#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 rb_root uprobes_tree = RB_ROOT;
static DEFINE_SPINLOCK(uprobes_treelock); /* serialize rbtree access */
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));
}
/**
- * is_bkpt_insn - check if instruction is breakpoint instruction.
+ * is_swbp_insn - check if instruction is breakpoint instruction.
* @insn: instruction to be checked.
- * Default implementation of is_bkpt_insn
+ * Default implementation of is_swbp_insn
* Returns true if @insn is a breakpoint instruction.
*/
-bool __weak is_bkpt_insn(uprobe_opcode_t *insn)
+bool __weak is_swbp_insn(uprobe_opcode_t *insn)
{
- return *insn == UPROBE_BKPT_INSN;
+ return *insn == UPROBE_SWBP_INSN;
}
/*
/*
* write_opcode - write the opcode at a given virtual address.
+ * @auprobe: arch breakpointing information.
* @mm: the probed process address space.
- * @arch_uprobe: the breakpointing information.
* @vaddr: the virtual address to store the opcode.
* @opcode: opcode to be written at @vaddr.
*
* For mm @mm, write the opcode at @vaddr.
* Return 0 (success) or a negative errno.
*/
-static int write_opcode(struct mm_struct *mm, struct arch_uprobe *auprobe,
+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;
* adding probes in write mapped pages since the breakpoints
* might end up in the file copy.
*/
- if (!valid_vma(vma, is_bkpt_insn(&opcode)))
+ if (!valid_vma(vma, is_swbp_insn(&opcode)))
goto put_out;
uprobe = container_of(auprobe, struct uprobe, arch);
/* poke the new insn in, ASSUMES we don't cross page boundary */
vaddr &= ~PAGE_MASK;
- BUG_ON(vaddr + UPROBE_BKPT_INSN_SIZE > PAGE_SIZE);
- memcpy(vaddr_new + vaddr, &opcode, UPROBE_BKPT_INSN_SIZE);
+ 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);
void *vaddr_new;
int ret;
- ret = get_user_pages(NULL, mm, vaddr, 1, 0, 0, &page, NULL);
+ ret = get_user_pages(NULL, mm, vaddr, 1, 0, 1, &page, NULL);
if (ret <= 0)
return ret;
lock_page(page);
vaddr_new = kmap_atomic(page);
vaddr &= ~PAGE_MASK;
- memcpy(opcode, vaddr_new + vaddr, UPROBE_BKPT_INSN_SIZE);
+ memcpy(opcode, vaddr_new + vaddr, UPROBE_SWBP_INSN_SIZE);
kunmap_atomic(vaddr_new);
unlock_page(page);
return 0;
}
-static int is_bkpt_at_addr(struct mm_struct *mm, unsigned long vaddr)
+static int is_swbp_at_addr(struct mm_struct *mm, unsigned long vaddr)
{
uprobe_opcode_t opcode;
int result;
+ if (current->mm == mm) {
+ pagefault_disable();
+ result = __copy_from_user_inatomic(&opcode, (void __user*)vaddr,
+ sizeof(opcode));
+ pagefault_enable();
+
+ if (likely(result == 0))
+ goto out;
+ }
+
result = read_opcode(mm, vaddr, &opcode);
if (result)
return result;
-
- if (is_bkpt_insn(&opcode))
+out:
+ if (is_swbp_insn(&opcode))
return 1;
return 0;
}
/**
- * set_bkpt - store breakpoint at a given address.
+ * set_swbp - store breakpoint at a given address.
+ * @auprobe: arch specific probepoint information.
* @mm: the probed process address space.
- * @uprobe: the probepoint information.
* @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_bkpt(struct mm_struct *mm, struct arch_uprobe *auprobe, unsigned long vaddr)
+int __weak set_swbp(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr)
{
int result;
- result = is_bkpt_at_addr(mm, vaddr);
+ result = is_swbp_at_addr(mm, vaddr);
if (result == 1)
return -EEXIST;
if (result)
return result;
- return write_opcode(mm, auprobe, vaddr, UPROBE_BKPT_INSN);
+ return write_opcode(auprobe, mm, vaddr, UPROBE_SWBP_INSN);
}
/**
* set_orig_insn - Restore the original instruction.
