diff options
Diffstat (limited to 'kernel/events/uprobes.c')
| -rw-r--r-- | kernel/events/uprobes.c | 2360 |
1 files changed, 2360 insertions, 0 deletions
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c new file mode 100644 index 000000000..826a2355d --- /dev/null +++ b/kernel/events/uprobes.c @@ -0,0 +1,2360 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * User-space Probes (UProbes) + * + * Copyright (C) IBM Corporation, 2008-2012 + * Authors: + * Srikar Dronamraju + * Jim Keniston + * Copyright (C) 2011-2012 Red Hat, Inc., Peter Zijlstra + */ + +#include <linux/kernel.h> +#include <linux/highmem.h> +#include <linux/pagemap.h> /* read_mapping_page */ +#include <linux/slab.h> +#include <linux/sched.h> +#include <linux/sched/mm.h> +#include <linux/sched/coredump.h> +#include <linux/export.h> +#include <linux/rmap.h> /* anon_vma_prepare */ +#include <linux/mmu_notifier.h> /* set_pte_at_notify */ +#include <linux/swap.h> /* try_to_free_swap */ +#include <linux/ptrace.h> /* user_enable_single_step */ +#include <linux/kdebug.h> /* notifier mechanism */ +#include "../../mm/internal.h" /* munlock_vma_page */ +#include <linux/percpu-rwsem.h> +#include <linux/task_work.h> +#include <linux/shmem_fs.h> +#include <linux/khugepaged.h> + +#include <linux/uprobes.h> + +#define UINSNS_PER_PAGE (PAGE_SIZE/UPROBE_XOL_SLOT_BYTES) +#define MAX_UPROBE_XOL_SLOTS UINSNS_PER_PAGE + +static struct rb_root uprobes_tree = RB_ROOT; +/* + * allows us to skip the uprobe_mmap if there are no uprobe events active + * at this time. Probably a fine grained per inode count is better? + */ +#define no_uprobe_events() RB_EMPTY_ROOT(&uprobes_tree) + +static DEFINE_SPINLOCK(uprobes_treelock); /* serialize rbtree access */ + +#define UPROBES_HASH_SZ 13 +/* serialize uprobe->pending_list */ +static struct mutex uprobes_mmap_mutex[UPROBES_HASH_SZ]; +#define uprobes_mmap_hash(v) (&uprobes_mmap_mutex[((unsigned long)(v)) % UPROBES_HASH_SZ]) + +DEFINE_STATIC_PERCPU_RWSEM(dup_mmap_sem); + +/* Have a copy of original instruction */ +#define UPROBE_COPY_INSN 0 + +struct uprobe { + struct rb_node rb_node; /* node in the rb tree */ + refcount_t ref; + struct rw_semaphore register_rwsem; + struct rw_semaphore consumer_rwsem; + struct list_head pending_list; + struct uprobe_consumer *consumers; + struct inode *inode; /* Also hold a ref to inode */ + loff_t offset; + loff_t ref_ctr_offset; + unsigned long flags; + + /* + * The generic code assumes that it has two members of unknown type + * owned by the arch-specific code: + * + * insn - copy_insn() saves the original instruction here for + * arch_uprobe_analyze_insn(). + * + * ixol - potentially modified instruction to execute out of + * line, copied to xol_area by xol_get_insn_slot(). + */ + struct arch_uprobe arch; +}; + +struct delayed_uprobe { + struct list_head list; + struct uprobe *uprobe; + struct mm_struct *mm; +}; + +static DEFINE_MUTEX(delayed_uprobe_lock); +static LIST_HEAD(delayed_uprobe_list); + +/* + * Execute out of line area: anonymous executable mapping installed + * by the probed task to execute the copy of the original instruction + * mangled by set_swbp(). + * + * On a breakpoint hit, thread contests for a slot. It frees the + * slot after singlestep. Currently a fixed number of slots are + * allocated. + */ +struct xol_area { + wait_queue_head_t wq; /* if all slots are busy */ + atomic_t slot_count; /* number of in-use slots */ + unsigned long *bitmap; /* 0 = free slot */ + + struct vm_special_mapping xol_mapping; + struct page *pages[2]; + /* + * We keep the vma's vm_start rather than a pointer to the vma + * itself. The probed process or a naughty kernel module could make + * the vma go away, and we must handle that reasonably gracefully. + */ + unsigned long vaddr; /* Page(s) of instruction slots */ +}; + +/* + * valid_vma: Verify if the specified vma is an executable vma + * Relax restrictions while unregistering: vm_flags might have + * changed after breakpoint was inserted. + * - is_register: indicates if we are in register context. + * - Return 1 if the specified virtual address is in an + * executable vma. + */ +static bool valid_vma(struct vm_area_struct *vma, bool is_register) +{ + vm_flags_t flags = VM_HUGETLB | VM_MAYEXEC | VM_MAYSHARE; + + if (is_register) + flags |= VM_WRITE; + + return vma->vm_file && (vma->vm_flags & flags) == VM_MAYEXEC; +} + +static unsigned long offset_to_vaddr(struct vm_area_struct *vma, loff_t offset) +{ + return vma->vm_start + offset - ((loff_t)vma->vm_pgoff << PAGE_SHIFT); +} + +static loff_t vaddr_to_offset(struct vm_area_struct *vma, unsigned long vaddr) +{ + return ((loff_t)vma->vm_pgoff << PAGE_SHIFT) + (vaddr - vma->vm_start); +} + +/** + * __replace_page - replace page in vma by new page. + * based on replace_page in mm/ksm.c + * + * @vma: vma that holds the pte pointing to page + * @addr: address the old @page is mapped at + * @old_page: the page we are replacing by new_page + * @new_page: the modified page we replace page by + * + * If @new_page is NULL, only unmap @old_page. + * + * Returns 0 on success, negative error code otherwise. + */ +static int __replace_page(struct vm_area_struct *vma, unsigned long addr, + struct page *old_page, struct page *new_page) +{ + struct mm_struct *mm = vma->vm_mm; + struct page_vma_mapped_walk pvmw = { + .page = compound_head(old_page), + .vma = vma, + .address = addr, + }; + int err; + struct mmu_notifier_range range; + + mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, mm, addr, + addr + PAGE_SIZE); + + if (new_page) { + err = mem_cgroup_charge(new_page, vma->vm_mm, GFP_KERNEL); + if (err) + return err; + } + + /* For try_to_free_swap() and munlock_vma_page() below */ + lock_page(old_page); + + mmu_notifier_invalidate_range_start(&range); + err = -EAGAIN; + if (!page_vma_mapped_walk(&pvmw)) + goto unlock; + VM_BUG_ON_PAGE(addr != pvmw.address, old_page); + + if (new_page) { + get_page(new_page); + page_add_new_anon_rmap(new_page, vma, addr, false); + lru_cache_add_inactive_or_unevictable(new_page, vma); + } else + /* no new page, just dec_mm_counter for old_page */ + dec_mm_counter(mm, MM_ANONPAGES); + + if (!PageAnon(old_page)) { + dec_mm_counter(mm, mm_counter_file(old_page)); + inc_mm_counter(mm, MM_ANONPAGES); + } + + flush_cache_page(vma, addr, pte_pfn(*pvmw.pte)); + ptep_clear_flush_notify(vma, addr, pvmw.pte); + if (new_page) + set_pte_at_notify(mm, addr, pvmw.pte, + mk_pte(new_page, vma->vm_page_prot)); + + page_remove_rmap(old_page, false); + if (!page_mapped(old_page)) + try_to_free_swap(old_page); + page_vma_mapped_walk_done(&pvmw); + + if ((vma->vm_flags & VM_LOCKED) && !PageCompound(old_page)) + munlock_vma_page(old_page); + put_page(old_page); + + err = 0; + unlock: + mmu_notifier_invalidate_range_end(&range); + unlock_page(old_page); + return err; +} + +/** + * is_swbp_insn - check if instruction is breakpoint instruction. + * @insn: instruction to be checked. + * Default implementation of is_swbp_insn + * Returns true if @insn is a breakpoint instruction. + */ +bool __weak is_swbp_insn(uprobe_opcode_t *insn) +{ + return *insn == UPROBE_SWBP_INSN; +} + +/** + * is_trap_insn - check if instruction is breakpoint instruction. + * @insn: instruction to be checked. + * Default implementation of is_trap_insn + * Returns true if @insn is a breakpoint instruction. + * + * This function is needed for the case where an architecture has multiple + * trap instructions (like powerpc). + */ +bool __weak is_trap_insn(uprobe_opcode_t *insn) +{ + return is_swbp_insn(insn); +} + +static void copy_from_page(struct page *page, unsigned long vaddr, void *dst, int len) +{ + void *kaddr = kmap_atomic(page); + memcpy(dst, kaddr + (vaddr & ~PAGE_MASK), len); + kunmap_atomic(kaddr); +} + +static void copy_to_page(struct page *page, unsigned long vaddr, const void *src, int len) +{ + void *kaddr = kmap_atomic(page); + memcpy(kaddr + (vaddr & ~PAGE_MASK), src, len); + kunmap_atomic(kaddr); +} + +static int verify_opcode(struct page *page, unsigned long vaddr, uprobe_opcode_t *new_opcode) +{ + uprobe_opcode_t old_opcode; + bool is_swbp; + + /* + * Note: We only check if the old_opcode is UPROBE_SWBP_INSN here. + * We do not check if it is any other 'trap variant' which could + * be conditional trap instruction such as the one powerpc supports. + * + * The logic is that we do not care if the underlying instruction + * is a trap variant; uprobes always wins over any other (gdb) + * breakpoint. + */ + copy_from_page(page, vaddr, &old_opcode, UPROBE_SWBP_INSN_SIZE); + is_swbp = is_swbp_insn(&old_opcode); + + if (is_swbp_insn(new_opcode)) { + if (is_swbp) /* register: already installed? */ + return 0; + } else { + if (!is_swbp) /* unregister: was it changed by us? */ + return 0; + } + + return 1; +} + +static struct delayed_uprobe * +delayed_uprobe_check(struct uprobe *uprobe, struct mm_struct *mm) +{ + struct delayed_uprobe *du; + + list_for_each_entry(du, &delayed_uprobe_list, list) + if (du->uprobe == uprobe && du->mm == mm) + return du; + return NULL; +} + +static int delayed_uprobe_add(struct uprobe *uprobe, struct mm_struct *mm) +{ + struct delayed_uprobe *du; + + if (delayed_uprobe_check(uprobe, mm)) + return 0; + + du = kzalloc(sizeof(*du), GFP_KERNEL); + if (!du) + return -ENOMEM; + + du->uprobe = uprobe; + du->mm = mm; + list_add(&du->list, &delayed_uprobe_list); + return 0; +} + +static void delayed_uprobe_delete(struct delayed_uprobe *du) +{ + if (WARN_ON(!du)) + return; + list_del(&du->list); + kfree(du); +} + +static void delayed_uprobe_remove(struct uprobe *uprobe, struct mm_struct *mm) +{ + struct list_head *pos, *q; + struct delayed_uprobe *du; + + if (!uprobe && !mm) + return; + + list_for_each_safe(pos, q, &delayed_uprobe_list) { + du = list_entry(pos, struct delayed_uprobe, list); + + if (uprobe && du->uprobe != uprobe) + continue; + if (mm && du->mm != mm) + continue; + + delayed_uprobe_delete(du); + } +} + +static bool valid_ref_ctr_vma(struct uprobe *uprobe, + struct vm_area_struct *vma) +{ + unsigned long vaddr = offset_to_vaddr(vma, uprobe->ref_ctr_offset); + + return uprobe->ref_ctr_offset && + vma->vm_file && + file_inode(vma->vm_file) == uprobe->inode && + (vma->vm_flags & (VM_WRITE|VM_SHARED)) == VM_WRITE && + vma->vm_start <= vaddr && + vma->vm_end > vaddr; +} + +static struct vm_area_struct * +find_ref_ctr_vma(struct uprobe *uprobe, struct mm_struct *mm) +{ + struct vm_area_struct *tmp; + + for (tmp = mm->mmap; tmp; tmp = tmp->vm_next) + if (valid_ref_ctr_vma(uprobe, tmp)) + return tmp; + + return NULL; +} + +static int +__update_ref_ctr(struct mm_struct *mm, unsigned long vaddr, short d) +{ + void *kaddr; + struct page *page; + struct vm_area_struct *vma; + int ret; + short *ptr; + + if (!vaddr || !d) + return -EINVAL; + + ret = get_user_pages_remote(mm, vaddr, 1, + FOLL_WRITE, &page, &vma, NULL); + if (unlikely(ret <= 0)) { + /* + * We are asking for 1 page. If get_user_pages_remote() fails, + * it may return 0, in that case we have to return error. + */ + return ret == 0 ? -EBUSY : ret; + } + + kaddr = kmap_atomic(page); + ptr = kaddr + (vaddr & ~PAGE_MASK); + + if (unlikely(*ptr + d < 0)) { + pr_warn("ref_ctr going negative. vaddr: 0x%lx, " + "curr val: %d, delta: %d\n", vaddr, *ptr, d); + ret = -EINVAL; + goto out; + } + + *ptr += d; + ret = 0; +out: + kunmap_atomic(kaddr); + put_page(page); + return ret; +} + +static void update_ref_ctr_warn(struct uprobe *uprobe, + struct mm_struct *mm, short d) +{ + pr_warn("ref_ctr %s failed for inode: 0x%lx offset: " + "0x%llx ref_ctr_offset: 0x%llx of mm: 0x%pK\n", + d > 0 ? "increment" : "decrement", uprobe->inode->i_ino, + (unsigned long long) uprobe->offset, + (unsigned long long) uprobe->ref_ctr_offset, mm); +} + +static int update_ref_ctr(struct uprobe *uprobe, struct mm_struct *mm, + short d) +{ + struct vm_area_struct *rc_vma; + unsigned long rc_vaddr; + int ret = 0; + + rc_vma = find_ref_ctr_vma(uprobe, mm); + + if (rc_vma) { + rc_vaddr = offset_to_vaddr(rc_vma, uprobe->ref_ctr_offset); + ret = __update_ref_ctr(mm, rc_vaddr, d); + if (ret) + update_ref_ctr_warn(uprobe, mm, d); + + if (d > 0) + return ret; + } + + mutex_lock(&delayed_uprobe_lock); + if (d > 0) + ret = delayed_uprobe_add(uprobe, mm); + else + delayed_uprobe_remove(uprobe, mm); + mutex_unlock(&delayed_uprobe_lock); + + return ret; +} + +/* + * NOTE: + * Expect the breakpoint instruction to be the smallest size instruction for + * the architecture. If an arch has variable length instruction and the + * breakpoint instruction is not of the smallest length instruction + * supported by that architecture then we need to modify is_trap_at_addr and + * uprobe_write_opcode accordingly. This would never be a problem for archs + * that have fixed length instructions. + * + * uprobe_write_opcode - write the opcode at a given virtual address. + * @mm: the probed process address space. + * @vaddr: the virtual address to store the opcode. + * @opcode: opcode to be written at @vaddr. + * + * Called with mm->mmap_lock held for write. + * Return 0 (success) or a negative errno. + */ +int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm, + unsigned long vaddr, uprobe_opcode_t opcode) +{ + struct uprobe *uprobe; + struct page *old_page, *new_page; + struct vm_area_struct *vma; + int ret, is_register, ref_ctr_updated = 0; + bool orig_page_huge = false; + unsigned int gup_flags = FOLL_FORCE; + + is_register = is_swbp_insn(&opcode); + uprobe = container_of(auprobe, struct uprobe, arch); + +retry: + if (is_register) + gup_flags |= FOLL_SPLIT_PMD; + /* Read the page with vaddr into memory */ + ret = get_user_pages_remote(mm, vaddr, 1, gup_flags, + &old_page, &vma, NULL); + if (ret <= 0) + return ret; + + ret = verify_opcode(old_page, vaddr, &opcode); + if (ret <= 0) + goto put_old; + + if (WARN(!is_register && PageCompound(old_page), + "uprobe unregister should never work on compound page\n")) { + ret = -EINVAL; + goto put_old; + } + + /* We are going to replace instruction, update ref_ctr. */ + if (!ref_ctr_updated && uprobe->ref_ctr_offset) { + ret = update_ref_ctr(uprobe, mm, is_register ? 