Add comments to explain what is happening in the x86 arch ftrace code. Signed-off-by: Steven Rostedt --- arch/x86/kernel/ftrace.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) Index: linux-compile.git/arch/x86/kernel/ftrace.c =================================================================== --- linux-compile.git.orig/arch/x86/kernel/ftrace.c 2008-10-22 15:23:20.000000000 -0400 +++ linux-compile.git/arch/x86/kernel/ftrace.c 2008-10-22 15:24:15.000000000 -0400 @@ -66,18 +66,23 @@ ftrace_modify_code(unsigned long ip, uns /* * Note: Due to modules and __init, code can * disappear and change, we need to protect against faulting - * as well as code changing. + * as well as code changing. We do this by using the + * __copy_*_user functions. * * No real locking needed, this code is run through * kstop_machine, or before SMP starts. */ + + /* read the text we want to modify */ if (__copy_from_user_inatomic(replaced, (char __user *)ip, MCOUNT_INSN_SIZE)) return -EFAULT; + /* Make sure it is what we expect it to be */ if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0) return -EINVAL; + /* replace the text with the new text */ if (__copy_to_user_inatomic((char __user *)ip, new_code, MCOUNT_INSN_SIZE)) return -EPERM; -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/