swh:1:snp:3c665ee4f67729f27f2e40193ab88e7298cf0fef
Tip revision: 84a1caf1453c3d44050bd22db958af4a7f99315c authored by Linus Torvalds on 14 July 2012, 22:40:28 UTC
Linux 3.5-rc7
Linux 3.5-rc7
Tip revision: 84a1caf
uprobes.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 <linux/uprobes.h>
#define UINSNS_PER_PAGE (PAGE_SIZE/UPROBE_XOL_SLOT_BYTES)
#define MAX_UPROBE_XOL_SLOTS UINSNS_PER_PAGE
static struct srcu_struct uprobes_srcu;
static struct rb_root uprobes_tree = RB_ROOT;
static DEFINE_SPINLOCK(uprobes_treelock); /* serialize rbtree access */
#define UPROBES_HASH_SZ 13
/* 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);
/*
* Maintain a temporary per vma info that can be used to search if a vma
* has already been handled. This structure is introduced since extending
* vm_area_struct wasnt recommended.
*/
struct vma_info {
struct list_head probe_list;
struct mm_struct *mm;
loff_t vaddr;
};
struct uprobe {
struct rb_node rb_node; /* node in the rb tree */
atomic_t ref;
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;
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)
{
if (!vma->vm_file)
return false;
if (!is_register)
return true;
if ((vma->vm_flags & (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)) == (VM_READ|VM_EXEC))
return true;
return false;
}
static loff_t vma_address(struct vm_area_struct *vma, loff_t offset)
{
loff_t vaddr;
vaddr = vma->vm_start + offset;
vaddr -= vma->vm_pgoff << PAGE_SHIFT;
return vaddr;
}
/**
* __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
* @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, struct page *page, struct page *kpage)
{
struct mm_struct *mm = vma->vm_mm;
pgd_t *pgd;
pud_t *pud;
pmd_t *pmd;
pte_t *ptep;
spinlock_t *ptl;
unsigned long addr;
int err = -EFAULT;
addr = page_address_in_vma(page, vma);
if (addr == -EFAULT)
goto out;
pgd = pgd_offset(mm, addr);
if (!pgd_present(*pgd))
goto out;
pud = pud_offset(pgd, addr);
if (!pud_present(*pud))
goto out;
pmd = pmd_offset(pud, addr);
if (!pmd_present(*pmd))
goto out;
ptep = pte_offset_map_lock(mm, pmd, addr, &ptl);
if (!ptep)
goto out;
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);
put_page(page);
pte_unmap_unlock(ptep, ptl);
err = 0;
out:
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;
}
/*
* 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 read_opcode /
* 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.
* @auprobe: arch breakpointing 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_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 arch_uprobe *auprobe, struct mm_struct *mm,
unsigned long vaddr, uprobe_opcode_t opcode)
{
struct page *old_page, *new_page;
struct address_space *mapping;
void *vaddr_old, *vaddr_new;
struct vm_area_struct *vma;
struct uprobe *uprobe;
loff_t addr;
int ret;
/* Read the page with vaddr into memory */
ret = get_user_pages(NULL, mm, vaddr, 1, 0, 0, &old_page, &vma);
if (ret <= 0)
return ret;
ret = -EINVAL;
/*
* We are interested in text pages only. Our pages of interest
* should be mapped for read and execute only. We desist from
* adding probes in write mapped pages since the breakpoints
* might end up in the file copy.
