Messages in this thread | | | Date | Thu, 21 Jun 2018 19:54:10 +0200 | From | Stefan Agner <> | Subject | Re: [PATCH] ARM: ftrace: Only set kernel memory back to read-only after boot |
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On 21.06.2018 18:50, Steven Rostedt wrote: > On Thu, 21 Jun 2018 12:47:10 -0400 > Steven Rostedt <rostedt@goodmis.org> wrote: > >> From: Steven Rostedt (VMware) <rostedt@goodmis.org> >> >> Dynamic ftrace requires modifying the code segments that are usually >> set to read-only. To do this, a per arch function is called both before >> and after the ftrace modifications are performed. The "before" function >> will set kernel code text to read-write to allow for ftrace to make the >> modifications, and the "after" function will set the kernel code text >> back to "read-only" to keep the kernel code text protected. >> >> The issue happens when dynamic ftrace is tested at boot up. The test is >> done before the kernel code text has been set to read-only. But the >> "before" and "after" calls are still performed. The "after" call will >> change the kernel code text to read-only prematurely, and other boot >> code that expects this code to be read-write will fail. >> >> The solution is to add a variable that is set when the kernel code text >> is expected to be converted to read-only, and make the ftrace "before" >> and "after" calls do nothing if that variable is not yet set. This is >> similar to the x86 solution from commit 162396309745 ("ftrace, x86: >> make kernel text writable only for conversions"). >> >> Reported-by: Stefan Agner <stefan@agner.ch> >> Tested-by: Stefan Agner <stefan@agner.ch> >> Link: http://lkml.kernel.org/r/20180620212906.24b7b66e@vmware.local.home >> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> >> --- > > Perhaps I should have Cc'd stable too? >
As it is self tests only which are broken probably not super important. But then, the fix is also rather clean and safe IMHO, so why not.
-- Stefan
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