1 : -1); + if (ret) + goto put_old; + + ref_ctr_updated = 1; + } + + ret = 0; + if (!is_register && !PageAnon(old_page)) + goto put_old; + + ret = anon_vma_prepare(vma); + if (ret) + goto put_old; + + ret = -ENOMEM; + new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vaddr); + if (!new_page) + goto put_old; + + __SetPageUptodate(new_page); + copy_highpage(new_page, old_page); + copy_to_page(new_page, vaddr, &opcode, UPROBE_SWBP_INSN_SIZE); + + if (!is_register) { + struct page *orig_page; + pgoff_t index; + + VM_BUG_ON_PAGE(!PageAnon(old_page), old_page); + + index = vaddr_to_offset(vma, vaddr & PAGE_MASK) >> PAGE_SHIFT; + orig_page = find_get_page(vma->vm_file->f_inode->i_mapping, + index); + + if (orig_page) { + if (PageUptodate(orig_page) && + pages_identical(new_page, orig_page)) { + /* let go new_page */ + put_page(new_page); + new_page = NULL; + + if (PageCompound(orig_page)) + orig_page_huge = true; + } + put_page(orig_page); + } + } + + ret = __replace_page(vma, vaddr, old_page, new_page); + if (new_page) + put_page(new_page); +put_old: + put_page(old_page); + + if (unlikely(ret == -EAGAIN)) + goto retry; + + /* Revert back reference counter if instruction update failed. */ + if (ret && is_register && ref_ctr_updated) + update_ref_ctr(uprobe, mm, -1); + + /* try collapse pmd for compound page */ + if (!ret && orig_page_huge) + collapse_pte_mapped_thp(mm, vaddr); + + return ret; +} + +/** + * set_swbp - store breakpoint at a given address. + * @auprobe: arch specific probepoint information. + * @mm: the probed process address space. + * @vaddr: the virtual address to insert the opcode. + * + * For mm @mm, store the breakpoint instruction at @vaddr. + * Return 0 (success) or a negative errno. + */ +int __weak set_swbp(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr) +{ + return uprobe_write_opcode(auprobe, mm, vaddr, UPROBE_SWBP_INSN); +} + +/** + * set_orig_insn - Restore the original instruction. + * @mm: the probed process address space. + * @auprobe: arch specific probepoint information. + * @vaddr: the virtual address to insert the opcode. + * + * For mm @mm, restore the original opcode (opcode) at @vaddr. + * Return 0 (success) or a negative errno. + */ +int __weak +set_orig_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr) +{ + return uprobe_write_opcode(auprobe, mm, vaddr, + *(uprobe_opcode_t *)&auprobe->insn); +} + +static struct uprobe *get_uprobe(struct uprobe *uprobe) +{ + refcount_inc(&uprobe->ref); + return uprobe; +} + +static void put_uprobe(struct uprobe *uprobe) +{ + if (refcount_dec_and_test(&uprobe->ref)) { + /* + * If application munmap(exec_vma) before uprobe_unregister() + * gets called, we don't get a chance to remove uprobe from + * delayed_uprobe_list from remove_breakpoint(). Do it here. + */ + mutex_lock(&delayed_uprobe_lock); + delayed_uprobe_remove(uprobe, NULL); + mutex_unlock(&delayed_uprobe_lock); + kfree(uprobe); + } +} + +static int match_uprobe(struct uprobe *l, struct uprobe *r) +{ + if (l->inode < r->inode) + return -1; + + if (l->inode > r->inode) + return 1; + + if (l->offset < r->offset) + return -1; + + if (l->offset > r->offset) + return 1; + + return 0; +} + +static struct uprobe *__find_uprobe(struct inode *inode, loff_t offset) +{ + struct uprobe u = { .inode = inode, .offset = offset }; + struct rb_node *n = uprobes_tree.rb_node; + struct uprobe *uprobe; + int match; + + while (n) { + uprobe = rb_entry(n, struct uprobe, rb_node); + match = match_uprobe(&u, uprobe); + if (!match) + return get_uprobe(uprobe); + + if (match < 0) + n = n->rb_left; + else + n = n->rb_right; + } + return NULL; +} + +/* + * Find a uprobe corresponding to a given inode:offset + * Acquires uprobes_treelock + */ +static struct uprobe *find_uprobe(struct inode *inode, loff_t offset) +{ + struct uprobe *uprobe; + + spin_lock(&uprobes_treelock); + uprobe = __find_uprobe(inode, offset); + spin_unlock(&uprobes_treelock); + + return uprobe; +} + +static struct uprobe *__insert_uprobe(struct uprobe *uprobe) +{ + struct rb_node **p = &uprobes_tree.rb_node; + struct rb_node *parent = NULL; + struct uprobe *u; + int match; + + while (*p) { + parent = *p; + u = rb_entry(parent, struct uprobe, rb_node); + match = match_uprobe(uprobe, u); + if (!match) + return get_uprobe(u); + + if (match < 0) + p = &parent->rb_left; + else + p = &parent->rb_right; + + } + + u = NULL; + rb_link_node(&uprobe->rb_node, parent, p); + rb_insert_color(&uprobe->rb_node, &uprobes_tree); + /* get access + creation ref */ + refcount_set(&uprobe->ref, 2); + + return u; +} + +/* + * Acquire uprobes_treelock. + * Matching uprobe already exists in rbtree; + * increment (access refcount) and return the matching uprobe. + * + * No matching uprobe; insert the uprobe in rb_tree; + * get a double refcount (access + creation) and return NULL. + */ +static struct uprobe *insert_uprobe(struct uprobe *uprobe) +{ + struct uprobe *u; + + spin_lock(&uprobes_treelock); + u = __insert_uprobe(uprobe); + spin_unlock(&uprobes_treelock); + + return u; +} + +static void +ref_ctr_mismatch_warn(struct uprobe *cur_uprobe, struct uprobe *uprobe) +{ + pr_warn("ref_ctr_offset mismatch. inode: 0x%lx offset: 0x%llx " + "ref_ctr_offset(old): 0x%llx ref_ctr_offset(new): 0x%llx\n", + uprobe->inode->i_ino, (unsigned long long) uprobe->offset, + (unsigned long long) cur_uprobe->ref_ctr_offset, + (unsigned long long) uprobe->ref_ctr_offset); +} + +static struct uprobe *alloc_uprobe(struct inode *inode, loff_t offset, + loff_t ref_ctr_offset) +{ + struct uprobe *uprobe, *cur_uprobe; + + uprobe = kzalloc(sizeof(struct uprobe), GFP_KERNEL); + if (!uprobe) + return NULL; + + uprobe->inode = inode; + uprobe->offset = offset; + uprobe->ref_ctr_offset = ref_ctr_offset; + init_rwsem(&uprobe->register_rwsem); + init_rwsem(&uprobe->consumer_rwsem); + + /* add to uprobes_tree, sorted on inode:offset */ + cur_uprobe = insert_uprobe(uprobe); + /* a uprobe exists for this inode:offset combination */ + if (cur_uprobe) { + if (cur_uprobe->ref_ctr_offset != uprobe->ref_ctr_offset) { + ref_ctr_mismatch_warn(cur_uprobe, uprobe); + put_uprobe(cur_uprobe); + kfree(uprobe); + return ERR_PTR(-EINVAL); + } + kfree(uprobe); + uprobe = cur_uprobe; + } + + return uprobe; +} + +static void consumer_add(struct uprobe *uprobe, struct uprobe_consumer *uc) +{ + down_write(&uprobe->consumer_rwsem); + uc->next = uprobe->consumers; + uprobe->consumers = uc; + up_write(&uprobe->consumer_rwsem); +} + +/* + * For uprobe @uprobe, delete the consumer @uc. + * Return true if the @uc is deleted successfully + * or return false. + */ +static bool consumer_del(struct uprobe *uprobe, struct uprobe_consumer *uc) +{ + struct uprobe_consumer **con; + bool ret = false; + + down_write(&uprobe->consumer_rwsem); + for (con = &uprobe->consumers; *con; con = &(*con)->next) { + if (*con == uc) { + *con = uc->next; + ret = true; + break; + } + } + up_write(&uprobe->consumer_rwsem); + + return ret; +} + +static int __copy_insn(struct address_space *mapping, struct file *filp, + void *insn, int nbytes, loff_t offset) +{ + struct page *page; + /* + * Ensure that the page that has the original instruction is populated + * and in page-cache. If ->readpage == NULL it must be shmem_mapping(), + * see uprobe_register(). + */ + if (mapping->a_ops->readpage) + page = read_mapping_page(mapping, offset >> PAGE_SHIFT, filp); + else + page = shmem_read_mapping_page(mapping, offset >> PAGE_SHIFT); + if (IS_ERR(page)) + return PTR_ERR(page); + + copy_from_page(page, offset, insn, nbytes); + put_page(page); + + return 0; +} + +static int copy_insn(struct uprobe *uprobe, struct file *filp) +{ + struct address_space *mapping = uprobe->inode->i_mapping; + loff_t offs = uprobe->offset; + void *insn = &uprobe->arch.insn; + int size = sizeof(uprobe->arch.insn); + int len, err = -EIO; + + /* Copy only available bytes, -EIO if nothing was read */ + do { + if (offs >= i_size_read(uprobe->inode)) + break; + + len = min_t(int, size, PAGE_SIZE - (offs & ~PAGE_MASK)); + err = __copy_insn(mapping, filp, insn, len, offs); + if (err) + break; + + insn += len; + offs += len; + size -= len; + } while (size); + + return err; +} + +static int prepare_uprobe(struct uprobe *uprobe, struct file *file, + struct mm_struct *mm, unsigned long vaddr) +{ + int ret = 0; + + if (test_bit(UPROBE_COPY_INSN, &uprobe->flags)) + return ret; + + /* TODO: