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32 results

vdso.c

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  • vdso.c 11.28 KiB
    // SPDX-License-Identifier: GPL-2.0-or-later
    
    /*
     *    Copyright (C) 2004 Benjamin Herrenschmidt, IBM Corp.
     *			 <benh@kernel.crashing.org>
     */
    
    #include <linux/errno.h>
    #include <linux/sched.h>
    #include <linux/kernel.h>
    #include <linux/mm.h>
    #include <linux/smp.h>
    #include <linux/stddef.h>
    #include <linux/unistd.h>
    #include <linux/slab.h>
    #include <linux/user.h>
    #include <linux/elf.h>
    #include <linux/security.h>
    #include <linux/memblock.h>
    #include <linux/syscalls.h>
    #include <linux/time_namespace.h>
    #include <vdso/datapage.h>
    
    #include <asm/syscall.h>
    #include <asm/processor.h>
    #include <asm/mmu.h>
    #include <asm/mmu_context.h>
    #include <asm/machdep.h>
    #include <asm/cputable.h>
    #include <asm/sections.h>
    #include <asm/firmware.h>
    #include <asm/vdso.h>
    #include <asm/vdso_datapage.h>
    #include <asm/setup.h>
    
    /* The alignment of the vDSO */
    #define VDSO_ALIGNMENT	(1 << 16)
    
    extern char vdso32_start, vdso32_end;
    extern char vdso64_start, vdso64_end;
    
    /*
     * The vdso data page (aka. systemcfg for old ppc64 fans) is here.
     * Once the early boot kernel code no longer needs to muck around
     * with it, it will become dynamically allocated
     */
    static union {
    	struct vdso_arch_data	data;
    	u8			page[PAGE_SIZE];
    } vdso_data_store __page_aligned_data;
    struct vdso_arch_data *vdso_data = &vdso_data_store.data;
    
    enum vvar_pages {
    	VVAR_DATA_PAGE_OFFSET,
    	VVAR_TIMENS_PAGE_OFFSET,
    	VVAR_NR_PAGES,
    };
    
    static int vdso_mremap(const struct vm_special_mapping *sm, struct vm_area_struct *new_vma,
    		       unsigned long text_size)
    {
    	unsigned long new_size = new_vma->vm_end - new_vma->vm_start;
    
    	if (new_size != text_size)
    		return -EINVAL;
    
    	current->mm->context.vdso = (void __user *)new_vma->vm_start;
    
    	return 0;
    }
    
    static int vdso32_mremap(const struct vm_special_mapping *sm, struct vm_area_struct *new_vma)
    {
    	return vdso_mremap(sm, new_vma, &vdso32_end - &vdso32_start);
    }
    
    static int vdso64_mremap(const struct vm_special_mapping *sm, struct vm_area_struct *new_vma)
    {
    	return vdso_mremap(sm, new_vma, &vdso64_end - &vdso64_start);
    }
    
    static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
    			     struct vm_area_struct *vma, struct vm_fault *vmf);
    
    static struct vm_special_mapping vvar_spec __ro_after_init = {
    	.name = "[vvar]",
    	.fault = vvar_fault,
    };
    
    static struct vm_special_mapping vdso32_spec __ro_after_init = {
    	.name = "[vdso]",
    	.mremap = vdso32_mremap,
    };
    
    static struct vm_special_mapping vdso64_spec __ro_after_init = {
    	.name = "[vdso]",
    	.mremap = vdso64_mremap,
    };
    
    #ifdef CONFIG_TIME_NS
    struct vdso_data *arch_get_vdso_data(void *vvar_page)
    {
    	return ((struct vdso_arch_data *)vvar_page)->data;
    }
    
