uprobes: Move to kernel/events/

Consolidate the uprobes code under kernel/events/, where the various
core kernel event handling routines live.

Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Jim Keniston <jkenisto@us.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: Anton Arapov <anton@redhat.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Link: http://lkml.kernel.org/n/tip-biuyhhwohxgbp2vzbap5yr8o@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 1014 insertions, 0 deletions

diff --git a/kernel/events/Makefile b/kernel/events/Makefile
index 22d901f9caf..103f5d147b2 100644
--- a/kernel/events/Makefile
+++ b/kernel/events/Makefile
@@ -3,4 +3,7 @@ CFLAGS_REMOVE_core.o = -pg
 endif
 
 obj-y := core.o ring_buffer.o callchain.o
+
 obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o
+obj-$(CONFIG_UPROBES) += uprobes.o
+
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
new file mode 100644
index 00000000000..884817f1b0d
--- /dev/null
+++ b/kernel/events/uprobes.c
@@ -0,0 +1,1011 @@
+/*
+ * 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, 2008-2011
+ * Authors:
+ *	Srikar Dronamraju
+ *	Jim Keniston
+ */
+
+#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/uprobes.h>
+
+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;
+};
+
+/*
+ * 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);
+
+	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_bkpt_insn - check if instruction is breakpoint instruction.
+ * @insn: instruction to be checked.
+ * Default implementation of is_bkpt_insn
+ * Returns true if @insn is a breakpoint instruction.
+ */
+bool __weak is_bkpt_insn(uprobe_opcode_t *insn)
+{
+	return *insn == UPROBES_BKPT_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.
+ * @mm: the probed process address space.
+ * @uprobe: the breakpointing information.
+ * @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, struct uprobe *uprobe,
+			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;
+	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_bkpt_insn(&opcode)))
+		goto put_out;
+
+	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_opcode_sz > PAGE_SIZE);
+	memcpy(vaddr_new + vaddr, &opcode, uprobe_opcode_sz);
+
+	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_opcode_sz);
+	kunmap_atomic(vaddr_new);
+	unlock_page(page);
+
+	put_page(page);
+
+	return 0;
+}
+
+static int is_bkpt_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_bkpt_insn(&opcode))
+		return 1;
+
+	return 0;
+}
+
+/**
+ * set_bkpt - store breakpoint at a given address.
+ * @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 uprobe *uprobe, unsigned long vaddr)
+{
+	int result;
+
+	result = is_bkpt_at_addr(mm, vaddr);
+	if (result == 1)
+		return -EEXIST;
+
+	if (result)
+		return result;
+
+	return write_opcode(mm, uprobe, vaddr, UPROBES_BKPT_INSN);
+}
+
+/**
+ * set_orig_insn - Restore the original instruction.
+ * @mm: the probed process address space.
+ * @uprobe: the 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 mm_struct *mm, struct uprobe *uprobe, unsigned long vaddr, bool verify)
+{
+	if (verify) {
+		int result;
+
+		result = is_bkpt_at_addr(mm, vaddr);
+		if (!result)
+			return -EINVAL;
+
+		if (result != 1)
+			return result;
+	}
+	return write_opcode(mm, uprobe, vaddr, *(uprobe_opcode_t *)uprobe->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);
+
+	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;
+}
+
+/* Returns the previous consumer */
+static struct uprobe_consumer *
+consumer_add(struct uprobe *uprobe, struct uprobe_consumer *consumer)
+{
+	down_write(&uprobe->consumer_rwsem);
+	consumer->next = uprobe->consumers;
+	uprobe->consumers = consumer;
+	up_write(&uprobe->consumer_rwsem);
+
+	return consumer->next;
+}
+
+/*
+ * For uprobe @uprobe, delete the consumer @consumer.
+ * Return true if the @consumer is deleted successfully
+ * or return false.
+ */
+static bool consumer_del(struct uprobe *uprobe, struct uprobe_consumer *consumer)
+{
+	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;
+			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->insn + nbytes,
+				bytes - nbytes, uprobe->offset + nbytes))
+			return -ENOMEM;
+
+		bytes = nbytes;
+	}
+	return __copy_insn(mapping, vma, uprobe->insn, bytes, uprobe->offset);
+}
+
+static int install_breakpoint(struct mm_struct *mm, struct uprobe *uprobe,
+				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 & UPROBES_COPY_INSN)) {
+		ret = copy_insn(uprobe, vma, addr);
+		if (ret)
+			return ret;
+
+		if (is_bkpt_insn((uprobe_opcode_t *)uprobe->insn))
+			return -EEXIST;
+
+		ret = arch_uprobes_analyze_insn(mm, uprobe);
+		if (ret)
+			return ret;
+
+		uprobe->flags |= UPROBES_COPY_INSN;
+	}
+	ret = set_bkpt(mm, uprobe, addr);
+
+	return ret;
+}
+
+static void remove_breakpoint(struct mm_struct *mm, struct uprobe *uprobe, loff_t vaddr)
+{
+	set_orig_insn(mm, uprobe, (unsigned long)vaddr, true);
+}
+
+static void delete_uprobe(struct uprobe *uprobe)
+{
+	unsigned long flags;
+
+	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 list_head *head,
+			loff_t offset, struct address_space *mapping,
+			struct vma_info *vi, 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 list_head *head, loff_t offset, struct address_space *mapping,
+		   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(head, offset, mapping, vi, 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(&try_list, uprobe->offset, mapping, 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(mm, uprobe, vma, vi->vaddr);
+		else
+			remove_breakpoint(mm, uprobe, 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.
+ * @consumer: 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
+ * 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)
+{
+	struct uprobe *uprobe;
+	int ret;
+
+	if (!inode || !consumer || consumer->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, consumer)) {
+		ret = __uprobe_register(uprobe);
+		if (ret) {
+			uprobe->consumers = NULL;
+			__uprobe_unregister(uprobe);
+		} else {
+			uprobe->flags |= UPROBES_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.
+ * @consumer: identify which probe if multiple probes are colocated.
+ */
+void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *consumer)
+{
+	struct uprobe *uprobe;
+
+	if (!inode || !consumer)
+		return;
+
+	uprobe = find_uprobe(inode, offset);
+	if (!uprobe)
+		return;
+
+	mutex_lock(uprobes_hash(inode));
+
+	if (consumer_del(uprobe, consumer)) {
+		if (!uprobe->consumers) {
+			__uprobe_unregister(uprobe);
+			uprobe->flags &= ~UPROBES_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;
+
+	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;
+
+	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;
+			}
+		}
+		put_uprobe(uprobe);
+	}
+
+	mutex_unlock(uprobes_mmap_hash(inode));
+
+	return ret;
+}
+
+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 0;
+}
+
+static void __exit exit_uprobes(void)
+{
+}
+
+module_init(init_uprobes);
+module_exit(exit_uprobes);