kernel_optimize_test/kernel/events/uprobes.c
Oleg Nesterov 4710f05fd1 uprobes: Fix prepare_uprobe() race with itself
install_breakpoint() is called under mm->mmap_sem, this protects
set_swbp() but not prepare_uprobe(). Two or more different tasks
can call install_breakpoint()->prepare_uprobe() at the same time,
this leads to numerous problems if UPROBE_COPY_INSN is not set.

Just for example, the second copy_insn() can corrupt the already
analyzed/fixuped uprobe->arch.insn and race with handle_swbp().

This patch simply adds uprobe->copy_mutex to serialize this code.
We could probably reuse ->consumer_rwsem, but this would mean that
consumer->handler() can not use mm->mmap_sem, not good.

Note: this is another temporary ugly hack until we move this logic
into uprobe_register().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
2012-10-07 21:19:43 +02:00

1611 lines
38 KiB
C

/*
* User-space Probes (UProbes)
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* Copyright (C) IBM Corporation, 2008-2012
* Authors:
* Srikar Dronamraju
* Jim Keniston
* Copyright (C) 2011-2012 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
*/
#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/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/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;
static DEFINE_SPINLOCK(uprobes_treelock); /* serialize rbtree access */
#define UPROBES_HASH_SZ 13
/*
* We need separate register/unregister and mmap/munmap lock hashes because
* of mmap_sem nesting.
*
* uprobe_register() needs to install probes on (potentially) all processes
* and thus needs to acquire multiple mmap_sems (consequtively, not
* concurrently), whereas uprobe_mmap() is called while holding mmap_sem
* for the particular process doing the mmap.
*
* uprobe_register()->register_for_each_vma() needs to drop/acquire mmap_sem
* because of lock order against i_mmap_mutex. This means there's a hole in
* the register vma iteration where a mmap() can happen.
*
* Thus uprobe_register() can race with uprobe_mmap() and we can try and
* install a probe where one is already installed.
*/
/* serialize (un)register */
static struct mutex uprobes_mutex[UPROBES_HASH_SZ];
#define uprobes_hash(v) (&uprobes_mutex[((unsigned long)(v)) % UPROBES_HASH_SZ])
/* 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])
/*
* uprobe_events 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?
*/
static atomic_t uprobe_events = ATOMIC_INIT(0);
/* Have a copy of original instruction */
#define UPROBE_COPY_INSN 0x1
/* Dont run handlers when first register/ last unregister in progress*/
#define UPROBE_RUN_HANDLER 0x2
/* Can skip singlestep */
#define UPROBE_SKIP_SSTEP 0x4
struct uprobe {
struct rb_node rb_node; /* node in the rb tree */
atomic_t ref;
struct rw_semaphore consumer_rwsem;
struct mutex copy_mutex; /* TODO: kill me and UPROBE_COPY_INSN */
struct list_head pending_list;
struct uprobe_consumer *consumers;
struct inode *inode; /* Also hold a ref to inode */
loff_t offset;
int flags;
struct arch_uprobe arch;
};
/*
* 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_SHARED;
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
* @page: the cowed page we are replacing by kpage
* @kpage: the modified page we replace page by
*
* Returns 0 on success, -EFAULT on failure.
*/
static int __replace_page(struct vm_area_struct *vma, unsigned long addr,
struct page *page, struct page *kpage)
{
struct mm_struct *mm = vma->vm_mm;
spinlock_t *ptl;
pte_t *ptep;
int err;
/* For try_to_free_swap() and munlock_vma_page() below */
lock_page(page);
err = -EAGAIN;
ptep = page_check_address(page, mm, addr, &ptl, 0);
if (!ptep)
goto unlock;
get_page(kpage);
page_add_new_anon_rmap(kpage, vma, addr);
if (!PageAnon(page)) {
dec_mm_counter(mm, MM_FILEPAGES);
inc_mm_counter(mm, MM_ANONPAGES);
}
flush_cache_page(vma, addr, pte_pfn(*ptep));
ptep_clear_flush(vma, addr, ptep);
set_pte_at_notify(mm, addr, ptep, mk_pte(kpage, vma->vm_page_prot));
page_remove_rmap(page);
if (!page_mapped(page))
try_to_free_swap(page);
pte_unmap_unlock(ptep, ptl);
if (vma->vm_flags & VM_LOCKED)
munlock_vma_page(page);
put_page(page);
err = 0;
unlock:
unlock_page(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;
}
static void copy_opcode(struct page *page, unsigned long vaddr, uprobe_opcode_t *opcode)
{
void *kaddr = kmap_atomic(page);
memcpy(opcode, kaddr + (vaddr & ~PAGE_MASK), UPROBE_SWBP_INSN_SIZE);
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;
copy_opcode(page, vaddr, &old_opcode);
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;
}
/*
* 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_swbp_at_addr and
* write_opcode accordingly. This would never be a problem for archs that
* have fixed length instructions.