    /*
     * The vvar mapping contains data for a specific time namespace, so when a task
     * changes namespace we must unmap its vvar data for the old namespace.
     * Subsequent faults will map in data for the new namespace.
     *
     * For more details see timens_setup_vdso_data().
     */
    int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
    {
    	struct mm_struct *mm = task->mm;
    	VMA_ITERATOR(vmi, mm, 0);
    	struct vm_area_struct *vma;
    
    	mmap_read_lock(mm);
    	for_each_vma(vmi, vma) {
    		unsigned long size = vma->vm_end - vma->vm_start;
    
    		if (vma_is_special_mapping(vma, &vvar_spec))
    			zap_page_range(vma, vma->vm_start, size);
    	}
    	mmap_read_unlock(mm);
    
    	return 0;
    }
    
    static struct page *find_timens_vvar_page(struct vm_area_struct *vma)
    {
    	if (likely(vma->vm_mm == current->mm))
    		return current->nsproxy->time_ns->vvar_page;
    
    	/*
    	 * VM_PFNMAP | VM_IO protect .fault() handler from being called
    	 * through interfaces like /proc/$pid/mem or
    	 * process_vm_{readv,writev}() as long as there's no .access()
    	 * in special_mapping_vmops.
    	 * For more details check_vma_flags() and __access_remote_vm()
    	 */
    	WARN(1, "vvar_page accessed remotely");
    
    	return NULL;
    }
    #else
    static struct page *find_timens_vvar_page(struct vm_area_struct *vma)
    {
    	return NULL;
    }
    #endif
    
    static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
    			     struct vm_area_struct *vma, struct vm_fault *vmf)
    {
    	struct page *timens_page = find_timens_vvar_page(vma);
    	unsigned long pfn;
    
    	switch (vmf->pgoff) {
    	case VVAR_DATA_PAGE_OFFSET:
    		if (timens_page)
    			pfn = page_to_pfn(timens_page);
    		else
    			pfn = virt_to_pfn(vdso_data);
    		break;
    #ifdef CONFIG_TIME_NS
    	case VVAR_TIMENS_PAGE_OFFSET:
    		/*
    		 * If a task belongs to a time namespace then a namespace
    		 * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and
    		 * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET
    		 * offset.
    		 * See also the comment near timens_setup_vdso_data().
    		 */
    		if (!timens_page)
    			return VM_FAULT_SIGBUS;
    		pfn = virt_to_pfn(vdso_data);
    		break;
    #endif /* CONFIG_TIME_NS */
    	default:
    		return VM_FAULT_SIGBUS;
    	}
    
    	return vmf_insert_pfn(vma, vmf->address, pfn);
    }
    
    /*
     * This is called from binfmt_elf, we create the special vma for the
     * vDSO and insert it into the mm struct tree
     */
    static int __arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
    {
    	unsigned long vdso_size, vdso_base, mappings_size;
    	struct vm_special_mapping *vdso_spec;
    	unsigned long vvar_size = VVAR_NR_PAGES * PAGE_SIZE;
    	struct mm_struct *mm = current->mm;
    	struct vm_area_struct *vma;
    
    	if (is_32bit_task()) {
    		vdso_spec = &vdso32_spec;
    		vdso_size = &vdso32_end - &vdso32_start;
    		vdso_base = VDSO32_MBASE;
    	} else {
    		vdso_spec = &vdso64_spec;
    		vdso_size = &vdso64_end - &vdso64_start;
    		/*
    		 * On 64bit we don't have a preferred map address. This
    		 * allows get_unmapped_area to find an area near other mmaps
    		 * and most likely share a SLB entry.
    		 */
    		vdso_base = 0;
    	}
    
    	mappings_size = vdso_size + vvar_size;
    	mappings_size += (VDSO_ALIGNMENT - 1) & PAGE_MASK;
    
    	/*
    	 * pick a base address for the vDSO in process space. We try to put it
    	 * at vdso_base which is the "natural" base for it, but we might fail
    	 * and end up putting it elsewhere.
    	 * Add enough to the size so that the result can be aligned.
    	 */
    	vdso_base = get_unmapped_area(NULL, vdso_base, mappings_size, 0, 0);
    	if (IS_ERR_VALUE(vdso_base))
    		return vdso_base;
    