*/
if (!valid_vma(vma, is_swbp_insn(&opcode)))
goto put_out;
uprobe = container_of(auprobe, struct uprobe, arch);
mapping = uprobe->inode->i_mapping;
if (mapping != vma->vm_file->f_mapping)
goto put_out;
addr = vma_address(vma, uprobe->offset);
if (vaddr != (unsigned long)addr)
goto put_out;
ret = -ENOMEM;
new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vaddr);
if (!new_page)
goto put_out;
__SetPageUptodate(new_page);
/*
* lock page will serialize against do_wp_page()'s
* PageAnon() handling
*/
lock_page(old_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);
/* poke the new insn in, ASSUMES we don't cross page boundary */
vaddr &= ~PAGE_MASK;
BUG_ON(vaddr + UPROBE_SWBP_INSN_SIZE > PAGE_SIZE);
memcpy(vaddr_new + vaddr, &opcode, UPROBE_SWBP_INSN_SIZE);
kunmap_atomic(vaddr_new);
kunmap_atomic(vaddr_old);
ret = anon_vma_prepare(vma);
if (ret)
goto unlock_out;
lock_page(new_page);
ret = __replace_page(vma, old_page, new_page);
unlock_page(new_page);
unlock_out:
unlock_page(old_page);
page_cache_release(new_page);
put_out:
put_page(old_page);
return ret;
}
/**
* read_opcode - read the opcode at a given virtual address.
* @mm: the probed process address space.
* @vaddr: the virtual address to read the opcode.
* @opcode: location to store the read opcode.
*
* Called with mm->mmap_sem held (for read and with a reference to
* mm.
*
* For mm @mm, read the opcode at @vaddr and store it in @opcode.
* Return 0 (success) or a negative errno.
*/
static int read_opcode(struct mm_struct *mm, unsigned long vaddr, uprobe_opcode_t *opcode)
{
struct page *page;
void *vaddr_new;
int ret;
ret = get_user_pages(NULL, mm, vaddr, 1, 0, 0, &page, NULL);
if (ret <= 0)
return ret;
lock_page(page);
vaddr_new = kmap_atomic(page);
vaddr &= ~PAGE_MASK;
memcpy(opcode, vaddr_new + vaddr, UPROBE_SWBP_INSN_SIZE);
kunmap_atomic(vaddr_new);
unlock_page(page);
put_page(page);
return 0;
}
static int is_swbp_at_addr(struct mm_struct *mm, unsigned long vaddr)
{
uprobe_opcode_t opcode;
int result;
result = read_opcode(mm, vaddr, &opcode);
if (result)
return result;
if (is_swbp_insn(&opcode))
return 1;
return 0;
}
/**
* 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)
{
int result;
result = is_swbp_at_addr(mm, vaddr);
if (result == 1)
return -EEXIST;
if (result)
return result;
return 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.
* @verify: if true, verify existance of breakpoint instruction.
*
* 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, bool verify)
{
if (verify) {
int result;
result = is_swbp_at_addr(mm, vaddr);
if (!result)
return -EINVAL;
if (result != 1)
return result;
}
return write_opcode(auprobe, 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;
unsigned long flags;
spin_lock_irqsave(&uprobes_treelock, flags);
uprobe = __find_uprobe(inode, offset);
spin_unlock_irqrestore(&uprobes_treelock, flags);
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)
{
unsigned long flags;
struct uprobe *u;
spin_lock_irqsave(&uprobes_treelock, flags);
u = __insert_uprobe(uprobe);
spin_unlock_irqrestore(&uprobes_treelock, flags);
/* 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);
INIT_LIST_HEAD(&uprobe->pending_list);
/* 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 vm_area_struct *vma, char *insn,
unsigned long nbytes, unsigned long offset)
{
struct file *filp = vma->vm_file;
struct page *page;
void *vaddr;
unsigned long off1;
unsigned long idx;
if (!filp)
return -EINVAL;
idx = (unsigned long)(offset >> PAGE_CACHE_SHIFT);
off1 = 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 + off1, nbytes);
kunmap_atomic(vaddr);
page_cache_release(page);
return 0;
}
static int
copy_insn(struct uprobe *uprobe, struct vm_area_struct *vma, unsigned long addr)
{
struct address_space *mapping;
unsigned long nbytes;
int bytes;
addr &= ~PAGE_MASK;
nbytes = PAGE_SIZE - addr;
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) {
if (__copy_insn(mapping, vma, uprobe->arch.insn + nbytes,
bytes - nbytes, uprobe->offset + nbytes))
return -ENOMEM;
bytes = nbytes;
}
return __copy_insn(mapping, vma, uprobe->arch.insn, bytes, uprobe->offset);
}
/*
* How mm->uprobes_state.count gets updated
* uprobe_mmap() increments the count if
* - it successfully adds a breakpoint.
