uprobes: Introduce uprobe_apply()

Currently it is not possible to change the filtering constraints after
uprobe_register(), so a consumer can not, say, start to trace a task/mm
which was previously filtered out, or remove the no longer needed bp's.

Introduce uprobe_apply() which simply does register_for_each_vma() again
to consult uprobe_consumer->filter() and install/remove the breakpoints.
The only complication is that register_for_each_vma() can no longer
assume that uprobe->consumers should be consulter if is_register == T,
so we change it to accept "struct uprobe_consumer *new" instead.

Unlike uprobe_register(), uprobe_apply(true) doesn't do "unregister" if
register_for_each_vma() fails, it is up to caller to handle the error.

Note: we probably need to cleanup the current interface, it is strange
that uprobe_apply/unregister need inode/offset. We should either change
uprobe_register() to return "struct uprobe *", or add a private ->uprobe
member in uprobe_consumer. And in the long term uprobe_apply() should
take a single argument, uprobe or consumer, even "bool add" should go
away.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>

diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
index 95d0002..02b83db 100644 (file)
--- a/include/linux/uprobes.h
+++ b/include/linux/uprobes.h
@@ -101,6 +101,7 @@ extern int __weak set_swbp(struct arch_uprobe *aup, struct mm_struct *mm, unsign
 extern int __weak set_orig_insn(struct arch_uprobe *aup, struct mm_struct *mm, unsigned long vaddr);
 extern bool __weak is_swbp_insn(uprobe_opcode_t *insn);
 extern int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer *uc);
+extern int uprobe_apply(struct inode *inode, loff_t offset, struct uprobe_consumer *uc, bool);
 extern void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *uc);
 extern int uprobe_mmap(struct vm_area_struct *vma);
 extern void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned long end);
@@ -124,6 +125,11 @@ uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer *uc)
 {
        return -ENOSYS;
 }
+static inline int
+uprobe_apply(struct inode *inode, loff_t offset, struct uprobe_consumer *uc, bool add)
+{
+       return -ENOSYS;
+}
 static inline void
 uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *uc)
 {

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 221fc58..a567c8c 100644 (file)
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -733,8 +733,10 @@ build_map_info(struct address_space *mapping, loff_t offset, bool is_register)
        return curr;
 }
 
-static int register_for_each_vma(struct uprobe *uprobe, bool is_register)
+static int
+register_for_each_vma(struct uprobe *uprobe, struct uprobe_consumer *new)
 {
+       bool is_register = !!new;
        struct map_info *info;
        int err = 0;
 
@@ -765,7 +767,7 @@ static int register_for_each_vma(struct uprobe *uprobe, bool is_register)
 
                if (is_register) {
                        /* consult only the "caller", new consumer. */
-                       if (consumer_filter(uprobe->consumers,
+                       if (consumer_filter(new,
                                        UPROBE_FILTER_REGISTER, mm))
                                err = install_breakpoint(uprobe, mm, vma, info->vaddr);
                } else if (test_bit(MMF_HAS_UPROBES, &mm->flags)) {
@@ -788,7 +790,7 @@ static int register_for_each_vma(struct uprobe *uprobe, bool is_register)
 static int __uprobe_register(struct uprobe *uprobe, struct uprobe_consumer *uc)
 {
        consumer_add(uprobe, uc);
-       return register_for_each_vma(uprobe, true);
+       return register_for_each_vma(uprobe, uc);
 }
 
 static void __uprobe_unregister(struct uprobe *uprobe, struct uprobe_consumer *uc)
@@ -798,7 +800,7 @@ static void __uprobe_unregister(struct uprobe *uprobe, struct uprobe_consumer *u
        if (!consumer_del(uprobe, uc))  /* WARN? */
                return;
 
-       err = register_for_each_vma(uprobe, false);
+       err = register_for_each_vma(uprobe, NULL);
        /* TODO : cant unregister? schedule a worker thread */
        if (!uprobe->consumers && !err)
                delete_uprobe(uprobe);
@@ -854,6 +856,35 @@ int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer *
 }
 EXPORT_SYMBOL_GPL(uprobe_register);
 
+/*
+ * uprobe_apply - 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: consumer which wants to add more or remove some breakpoints
+ * @add: add or remove the breakpoints
+ */
+int uprobe_apply(struct inode *inode, loff_t offset,
+                       struct uprobe_consumer *uc, bool add)
+{
+       struct uprobe *uprobe;
+       struct uprobe_consumer *con;
+       int ret = -ENOENT;
+
+       uprobe = find_uprobe(inode, offset);
+       if (!uprobe)
+               return ret;
+
+       down_write(&uprobe->register_rwsem);
+       for (con = uprobe->consumers; con && con != uc ; con = con->next)
+               ;
+       if (con)
+               ret = register_for_each_vma(uprobe, add ? uc : NULL);
+       up_write(&uprobe->register_rwsem);
+       put_uprobe(uprobe);
+
+       return ret;
+}
+
 /*
  * uprobe_unregister - unregister a already registered probe.
  * @inode: the file in which the probe has to be removed.