    	/* Add required alignment. */
    	vdso_base = ALIGN(vdso_base, VDSO_ALIGNMENT);
    
    	/*
    	 * Put vDSO base into mm struct. We need to do this before calling
    	 * install_special_mapping or the perf counter mmap tracking code
    	 * will fail to recognise it as a vDSO.
    	 */
    	mm->context.vdso = (void __user *)vdso_base + vvar_size;
    
    	vma = _install_special_mapping(mm, vdso_base, vvar_size,
    				       VM_READ | VM_MAYREAD | VM_IO |
    				       VM_DONTDUMP | VM_PFNMAP, &vvar_spec);
    	if (IS_ERR(vma))
    		return PTR_ERR(vma);
    
    	/*
    	 * our vma flags don't have VM_WRITE so by default, the process isn't
    	 * allowed to write those pages.
    	 * gdb can break that with ptrace interface, and thus trigger COW on
    	 * those pages but it's then your responsibility to never do that on
    	 * the "data" page of the vDSO or you'll stop getting kernel updates
    	 * and your nice userland gettimeofday will be totally dead.
    	 * It's fine to use that for setting breakpoints in the vDSO code
    	 * pages though.
    	 */
    	vma = _install_special_mapping(mm, vdso_base + vvar_size, vdso_size,
    				       VM_READ | VM_EXEC | VM_MAYREAD |
    				       VM_MAYWRITE | VM_MAYEXEC, vdso_spec);
    	if (IS_ERR(vma))
    		do_munmap(mm, vdso_base, vvar_size, NULL);
    
    	return PTR_ERR_OR_ZERO(vma);
    }
    
    int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
    {
    	struct mm_struct *mm = current->mm;
    	int rc;
    
    	mm->context.vdso = NULL;
    
    	if (mmap_write_lock_killable(mm))
    		return -EINTR;
    
    	rc = __arch_setup_additional_pages(bprm, uses_interp);
    	if (rc)
    		mm->context.vdso = NULL;
    
    	mmap_write_unlock(mm);
    	return rc;
    }
    
    #define VDSO_DO_FIXUPS(type, value, bits, sec) do {					\
    	void *__start = (void *)VDSO##bits##_SYMBOL(&vdso##bits##_start, sec##_start);	\
    	void *__end = (void *)VDSO##bits##_SYMBOL(&vdso##bits##_start, sec##_end);	\
    											\
    	do_##type##_fixups((value), __start, __end);					\
    } while (0)
    
    static void __init vdso_fixup_features(void)
    {
    #ifdef CONFIG_PPC64
    	VDSO_DO_FIXUPS(feature, cur_cpu_spec->cpu_features, 64, ftr_fixup);
    	VDSO_DO_FIXUPS(feature, cur_cpu_spec->mmu_features, 64, mmu_ftr_fixup);
    	VDSO_DO_FIXUPS(feature, powerpc_firmware_features, 64, fw_ftr_fixup);
    	VDSO_DO_FIXUPS(lwsync, cur_cpu_spec->cpu_features, 64, lwsync_fixup);
    #endif /* CONFIG_PPC64 */
    
    #ifdef CONFIG_VDSO32
    	VDSO_DO_FIXUPS(feature, cur_cpu_spec->cpu_features, 32, ftr_fixup);
    	VDSO_DO_FIXUPS(feature, cur_cpu_spec->mmu_features, 32, mmu_ftr_fixup);
    #ifdef CONFIG_PPC64
    	VDSO_DO_FIXUPS(feature, powerpc_firmware_features, 32, fw_ftr_fixup);
    #endif /* CONFIG_PPC64 */
    	VDSO_DO_FIXUPS(lwsync, cur_cpu_spec->cpu_features, 32, lwsync_fixup);
    #endif
    }
    