* - it cannot add a breakpoint, but sees that there is a underlying
* breakpoint (via a is_swbp_at_addr()).
*
* uprobe_munmap() decrements the count if
* - it sees a underlying breakpoint, (via is_swbp_at_addr)
* (Subsequent uprobe_unregister wouldnt find the breakpoint
* unless a uprobe_mmap kicks in, since the old vma would be
* dropped just after uprobe_munmap.)
*
* uprobe_register increments the count if:
* - it successfully adds a breakpoint.
*
* uprobe_unregister decrements the count if:
* - it sees a underlying breakpoint and removes successfully.
* (via is_swbp_at_addr)
* (Subsequent uprobe_munmap wouldnt find the breakpoint
* since there is no underlying breakpoint after the
* breakpoint removal.)
*/
static int
install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm,
struct vm_area_struct *vma, loff_t vaddr)
{
unsigned long addr;
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 -EEXIST;
addr = (unsigned long)vaddr;
if (!(uprobe->flags & UPROBE_COPY_INSN)) {
ret = copy_insn(uprobe, vma, addr);
if (ret)
return ret;
if (is_swbp_insn((uprobe_opcode_t *)uprobe->arch.insn))
return -EEXIST;
ret = arch_uprobe_analyze_insn(&uprobe->arch, mm);
if (ret)
return ret;
uprobe->flags |= UPROBE_COPY_INSN;
}
/*
* Ideally, should be updating the probe count after the breakpoint
* has been successfully inserted. However a thread could hit the
* breakpoint we just inserted even before the probe count is
* incremented. If this is the first breakpoint placed, breakpoint
* notifier might ignore uprobes and pass the trap to the thread.
* Hence increment before and decrement on failure.
*/
atomic_inc(&mm->uprobes_state.count);
ret = set_swbp(&uprobe->arch, mm, addr);
if (ret)
atomic_dec(&mm->uprobes_state.count);
return ret;
}
static void
remove_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, loff_t vaddr)
{
if (!set_orig_insn(&uprobe->arch, mm, (unsigned long)vaddr, true))
atomic_dec(&mm->uprobes_state.count);
}
/*
* There could be threads that have hit the breakpoint and are entering the
* notifier code and trying to acquire the uprobes_treelock. The thread
* calling delete_uprobe() that is removing the uprobe from the rb_tree can
* race with these threads and might acquire the uprobes_treelock compared
* to some of the breakpoint hit threads. In such a case, the breakpoint
* hit threads will not find the uprobe. The current unregistering thread
* waits till all other threads have hit a breakpoint, to acquire the
* uprobes_treelock before the uprobe is removed from the rbtree.
*/
static void delete_uprobe(struct uprobe *uprobe)
{
unsigned long flags;
synchronize_srcu(&uprobes_srcu);
spin_lock_irqsave(&uprobes_treelock, flags);
rb_erase(&uprobe->rb_node, &uprobes_tree);
spin_unlock_irqrestore(&uprobes_treelock, flags);
iput(uprobe->inode);
put_uprobe(uprobe);
atomic_dec(&uprobe_events);
}
static struct vma_info *
__find_next_vma_info(struct address_space *mapping, struct list_head *head,
struct vma_info *vi, loff_t offset, bool is_register)
{
struct prio_tree_iter iter;
struct vm_area_struct *vma;
struct vma_info *tmpvi;
unsigned long pgoff;
int existing_vma;
loff_t vaddr;
pgoff = offset >> PAGE_SHIFT;
vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
if (!valid_vma(vma, is_register))
continue;
existing_vma = 0;
vaddr = vma_address(vma, offset);
list_for_each_entry(tmpvi, head, probe_list) {
if (tmpvi->mm == vma->vm_mm && tmpvi->vaddr == vaddr) {
existing_vma = 1;
break;
}
}
/*
* Another vma needs a probe to be installed. However skip
* installing the probe if the vma is about to be unlinked.
