Re: [patch] HEAD patch to add -fstack-protector support for x86-64 kernels

[Paolo Bonzini <bonzini at gnu dot org>]

Arjan van de Ven wrote:
> Hi,
>
> The patch below (bootstrapped) adds support for (linux) kernel-side use
> of -fstack-protector. The kernel uses a different segment register (gs
> instead of fs) for the local storage, so for this to work gcc needs to
> emit gs: relative code for -fstack-protector for the -mcmodel=kernel
> code. I've also attached a testcase for this patch to go with this. The
> patch is against the SVN tree from about 2 hours ago.

You do not need a pattern.  Instead, in the stack_tls_protect_set_di 
pattern you can have as the code template.

{
  if (ix86_cmodel != CM_KERNEL)
    return "mov{q}\t{%%fs:%P1, %2|%2, QWORD PTR %%fs:%P1}\;mov{q}\t{%2, 
%0|%0, %2}\;xor{l}\t%k2, %k2"
  else
    return "mov{q}\t{%%gs:%P1, %2|%2, QWORD PTR %%gs:%P1}\;mov{q}\t{%2, 
%0|%0, %2}\;xor{l}\t%k2, %k2"
}

Paolo