linux/kernel/events/uprobes.c
Ryan Roberts c33c794828 mm: ptep_get() conversion
Convert all instances of direct pte_t* dereferencing to instead use
ptep_get() helper.  This means that by default, the accesses change from a
C dereference to a READ_ONCE().  This is technically the correct thing to
do since where pgtables are modified by HW (for access/dirty) they are
volatile and therefore we should always ensure READ_ONCE() semantics.

But more importantly, by always using the helper, it can be overridden by
the architecture to fully encapsulate the contents of the pte.  Arch code
is deliberately not converted, as the arch code knows best.  It is
intended that arch code (arm64) will override the default with its own
implementation that can (e.g.) hide certain bits from the core code, or
determine young/dirty status by mixing in state from another source.

Conversion was done using Coccinelle:

----

// $ make coccicheck \
//          COCCI=ptepget.cocci \
//          SPFLAGS="--include-headers" \
//          MODE=patch

virtual patch

@ depends on patch @
pte_t *v;
@@

- *v
+ ptep_get(v)

----

Then reviewed and hand-edited to avoid multiple unnecessary calls to
ptep_get(), instead opting to store the result of a single call in a
variable, where it is correct to do so.  This aims to negate any cost of
READ_ONCE() and will benefit arch-overrides that may be more complex.

Included is a fix for an issue in an earlier version of this patch that
was pointed out by kernel test robot.  The issue arose because config
MMU=n elides definition of the ptep helper functions, including
ptep_get().  HUGETLB_PAGE=n configs still define a simple
huge_ptep_clear_flush() for linking purposes, which dereferences the ptep.
So when both configs are disabled, this caused a build error because
ptep_get() is not defined.  Fix by continuing to do a direct dereference
when MMU=n.  This is safe because for this config the arch code cannot be
trying to virtualize the ptes because none of the ptep helpers are
defined.

Link: https://lkml.kernel.org/r/20230612151545.3317766-4-ryan.roberts@arm.com
Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/oe-kbuild-all/202305120142.yXsNEo6H-lkp@intel.com/
Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Dave Airlie <airlied@gmail.com>
Cc: Dimitri Sivanich <dimitri.sivanich@hpe.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: SeongJae Park <sj@kernel.org>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Uladzislau Rezki (Sony) <urezki@gmail.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2023-06-19 16:19:25 -07:00

2356 lines
57 KiB
C

// 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> /* folio_free_swap */
#include <linux/ptrace.h> /* user_enable_single_step */
#include <linux/kdebug.h> /* notifier mechanism */
#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 folio *old_folio = page_folio(old_page);
struct folio *new_folio;
struct mm_struct *mm = vma->vm_mm;
DEFINE_FOLIO_VMA_WALK(pvmw, old_folio, vma, addr, 0);
int err;
struct mmu_notifier_range range;
mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, mm, addr,
addr + PAGE_SIZE);
if (new_page) {
new_folio = page_folio(new_page);
err = mem_cgroup_charge(new_folio, vma->vm_mm, GFP_KERNEL);
if (err)
return err;
}
/* For folio_free_swap() below */
folio_lock(old_folio);
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) {
folio_get(new_folio);
page_add_new_anon_rmap(new_page, vma, addr);
folio_add_lru_vma(new_folio, vma);
} else
/* no new page, just dec_mm_counter for old_page */
dec_mm_counter(mm, MM_ANONPAGES);
if (!folio_test_anon(old_folio)) {
dec_mm_counter(mm, mm_counter_file(old_page));
inc_mm_counter(mm, MM_ANONPAGES);
}
flush_cache_page(vma, addr, pte_pfn(ptep_get(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, vma, false);
if (!folio_mapped(old_folio))
folio_free_swap(old_folio);
page_vma_mapped_walk_done(&pvmw);
folio_put(old_folio);
err = 0;
unlock:
mmu_notifier_invalidate_range_end(&range);
folio_unlock(old_folio);
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)
{
VMA_ITERATOR(vmi, mm, 0);
struct vm_area_struct *tmp;
for_each_vma(vmi, tmp)
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;
int ret;
short *ptr;
if (!vaddr || !d)
return -EINVAL;
ret = get_user_pages_remote(mm, vaddr, 1,
FOLL_WRITE, &page, 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.
* @auprobe: arch specific probepoint information.
* @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 */
old_page = get_user_page_vma_remote(mm, vaddr, gup_flags, &vma);
if (IS_ERR_OR_NULL(old_page))
return old_page ? PTR_ERR(old_page) : 0;
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, false);
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 __always_inline
int uprobe_cmp(const struct inode *l_inode, const loff_t l_offset,
const 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;
}
#define __node_2_uprobe(node) \
rb_entry((node), struct uprobe, rb_node)
struct __uprobe_key {
struct inode *inode;
loff_t offset;
};
static inline int __uprobe_cmp_key(const void *key, const struct rb_node *b)
{
const struct __uprobe_key *a = key;
return uprobe_cmp(a->inode, a->offset, __node_2_uprobe(b));
}
static inline int __uprobe_cmp(struct rb_node *a, const struct rb_node *b)
{
struct uprobe *u = __node_2_uprobe(a);
return uprobe_cmp(u->inode, u->offset, __node_2_uprobe(b));
}
static struct uprobe *__find_uprobe(struct inode *inode, loff_t offset)
{
struct __uprobe_key key = {
.inode = inode,
.offset = offset,
};
struct rb_node *node = rb_find(&key, &uprobes_tree, __uprobe_cmp_key);
if (node)
return get_uprobe(__node_2_uprobe(node));
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 *node;
node = rb_find_add(&uprobe->rb_node, &uprobes_tree, __uprobe_cmp);
if (node)
return get_uprobe(__node_2_uprobe(node));
/* get access + creation ref */
refcount_set(&uprobe->ref, 2);
return NULL;
}
/*
* 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 ->read_folio == NULL it must be shmem_mapping(),
* see uprobe_register().
*/
if (mapping->a_ops->read_folio)
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->read_folio &&
!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)
{
VMA_ITERATOR(vmi, mm, 0);
struct vm_area_struct *vma;
int err = 0;
mmap_read_lock(mm);
for_each_vma(vmi, vma) {
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_merge 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)
{
VMA_ITERATOR(vmi, mm, 0);
struct vm_area_struct *vma;
for_each_vma(vmi, vma) {
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);
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 = vma_lookup(mm, bp_vaddr);
if (vma) {
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(&current->sighand->siglock);
recalc_sigpending(); /* see uprobe_deny_signal() */
spin_unlock_irq(&current->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, &current->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));
}