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7c0c01a216
When the generic vDSO does not provide time functions, as for example on
riscv32, then the time data store is not necessary.
Avoid allocating these time data pages when not used.
Fixes: df7fcbefa7 ("vdso: Add generic time data storage")
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250826-vdso-cleanups-v1-1-d9b65750e49f@linutronix.de
130 lines
3.8 KiB
C
130 lines
3.8 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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#include <linux/linkage.h>
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#include <linux/mmap_lock.h>
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#include <linux/mm.h>
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#include <linux/time_namespace.h>
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#include <linux/types.h>
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#include <linux/vdso_datastore.h>
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#include <vdso/datapage.h>
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/*
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* The vDSO data page.
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*/
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#ifdef CONFIG_GENERIC_GETTIMEOFDAY
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static union {
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struct vdso_time_data data;
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u8 page[PAGE_SIZE];
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} vdso_time_data_store __page_aligned_data;
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struct vdso_time_data *vdso_k_time_data = &vdso_time_data_store.data;
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static_assert(sizeof(vdso_time_data_store) == PAGE_SIZE);
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#endif /* CONFIG_GENERIC_GETTIMEOFDAY */
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#ifdef CONFIG_VDSO_GETRANDOM
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static union {
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struct vdso_rng_data data;
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u8 page[PAGE_SIZE];
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} vdso_rng_data_store __page_aligned_data;
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struct vdso_rng_data *vdso_k_rng_data = &vdso_rng_data_store.data;
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static_assert(sizeof(vdso_rng_data_store) == PAGE_SIZE);
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#endif /* CONFIG_VDSO_GETRANDOM */
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#ifdef CONFIG_ARCH_HAS_VDSO_ARCH_DATA
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static union {
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struct vdso_arch_data data;
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u8 page[VDSO_ARCH_DATA_SIZE];
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} vdso_arch_data_store __page_aligned_data;
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struct vdso_arch_data *vdso_k_arch_data = &vdso_arch_data_store.data;
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#endif /* CONFIG_ARCH_HAS_VDSO_ARCH_DATA */
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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 addr, pfn;
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vm_fault_t err;
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switch (vmf->pgoff) {
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case VDSO_TIME_PAGE_OFFSET:
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if (!IS_ENABLED(CONFIG_GENERIC_GETTIMEOFDAY))
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return VM_FAULT_SIGBUS;
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pfn = __phys_to_pfn(__pa_symbol(vdso_k_time_data));
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if (timens_page) {
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/*
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* Fault in VVAR page too, since it will be accessed
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* to get clock data anyway.
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*/
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addr = vmf->address + VDSO_TIMENS_PAGE_OFFSET * PAGE_SIZE;
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err = vmf_insert_pfn(vma, addr, pfn);
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if (unlikely(err & VM_FAULT_ERROR))
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return err;
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pfn = page_to_pfn(timens_page);
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}
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break;
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case VDSO_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 (!IS_ENABLED(CONFIG_TIME_NS) || !timens_page)
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return VM_FAULT_SIGBUS;
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pfn = __phys_to_pfn(__pa_symbol(vdso_k_time_data));
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break;
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case VDSO_RNG_PAGE_OFFSET:
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if (!IS_ENABLED(CONFIG_VDSO_GETRANDOM))
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return VM_FAULT_SIGBUS;
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pfn = __phys_to_pfn(__pa_symbol(vdso_k_rng_data));
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break;
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case VDSO_ARCH_PAGES_START ... VDSO_ARCH_PAGES_END:
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if (!IS_ENABLED(CONFIG_ARCH_HAS_VDSO_ARCH_DATA))
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return VM_FAULT_SIGBUS;
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pfn = __phys_to_pfn(__pa_symbol(vdso_k_arch_data)) +
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vmf->pgoff - VDSO_ARCH_PAGES_START;
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break;
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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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const struct vm_special_mapping vdso_vvar_mapping = {
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.name = "[vvar]",
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.fault = vvar_fault,
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};
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struct vm_area_struct *vdso_install_vvar_mapping(struct mm_struct *mm, unsigned long addr)
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{
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return _install_special_mapping(mm, addr, VDSO_NR_PAGES * PAGE_SIZE,
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VM_READ | VM_MAYREAD | VM_IO | VM_DONTDUMP |
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VM_PFNMAP | VM_SEALED_SYSMAP,
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&vdso_vvar_mapping);
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}
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#ifdef CONFIG_TIME_NS
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/*
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* The vvar page layout depends on whether a task belongs to the root or
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* non-root time namespace. Whenever a task changes its namespace, the VVAR
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* page tables are cleared and then they will be re-faulted with a
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* corresponding layout.
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* See also the comment near timens_setup_vdso_clock_data() for details.
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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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VMA_ITERATOR(vmi, mm, 0);
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mmap_read_lock(mm);
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for_each_vma(vmi, vma) {
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if (vma_is_special_mapping(vma, &vdso_vvar_mapping))
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zap_vma_pages(vma);
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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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#endif
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