ftrace/x86/extable: Add is_ftrace_trampoline() function
Stack traces that happen from function tracing check if the address
on the stack is a __kernel_text_address(). That is, is the address
kernel code. This calls core_kernel_text() which returns true
if the address is part of the builtin kernel code. It also calls
is_module_text_address() which returns true if the address belongs
to module code.
But what is missing is ftrace dynamically allocated trampolines.
These trampolines are allocated for individual ftrace_ops that
call the ftrace_ops callback functions directly. But if they do a
stack trace, the code checking the stack wont detect them as they
are neither core kernel code nor module address space.
Adding another field to ftrace_ops that also stores the size of
the trampoline assigned to it we can create a new function called
is_ftrace_trampoline() that returns true if the address is a
dynamically allocate ftrace trampoline. Note, it ignores trampolines
that are not dynamically allocated as they will return true with
the core_kernel_text() function.
Link: http://lkml.kernel.org/r/20141119034829.497125839@goodmis.org
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 619e37c..7b2616f 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -150,6 +150,7 @@
struct ftrace_ops_hash *func_hash;
struct ftrace_ops_hash old_hash;
unsigned long trampoline;
+ unsigned long trampoline_size;
#endif
};
@@ -297,6 +298,8 @@
extern int ftrace_nr_registered_ops(void);
+bool is_ftrace_trampoline(unsigned long addr);
+
/*
* The dyn_ftrace record's flags field is split into two parts.
* the first part which is '0-FTRACE_REF_MAX' is a counter of
@@ -596,6 +599,11 @@
size_t cnt, loff_t *ppos) { return -ENODEV; }
static inline int
ftrace_regex_release(struct inode *inode, struct file *file) { return -ENODEV; }
+
+static inline bool is_ftrace_trampoline(unsigned long addr)
+{
+ return false;
+}
#endif /* CONFIG_DYNAMIC_FTRACE */
/* totally disable ftrace - can not re-enable after this */