*/
/*
* 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_sem held (for read and with a reference to
* mm).
*
* For mm @mm, write the opcode at @vaddr.
* Return 0 (success) or a negative errno.
*/
static int write_opcode(struct mm_struct *mm, unsigned long vaddr,
uprobe_opcode_t opcode)
{
struct page *old_page, *new_page;
void *vaddr_old, *vaddr_new;
struct vm_area_struct *vma;
int ret;
retry:
/* Read the page with vaddr into memory */
ret = get_user_pages(NULL, mm, vaddr, 1, 0, 1, &old_page, &vma);
if (ret <= 0)
return ret;
ret = verify_opcode(old_page, vaddr, &opcode);
if (ret <= 0)
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 the page now that we've got it stable */
vaddr_old = kmap_atomic(old_page);
vaddr_new = kmap_atomic(new_page);
memcpy(vaddr_new, vaddr_old, PAGE_SIZE);
memcpy(vaddr_new + (vaddr & ~PAGE_MASK), &opcode, UPROBE_SWBP_INSN_SIZE);
kunmap_atomic(vaddr_new);
kunmap_atomic(vaddr_old);
ret = anon_vma_prepare(vma);
if (ret)
goto put_new;
ret = __replace_page(vma, vaddr, old_page, new_page);
put_new:
page_cache_release(new_page);
put_old:
put_page(old_page);
if (unlikely(ret == -EAGAIN))
goto retry;
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 write_opcode(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 write_opcode(mm, vaddr, *(uprobe_opcode_t *)auprobe->insn);
}
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) {
atomic_inc(&uprobe->ref);
return 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) {
atomic_inc(&u->ref);
return 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 */
atomic_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);
/* For now assume that the instruction need not be single-stepped */
uprobe->flags |= UPROBE_SKIP_SSTEP;
return u;
}
static void put_uprobe(struct uprobe *uprobe)
{
if (atomic_dec_and_test(&uprobe->ref))
kfree(uprobe);
}
static struct uprobe *alloc_uprobe(struct inode *inode, loff_t offset)
{
struct uprobe *uprobe, *cur_uprobe;
uprobe = kzalloc(sizeof(struct uprobe), GFP_KERNEL);
if (!uprobe)
return NULL;
uprobe->inode = igrab(inode);
uprobe->offset = offset;
init_rwsem(&uprobe->consumer_rwsem);
mutex_init(&uprobe->copy_mutex);
/* add to uprobes_tree, sorted on inode:offset */
cur_uprobe = insert_uprobe(uprobe);
/* a uprobe exists for this inode:offset combination */
if (cur_uprobe) {
kfree(uprobe);
uprobe = cur_uprobe;
iput(inode);
} else {
atomic_inc(&uprobe_events);
}
return uprobe;
}
static void handler_chain(struct uprobe *uprobe, struct pt_regs *regs)
{
struct uprobe_consumer *uc;
if (!(uprobe->flags & UPROBE_RUN_HANDLER))
return;
down_read(&uprobe->consumer_rwsem);
for (uc = uprobe->consumers; uc; uc = uc->next) {
if (!uc->filter || uc->filter(uc, current))
uc->handler(uc, regs);
}
up_read(&uprobe->consumer_rwsem);
}
/* Returns the previous consumer */
static struct uprobe_consumer *
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);
return uc->next;
}
/*
* 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, char *insn,
unsigned long nbytes, loff_t offset)
{
struct page *page;
void *vaddr;
unsigned long off;
pgoff_t idx;
if (!filp)
return -EINVAL;
if (!mapping->a_ops->readpage)
return -EIO;
idx = offset >> PAGE_CACHE_SHIFT;
off = offset & ~PAGE_MASK;
/*
* Ensure that the page that has the original instruction is
* populated and in page-cache.
