On Thu, 21 Jun 2018 12:47:10 -0400 Steven Rostedt <[email protected]> wrote:
> From: Steven Rostedt (VMware) <[email protected]> > > 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 <[email protected]> > Tested-by: Stefan Agner <[email protected]> > Link: http://lkml.kernel.org/r/[email protected] > Signed-off-by: Steven Rostedt (VMware) <[email protected]> > --- Perhaps I should have Cc'd stable too? -- Steve
