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Date: Fri, 13 Oct 2017 20:03:59 +0300
From: Alexander Popov <>
To: Ingo Molnar <>
 Laura Abbott <>, Mark Rutland <>,
 Ard Biesheuvel <>,
 Andy Lutomirski <>,,
 Linus Torvalds <>,
 Andy Lutomirski <>, Borislav Petkov <>,
 Thomas Gleixner <>, "H. Peter Anvin" <>,
 Peter Zijlstra <>
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,

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