*/
page = read_mapping_page(mapping, idx, filp);
if (IS_ERR(page))
return PTR_ERR(page);
vaddr = kmap_atomic(page);
memcpy(insn, vaddr + off, nbytes);
kunmap_atomic(vaddr);
page_cache_release(page);
return 0;
}
static int copy_insn(struct uprobe *uprobe, struct file *filp)
{
struct address_space *mapping;
unsigned long nbytes;
int bytes;
nbytes = PAGE_SIZE - (uprobe->offset & ~PAGE_MASK);
mapping = uprobe->inode->i_mapping;
/* Instruction at end of binary; copy only available bytes */
if (uprobe->offset + MAX_UINSN_BYTES > uprobe->inode->i_size)
bytes = uprobe->inode->i_size - uprobe->offset;
else
bytes = MAX_UINSN_BYTES;
/* Instruction at the page-boundary; copy bytes in second page */
if (nbytes < bytes) {
int err = __copy_insn(mapping, filp, uprobe->arch.insn + nbytes,
bytes - nbytes, uprobe->offset + nbytes);
if (err)
return err;
bytes = nbytes;
}
return __copy_insn(mapping, filp, uprobe->arch.insn, bytes, uprobe->offset);
}
static int prepare_uprobe(struct uprobe *uprobe, struct file *file,
struct mm_struct *mm, unsigned long vaddr)
{
int ret = 0;
if (uprobe->flags & UPROBE_COPY_INSN)
return ret;
mutex_lock(&uprobe->copy_mutex);
if (uprobe->flags & UPROBE_COPY_INSN)
goto out;
ret = copy_insn(uprobe, file);
if (ret)
goto out;
ret = -ENOTSUPP;
if (is_swbp_insn((uprobe_opcode_t *)uprobe->arch.insn))
goto out;
ret = arch_uprobe_analyze_insn(&uprobe->arch, mm, vaddr);
if (ret)
goto out;
/* write_opcode() assumes we don't cross page boundary */
BUG_ON((uprobe->offset & ~PAGE_MASK) +
UPROBE_SWBP_INSN_SIZE > PAGE_SIZE);
smp_wmb(); /* pairs with rmb() in find_active_uprobe() */
uprobe->flags |= UPROBE_COPY_INSN;
out:
mutex_unlock(&uprobe->copy_mutex);
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;
/*
* If probe is being deleted, unregister thread could be done with
* the vma-rmap-walk through. Adding a probe now can be fatal since
* nobody will be able to cleanup. Also we could be from fork or
* mremap path, where the probe might have already been inserted.
* Hence behave as if probe already existed.
