diff options
Diffstat (limited to 'arch/arm64/kernel/vdso.c')
| -rw-r--r-- | arch/arm64/kernel/vdso.c | 475 |
1 files changed, 475 insertions, 0 deletions
diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c new file mode 100644 index 000000000..6ebb8dea5 --- /dev/null +++ b/arch/arm64/kernel/vdso.c @@ -0,0 +1,475 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * VDSO implementations. + * + * Copyright (C) 2012 ARM Limited + * + * Author: Will Deacon <will.deacon@arm.com> + */ + +#include <linux/cache.h> +#include <linux/clocksource.h> +#include <linux/elf.h> +#include <linux/err.h> +#include <linux/errno.h> +#include <linux/gfp.h> +#include <linux/kernel.h> +#include <linux/mm.h> +#include <linux/sched.h> +#include <linux/signal.h> +#include <linux/slab.h> +#include <linux/time_namespace.h> +#include <linux/timekeeper_internal.h> +#include <linux/vmalloc.h> +#include <vdso/datapage.h> +#include <vdso/helpers.h> +#include <vdso/vsyscall.h> + +#include <asm/cacheflush.h> +#include <asm/signal32.h> +#include <asm/vdso.h> + +enum vdso_abi { + VDSO_ABI_AA64, + VDSO_ABI_AA32, +}; + +enum vvar_pages { + VVAR_DATA_PAGE_OFFSET, + VVAR_TIMENS_PAGE_OFFSET, + VVAR_NR_PAGES, +}; + +struct vdso_abi_info { + const char *name; + const char *vdso_code_start; + const char *vdso_code_end; + unsigned long vdso_pages; + /* Data Mapping */ + struct vm_special_mapping *dm; + /* Code Mapping */ + struct vm_special_mapping *cm; +}; + +static struct vdso_abi_info vdso_info[] __ro_after_init = { + [VDSO_ABI_AA64] = { + .name = "vdso", + .vdso_code_start = vdso_start, + .vdso_code_end = vdso_end, + }, +#ifdef CONFIG_COMPAT_VDSO + [VDSO_ABI_AA32] = { + .name = "vdso32", + .vdso_code_start = vdso32_start, + .vdso_code_end = vdso32_end, + }, +#endif /* CONFIG_COMPAT_VDSO */ +}; + +/* + * The vDSO data page. + */ +static union { + struct vdso_data data[CS_BASES]; + u8 page[PAGE_SIZE]; +} vdso_data_store __page_aligned_data; +struct vdso_data *vdso_data = vdso_data_store.data; + +static int vdso_mremap(const struct vm_special_mapping *sm, + struct vm_area_struct *new_vma) +{ + current->mm->context.vdso = (void *)new_vma->vm_start; + + return 0; +} + +static int __init __vdso_init(enum vdso_abi abi) +{ + int i; + struct page **vdso_pagelist; + unsigned long pfn; + + if (memcmp(vdso_info[abi].vdso_code_start, "\177ELF", 4)) { + pr_err("vDSO is not a valid ELF object!\n"); + return -EINVAL; + } + + vdso_info[abi].vdso_pages = ( + vdso_info[abi].vdso_code_end - + vdso_info[abi].vdso_code_start) >> + PAGE_SHIFT; + + vdso_pagelist = kcalloc(vdso_info[abi].vdso_pages, + sizeof(struct page *), + GFP_KERNEL); + if (vdso_pagelist == NULL) + return -ENOMEM; + + /* Grab the vDSO code pages. */ + pfn = sym_to_pfn(vdso_info[abi].vdso_code_start); + + for (i = 0; i < vdso_info[abi].vdso_pages; i++) + vdso_pagelist[i] = pfn_to_page(pfn + i); + + vdso_info[abi].cm->pages = vdso_pagelist; + + return 0; +} + +#ifdef CONFIG_TIME_NS +struct vdso_data *arch_get_vdso_data(void *vvar_page) +{ + return (struct vdso_data *)(vvar_page); +} + +/* + * 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; + struct vm_area_struct *vma; + VMA_ITERATOR(vmi, mm, 