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Subject[PATCH 3/7] 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>
---
include/linux/uprobes.h | 6 ++++++
kernel/events/uprobes.c | 39 +++++++++++++++++++++++++++++++++++----
2 files changed, 41 insertions(+), 4 deletions(-)

diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
index 95d0002..02b83db 100644
--- 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 23340a7..2bcd08e 100644
--- 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);
@@ -855,6 +857,35 @@ 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.
* @offset: offset from the start of the file.
--
1.5.5.1


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