*/
if (!uprobe->consumers)
return 0;
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)
{
/* can happen if uprobe_register() fails */
if (!test_bit(MMF_HAS_UPROBES, &mm->flags))
return 0;
set_bit(MMF_RECALC_UPROBES, &mm->flags);
return set_orig_insn(&uprobe->arch, mm, vaddr);
}
/*
* 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)
{
spin_lock(&uprobes_treelock);
rb_erase(&uprobe->rb_node, &uprobes_tree);
spin_unlock(&uprobes_treelock);
iput(uprobe->inode);
put_uprobe(uprobe);
atomic_dec(&uprobe_events);
}
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 prio_tree_iter iter;
struct vm_area_struct *vma;
struct map_info *curr = NULL;
struct map_info *prev = NULL;
struct map_info *info;
int more = 0;
again:
mutex_lock(&mapping->i_mmap_mutex);
vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
if (!valid_vma(vma, is_register))
continue;
if (!prev && !more) {
/*
* Needs GFP_NOWAIT to avoid i_mmap_mutex 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 (!atomic_inc_not_zero(&vma->vm_mm->mm_users))
continue;
info = prev;
prev = prev->next;
info->next = curr;
curr = info;
info->mm = vma->vm_mm;
info->vaddr = offset_to_vaddr(vma, offset);
}
mutex_unlock(&mapping->i_mmap_mutex);
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, bool is_register)
{
struct map_info *info;
int err = 0;
info = build_map_info(uprobe->inode->i_mapping,
uprobe->offset, is_register);
if (IS_ERR(info))
return PTR_ERR(info);
while (info) {
struct mm_struct *mm = info->mm;
struct vm_area_struct *vma;
if (err && is_register)
goto free;
down_write(&mm->mmap_sem);
vma = find_vma(mm, info->vaddr);
if (!vma || !valid_vma(vma, is_register) ||
vma->vm_file->f_mapping->host != uprobe->inode)
goto unlock;
if (vma->vm_start > info->vaddr ||
vaddr_to_offset(vma, info->vaddr) != uprobe->offset)
goto unlock;
if (is_register)
err = install_breakpoint(uprobe, mm, vma, info->vaddr);
else
err |= remove_breakpoint(uprobe, mm, info->vaddr);
unlock:
up_write(&mm->mmap_sem);
free:
mmput(mm);
info = free_map_info(info);
}
return err;
}
static int __uprobe_register(struct uprobe *uprobe)
{
return register_for_each_vma(uprobe, true);
}
static void __uprobe_unregister(struct uprobe *uprobe)
{
if (!register_for_each_vma(uprobe, false))
delete_uprobe(uprobe);
/* TODO : cant unregister? schedule a worker thread */
}
/*
* 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.
*
* Return errno if it cannot successully install probes
* else return 0 (success)
*/
int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer *uc)
{
struct uprobe *uprobe;
int ret;
if (!inode || !uc || uc->next)
return -EINVAL;
if (offset > i_size_read(inode))
return -EINVAL;
ret = 0;
mutex_lock(uprobes_hash(inode));
uprobe = alloc_uprobe(inode, offset);
if (!uprobe) {
ret = -ENOMEM;
} else if (!consumer_add(uprobe, uc)) {
ret = __uprobe_register(uprobe);
if (ret) {
uprobe->consumers = NULL;
__uprobe_unregister(uprobe);
} else {
uprobe->flags |= UPROBE_RUN_HANDLER;
}
}
mutex_unlock(uprobes_hash(inode));
if (uprobe)
put_uprobe(uprobe);
return ret;
}
/*
* uprobe_unregister - unregister a 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;
if (!inode || !uc)
return;
uprobe = find_uprobe(inode, offset);
if (!uprobe)
return;
mutex_lock(uprobes_hash(inode));
if (consumer_del(uprobe, uc)) {
if (!uprobe->consumers) {
__uprobe_unregister(uprobe);
uprobe->flags &= ~UPROBE_RUN_HANDLER;
}
}
mutex_unlock(uprobes_hash(inode));
if (uprobe)
put_uprobe(uprobe);
}
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);
atomic_inc(&u->ref);
}
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);
atomic_inc(&u->ref);
}
}
spin_unlock(&uprobes_treelock);
}
/*
* Called from mmap_region/vma_adjust with mm->mmap_sem 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 (!atomic_read(&uprobe_events) || !valid_vma(vma, true))
return 0;
inode = vma->vm_file->f_mapping->host;
if (!inode)
return 0;
mutex_lock(uprobes_mmap_hash(inode));
build_probe_list(inode, vma, vma->vm_start, vma->vm_end, &tmp_list);
list_for_each_entry_safe(uprobe, u, &tmp_list, pending_list) {
if (!fatal_signal_pending(current)) {
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 = vma->vm_file->f_mapping->host;
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 (!atomic_read(&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 xol_area *area)
{
struct mm_struct *mm;
int ret;
area->page = alloc_page(GFP_HIGHUSER);
if (!area->page)
return -ENOMEM;
ret = -EALREADY;
mm = current->mm;
down_write(&mm->mmap_sem);
if (mm->uprobes_state.xol_area)
goto fail;
ret = -ENOMEM;
/* 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 (area->vaddr & ~PAGE_MASK) {
ret = area->vaddr;
goto fail;
}
ret = install_special_mapping(mm, area->vaddr, PAGE_SIZE,
VM_EXEC|VM_MAYEXEC|VM_DONTCOPY|VM_IO, &area->page);
if (ret)
goto fail;
smp_wmb(); /* pairs with get_xol_area() */
mm->uprobes_state.xol_area = area;
ret = 0;
fail:
up_write(&mm->mmap_sem);
if (ret)
__free_page(area->page);
return ret;
}
static struct xol_area *get_xol_area(struct mm_struct *mm)
{
struct xol_area *area;
area = mm->uprobes_state.xol_area;
smp_read_barrier_depends(); /* pairs with wmb in xol_add_vma() */
return area;
}
/*
* xol_alloc_area - Allocate process's xol_area.