move this into _register, until then we abuse this sem. */ + down_write(&uprobe->consumer_rwsem); + if (test_bit(UPROBE_COPY_INSN, &uprobe->flags)) + goto out; + + ret = copy_insn(uprobe, file); + if (ret) + goto out; + + ret = -ENOTSUPP; + if (is_trap_insn((uprobe_opcode_t *)&uprobe->arch.insn)) + goto out; + + ret = arch_uprobe_analyze_insn(&uprobe->arch, mm, vaddr); + if (ret) + goto out; + + smp_wmb(); /* pairs with the smp_rmb() in handle_swbp() */ + set_bit(UPROBE_COPY_INSN, &uprobe->flags); + + out: + up_write(&uprobe->consumer_rwsem); + + return ret; +} + +static inline bool consumer_filter(struct uprobe_consumer *uc, + enum uprobe_filter_ctx ctx, struct mm_struct *mm) +{ + return !uc->filter || uc->filter(uc, ctx, mm); +} + +static bool filter_chain(struct uprobe *uprobe, + enum uprobe_filter_ctx ctx, struct mm_struct *mm) +{ + struct uprobe_consumer *uc; + bool ret = false; + + down_read(&uprobe->consumer_rwsem); + for (uc = uprobe->consumers; uc; uc = uc->next) { + ret = consumer_filter(uc, ctx, mm); + if (ret) + break; + } + up_read(&uprobe->consumer_rwsem); + + return ret; +} + +static int +install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, + struct vm_area_struct *vma, unsigned long vaddr) +{ + bool first_uprobe; + int ret; + + ret = prepare_uprobe(uprobe, vma->vm_file, mm, vaddr); + if (ret) + return ret; + + /* + * set MMF_HAS_UPROBES in advance for uprobe_pre_sstep_notifier(), + * the task can hit this breakpoint right after __replace_page(). + */ + first_uprobe = !test_bit(MMF_HAS_UPROBES, &mm->flags); + if (first_uprobe) + set_bit(MMF_HAS_UPROBES, &mm->flags); + + ret = set_swbp(&uprobe->arch, mm, vaddr); + if (!ret) + clear_bit(MMF_RECALC_UPROBES, &mm->flags); + else if (first_uprobe) + clear_bit(MMF_HAS_UPROBES, &mm->flags); + + return ret; +} + +static int +remove_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, unsigned long vaddr) +{ + set_bit(MMF_RECALC_UPROBES, &mm->flags); + return set_orig_insn(&uprobe->arch, mm, vaddr); +} + +static inline bool uprobe_is_active(struct uprobe *uprobe) +{ + return !RB_EMPTY_NODE(&uprobe->rb_node); +} +/* + * There could be threads that have already hit the breakpoint. They + * will recheck the current insn and restart if find_uprobe() fails. + * See find_active_uprobe(). + */ +static void delete_uprobe(struct uprobe *uprobe) +{ + if (WARN_ON(!uprobe_is_active(uprobe))) + return; + + spin_lock(&uprobes_treelock); + rb_erase(&uprobe->rb_node, &uprobes_tree); + spin_unlock(&uprobes_treelock); + RB_CLEAR_NODE(&uprobe->rb_node); /* for uprobe_is_active() */ + put_uprobe(uprobe); +} + +struct map_info { + struct map_info *next; + struct mm_struct *mm; + unsigned long vaddr; +}; + +static inline struct map_info *free_map_info(struct map_info *info) +{ + struct map_info *next = info->next; + kfree(info); + return next; +} + +static struct map_info * +build_map_info(struct address_space *mapping, loff_t offset, bool is_register) +{ + unsigned long pgoff = offset >> PAGE_SHIFT; + struct vm_area_struct *vma; + struct map_info *curr = NULL; + struct map_info *prev = NULL; + struct map_info *info; + int more = 0; + + again: + i_mmap_lock_read(mapping); + vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) { + if (!valid_vma(vma, is_register)) + continue; + + if (!prev && !more) { + /* + * Needs GFP_NOWAIT to avoid i_mmap_rwsem recursion through + * reclaim. This is optimistic, no harm done if it fails. + */ + prev = kmalloc(sizeof(struct map_info), + GFP_NOWAIT | __GFP_NOMEMALLOC | __GFP_NOWARN); + if (prev) + prev->next = NULL; + } + if (!prev) { + more++; + continue; + } + + if (!mmget_not_zero(vma->vm_mm)) + continue; + + info = prev; + prev = prev->next; + info->next = curr; + curr = info; + + info->mm = vma->vm_mm; + info->vaddr = offset_to_vaddr(vma, offset); + } + i_mmap_unlock_read(mapping); + + if (!more) + goto out; + + prev = curr; + while (curr) { + mmput(curr->mm); + curr = curr->next; + } + + do { + info = kmalloc(sizeof(struct map_info), GFP_KERNEL); + if (!info) { + curr = ERR_PTR(-ENOMEM); + goto out; + } + info->next = prev; + prev = info; + } while (--more); + + goto again; + out: + while (prev) + prev = free_map_info(prev); + return curr; +} + +static int +register_for_each_vma(struct uprobe *uprobe, struct uprobe_consumer *new) +{ + bool is_register = !!new; + struct map_info *info; + int err = 0; + + percpu_down_write(&dup_mmap_sem); + info = build_map_info(uprobe->inode->i_mapping, + uprobe->offset, is_register); + if (IS_ERR(info)) { + err = PTR_ERR(info); + goto out; + } + + while (info) { + struct mm_struct *mm = info->mm; + struct vm_area_struct *vma; + + if (err && is_register) + goto free; + + mmap_write_lock(mm); + vma = find_vma(mm, info->vaddr); + if (!vma || !valid_vma(vma, is_register) || + file_inode(vma->vm_file) != uprobe->inode) + goto unlock; + + if (vma->vm_start > info->vaddr || + vaddr_to_offset(vma, info->vaddr) != uprobe->offset) + goto unlock; + + if (is_register) { + /* consult only the "caller", new consumer. */ + if (consumer_filter(new, + UPROBE_FILTER_REGISTER, mm)) + err = install_breakpoint(uprobe, mm, vma, info->vaddr); + } else if (test_bit(MMF_HAS_UPROBES, &mm->flags)) { + if (!filter_chain(uprobe, + UPROBE_FILTER_UNREGISTER, mm)) + err |= remove_breakpoint(uprobe, mm, info->vaddr); + } + + unlock: + mmap_write_unlock(mm); + free: + mmput(mm); + info = free_map_info(info); + } + out: + percpu_up_write(&dup_mmap_sem); + return err; +} + +static void +__uprobe_unregister(struct uprobe *uprobe, struct uprobe_consumer *uc) +{ + int err; + + if (WARN_ON(!consumer_del(uprobe, uc))) + return; + + err = register_for_each_vma(uprobe, NULL); + /* TODO : cant unregister? schedule a worker thread */ + if (!uprobe->consumers && !err) + delete_uprobe(uprobe); +} + +/* + * uprobe_unregister - unregister an already registered probe. + * @inode: the file in which the probe has to be removed. + * @offset: offset from the start of the file. + * @uc: identify which probe if multiple probes are colocated. + */ +void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *uc) +{ + struct uprobe *uprobe; + + uprobe = find_uprobe(inode, offset); + if (WARN_ON(!uprobe)) + return; + + down_write(&uprobe->register_rwsem); + __uprobe_unregister(uprobe, uc); + up_write(&uprobe->register_rwsem); + put_uprobe(uprobe); +} +EXPORT_SYMBOL_GPL(uprobe_unregister); + +/* + * __uprobe_register - register a probe + * @inode: the file in which the probe has to be placed. + * @offset: offset from the start of the file. + * @uc: information on howto handle the probe.. + * + * Apart from the access refcount, __uprobe_register() takes a creation + * refcount (thro alloc_uprobe) if and only if this @uprobe is getting + * inserted into the rbtree (i.e first consumer for a @inode:@offset + * tuple). Creation refcount stops uprobe_unregister from freeing the + * @uprobe even before the register operation is complete. Creation + * refcount is released when the last @uc for the @uprobe + * unregisters. Caller of __uprobe_register() is required to keep @inode + * (and the containing mount) referenced. + * + * Return errno if it cannot successully install probes + * else return 0 (success) + */ +static int __uprobe_register(struct inode *inode, loff_t offset, + loff_t ref_ctr_offset, struct uprobe_consumer *uc) +{ + struct uprobe *uprobe; + int ret; + + /* Uprobe must have at least one set consumer */ + if (!uc->handler && !uc->ret_handler) + return -EINVAL; + + /* copy_insn() uses