* @mm: the probed process address space.
- * @uprobe: the probepoint information.
+ * @auprobe: arch specific probepoint information.
* @vaddr: the virtual address to insert the opcode.
* @verify: if true, verify existance of breakpoint instruction.
*
* Return 0 (success) or a negative errno.
*/
int __weak
-set_orig_insn(struct mm_struct *mm, struct arch_uprobe *auprobe, unsigned long vaddr, bool verify)
+set_orig_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr, bool verify)
{
if (verify) {
int result;
- result = is_bkpt_at_addr(mm, vaddr);
+ result = is_swbp_at_addr(mm, vaddr);
if (!result)
return -EINVAL;
if (result != 1)
return result;
}
- return write_opcode(mm, auprobe, vaddr, *(uprobe_opcode_t *)auprobe->insn);
+ return write_opcode(auprobe, mm, vaddr, *(uprobe_opcode_t *)auprobe->insn);
}
static int match_uprobe(struct uprobe *l, struct uprobe *r)
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;
}
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 *consumer)
+consumer_add(struct uprobe *uprobe, struct uprobe_consumer *uc)
{
down_write(&uprobe->consumer_rwsem);
- consumer->next = uprobe->consumers;
- uprobe->consumers = consumer;
+ uc->next = uprobe->consumers;
+ uprobe->consumers = uc;
up_write(&uprobe->consumer_rwsem);
- return consumer->next;
+ return uc->next;
}
/*
- * For uprobe @uprobe, delete the consumer @consumer.
- * Return true if the @consumer is deleted successfully
+ * 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 *consumer)
+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 == consumer) {
- *con = consumer->next;
+ if (*con == uc) {
+ *con = uc->next;
ret = true;
break;
}
return ret;
}
-static int __copy_insn(struct address_space *mapping,
- struct vm_area_struct *vma, char *insn,
+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;
return 0;
}
-static int copy_insn(struct uprobe *uprobe, struct vm_area_struct *vma, unsigned long addr)
+static int
+copy_insn(struct uprobe *uprobe, struct vm_area_struct *vma, unsigned long addr)
{
struct address_space *mapping;
unsigned long nbytes;
return __copy_insn(mapping, vma, uprobe->arch.insn, bytes, uprobe->offset);
}
-static int install_breakpoint(struct mm_struct *mm, struct uprobe *uprobe,
- struct vm_area_struct *vma, loff_t vaddr)
+/*
+ * 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 (ret)
return ret;
- if (is_bkpt_insn((uprobe_opcode_t *)uprobe->arch.insn))
+ if (is_swbp_insn((uprobe_opcode_t *)uprobe->arch.insn))
return -EEXIST;
- ret = arch_uprobes_analyze_insn(mm, &uprobe->arch);
+ ret = arch_uprobe_analyze_insn(&uprobe->arch, mm, addr);
if (ret)
return ret;
uprobe->flags |= UPROBE_COPY_INSN;
}
- ret = set_bkpt(mm, &uprobe->arch, addr);
+
+ /*
+ * 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 mm_struct *mm, struct uprobe *uprobe, loff_t vaddr)
+static void
+remove_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, loff_t vaddr)
{
- set_orig_insn(mm, &uprobe->arch, (unsigned long)vaddr, true);
+ if (!set_orig_insn(&uprobe->arch, mm, (unsigned long)vaddr, true))
+ atomic_dec(&mm->uprobes_state.count);
}
+/*
+ * 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)
{
unsigned long flags;
atomic_dec(&uprobe_events);
}
-static struct vma_info *__find_next_vma_info(struct list_head *head,
- loff_t offset, struct address_space *mapping,
- struct vma_info *vi, bool is_register)
+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;
* yet been inserted.
