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Message-ID: <1449214067-12177-5-git-send-email-huawei.libin@huawei.com> Date: Fri, 4 Dec 2015 15:27:46 +0800 From: Li Bin <huawei.libin@...wei.com> To: <rostedt@...dmis.org>, <mingo@...hat.com> CC: <linux-kernel@...r.kernel.org>, Li Bin <huawei.libin@...wei.com>, <linux-sh@...r.kernel.org> Subject: [PATCH 4/5] sh: ftrace: fix the comments for ftrace_modify_code There is no need to worry about module and __init text disappearing case, because that ftrace has a module notifier that is called when a module is being unloaded and before the text goes away and this code grabs the ftrace_lock mutex and removes the module functions from the ftrace list, such that it will no longer do any modifications to that module's text, the update to make functions be traced or not is done under the ftrace_lock mutex as well. And by now, __init section codes should not been modified by ftrace, because it is black listed in recordmcount.c and ignored by ftrace. Cc: linux-sh@...r.kernel.org Suggested-by: Steven Rostedt <rostedt@...dmis.org> Signed-off-by: Li Bin <huawei.libin@...wei.com> --- arch/sh/kernel/ftrace.c | 13 ++++++------- 1 files changed, 6 insertions(+), 7 deletions(-) diff --git a/arch/sh/kernel/ftrace.c b/arch/sh/kernel/ftrace.c index 079d70e..b696f92 100644 --- a/arch/sh/kernel/ftrace.c +++ b/arch/sh/kernel/ftrace.c @@ -212,13 +212,12 @@ static int ftrace_modify_code(unsigned long ip, unsigned char *old_code, unsigned char replaced[MCOUNT_INSN_SIZE]; /* - * Note: Due to modules and __init, code can - * disappear and change, we need to protect against faulting - * as well as code changing. We do this by using the - * probe_kernel_* functions. - * - * No real locking needed, this code is run through - * kstop_machine, or before SMP starts. + * Note: + * We are paranoid about modifying text, as if a bug were to happen, it + * could cause us to read or write to someplace that could cause harm. + * Carefully read and modify the code with aarch64_insn_*() which uses + * probe_kernel_*(), and make sure what we read is what we expected it + * to be before modifying it. */ /* read the text we want to modify */ -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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