read_mapping_page() or shmem_read_mapping_page() */ + if (!inode->i_mapping->a_ops->readpage && !shmem_mapping(inode->i_mapping)) + return -EIO; + /* Racy, just to catch the obvious mistakes */ + if (offset > i_size_read(inode)) + return -EINVAL; + + /* + * This ensures that copy_from_page(), copy_to_page() and + * __update_ref_ctr() can't cross page boundary. + */ + if (!IS_ALIGNED(offset, UPROBE_SWBP_INSN_SIZE)) + return -EINVAL; + if (!IS_ALIGNED(ref_ctr_offset, sizeof(short))) + return -EINVAL; + + retry: + uprobe = alloc_uprobe(inode, offset, ref_ctr_offset); + if (!uprobe) + return -ENOMEM; + if (IS_ERR(uprobe)) + return PTR_ERR(uprobe); + + /* + * We can race with uprobe_unregister()->delete_uprobe(). + * Check uprobe_is_active() and retry if it is false. + */ + down_write(&uprobe->register_rwsem); + ret = -EAGAIN; + if (likely(uprobe_is_active(uprobe))) { + consumer_add(uprobe, uc); + ret = register_for_each_vma(uprobe, uc); + if (ret) + __uprobe_unregister(uprobe, uc); + } + up_write(&uprobe->register_rwsem); + put_uprobe(uprobe); + + if (unlikely(ret == -EAGAIN)) + goto retry; + return ret; +} + +int uprobe_register(struct inode *inode, loff_t offset, + struct uprobe_consumer *uc) +{ + return __uprobe_register(inode, offset, 0, uc); +} +EXPORT_SYMBOL_GPL(uprobe_register); + +int uprobe_register_refctr(struct inode *inode, loff_t offset, + loff_t ref_ctr_offset, struct uprobe_consumer *uc) +{ + return __uprobe_register(inode, offset, ref_ctr_offset, uc); +} +EXPORT_SYMBOL_GPL(uprobe_register_refctr); + +/* + * uprobe_apply - unregister an already registered probe. + * @inode: the file in which the probe has to be removed. + * @offset: offset from the start of the file. + * @uc: consumer which wants to add more or remove some breakpoints + * @add: add or remove the breakpoints + */ +int uprobe_apply(struct inode *inode, loff_t offset, + struct uprobe_consumer *uc, bool add) +{ + struct uprobe *uprobe; + struct uprobe_consumer *con; + int ret = -ENOENT; + + uprobe = find_uprobe(inode, offset); + if (WARN_ON(!uprobe)) + return ret; + + down_write(&uprobe->register_rwsem); + for (con = uprobe->consumers; con && con != uc ; con = con->next) + ; + if (con) + ret = register_for_each_vma(uprobe, add ? uc : NULL); + up_write(&uprobe->register_rwsem); + put_uprobe(uprobe); + + return ret; +} + +static int unapply_uprobe(struct uprobe *uprobe, struct mm_struct *mm) +{ + struct vm_area_struct *vma; + int err = 0; + + mmap_read_lock(mm); + for (vma = mm->mmap; vma; vma = vma->vm_next) { + unsigned long vaddr; + loff_t offset; + + if (!valid_vma(vma, false) || + file_inode(vma->vm_file) != uprobe->inode) + continue; + + offset = (loff_t)vma->vm_pgoff << PAGE_SHIFT; + if (uprobe->offset < offset || + uprobe->offset >= offset + vma->vm_end - vma->vm_start) + continue; + + vaddr = offset_to_vaddr(vma, uprobe->offset); + err |= remove_breakpoint(uprobe, mm, vaddr); + } + mmap_read_unlock(mm); + + return err; +} + +static struct rb_node * +find_node_in_range(struct inode *inode, loff_t min, loff_t max) +{ + struct rb_node *n = uprobes_tree.rb_node; + + while (n) { + struct uprobe *u = rb_entry(n, struct uprobe, rb_node); + + if (inode < u->inode) { + n = n->rb_left; + } else if (inode > u->inode) { + n = n->rb_right; + } else { + if (max < u->offset) + n = n->rb_left; + else if (min > u->offset) + n = n->rb_right; + else + break; + } + } + + return n; +} + +/* + * For a given range in vma, build a list of probes that need to be inserted. + */ +static void build_probe_list(struct inode *inode, + struct vm_area_struct *vma, + unsigned long start, unsigned long end, + struct list_head *head) +{ + loff_t min, max; + struct rb_node *n, *t; + struct uprobe *u; + + INIT_LIST_HEAD(head); + min = vaddr_to_offset(vma, start); + max = min + (end - start) - 1; + + spin_lock(&uprobes_treelock); + n = find_node_in_range(inode, min, max); + if (n) { + for (t = n; t; t = rb_prev(t)) { + u = rb_entry(t, struct uprobe, rb_node); + if (u->inode != inode || u->offset < min) + break; + list_add(&u->pending_list, head); + get_uprobe(u); + } + for (t = n; (t = rb_next(t)); ) { + u = rb_entry(t, struct uprobe, rb_node); + if (u->inode != inode || u->offset > max) + break; + list_add(&u->pending_list, head); + get_uprobe(u); + } + } + spin_unlock(&uprobes_treelock); +} + +/* @vma contains reference counter, not the probed instruction. */ +static int delayed_ref_ctr_inc(struct vm_area_struct *vma) +{ + struct list_head *pos, *q; + struct delayed_uprobe *du; + unsigned long vaddr; + int ret = 0, err = 0; + + mutex_lock(&delayed_uprobe_lock); + list_for_each_safe(pos, q, &delayed_uprobe_list) { + du = list_entry(pos, struct delayed_uprobe, list); + + if (du->mm != vma->vm_mm || + !valid_ref_ctr_vma(du->uprobe, vma)) + continue; + + vaddr = offset_to_vaddr(vma, du->uprobe->ref_ctr_offset); + ret = __update_ref_ctr(vma->vm_mm, vaddr, 1); + if (ret) { + update_ref_ctr_warn(du->uprobe, vma->vm_mm, 1); + if (!err) + err = ret; + } + delayed_uprobe_delete(du); + } + mutex_unlock(&delayed_uprobe_lock); + return err; +} + +/* + * Called from mmap_region/vma_adjust with mm->mmap_lock acquired. + * + * Currently we ignore all errors and always return 0, the callers + * can't handle the failure anyway. + */ +int uprobe_mmap(struct vm_area_struct *vma) +{ + struct list_head tmp_list; + struct uprobe *uprobe, *u; + struct inode *inode; + + if (no_uprobe_events()) + return 0; + + if (vma->vm_file && + (vma->vm_flags & (VM_WRITE|VM_SHARED)) == VM_WRITE && + test_bit(MMF_HAS_UPROBES, &vma->vm_mm->flags)) + delayed_ref_ctr_inc(vma); + + if (!valid_vma(vma, true)) + return 0; + + inode = file_inode(vma->vm_file); + if (!inode) + return 0; + + mutex_lock(uprobes_mmap_hash(inode)); + build_probe_list(inode, vma, vma->vm_start, vma->vm_end, &tmp_list); + /* + * We can race with uprobe_unregister(), this uprobe can be already + * removed. But in this case filter_chain() must return false, all + * consumers have gone away. + */ + list_for_each_entry_safe(uprobe, u, &tmp_list, pending_list) { + if (!fatal_signal_pending(current) && + filter_chain(uprobe, UPROBE_FILTER_MMAP, vma->vm_mm)) { + unsigned long vaddr = offset_to_vaddr(vma, uprobe->offset); + install_breakpoint(uprobe, vma->vm_mm, vma, vaddr); + } + put_uprobe(uprobe); + } + mutex_unlock(uprobes_mmap_hash(inode)); + + return 0; +} + +static bool +vma_has_uprobes(struct vm_area_struct *vma, unsigned long start, unsigned long end) +{ + loff_t min, max; + struct inode *inode; + struct rb_node *n; + + inode = file_inode(vma->vm_file); + + min = vaddr_to_offset(vma, start); + max = min + (end - start) - 1; + + spin_lock(&uprobes_treelock); + n = find_node_in_range(inode, min, max); + spin_unlock(&uprobes_treelock); + + return !!n; +} + +/* + * Called in context of a munmap of a vma. + */ +void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned long end) +{ + if (no_uprobe_events() || !valid_vma(vma, false)) + return; + + if (!atomic_read(&vma->vm_mm->mm_users)) /* called by mmput() ? */ + return; + + if (!test_bit(MMF_HAS_UPROBES, &vma->vm_mm->flags) || + test_bit(MMF_RECALC_UPROBES, &vma->vm_mm->flags)) + return; + + if (vma_has_uprobes(vma, start, end)) + set_bit(MMF_RECALC_UPROBES, &vma->vm_mm->flags); +} + +/* Slot allocation for XOL */ +static int xol_add_vma(struct mm_struct *mm, struct xol_area *area) +{ + struct vm_area_struct *vma; + int ret; + + if (mmap_write_lock_killable(mm)) + return -EINTR; + + if (mm->uprobes_state.xol_area) { + ret = -EALREADY; + goto fail; + } + + if (!area->vaddr) { + /* Try to map as high as possible, this is only a hint. */ + area->vaddr = get_unmapped_area(NULL, TASK_SIZE - PAGE_SIZE, + PAGE_SIZE, 0, 0); + if (IS_ERR_VALUE(area->vaddr)) { + ret = area->vaddr; + goto fail; + } + } + + vma = _install_special_mapping(mm, area->vaddr, PAGE_SIZE, + VM_EXEC|VM_MAYEXEC|VM_DONTCOPY|VM_IO, + &area->xol_mapping); + if (IS_ERR(vma)) { + ret = PTR_ERR(vma); + goto fail; + } + + ret = 0; + /* pairs with get_xol_area() */ + smp_store_release(&mm->uprobes_state.xol_area, area); /* ^^^ */ + fail: + mmap_write_unlock(mm); + + return ret; +} + +static struct xol_area *__create_xol_area(unsigned long vaddr) +{ + struct mm_struct *mm = current->mm; + uprobe_opcode_t insn = UPROBE_SWBP_INSN; + struct xol_area *area; + + area = kmalloc(sizeof(*area), GFP_KERNEL); + if (unlikely(!area)) + goto out; + + area->bitmap = kcalloc(BITS_TO_LONGS(UINSNS_PER_PAGE), sizeof(long), + GFP_KERNEL); + if (!area->bitmap) + goto free_area; + + area->xol_mapping.name = "[uprobes]"; + area->xol_mapping.fault = NULL; + area->xol_mapping.pages = area->pages; + area->pages[0] = alloc_page(GFP_HIGHUSER); + if (!area->pages[0]) + goto free_bitmap; + area->pages[1] = NULL; + + area->vaddr = vaddr; + init_waitqueue_head(&area->wq); + /* Reserve the 1st slot for get_trampoline_vaddr() */ + set_bit(0, area->bitmap); + atomic_set(&area->slot_count, 1); + arch_uprobe_copy_ixol(area->pages[0], 0, &insn, UPROBE_SWBP_INSN_SIZE); + + if (!xol_add_vma(mm, area)) + return area; + + __free_page(area->pages[0]); + free_bitmap: + kfree(area->bitmap); + free_area: + kfree(area); + out: + return NULL; +} + +/* + * get_xol_area - Allocate process's xol_area if necessary. + * This area will be used for storing instructions for execution out of line. + * + * Returns the allocated area or NULL. + */ +static struct xol_area *get_xol_area(void) +{ + struct mm_struct *mm = current->mm; + struct xol_area *area; + + if (!mm->uprobes_state.xol_area) + __create_xol_area(0); + + /* Pairs with xol_add_vma() smp_store_release() */ + area = READ_ONCE(mm->uprobes_state.xol_area); /* ^^^ */ + return area; +} + +/* + * uprobe_clear_state - Free the area allocated for slots. + */ +void uprobe_clear_state(struct mm_struct *mm) +{ + struct xol_area *area = mm->uprobes_state.xol_area; + + mutex_lock(&delayed_uprobe_lock); + delayed_uprobe_remove(NULL, mm); + mutex_unlock(&delayed_uprobe_lock); + + if (!area) + return; + + put_page(area->pages[0]); + kfree(area->bitmap); + kfree(area); +} + +void uprobe_start_dup_mmap(void) +{ + percpu_down_read(&dup_mmap_sem); +} + +void uprobe_end_dup_mmap(void) +{ + percpu_up_read(&dup_mmap_sem); +} + +void uprobe_dup_mmap(struct mm_struct *oldmm, struct mm_struct *newmm) +{ + if (test_bit(MMF_HAS_UPROBES, &oldmm->flags)) { + set_bit(MMF_HAS_UPROBES, &newmm->flags); + /* unconditionally, dup_mmap() skips VM_DONTCOPY vmas */ + set_bit(MMF_RECALC_UPROBES, &newmm->flags); + } +} + +/* + * - search for a free slot. + */ +static unsigned long xol_take_insn_slot(struct xol_area *area) +{ + unsigned long slot_addr; + int slot_nr; + + do { + slot_nr = find_first_zero_bit(area->bitmap, UINSNS_PER_PAGE); + if (slot_nr < UINSNS_PER_PAGE) { + if (!test_and_set_bit(slot_nr, area->bitmap)) + break; + + slot_nr = UINSNS_PER_PAGE; + continue; + } + wait_event(area->wq, (atomic_read(&area->slot_count) < UINSNS_PER_PAGE)); + } while (slot_nr >= UINSNS_PER_PAGE); + + slot_addr = area->vaddr + (slot_nr * UPROBE_XOL_SLOT_BYTES); + atomic_inc(&area->slot_count); + + return slot_addr; +} + +/* + * xol_get_insn_slot - allocate a slot for xol. + * Returns the allocated slot address or 0. + */ +static unsigned long xol_get_insn_slot(struct uprobe *uprobe) +{ + struct xol_area *area; + unsigned long xol_vaddr; + + area = get_xol_area(); + if (!area) + return 0; + + xol_vaddr = xol_take_insn_slot(area); + if (unlikely(!xol_vaddr)) + return 0; + + arch_uprobe_copy_ixol(area->pages[0], xol_vaddr, + &uprobe->arch.ixol, sizeof(uprobe->arch.ixol)); + + return xol_vaddr; +} + +/* + * xol_free_insn_slot - If slot was earlier allocated by + * @xol_get_insn_slot(), make the slot available for + * subsequent requests. + */ +static void xol_free_insn_slot(struct task_struct *tsk) +{ + struct xol_area *area; + unsigned long vma_end; + unsigned long slot_addr; + + if (!tsk->mm || !tsk->mm->uprobes_state.xol_area || !tsk->utask) + return; + + slot_addr = tsk->utask->xol_vaddr; + if (unlikely(!slot_addr)) + return; + + area = tsk->mm->uprobes_state.xol_area; + vma_end = area->vaddr + PAGE_SIZE; + if (area->vaddr <= slot_addr && slot_addr < vma_end) { + unsigned long offset; + int slot_nr; + + offset = slot_addr - area->vaddr; + slot_nr = offset / UPROBE_XOL_SLOT_BYTES; + if (slot_nr >= UINSNS_PER_PAGE) + return; + + clear_bit(slot_nr, area->bitmap); + atomic_dec(&area->slot_count); + smp_mb__after_atomic(); /* pairs with prepare_to_wait() */ + if (waitqueue_active(&area->wq)) + wake_up(&area->wq); + + tsk->utask->xol_vaddr = 0; + } +} + +void __weak arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr, + void *src, unsigned long len) +{ + /* Initialize the slot */ + copy_to_page(page, vaddr, src, len); + + /* + * We probably need flush_icache_user_page() but it needs vma. + * This should work on most of architectures by default. If + * architecture needs to do something different it can define + * its own version of the function. + */ + flush_dcache_page(page); +} + +/** + * uprobe_get_swbp_addr - compute address of swbp given post-swbp regs + * @regs: Reflects the saved state of the task after it has hit a breakpoint + * instruction. + * Return the address of the breakpoint instruction. + */ +unsigned long __weak uprobe_get_swbp_addr(struct pt_regs *regs) +{ + return instruction_pointer(regs) - UPROBE_SWBP_INSN_SIZE; +} + +unsigned long uprobe_get_trap_addr(struct pt_regs *regs) +{ + struct uprobe_task *utask = current->utask; + + if (unlikely(utask && utask->active_uprobe)) + return utask->vaddr; + + return instruction_pointer(regs); +} + +static struct return_instance *free_ret_instance(struct return_instance *ri) +{ + struct return_instance *next = ri->next; + put_uprobe(ri->uprobe); + kfree(ri); + return next; +} + +/* + * Called with no locks held. + * Called in context of an exiting or an exec-ing thread. + */ +void uprobe_free_utask(struct task_struct *t) +{ + struct uprobe_task *utask = t->utask; + struct return_instance *ri; + + if (!utask) + return; + + if (utask->active_uprobe) + put_uprobe(utask->active_uprobe); + + ri = utask->return_instances; + while (ri) + ri = free_ret_instance(ri); + + xol_free_insn_slot(t); + kfree(utask); + t->utask = NULL; +} + +/* + * Allocate a uprobe_task object for the task if necessary. + * Called when the thread hits a breakpoint. + * + * Returns: + * - pointer to new uprobe_task on success + * - NULL otherwise + */ +static struct uprobe_task *get_utask(void) +{ + if (!current->utask) + current->utask = kzalloc(sizeof(struct uprobe_task), GFP_KERNEL); + return current->utask; +} + +static int dup_utask(struct task_struct *t, struct uprobe_task *o_utask) +{ + struct uprobe_task *n_utask; + struct return_instance **p, *o, *n; + + n_utask = kzalloc(sizeof(struct uprobe_task), GFP_KERNEL); + if (!n_utask) + return -ENOMEM; + t->utask = n_utask; + + p = &n_utask->return_instances; + for (o = o_utask->return_instances; o; o = o->next) { + n = kmalloc(sizeof(struct return_instance), GFP_KERNEL); + if (!n) + return -ENOMEM; + + *n = *o; + get_uprobe(n->uprobe); + n->next = NULL; + + *p = n; + p = &n->next; + n_utask->depth++; + } + + return 0; +} + +static void uprobe_warn(struct task_struct *t, const char *msg) +{ + pr_warn("uprobe: %s:%d failed to %s\n", + current->comm, current->pid, msg); +} + +static void dup_xol_work(struct callback_head *work) +{ + if (current->flags & PF_EXITING) + return; + + if (!