[Qemu-commits] [qemu/qemu] 63678e: configure: add option to disable -fstack-protector...

[GitHub]

  Branch: refs/heads/master
  Home:   https://github.com/qemu/qemu
  Commit: 63678e17cf399ff81b93417fe7bee8d6ef6b6b1b
      
https://github.com/qemu/qemu/commit/63678e17cf399ff81b93417fe7bee8d6ef6b6b1b
  Author: Steven Noonan <address@hidden>
  Date:   2014-03-31 (Mon, 31 Mar 2014)

  Changed paths:
    M configure

  Log Message:
  -----------
  configure: add option to disable -fstack-protector flags

The -fstack-protector flag family is useful for ensuring safety and for
debugging, but has a performance impact. Here are some boot time comparisons of
the various versions of -fstack-protector using qemu-system-arm on an x86_64
host:

    # -fstack-protector-all
    Startup finished in 1.810s (kernel) + 12.331s (initrd) + 49.016s 
(userspace) = 1min 3.159s
    Startup finished in 1.801s (kernel) + 12.287s (initrd) + 47.925s 
(userspace) = 1min 2.013s
    Startup finished in 1.812s (kernel) + 12.302s (initrd) + 47.995s 
(userspace) = 1min 2.111s

    # -fstack-protector-strong
    Startup finished in 1.744s (kernel) + 11.223s (initrd) + 44.688s 
(userspace) = 57.657s
    Startup finished in 1.721s (kernel) + 11.222s (initrd) + 44.194s 
(userspace) = 57.138s
    Startup finished in 1.693s (kernel) + 11.250s (initrd) + 44.426s 
(userspace) = 57.370s

    # -fstack-protector
    Startup finished in 1.705s (kernel) + 11.409s (initrd) + 43.563s 
(userspace) = 56.677s
    Startup finished in 1.877s (kernel) + 11.137s (initrd) + 43.719s 
(userspace) = 56.734s
    Startup finished in 1.708s (kernel) + 11.141s (initrd) + 43.628s 
(userspace) = 56.478s

    # no stack protector
    Startup finished in 1.743s (kernel) + 11.190s (initrd) + 43.709s 
(userspace) = 56.643s
    Startup finished in 1.763s (kernel) + 11.216s (initrd) + 43.767s 
(userspace) = 56.747s
    Startup finished in 1.711s (kernel) + 11.283s (initrd) + 43.878s 
(userspace) = 56.873s

This patch introduces a configure option to disable the stack protector
entirely, and conditional stack protector flag selection (in order,
based on availability): -fstack-protector-strong, -fstack-protector-all,
no stack protector.

Signed-off-by: Steven Noonan <address@hidden>
Cc: Anthony Liguori <address@hidden>
Reviewed-by: Stefan Weil <address@hidden>
[Prefer -fstack-protector-all to -fstack-protector, suggested by
 Laurent Desnogues. - Paolo]
Signed-off-by: Paolo Bonzini <address@hidden>
Signed-off-by: Peter Maydell <address@hidden>