Date: Fri, 13 Oct 2017 20:03:59 +0300 From: Alexander Popov <alex.popov@...ux.com> To: Ingo Molnar <mingo@...nel.org> Cc: kernel-hardening@...ts.openwall.com, keescook@...omium.org, pageexec@...email.hu, spender@...ecurity.net, tycho@...ker.com, Laura Abbott <labbott@...hat.com>, Mark Rutland <mark.rutland@....com>, Ard Biesheuvel <ard.biesheuvel@...aro.org>, Andy Lutomirski <luto@...capital.net>, x86@...nel.org, Linus Torvalds <torvalds@...ux-foundation.org>, Andy Lutomirski <luto@...nel.org>, Borislav Petkov <bp@...en8.de>, Thomas Gleixner <tglx@...utronix.de>, "H. Peter Anvin" <hpa@...or.com>, Peter Zijlstra <a.p.zijlstra@...llo.nl> Subject: Re: [PATCH RFC v4 1/3] gcc-plugins: Add STACKLEAK erasing the kernel stack at the end of syscalls Hello Ingo, On 05.10.2017 10:27, Ingo Molnar wrote: > - The GCC plugin adds instrumentation in form of extra 'track_stack()' and > 'check_alloca()' calls. Could you please provide a frequency analysis of the > impact of this: x86-64 defconfig vmlinux size before/after the patch, and the > number of instrumentation function calls inserted, compared to the number of > functions? Size of vmlinux (x86_64_defconfig): file size: - STACKLEAK disabled: 35014784 bytes - STACKLEAK enabled: 35044952 bytes (+0.086%) .text section size (calculated by size utility): - STACKLEAK disabled: 10752983 - STACKLEAK enabled: 11062221 (+2.876%) The readelf utility shows 45602 functions in vmlinux. The STACKLEAK gcc plugin inserted 36 check_alloca() calls and 1265 track_stack() calls (42274 calls are inserted during GIMPLE pass and 41009 calls are deleted during RTL pass). So 2.853% of functions are instrumented. I will add this information to the cover letter of the 5'th version, which I'm currently preparing. Best regards, Alexander
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