* This area will be used for storing instructions for execution out of
* line.
*
* Returns the allocated area or NULL.
*/
static struct xol_area *xol_alloc_area(void)
{
struct xol_area *area;
area = kzalloc(sizeof(*area), GFP_KERNEL);
if (unlikely(!area))
return NULL;
area->bitmap = kzalloc(BITS_TO_LONGS(UINSNS_PER_PAGE) * sizeof(long), GFP_KERNEL);
if (!area->bitmap)
goto fail;
init_waitqueue_head(&area->wq);
if (!xol_add_vma(area))
return area;
fail:
kfree(area->bitmap);
kfree(area);
return get_xol_area(current->mm);
}
/*
* 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;
if (!area)
return;
put_page(area->page);
kfree(area->bitmap);
kfree(area);
}
void uprobe_dup_mmap(struct mm_struct *oldmm, struct mm_struct *newmm)
{
newmm->uprobes_state.xol_area = NULL;
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 - If was not allocated a slot, then
* allocate a slot.
* Returns the allocated slot address or 0.
*/
static unsigned long xol_get_insn_slot(struct uprobe *uprobe, unsigned long slot_addr)
{
struct xol_area *area;
unsigned long offset;
void *vaddr;
area = get_xol_area(current->mm);
if (!area) {
area = xol_alloc_area();
if (!area)
return 0;
}
current->utask->xol_vaddr = xol_take_insn_slot(area);
/*
* Initialize the slot if xol_vaddr points to valid
* instruction slot.
*/
if (unlikely(!current->utask->xol_vaddr))
return 0;
current->utask->vaddr = slot_addr;
offset = current->utask->xol_vaddr & ~PAGE_MASK;
vaddr = kmap_atomic(area->page);
memcpy(vaddr + offset, uprobe->arch.insn, MAX_UINSN_BYTES);
kunmap_atomic(vaddr);
return current->utask->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 || IS_ERR_VALUE(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);
if (waitqueue_active(&area->wq))
wake_up(&area->wq);
tsk->utask->xol_vaddr = 0;
}
}
/**
* 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;
}
/*
* Called with no locks held.
* Called in context of a exiting or a exec-ing thread.
*/
void uprobe_free_utask(struct task_struct *t)
{
struct uprobe_task *utask = t->utask;
if (!utask)
return;
if (utask->active_uprobe)
put_uprobe(utask->active_uprobe);
xol_free_insn_slot(t);
kfree(utask);
t->utask = NULL;
}
/*
* Called in context of a new clone/fork from copy_process.
*/
void uprobe_copy_process(struct task_struct *t)
{
t->utask = NULL;
}
/*
* Allocate a uprobe_task object for the task.
* Called when the thread hits a breakpoint for the first time.
*
* Returns:
* - pointer to new uprobe_task on success
* - NULL otherwise
*/
static struct uprobe_task *add_utask(void)
{
struct uprobe_task *utask;
utask = kzalloc(sizeof *utask, GFP_KERNEL);
if (unlikely(!utask))
return NULL;
current->utask = utask;
return utask;
}
/* Prepare to single-step probed instruction out of line. */
static int
pre_ssout(struct uprobe *uprobe, struct pt_regs *regs, unsigned long vaddr)
{
if (xol_get_insn_slot(uprobe, vaddr) && !arch_uprobe_pre_xol(&uprobe->arch, regs))
return 0;
return -EFAULT;
}
/*
* 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 (signal_pending(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);
set_tsk_thread_flag(t, TIF_NOTIFY_RESUME);
}
}
return true;
}
/*
* Avoid singlestepping the original instruction if the original instruction
* is a NOP or can be emulated.