0); + + mmap_read_lock(mm); + + for_each_vma(vmi, vma) { + unsigned long size = vma->vm_end - vma->vm_start; + + if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA64].dm)) + zap_page_range(vma, vma->vm_start, size); +#ifdef CONFIG_COMPAT_VDSO + if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA32].dm)) + zap_page_range(vma, vma->vm_start, size); +#endif + } + + 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 = sym_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 = sym_to_pfn(vdso_data); + break; +#endif /* CONFIG_TIME_NS */ + default: + return VM_FAULT_SIGBUS; + } + + return vmf_insert_pfn(vma, vmf->address, pfn); +} + +static int __setup_additional_pages(enum vdso_abi abi, + struct mm_struct *mm, + struct linux_binprm *bprm, + int uses_interp) +{ + unsigned long vdso_base, vdso_text_len, vdso_mapping_len; + unsigned long gp_flags = 0; + void *ret; + + BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES); + + vdso_text_len = vdso_info[abi].vdso_pages << PAGE_SHIFT; + /* Be sure to map the data page */ + vdso_mapping_len = vdso_text_len + VVAR_NR_PAGES * PAGE_SIZE; + + vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0); + if (IS_ERR_VALUE(vdso_base)) { + ret = ERR_PTR(vdso_base); + goto up_fail; + } + + ret = _install_special_mapping(mm, vdso_base, VVAR_NR_PAGES * PAGE_SIZE, + VM_READ|VM_MAYREAD|VM_PFNMAP, + vdso_info[abi].dm); + if (IS_ERR(ret)) + goto up_fail; + + if (IS_ENABLED(CONFIG_ARM64_BTI_KERNEL) && system_supports_bti()) + gp_flags = VM_ARM64_BTI; + + vdso_base += VVAR_NR_PAGES * PAGE_SIZE; + mm->context.vdso = (void *)vdso_base; + ret = _install_special_mapping(mm, vdso_base, vdso_text_len, + VM_READ|VM_EXEC|gp_flags| + VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC, + vdso_info[abi].cm); + if (IS_ERR(ret)) + goto up_fail; + + return 0; + +up_fail: + mm->context.vdso = NULL; + return PTR_ERR(ret); +} + +#ifdef CONFIG_COMPAT +/* + * Create and map the vectors page for AArch32 tasks. + */ +enum aarch32_map { + AA32_MAP_VECTORS, /* kuser helpers */ + AA32_MAP_SIGPAGE, + AA32_MAP_VVAR, + AA32_MAP_VDSO, +}; + +static struct page *aarch32_vectors_page __ro_after_init; +static struct page *aarch32_sig_page __ro_after_init; + +static int aarch32_sigpage_mremap(const struct vm_special_mapping *sm, + struct vm_area_struct *new_vma) +{ + current->mm->context.sigpage = (void *)new_vma->vm_start; + + return 0; +} + +static struct vm_special_mapping aarch32_vdso_maps[] = { + [AA32_MAP_VECTORS] = { + .name = "[vectors]", /* ABI */ + .pages = &aarch32_vectors_page, + }, + [AA32_MAP_SIGPAGE] = { + .name = "[sigpage]", /* ABI */ + .pages = &aarch32_sig_page, + .mremap = aarch32_sigpage_mremap, + }, + [AA32_MAP_VVAR] = { + .name = "[vvar]", + .fault = vvar_fault, + }, + [AA32_MAP_VDSO] = { + .name = "[vdso]", + .mremap = vdso_mremap, + }, +}; + +static int aarch32_alloc_kuser_vdso_page(void) +{ + extern char __kuser_helper_start[], __kuser_helper_end[]; + int kuser_sz = __kuser_helper_end - __kuser_helper_start; + unsigned long vdso_page; + + if (!IS_ENABLED(CONFIG_KUSER_HELPERS)) + return 0; + + vdso_page = get_zeroed_page(GFP_KERNEL); + if (!vdso_page) + return -ENOMEM; + + memcpy((void *)(vdso_page + 0x1000 - kuser_sz), __kuser_helper_start, + kuser_sz); + aarch32_vectors_page = virt_to_page((void *)vdso_page); + return 0; +} + +#define COMPAT_SIGPAGE_POISON_WORD 0xe7fddef1 +static int aarch32_alloc_sigpage(void) +{ + extern char __aarch32_sigret_code_start[], __aarch32_sigret_code_end[]; + int sigret_sz = __aarch32_sigret_code_end - __aarch32_sigret_code_start; + __le32 poison = cpu_to_le32(COMPAT_SIGPAGE_POISON_WORD); + void *sigpage; + + sigpage = (void *)__get_free_page(GFP_KERNEL); + if (!sigpage) + return -ENOMEM; + + memset32(sigpage, (__force u32)poison, PAGE_SIZE / sizeof(poison)); + memcpy(sigpage, __aarch32_sigret_code_start, sigret_sz); + aarch32_sig_page = virt_to_page(sigpage); + return 0; +} + +static int __init __aarch32_alloc_vdso_pages(void) +{ + + if (!IS_ENABLED(CONFIG_COMPAT_VDSO)) + return 0; + + vdso_info[VDSO_ABI_AA32].dm = &aarch32_vdso_maps[AA32_MAP_VVAR]; + vdso_info[VDSO_ABI_AA32].cm = &aarch32_vdso_maps[AA32_MAP_VDSO]; + + return __vdso_init(VDSO_ABI_AA32); +} + +static int __init aarch32_alloc_vdso_pages(void) +{ + int ret; + + ret = __aarch32_alloc_vdso_pages(); + if (ret) + return ret; + + ret = aarch32_alloc_sigpage(); + if (ret) + return ret; + + return aarch32_alloc_kuser_vdso_page(); +} +arch_initcall(aarch32_alloc_vdso_pages); + +static int aarch32_kuser_helpers_setup(struct mm_struct *mm) +{ + void *ret; + + if (!IS_ENABLED(CONFIG_KUSER_HELPERS)) + return 0; + + /* + * Avoid VM_MAYWRITE for compatibility with arch/arm/, where it's + * not safe to CoW the page containing the CPU exception vectors. + */ + ret = _install_special_mapping(mm, AARCH32_VECTORS_BASE, PAGE_SIZE, + VM_READ | VM_EXEC | + VM_MAYREAD | VM_MAYEXEC, + &aarch32_vdso_maps[AA32_MAP_VECTORS]); + + return PTR_ERR_OR_ZERO(ret); +} + +static int aarch32_sigreturn_setup(struct mm_struct *mm) +{ + unsigned long addr; + void *ret; + + addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0); + if (IS_ERR_VALUE(addr)) { + ret = ERR_PTR(addr); + goto out; + } + + /* + * VM_MAYWRITE is required to allow gdb to Copy-on-Write and + * set breakpoints. + */ + ret = _install_special_mapping(mm, addr, PAGE_SIZE, + VM_READ | VM_EXEC | VM_MAYREAD | + VM_MAYWRITE | VM_MAYEXEC, + &aarch32_vdso_maps[AA32_MAP_SIGPAGE]); + if (IS_ERR(ret)) + goto out; + + mm->context.sigpage = (void *)addr; + +out: + return PTR_ERR_OR_ZERO(ret); +} + +int aarch32_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 = aarch32_kuser_helpers_setup(mm); + if (ret) + goto out; + + if (IS_ENABLED(CONFIG_COMPAT_VDSO)) { + ret = __setup_additional_pages(VDSO_ABI_AA32, mm, bprm, + uses_interp); + if (ret) + goto out; + } + + ret = aarch32_sigreturn_setup(mm); +out: + mmap_write_unlock(mm); + return ret; +} +#endif /* CONFIG_COMPAT */ + +enum aarch64_map { + AA64_MAP_VVAR, + AA64_MAP_VDSO, +}; + +static struct vm_special_mapping aarch64_vdso_maps[] __ro_after_init = { + [AA64_MAP_VVAR] = { + .name = "[vvar]", + .fault = vvar_fault, + }, + [AA64_MAP_VDSO] = { + .name = "[vdso]", + .mremap = vdso_mremap, + }, +}; + +static int __init vdso_init(void) +{ + 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; +} |