    /*
     * Called from setup_arch to initialize the bitmap of available
     * syscalls in the systemcfg page
     */
    static void __init vdso_setup_syscall_map(void)
    {
    	unsigned int i;
    
    	for (i = 0; i < NR_syscalls; i++) {
    		if (sys_call_table[i] != (unsigned long)&sys_ni_syscall)
    			vdso_data->syscall_map[i >> 5] |= 0x80000000UL >> (i & 0x1f);
    		if (IS_ENABLED(CONFIG_COMPAT) &&
    		    compat_sys_call_table[i] != (unsigned long)&sys_ni_syscall)
    			vdso_data->compat_syscall_map[i >> 5] |= 0x80000000UL >> (i & 0x1f);
    	}
    }
    
    #ifdef CONFIG_PPC64
    int vdso_getcpu_init(void)
    {
    	unsigned long cpu, node, val;
    
    	/*
    	 * SPRG_VDSO contains the CPU in the bottom 16 bits and the NUMA node
    	 * in the next 16 bits.  The VDSO uses this to implement getcpu().
    	 */
    	cpu = get_cpu();
    	WARN_ON_ONCE(cpu > 0xffff);
    
    	node = cpu_to_node(cpu);
    	WARN_ON_ONCE(node > 0xffff);
    
    	val = (cpu & 0xffff) | ((node & 0xffff) << 16);
    	mtspr(SPRN_SPRG_VDSO_WRITE, val);
    	get_paca()->sprg_vdso = val;
    
    	put_cpu();
    
    	return 0;
    }
    /* We need to call this before SMP init */
    early_initcall(vdso_getcpu_init);
    #endif
    
    static struct page ** __init vdso_setup_pages(void *start, void *end)
    {
    	int i;
    	struct page **pagelist;
    	int pages = (end - start) >> PAGE_SHIFT;
    
    	pagelist = kcalloc(pages + 1, sizeof(struct page *), GFP_KERNEL);
    	if (!pagelist)
    		panic("%s: Cannot allocate page list for VDSO", __func__);
    
    	for (i = 0; i < pages; i++)
    		pagelist[i] = virt_to_page(start + i * PAGE_SIZE);
    
    	return pagelist;
    }
    
    static int __init vdso_init(void)
    {
    #ifdef CONFIG_PPC64
    	/*
    	 * Fill up the "systemcfg" stuff for backward compatibility
    	 */
    	strcpy((char *)vdso_data->eye_catcher, "SYSTEMCFG:PPC64");
    	vdso_data->version.major = SYSTEMCFG_MAJOR;
    	vdso_data->version.minor = SYSTEMCFG_MINOR;
    	vdso_data->processor = mfspr(SPRN_PVR);
    	/*
    	 * Fake the old platform number for pSeries and add
    	 * in LPAR bit if necessary
    	 */
    	vdso_data->platform = 0x100;
    	if (firmware_has_feature(FW_FEATURE_LPAR))
    		vdso_data->platform |= 1;
    	vdso_data->physicalMemorySize = memblock_phys_mem_size();
    	vdso_data->dcache_size = ppc64_caches.l1d.size;
    	vdso_data->dcache_line_size = ppc64_caches.l1d.line_size;
    	vdso_data->icache_size = ppc64_caches.l1i.size;
    	vdso_data->icache_line_size = ppc64_caches.l1i.line_size;
    	vdso_data->dcache_block_size = ppc64_caches.l1d.block_size;
    	vdso_data->icache_block_size = ppc64_caches.l1i.block_size;
    	vdso_data->dcache_log_block_size = ppc64_caches.l1d.log_block_size;
    	vdso_data->icache_log_block_size = ppc64_caches.l1i.log_block_size;
    #endif /* CONFIG_PPC64 */
    
    	vdso_setup_syscall_map();
    
    	vdso_fixup_features();
    
    	if (IS_ENABLED(CONFIG_VDSO32))
    		vdso32_spec.pages = vdso_setup_pages(&vdso32_start, &vdso32_end);
    
    	if (IS_ENABLED(CONFIG_PPC64))
    		vdso64_spec.pages = vdso_setup_pages(&vdso64_start, &vdso64_end);
    
    	smp_wmb();
    
    	return 0;
    }
    arch_initcall(vdso_init);