*/
if (!existing_vma && atomic_inc_not_zero(&vma->vm_mm->mm_users)) {
vi->mm = vma->vm_mm;
vi->vaddr = vaddr;
list_add(&vi->probe_list, head);
return vi;
}
}
return NULL;
}
/*
* Iterate in the rmap prio tree and find a vma where a probe has not
* yet been inserted.
*/
static struct vma_info *
find_next_vma_info(struct address_space *mapping, struct list_head *head,
loff_t offset, bool is_register)
{
struct vma_info *vi, *retvi;
vi = kzalloc(sizeof(struct vma_info), GFP_KERNEL);
if (!vi)
return ERR_PTR(-ENOMEM);
mutex_lock(&mapping->i_mmap_mutex);
retvi = __find_next_vma_info(mapping, head, vi, offset, is_register);
mutex_unlock(&mapping->i_mmap_mutex);
if (!retvi)
kfree(vi);
return retvi;
}
static int register_for_each_vma(struct uprobe *uprobe, bool is_register)
{
struct list_head try_list;
struct vm_area_struct *vma;
struct address_space *mapping;
struct vma_info *vi, *tmpvi;
struct mm_struct *mm;
loff_t vaddr;
int ret;
mapping = uprobe->inode->i_mapping;
INIT_LIST_HEAD(&try_list);
ret = 0;
for (;;) {
vi = find_next_vma_info(mapping, &try_list, uprobe->offset, is_register);
if (!vi)
break;
if (IS_ERR(vi)) {
ret = PTR_ERR(vi);
break;
}
mm = vi->mm;
down_read(&mm->mmap_sem);
vma = find_vma(mm, (unsigned long)vi->vaddr);
if (!vma || !valid_vma(vma, is_register)) {
list_del(&vi->probe_list);
kfree(vi);
up_read(&mm->mmap_sem);
mmput(mm);
continue;
}
vaddr = vma_address(vma, uprobe->offset);
if (vma->vm_file->f_mapping->host != uprobe->inode ||
vaddr != vi->vaddr) {
list_del(&vi->probe_list);
kfree(vi);
up_read(&mm->mmap_sem);
mmput(mm);
continue;
}
if (is_register)
ret = install_breakpoint(uprobe, mm, vma, vi->vaddr);
else
remove_breakpoint(uprobe, mm, vi->vaddr);
up_read(&mm->mmap_sem);
mmput(mm);
if (is_register) {
if (ret && ret == -EEXIST)
ret = 0;
if (ret)
break;
}
}
list_for_each_entry_safe(vi, tmpvi, &try_list, probe_list) {
list_del(&vi->probe_list);
kfree(vi);
}
return ret;
}
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 && !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));
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);
}
/*
* Of all the nodes that correspond to the given inode, return the node
* with the least offset.
*/
static struct rb_node *find_least_offset_node(struct inode *inode)
{
struct uprobe u = { .inode = inode, .offset = 0};
struct rb_node *n = uprobes_tree.rb_node;
struct rb_node *close_node = NULL;
struct uprobe *uprobe;
int match;
while (n) {
uprobe = rb_entry(n, struct uprobe, rb_node);
match = match_uprobe(&u, uprobe);
if (uprobe->inode == inode)
close_node = n;
if (!match)
return close_node;
if (match < 0)
n = n->rb_left;
else
n = n->rb_right;
}
return close_node;
}
/*
* For a given inode, build a list of probes that need to be inserted.
