Date: Mon, 4 Jun 2018 16:16:12 -0400 From: Steven Rostedt <rostedt@...dmis.org> To: Thomas Garnier <thgarnie@...gle.com> Cc: kernel-hardening@...ts.openwall.com, Ingo Molnar <mingo@...hat.com>, Thomas Gleixner <tglx@...utronix.de>, "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org, Francis Deslauriers <francis.deslauriers@...icios.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Andrew Morton <akpm@...ux-foundation.org>, "Peter Zijlstra (Intel)" <peterz@...radead.org>, Guenter Roeck <linux@...ck-us.net>, nixiaoming <nixiaoming@...wei.com>, James Hogan <jhogan@...nel.org>, linux-kernel@...r.kernel.org Subject: Re: [PATCH v4 21/27] x86/ftrace: Adapt function tracing for PIE support On Tue, 29 May 2018 15:15:22 -0700 Thomas Garnier <thgarnie@...gle.com> wrote: > When using -fPIE/PIC with function tracing, the compiler generates a > call through the GOT (call *__fentry__@...PCREL). This instruction > takes 6 bytes instead of 5 on the usual relative call. > > If PIE is enabled, replace the 6th byte of the GOT call by a 1-byte nop > so ftrace can handle the previous 5-bytes as before. > > Position Independent Executable (PIE) support will allow to extend the > KASLR randomization range 0xffffffff80000000. I thought you were going to write a update to recordmcount.c to handle this at compile time? -- Steve > > Signed-off-by: Thomas Garnier <thgarnie@...gle.com> > --- >
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