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ftrace/x86/extable: Add is_ftrace_trampoline() function

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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>
This commit is contained in:
Steven Rostedt (Red Hat)
2014-11-18 21:14:11 -05:00
committed by Steven Rostedt
parent 9960efeb80
commit aec0be2d6e
4 changed files with 59 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

7
kernel/extable.c
View File

@@ -18,6 +18,7 @@
#include <linux/ftrace.h>
#include <linux/memory.h>
#include <linux/module.h>
#include <linux/ftrace.h>
#include <linux/mutex.h>
#include <linux/init.h>
@@ -102,6 +103,8 @@ int __kernel_text_address(unsigned long addr)
return 1;
if (is_module_text_address(addr))
return 1;
if (is_ftrace_trampoline(addr))
return 1;
/*
* There might be init symbols in saved stacktraces.
* Give those symbols a chance to be printed in
@@ -119,7 +122,9 @@ int kernel_text_address(unsigned long addr)
{
if (core_kernel_text(addr))
return 1;
return is_module_text_address(addr);
if (is_module_text_address(addr))
return 1;
return is_ftrace_trampoline(addr);
}
/*