*/
static void build_probe_list(struct inode *inode, struct list_head *head)
{
struct uprobe *uprobe;
unsigned long flags;
struct rb_node *n;
spin_lock_irqsave(&uprobes_treelock, flags);
n = find_least_offset_node(inode);
for (; n; n = rb_next(n)) {
uprobe = rb_entry(n, struct uprobe, rb_node);
if (uprobe->inode != inode)
break;
list_add(&uprobe->pending_list, head);
atomic_inc(&uprobe->ref);
}
spin_unlock_irqrestore(&uprobes_treelock, flags);
}
/*
* Called from mmap_region.
* called with mm->mmap_sem acquired.
*
* Return -ve no if we fail to insert probes and we cannot
* bail-out.
* Return 0 otherwise. i.e:
*
* - successful insertion of probes
* - (or) no possible probes to be inserted.
* - (or) insertion of probes failed but we can bail-out.
*/
int uprobe_mmap(struct vm_area_struct *vma)
{
struct list_head tmp_list;
struct uprobe *uprobe, *u;
struct inode *inode;
int ret, count;
if (!atomic_read(&uprobe_events) || !valid_vma(vma, true))
return 0;
inode = vma->vm_file->f_mapping->host;
if (!inode)
return 0;
INIT_LIST_HEAD(&tmp_list);
mutex_lock(uprobes_mmap_hash(inode));
build_probe_list(inode, &tmp_list);
ret = 0;
count = 0;
list_for_each_entry_safe(uprobe, u, &tmp_list, pending_list) {
loff_t vaddr;
list_del(&uprobe->pending_list);
if (!ret) {
vaddr = vma_address(vma, uprobe->offset);
if (vaddr < vma->vm_start || vaddr >= vma->vm_end) {
put_uprobe(uprobe);
continue;
}
ret = install_breakpoint(uprobe, vma->vm_mm, vma, vaddr);
/* Ignore double add: */
if (ret == -EEXIST) {
ret = 0;
if (!is_swbp_at_addr(vma->vm_mm, vaddr))
continue;
/*
* Unable to insert a breakpoint, but
* breakpoint lies underneath. Increment the
* probe count.
*/
atomic_inc(&vma->vm_mm->uprobes_state.count);
}
if (!ret)
count++;
}
put_uprobe(uprobe);
}
mutex_unlock(uprobes_mmap_hash(inode));
if (ret)
atomic_sub(count, &vma->vm_mm->uprobes_state.count);
return ret;
}
/*
* Called in context of a munmap of a vma.
*/
void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned long end)
{
struct list_head tmp_list;
struct uprobe *uprobe, *u;
struct inode *inode;
if (!atomic_read(&uprobe_events) || !valid_vma(vma, false))
return;
if (!atomic_read(&vma->vm_mm->uprobes_state.count))
return;
inode = vma->vm_file->f_mapping->host;
if (!inode)
return;
INIT_LIST_HEAD(&tmp_list);
mutex_lock(uprobes_mmap_hash(inode));
build_probe_list(inode, &tmp_list);
list_for_each_entry_safe(uprobe, u, &tmp_list, pending_list) {
loff_t vaddr;
list_del(&uprobe->pending_list);
vaddr = vma_address(vma, uprobe->offset);
if (vaddr >= start && vaddr < end) {
/*
* An unregister could have removed the probe before
* unmap. So check before we decrement the count.
*/
if (is_swbp_at_addr(vma->vm_mm, vaddr) == 1)
atomic_dec(&vma->vm_mm->uprobes_state.count);
}
put_uprobe(uprobe);
}
mutex_unlock(uprobes_mmap_hash(inode));
}
/* 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);
}
/*
* uprobe_reset_state - Free the area allocated for slots.
