map(void)
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{
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unsigned int i;
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for (i = 0; i < NR_syscalls; i++) {
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if (sys_call_table[i] != (unsigned long)&sys_ni_syscall)
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vdso_data->syscall_map[i >> 5] |= 0x80000000UL >> (i & 0x1f);
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if (IS_ENABLED(CONFIG_COMPAT) &&
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compat_sys_call_table[i] != (unsigned long)&sys_ni_syscall)
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vdso_data->compat_syscall_map[i >> 5] |= 0x80000000UL >> (i & 0x1f);
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}
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}
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#ifdef CONFIG_PPC64
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int vdso_getcpu_init(void)
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{
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unsigned long cpu, node, val;
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/*
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* SPRG_VDSO contains the CPU in the bottom 16 bits and the NUMA node
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* in the next 16 bits. The VDSO uses this to implement getcpu().
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*/
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cpu = get_cpu();
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WARN_ON_ONCE(cpu > 0xffff);
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node = cpu_to_node(cpu);
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WARN_ON_ONCE(node > 0xffff);
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val = (cpu & 0xffff) | ((node & 0xffff) << 16);
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mtspr(SPRN_SPRG_VDSO_WRITE, val);
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get_paca()->sprg_vdso = val;
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put_cpu();
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return 0;
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}
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/* We need to call this before SMP init */
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early_initcall(vdso_getcpu_init);
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#endif
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static struct page ** __init vdso_setup_pages(void *start, void *end)
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{
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int i;
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struct page **pagelist;
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int pages = (end - start) >> PAGE_SHIFT;
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pagelist = kcalloc(pages + 1, sizeof(struct page *), GFP_KERNEL);
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if (!pagelist)
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panic("%s: Cannot allocate page list for VDSO", __func__);
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for (i = 0; i < pages; i++)
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pagelist[i] = virt_to_page(start + i * PAGE_SIZE);
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return pagelist;
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}
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static int __init vdso_init(void)
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{
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#ifdef CONFIG_PPC64
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/*
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* Fill up the "systemcfg" stuff for backward compatibility
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*/
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strcpy((char *)vdso_data->eye_catcher, "SYSTEMCFG:PPC64");
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vdso_data->version.major = SYSTEMCFG_MAJOR;
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vdso_data->version.minor = SYSTEMCFG_MINOR;
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vdso_data->processor = mfspr(SPRN_PVR);
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/*
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* Fake the old platform number for pSeries and add
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* in LPAR bit if necessary
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*/
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vdso_data->platform = 0x100;
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if (firmware_has_feature(FW_FEATURE_LPAR))
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vdso_data->platform |= 1;
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vdso_data->physicalMemorySize = memblock_phys_mem_size();
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vdso_data->dcache_size = ppc64_caches.l1d.size;
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vdso_data->dcache_line_size = ppc64_caches.l1d.line_size;
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vdso_data->icache_size = ppc64_caches.l1i.size;
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vdso_data->icache_line_size = ppc64_caches.l1i.line_size;
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vdso_data->dcache_block_size = ppc64_caches.l1d.block_size;
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vdso_data->icache_block_size = ppc64_caches.l1i.block_size;
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vdso_data->dcache_log_block_size = ppc64_caches.l1d.log_block_size;
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vdso_data->icache_log_block_size = ppc64_caches.l1i.log_block_size;
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#endif /* CONFIG_PPC64 */
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vdso_setup_syscall_map();
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vdso_fixup_features();
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if (IS_ENABLED(CONFIG_VDSO32))
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vdso32_spec.pages = vdso_setup_pages(&vdso32_start, &vdso32_end);
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if (IS_ENABLED(CONFIG_PPC64))
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vdso64_spec.pages = vdso_setup_pages(&vdso64_start, &vdso64_end);
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smp_wmb();
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return 0;
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}
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arch_initcall(vdso_init);
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