Commit-ID: da1816b1caeccdff04531e763bb35d7caa3ed19f
Gitweb: http://git.kernel.org/tip/da1816b1caeccdff04531e763bb35d7caa3ed19f
Author: Oleg Nesterov <oleg@xxxxxxxxxx>
AuthorDate: Sat, 29 Dec 2012 17:49:11 +0100
Committer: Oleg Nesterov <oleg@xxxxxxxxxx>
CommitDate: Fri, 8 Feb 2013 17:47:11 +0100
uprobes: Teach handler_chain() to filter out the probed task
Currrently the are 2 problems with pre-filtering:
1. It is not possible to add/remove a task (mm) after uprobe_register()
2. A forked child inherits all breakpoints and uprobe_consumer can not
control this.
This patch does the first step to improve the filtering. handler_chain()
removes the breakpoints installed by this uprobe from current->mm if all
handlers return UPROBE_HANDLER_REMOVE.
Note that handler_chain() relies on ->register_rwsem to avoid the race
with uprobe_register/unregister which can add/del a consumer, or even
remove and then insert the new uprobe at the same address.
Perhaps we will add uprobe_apply_mm(uprobe, mm, is_register) and teach
copy_mm() to do filter(UPROBE_FILTER_FORK), but I think this change makes
sense anyway.
Note: instead of checking the retcode from uc->handler, we could add
uc->filter(UPROBE_FILTER_BPHIT). But I think this is not optimal to
call 2 hooks in a row. This buys nothing, and if handler/filter do
something nontrivial they will probably do the same work twice.
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Acked-by: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
---
include/linux/uprobes.h | 3 +++
kernel/events/uprobes.c | 58 ++++++++++++++++++++++++++++++++++++++++---------
2 files changed, 51 insertions(+), 10 deletions(-)
diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
index c2df693..95d0002 100644
--- a/include/linux/uprobes.h
+++ b/include/linux/uprobes.h
@@ -35,6 +35,9 @@ struct inode;
# include <asm/uprobes.h>
#endif
+#define UPROBE_HANDLER_REMOVE 1
+#define UPROBE_HANDLER_MASK 1
+
enum uprobe_filter_ctx {
UPROBE_FILTER_REGISTER,
UPROBE_FILTER_UNREGISTER,
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index c2737be..04c104a 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -440,16 +440,6 @@ static struct uprobe *alloc_uprobe(struct inode *inode, loff_t offset)
return uprobe;
}
-static void handler_chain(struct uprobe *uprobe, struct pt_regs *regs)
-{
- struct uprobe_consumer *uc;
-
- down_read(&uprobe->register_rwsem);
- for (uc = uprobe->consumers; uc; uc = uc->next)
- uc->handler(uc, regs);
- up_read(&uprobe->register_rwsem);
-}
-
static void consumer_add(struct uprobe *uprobe, struct uprobe_consumer *uc)
{
down_write(&uprobe->consumer_rwsem);
@@ -882,6 +872,33 @@ void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consume
put_uprobe(uprobe);
}
+static int unapply_uprobe(struct uprobe *uprobe, struct mm_struct *mm)
+{
+ struct vm_area_struct *vma;
+ int err = 0;
+
+ down_read(&mm->mmap_sem);
+ for (vma = mm->mmap; vma; vma = vma->vm_next) {
+ unsigned long vaddr;
+ loff_t offset;
+
+ if (!valid_vma(vma, false) ||
+ vma->vm_file->f_mapping->host != uprobe->inode)
+ continue;
+
+ offset = (loff_t)vma->vm_pgoff << PAGE_SHIFT;
+ if (uprobe->offset < offset ||
+ uprobe->offset >= offset + vma->vm_end - vma->vm_start)
+ continue;
+
+ vaddr = offset_to_vaddr(vma, uprobe->offset);
+ err |= remove_breakpoint(uprobe, mm, vaddr);
+ }
+ up_read(&mm->mmap_sem);
+
+ return err;
+}
+
static struct rb_node *
find_node_in_range(struct inode *inode, loff_t min, loff_t max)
{
@@ -1435,6 +1452,27 @@ static struct uprobe *find_active_uprobe(unsigned long bp_vaddr, int *is_swbp)
return uprobe;
}
+static void handler_chain(struct uprobe *uprobe, struct pt_regs *regs)
+{
+ struct uprobe_consumer *uc;
+ int remove = UPROBE_HANDLER_REMOVE;
+
+ down_read(&uprobe->register_rwsem);
+ for (uc = uprobe->consumers; uc; uc = uc->next) {
+ int rc = uc->handler(uc, regs);
+
+ WARN(rc & ~UPROBE_HANDLER_MASK,
+ "bad rc=0x%x from %pf()\n", rc, uc->handler);
+ remove &= rc;
+ }
+
+ if (remove && uprobe->consumers) {
+ WARN_ON(!uprobe_is_active(uprobe));
+ unapply_uprobe(uprobe, current->mm);
+ }
+ up_read(&uprobe->register_rwsem);
+}
+
/*
* Run handler and ask thread to singlestep.
* Ensure all non-fatal signals cannot interrupt thread while it singlesteps.
--
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