*/
static struct vma_info *
-find_next_vma_info(struct list_head *head, loff_t offset, struct address_space *mapping,
- bool is_register)
+find_next_vma_info(struct address_space *mapping, struct list_head *head,
+ loff_t offset, bool is_register)
{
struct vma_info *vi, *retvi;
return ERR_PTR(-ENOMEM);
mutex_lock(&mapping->i_mmap_mutex);
- retvi = __find_next_vma_info(head, offset, mapping, vi, is_register);
+ retvi = __find_next_vma_info(mapping, head, vi, offset, is_register);
mutex_unlock(&mapping->i_mmap_mutex);
if (!retvi)
ret = 0;
for (;;) {
- vi = find_next_vma_info(&try_list, uprobe->offset, mapping, is_register);
+ vi = find_next_vma_info(mapping, &try_list, uprobe->offset, is_register);
if (!vi)
break;
}
mm = vi->mm;
- down_read(&mm->mmap_sem);
+ down_write(&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);
+ up_write(&mm->mmap_sem);
mmput(mm);
continue;
}
vaddr != vi->vaddr) {
list_del(&vi->probe_list);
kfree(vi);
- up_read(&mm->mmap_sem);
+ up_write(&mm->mmap_sem);
mmput(mm);
continue;
}
if (is_register)
- ret = install_breakpoint(mm, uprobe, vma, vi->vaddr);
+ ret = install_breakpoint(uprobe, mm, vma, vi->vaddr);
else
- remove_breakpoint(mm, uprobe, vi->vaddr);
+ remove_breakpoint(uprobe, mm, vi->vaddr);
- up_read(&mm->mmap_sem);
+ up_write(&mm->mmap_sem);
mmput(mm);
if (is_register) {
if (ret && ret == -EEXIST)
* uprobe_register - register a probe
* @inode: the file in which the probe has to be placed.
* @offset: offset from the start of the file.
- * @consumer: information on howto handle the probe..
+ * @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 @consumer for the @uprobe
+ * 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 *consumer)
+int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer *uc)
{
struct uprobe *uprobe;
int ret;
- if (!inode || !consumer || consumer->next)
+ if (!inode || !uc || uc->next)
return -EINVAL;
if (offset > i_size_read(inode))
mutex_lock(uprobes_hash(inode));
uprobe = alloc_uprobe(inode, offset);
- if (uprobe && !consumer_add(uprobe, consumer)) {
+ if (uprobe && !consumer_add(uprobe, uc)) {
ret = __uprobe_register(uprobe);
if (ret) {
uprobe->consumers = NULL;
* 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.
- * @consumer: identify which probe if multiple probes are colocated.
+ * @uc: identify which probe if multiple probes are colocated.
*/
-void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *consumer)
+void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *uc)
{
struct uprobe *uprobe;
- if (!inode || !consumer)
+ if (!inode || !uc)
return;
uprobe = find_uprobe(inode, offset);
mutex_lock(uprobes_hash(inode));
- if (consumer_del(uprobe, consumer)) {
+ if (consumer_del(uprobe, uc)) {
if (!uprobe->consumers) {
__uprobe_unregister(uprobe);
uprobe->flags &= ~UPROBE_RUN_HANDLER;
struct list_head tmp_list;
struct uprobe *uprobe, *u;
struct inode *inode;
- int ret;
+ int ret, count;
if (!atomic_read(&uprobe_events) || !valid_vma(vma, true))
return 0;
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) {
- ret = install_breakpoint(vma->vm_mm, uprobe, vma, vaddr);
- /* Ignore double add: */
- if (ret == -EEXIST)
- ret = 0;
+
+ 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 (!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;
+
+ 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;
+}
+
+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;
+ 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);
+ }
+
+ if (!uprobe)
+ *is_swbp = is_swbp_at_addr(mm, bp_vaddr);
+ } else {
+ *is_swbp = -EFAULT;
+ }
+ up_read(&mm->mmap_sem);
+
+ return uprobe;
+}
+
+/*
+ * 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;
+ }
+
+ 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);
+
+ 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;
mutex_init(&uprobes_mutex[i]);
mutex_init(&uprobes_mmap_mutex[i]);
}
- return 0;
+
+ return register_die_notifier(&uprobe_exception_nb);
}
+module_init(init_uprobes);
static void __exit exit_uprobes(void)
{
}
-
-module_init(init_uprobes);
module_exit(exit_uprobes);
projects / cascardo / linux.git / blobdiff