__create_xol_area(current->utask->dup_xol_addr) && + !fatal_signal_pending(current)) + uprobe_warn(current, "dup xol area"); +} + +/* + * Called in context of a new clone/fork from copy_process. + */ +void uprobe_copy_process(struct task_struct *t, unsigned long flags) +{ + struct uprobe_task *utask = current->utask; + struct mm_struct *mm = current->mm; + struct xol_area *area; + + t->utask = NULL; + + if (!utask || !utask->return_instances) + return; + + if (mm == t->mm && !(flags & CLONE_VFORK)) + return; + + if (dup_utask(t, utask)) + return uprobe_warn(t, "dup ret instances"); + + /* The task can fork() after dup_xol_work() fails */ + area = mm->uprobes_state.xol_area; + if (!area) + return uprobe_warn(t, "dup xol area"); + + if (mm == t->mm) + return; + + t->utask->dup_xol_addr = area->vaddr; + init_task_work(&t->utask->dup_xol_work, dup_xol_work); + task_work_add(t, &t->utask->dup_xol_work, TWA_RESUME); +} + +/* + * Current area->vaddr notion assume the trampoline address is always + * equal area->vaddr. + * + * Returns -1 in case the xol_area is not allocated. + */ +static unsigned long get_trampoline_vaddr(void) +{ + struct xol_area *area; + unsigned long trampoline_vaddr = -1; + + /* Pairs with xol_add_vma() smp_store_release() */ + area = READ_ONCE(current->mm->uprobes_state.xol_area); /* ^^^ */ + if (area) + trampoline_vaddr = area->vaddr; + + return trampoline_vaddr; +} + +static void cleanup_return_instances(struct uprobe_task *utask, bool chained, + struct pt_regs *regs) +{ + struct return_instance *ri = utask->return_instances; + enum rp_check ctx = chained ? RP_CHECK_CHAIN_CALL : RP_CHECK_CALL; + + while (ri && !arch_uretprobe_is_alive(ri, ctx, regs)) { + ri = free_ret_instance(ri); + utask->depth--; + } + utask->return_instances = ri; +} + +static void prepare_uretprobe(struct uprobe *uprobe, struct pt_regs *regs) +{ + struct return_instance *ri; + struct uprobe_task *utask; + unsigned long orig_ret_vaddr, trampoline_vaddr; + bool chained; + + if (!get_xol_area()) + return; + + utask = get_utask(); + if (!utask) + return; + + if (utask->depth >= MAX_URETPROBE_DEPTH) { + printk_ratelimited(KERN_INFO "uprobe: omit uretprobe due to" + " nestedness limit pid/tgid=%d/%d\n", + current->pid, current->tgid); + return; + } + + ri = kmalloc(sizeof(struct return_instance), GFP_KERNEL); + if (!ri) + return; + + trampoline_vaddr = get_trampoline_vaddr(); + orig_ret_vaddr = arch_uretprobe_hijack_return_addr(trampoline_vaddr, regs); + if (orig_ret_vaddr == -1) + goto fail; + + /* drop the entries invalidated by longjmp() */ + chained = (orig_ret_vaddr == trampoline_vaddr); + cleanup_return_instances(utask, chained, regs); + + /* + * We don't want to keep trampoline address in stack, rather keep the + * original return address of first caller thru all the consequent + * instances. This also makes breakpoint unwrapping easier. + */ + if (chained) { + if (!utask->return_instances) { + /* + * This situation is not possible. Likely we have an + * attack from user-space. + */ + uprobe_warn(current, "handle tail call"); + goto fail; + } + orig_ret_vaddr = utask->return_instances->orig_ret_vaddr; + } + + ri->uprobe = get_uprobe(uprobe); + ri->func = instruction_pointer(regs); + ri->stack = user_stack_pointer(regs); + ri->orig_ret_vaddr = orig_ret_vaddr; + ri->chained = chained; + + utask->depth++; + ri->next = utask->return_instances; + utask->return_instances = ri; + + return; + fail: + kfree(ri); +} + +/* Prepare to single-step probed instruction out of line. */ +static int +pre_ssout(struct uprobe *uprobe, struct pt_regs *regs, unsigned long bp_vaddr) +{ + struct uprobe_task *utask; + unsigned long xol_vaddr; + int err; + + utask = get_utask(); + if (!utask) + return -ENOMEM; + + xol_vaddr = xol_get_insn_slot(uprobe); + if (!xol_vaddr) + return -ENOMEM; + + utask->xol_vaddr = xol_vaddr; + utask->vaddr = bp_vaddr; + + err = arch_uprobe_pre_xol(&uprobe->arch, regs); + if (unlikely(err)) { + xol_free_insn_slot(current); + return err; + } + + utask->active_uprobe = uprobe; + utask->state = UTASK_SSTEP; + return 0; +} + +/* + * If we are singlestepping, then ensure this thread is not connected to + * non-fatal signals until completion of singlestep. When xol insn itself + * triggers the signal, restart the original insn even if the task is + * already SIGKILL'ed (since coredump should report the correct ip). This + * is even more important if the task has a handler for SIGSEGV/etc, The + * _same_ instruction should be repeated again after return from the signal + * handler, and SSTEP can never finish in this case. + */ +bool uprobe_deny_signal(void) +{ + struct task_struct *t = current; + struct uprobe_task *utask = t->utask; + + if (likely(!utask || !utask->active_uprobe)) + return false; + + WARN_ON_ONCE(utask->state != UTASK_SSTEP); + + if (task_sigpending(t)) { + spin_lock_irq(&t->sighand->siglock); + clear_tsk_thread_flag(t, TIF_SIGPENDING); + spin_unlock_irq(&t->sighand->siglock); + + if (__fatal_signal_pending(t) || arch_uprobe_xol_was_trapped(t)) { + utask->state = UTASK_SSTEP_TRAPPED; + set_tsk_thread_flag(t, TIF_UPROBE); + } + } + + return true; +} + +static void mmf_recalc_uprobes(struct mm_struct *mm) +{ + struct vm_area_struct *vma; + + for (vma = mm->mmap; vma; vma = vma->vm_next) { + if (!valid_vma(vma, false)) + continue; + /* + * This is not strictly accurate, we can race with + * uprobe_unregister() and see the already removed + * uprobe if delete_uprobe() was not yet called. + * Or this uprobe can be filtered out. + */ + if (vma_has_uprobes(vma, vma->vm_start, vma->vm_end)) + return; + } + + clear_bit(MMF_HAS_UPROBES, &mm->flags); +} + +static int is_trap_at_addr(struct mm_struct *mm, unsigned long vaddr) +{ + struct page *page; + uprobe_opcode_t opcode; + int result; + + if (WARN_ON_ONCE(!IS_ALIGNED(vaddr, UPROBE_SWBP_INSN_SIZE))) + return -EINVAL; + + pagefault_disable(); + result = __get_user(opcode, (uprobe_opcode_t __user *)vaddr); + pagefault_enable(); + + if (likely(result == 0)) + goto out; + + /* + * The NULL 'tsk' here ensures that any faults that occur here + * will not be accounted to the task. 