[PATCH 09/23] tracehook: tracehook_expect_breakpoints

Roland McGrath
2008-07-17T07:32:46Z

This adds tracehook_expect_breakpoints() as a formal hook for
the nommu code to use for its, "Is text-poking likely?" check
at mmap time. This names the actual semantics the code means
to test, and documents it.

Signed-off-by: Roland McGrath <roland@redhat.com>
---
include/linux/tracehook.h | 15 +++++++++++++++
mm/nommu.c | 4 ++--
2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/include/linux/tracehook.h b/include/linux/tracehook.h
index 6468ca0..e113e09 100644
--- a/include/linux/tracehook.h
+++ b/include/linux/tracehook.h
@@ -52,6 +52,21 @@
struct linux_binprm;

/**
+ * tracehook_expect_breakpoints - guess if task memory might be touched
+ * @task: current task, making a new mapping
+ *
+ * Return nonzero if @task is expected to want breakpoint insertion in
+ * its memory at some point. A zero return is no guarantee it won't
+ * be done, but this is a hint that it's known to be likely.
+ *
+ * May be called with @task->mm->mmap_sem held for writing.
+ */
+static inline int tracehook_expect_breakpoints(struct task_struct *task)
+{
+ return (task_ptrace(task) & PT_PTRACED) != 0;
+}
+
+/**
* tracehook_unsafe_exec - check for exec declared unsafe due to tracing
* @task: current task doing exec
*
diff --git a/mm/nommu.c b/mm/nommu.c
index 4462b6a..5edccd9 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -22,7 +22,7 @@
#include <linux/pagemap.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
-#include <linux/ptrace.h>
+#include <linux/tracehook.h>
#include <linux/blkdev.h>
#include <linux/backing-dev.h>
#include <linux/mount.h>
@@ -745,7 +745,7 @@ static unsigned long determine_vm_flags(struct file *file,
* it's being traced - otherwise breakpoints set in it may interfere
* with another untraced process
*/
- if ((flags & MAP_PRIVATE) && (current->ptrace & PT_PTRACED))
+ if ((flags & MAP_PRIVATE) && tracehook_expect_breakpoints(current))
vm_flags &= ~VM_MAYSHARE;

return vm_flags;