*/
void uprobe_reset_state(struct mm_struct *mm)
{
mm->uprobes_state.xol_area = NULL;
atomic_set(&mm->uprobes_state.count, 0);
}
/*
* - 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 (t->uprobe_srcu_id != -1)
srcu_read_unlock_raw(&uprobes_srcu, t->uprobe_srcu_id);
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;
t->uprobe_srcu_id = -1;
}
/*
* 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;
utask->active_uprobe = 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 (arch_uprobe_skip_sstep(&uprobe->arch, regs))
return true;
uprobe->flags &= ~UPROBE_SKIP_SSTEP;
return false;
}
/*
* 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 vm_area_struct *vma;
struct uprobe_task *utask;
struct uprobe *uprobe;
struct mm_struct *mm;
unsigned long bp_vaddr;
uprobe = NULL;
bp_vaddr = uprobe_get_swbp_addr(regs);
mm = current->mm;
down_read(&mm->mmap_sem);
vma = find_vma(mm, bp_vaddr);
if (vma && vma->vm_start <= bp_vaddr && valid_vma(vma, false)) {
struct inode *inode;
loff_t offset;
inode = vma->vm_file->f_mapping->host;
offset = bp_vaddr - vma->vm_start;
offset += (vma->vm_pgoff << PAGE_SHIFT);
uprobe = find_uprobe(inode, offset);
}
srcu_read_unlock_raw(&uprobes_srcu, current->uprobe_srcu_id);
current->uprobe_srcu_id = -1;
up_read(&mm->mmap_sem);
if (!uprobe) {
/* No matching uprobe; signal SIGTRAP. */
send_sig(SIGTRAP, current, 0);
return;
}
utask = current->utask;
if (!utask) {
utask = add_utask();
/* Cannot allocate; re-execute the instruction. */
if (!utask)
goto cleanup_ret;
}
utask->active_uprobe = uprobe;
handler_chain(uprobe, regs);
if (uprobe->flags & UPROBE_SKIP_SSTEP && can_skip_sstep(uprobe, regs))
goto cleanup_ret;
utask->state = UTASK_SSTEP;
if (!pre_ssout(uprobe, regs, bp_vaddr)) {
user_enable_single_step(current);
return;
}
cleanup_ret:
if (utask) {
utask->active_uprobe = NULL;
utask->state = UTASK_RUNNING;
}
if (uprobe) {
if (!(uprobe->flags & UPROBE_SKIP_SSTEP))
/*
* cannot singlestep; cannot skip instruction;
* re-execute the instruction.
*/
instruction_pointer_set(regs, bp_vaddr);
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);
put_uprobe(uprobe);
utask->active_uprobe = NULL;
utask->state = UTASK_RUNNING;
user_disable_single_step(current);
xol_free_insn_slot(current);
spin_lock_irq(¤t->sighand->siglock);
recalc_sigpending(); /* see uprobe_deny_signal() */
spin_unlock_irq(¤t->sighand->siglock);
}
/*
* On breakpoint hit, breakpoint notifier sets the TIF_UPROBE flag. (and on
* subsequent probe hits on the thread sets the state to UTASK_BP_HIT) and
* allows the thread to return from interrupt.
*
* On singlestep exception, singlestep notifier sets the TIF_UPROBE flag and
* also sets the state to UTASK_SSTEP_ACK 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;
utask = current->utask;
if (!utask || utask->state == UTASK_BP_HIT)
handle_swbp(regs);
else
handle_singlestep(utask, 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)
{
struct uprobe_task *utask;
if (!current->mm || !atomic_read(¤t->mm->uprobes_state.count))
/* task is currently not uprobed */
return 0;
utask = current->utask;
if (utask)
utask->state = UTASK_BP_HIT;
set_thread_flag(TIF_UPROBE);
current->uprobe_srcu_id = srcu_read_lock_raw(&uprobes_srcu);
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]);
}
init_srcu_struct(&uprobes_srcu);
return register_die_notifier(&uprobe_exception_nb);
}
module_init(init_uprobes);
static void __exit exit_uprobes(void)
{
}
module_exit(exit_uprobes);