*/
static bool can_skip_sstep(struct uprobe *uprobe, struct pt_regs *regs)
{
if (uprobe->flags & UPROBE_SKIP_SSTEP) {
if (arch_uprobe_skip_sstep(&uprobe->arch, regs))
return true;
uprobe->flags &= ~UPROBE_SKIP_SSTEP;
}
return false;
}
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.
*/
if (vma_has_uprobes(vma, vma->vm_start, vma->vm_end))
return;
}
clear_bit(MMF_HAS_UPROBES, &mm->flags);
}
static int is_swbp_at_addr(struct mm_struct *mm, unsigned long vaddr)
{
struct page *page;
uprobe_opcode_t opcode;
int result;
pagefault_disable();
result = __copy_from_user_inatomic(&opcode, (void __user*)vaddr,
sizeof(opcode));
pagefault_enable();
if (likely(result == 0))
goto out;
result = get_user_pages(NULL, mm, vaddr, 1, 0, 1, &page, NULL);
if (result < 0)
return result;
copy_opcode(page, vaddr, &opcode);
put_page(page);
out:
return is_swbp_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;
down_read(&mm->mmap_sem);
vma = find_vma(mm, bp_vaddr);
if (vma && vma->vm_start <= bp_vaddr) {
if (valid_vma(vma, false)) {
struct inode *inode = vma->vm_file->f_mapping->host;
loff_t offset = vaddr_to_offset(vma, bp_vaddr);
uprobe = find_uprobe(inode, offset);
}
if (!uprobe)
*is_swbp = is_swbp_at_addr(mm, bp_vaddr);
} else {
*is_swbp = -EFAULT;
}
if (!uprobe && test_and_clear_bit(MMF_RECALC_UPROBES, &mm->flags))
mmf_recalc_uprobes(mm);
up_read(&mm->mmap_sem);
return uprobe;
}
void __weak arch_uprobe_enable_step(struct arch_uprobe *arch)
{
user_enable_single_step(current);
}
void __weak arch_uprobe_disable_step(struct arch_uprobe *arch)
{
user_disable_single_step(current);
}
/*
* 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_task *utask;
struct uprobe *uprobe;
unsigned long bp_vaddr;
int uninitialized_var(is_swbp);
bp_vaddr = uprobe_get_swbp_addr(regs);
uprobe = find_active_uprobe(bp_vaddr, &is_swbp);
if (!uprobe) {
if (is_swbp > 0) {
/* No matching uprobe; signal SIGTRAP. */
send_sig(SIGTRAP, current, 0);
} 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;
}
/*
* 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.
*/
smp_rmb(); /* pairs with wmb() in install_breakpoint() */
if (unlikely(!(uprobe->flags & UPROBE_COPY_INSN)))
goto restart;
utask = current->utask;
if (!utask) {
utask = add_utask();
/* Cannot allocate; re-execute the instruction. */
if (!utask)
goto restart;
}
handler_chain(uprobe, regs);
if (can_skip_sstep(uprobe, regs))
goto out;
if (!pre_ssout(uprobe, regs, bp_vaddr)) {
arch_uprobe_enable_step(&uprobe->arch);
utask->active_uprobe = uprobe;
utask->state = UTASK_SSTEP;
return;
}
restart:
/*
* cannot singlestep; cannot skip instruction;
* re-execute the instruction.
*/
instruction_pointer_set(regs, bp_vaddr);
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;
uprobe = utask->active_uprobe;
if (utask->state == UTASK_SSTEP_ACK)
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);
arch_uprobe_disable_step(&uprobe->arch);
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);
}
/*
* 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 || !test_bit(MMF_HAS_UPROBES, &current->mm->flags))
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 */
};
static int __init init_uprobes(void)
{
int i;
for (i = 0; i < UPROBES_HASH_SZ; i++) {
mutex_init(&uprobes_mutex[i]);
mutex_init(&uprobes_mmap_mutex[i]);
}
return register_die_notifier(&uprobe_exception_nb);
}
module_init(init_uprobes);
static void __exit exit_uprobes(void)
{
}
module_exit(exit_uprobes);