'mm' *is* current->mm, + * but we treat this as a 'remote' access since it is + * essentially a kernel access to the memory. + */ + result = get_user_pages_remote(mm, vaddr, 1, FOLL_FORCE, &page, + NULL, NULL); + if (result < 0) + return result; + + copy_from_page(page, vaddr, &opcode, UPROBE_SWBP_INSN_SIZE); + put_page(page); + out: + /* This needs to return true for any variant of the trap insn */ + return is_trap_insn(&opcode); +} + +static struct uprobe *find_active_uprobe(unsigned long bp_vaddr, int *is_swbp) +{ + struct mm_struct *mm = current->mm; + struct uprobe *uprobe = NULL; + struct vm_area_struct *vma; + + mmap_read_lock(mm); + vma = find_vma(mm, bp_vaddr); + if (vma && vma->vm_start <= bp_vaddr) { + if (valid_vma(vma, false)) { + struct inode *inode = file_inode(vma->vm_file); + loff_t offset = vaddr_to_offset(vma, bp_vaddr); + + uprobe = find_uprobe(inode, offset); + } + + if (!uprobe) + *is_swbp = is_trap_at_addr(mm, bp_vaddr); + } else { + *is_swbp = -EFAULT; + } + + if (!uprobe && test_and_clear_bit(MMF_RECALC_UPROBES, &mm->flags)) + mmf_recalc_uprobes(mm); + mmap_read_unlock(mm); + + return uprobe; +} + +static void handler_chain(struct uprobe *uprobe, struct pt_regs *regs) +{ + struct uprobe_consumer *uc; + int remove = UPROBE_HANDLER_REMOVE; + bool need_prep = false; /* prepare return uprobe, when needed */ + + down_read(&uprobe->register_rwsem); + for (uc = uprobe->consumers; uc; uc = uc->next) { + int rc = 0; + + if (uc->handler) { + rc = uc->handler(uc, regs); + WARN(rc & ~UPROBE_HANDLER_MASK, + "bad rc=0x%x from %ps()\n", rc, uc->handler); + } + + if (uc->ret_handler) + need_prep = true; + + remove &= rc; + } + + if (need_prep && !remove) + prepare_uretprobe(uprobe, regs); /* put bp at return */ + + if (remove && uprobe->consumers) { + WARN_ON(!uprobe_is_active(uprobe)); + unapply_uprobe(uprobe, current->mm); + } + up_read(&uprobe->register_rwsem); +} + +static void +handle_uretprobe_chain(struct return_instance *ri, struct pt_regs *regs) +{ + struct uprobe *uprobe = ri->uprobe; + struct uprobe_consumer *uc; + + down_read(&uprobe->register_rwsem); + for (uc = uprobe->consumers; uc; uc = uc->next) { + if (uc->ret_handler) + uc->ret_handler(uc, ri->func, regs); + } + up_read(&uprobe->register_rwsem); +} + +static struct return_instance *find_next_ret_chain(struct return_instance *ri) +{ + bool chained; + + do { + chained = ri->chained; + ri = ri->next; /* can't be NULL if chained */ + } while (chained); + + return ri; +} + +static void handle_trampoline(struct pt_regs *regs) +{ + struct uprobe_task *utask; + struct return_instance *ri, *next; + bool valid; + + utask = current->utask; + if (!utask) + goto sigill; + + ri = utask->return_instances; + if (!ri) + goto sigill; + + do { + /* + * We should throw out the frames invalidated by longjmp(). + * If this chain is valid, then the next one should be alive + * or NULL; the latter case means that nobody but ri->func + * could hit this trampoline on return. TODO: sigaltstack(). + */ + next = find_next_ret_chain(ri); + valid = !next || arch_uretprobe_is_alive(next, RP_CHECK_RET, regs); + + instruction_pointer_set(regs, ri->orig_ret_vaddr); + do { + if (valid) + handle_uretprobe_chain(ri, regs); + ri = free_ret_instance(ri); + utask->depth--; + } while (ri != next); + } while (!valid); + + utask->return_instances = ri; + return; + + sigill: + uprobe_warn(current, "handle uretprobe, sending SIGILL."); + force_sig(SIGILL); + +} + +bool __weak arch_uprobe_ignore(struct arch_uprobe *aup, struct pt_regs *regs) +{ + return false; +} + +bool __weak arch_uretprobe_is_alive(struct return_instance *ret, enum rp_check ctx, + struct pt_regs *regs) +{ + return true; +} + +/* + * Run handler and ask thread to singlestep. + * Ensure all non-fatal signals cannot interrupt thread while it singlesteps. + */ +static void handle_swbp(struct pt_regs *regs) +{ + struct uprobe *uprobe; + unsigned long bp_vaddr; + int is_swbp; + + bp_vaddr = uprobe_get_swbp_addr(regs); + if (bp_vaddr == get_trampoline_vaddr()) + return handle_trampoline(regs); + + uprobe = find_active_uprobe(bp_vaddr, &is_swbp); + if (!uprobe) { + if (is_swbp > 0) { + /* No matching uprobe; signal SIGTRAP. */ + force_sig(SIGTRAP); + } else { + /* + * Either we raced with uprobe_unregister() or we can't + * access this memory. The latter is only possible if + * another thread plays with our ->mm. In both cases + * we can simply restart. If this vma was unmapped we + * can pretend this insn was not executed yet and get + * the (correct) SIGSEGV after restart. + */ + instruction_pointer_set(regs, bp_vaddr); + } + return; + } + + /* change it in advance for ->handler() and restart */ + instruction_pointer_set(regs, bp_vaddr); + + /* + * TODO: move copy_insn/etc into _register and remove this hack. + * After we hit the bp, _unregister + _register can install the + * new and not-yet-analyzed uprobe at the same address, restart. + */ + if (unlikely(!test_bit(UPROBE_COPY_INSN, &uprobe->flags))) + goto out; + + /* + * Pairs with the smp_wmb() in prepare_uprobe(). + * + * Guarantees that if we see the UPROBE_COPY_INSN bit set, then + * we must also see the stores to &uprobe->arch performed by the + * prepare_uprobe() call. + */ + smp_rmb(); + + /* Tracing handlers use ->utask to communicate with fetch methods */ + if (!get_utask()) + goto out; + + if (arch_uprobe_ignore(&uprobe->arch, regs)) + goto out; + + handler_chain(uprobe, regs); + + if (arch_uprobe_skip_sstep(&uprobe->arch, regs)) + goto out; + + if (!pre_ssout(uprobe, regs, bp_vaddr)) + return; + + /* arch_uprobe_skip_sstep() succeeded, or restart if can't singlestep */ +out: + put_uprobe(uprobe); +} + +/* + * Perform required fix-ups and disable singlestep. + * Allow pending signals to take effect. + */ +static void handle_singlestep(struct uprobe_task *utask, struct pt_regs *regs) +{ + struct uprobe *uprobe; + int err = 0; + + uprobe = utask->active_uprobe; + if (utask->state == UTASK_SSTEP_ACK) + err = arch_uprobe_post_xol(&uprobe->arch, regs); + else if (utask->state == UTASK_SSTEP_TRAPPED) + arch_uprobe_abort_xol(&uprobe->arch, regs); + else + WARN_ON_ONCE(1); + + put_uprobe(uprobe); + utask->active_uprobe = NULL; + utask->state = UTASK_RUNNING; + xol_free_insn_slot(current); + + spin_lock_irq(¤t->sighand->siglock); + recalc_sigpending(); /* see uprobe_deny_signal() */ + spin_unlock_irq(¤t->sighand->siglock); + + if (unlikely(err)) { + uprobe_warn(current, "execute the probed insn, sending SIGILL."); + force_sig(SIGILL); + } +} + +/* + * On breakpoint hit, breakpoint notifier sets the TIF_UPROBE flag and + * allows the thread to return from interrupt. After that handle_swbp() + * sets utask->active_uprobe. + * + * On singlestep exception, singlestep notifier sets the TIF_UPROBE flag + * and allows the thread to return from interrupt. + * + * While returning to userspace, thread notices the TIF_UPROBE flag and calls + * uprobe_notify_resume(). + */ +void uprobe_notify_resume(struct pt_regs *regs) +{ + struct uprobe_task *utask; + + clear_thread_flag(TIF_UPROBE); + + utask = current->utask; + if (utask && utask->active_uprobe) + handle_singlestep(utask, regs); + else + handle_swbp(regs); +} + +/* + * uprobe_pre_sstep_notifier gets called from interrupt context as part of + * notifier mechanism. Set TIF_UPROBE flag and indicate breakpoint hit. + */ +int uprobe_pre_sstep_notifier(struct pt_regs *regs) +{ + if (!current->mm) + return 0; + + if (!test_bit(MMF_HAS_UPROBES, ¤t->mm->flags) && + (!current->utask || !current->utask->return_instances)) + return 0; + + set_thread_flag(TIF_UPROBE); + return 1; +} + +/* + * uprobe_post_sstep_notifier gets called in interrupt context as part of notifier + * mechanism. Set TIF_UPROBE flag and indicate completion of singlestep. + */ +int uprobe_post_sstep_notifier(struct pt_regs *regs) +{ + struct uprobe_task *utask = current->utask; + + if (!current->mm || !utask || !utask->active_uprobe) + /* task is currently not uprobed */ + return 0; + + utask->state = UTASK_SSTEP_ACK; + set_thread_flag(TIF_UPROBE); + return 1; +} + +static struct notifier_block uprobe_exception_nb = { + .notifier_call = arch_uprobe_exception_notify, + .priority = INT_MAX-1, /* notified after kprobes, kgdb */ +}; + +void __init uprobes_init(void) +{ + int i; + + for (i = 0; i < UPROBES_HASH_SZ; i++) + mutex_init(&uprobes_mmap_mutex[i]); + + BUG_ON(register_die_notifier(&uprobe_exception_nb)); +} |