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From: "dmalcolm at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug analyzer/108968] fanalyzer false positive with the
 uninitalised-ness of the stack pointer
Date: Thu, 02 Mar 2023 21:46:58 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108968

--- Comment #16 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
Minimized version of attachment 54572:

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
struct cpu_info {
  /* [...snip...] */
  struct vcpu *current_vcpu;
  /* [...snip...] */
};

struct vcpu
{
  /* [...snip...] */
  struct domain *domain;
  /* [...snip...] */
};

static __inline__ struct cpu_info *get_cpu_info_from_stack(unsigned long sp)
{
  return (struct cpu_info *)((sp | ((((1L) << 12) << 3) - 1)) + 1) - 1;
}

static __inline__ struct cpu_info *get_cpu_info(void)
{
  register unsigned long sp asm("rsp");
  return get_cpu_info_from_stack(sp);
}

void foo(char *other)
{
  char *ptr =3D ((void*)0);
  if ( ((get_cpu_info()->current_vcpu))->domain )
    ptr =3D other;
  asm volatile ("cmc");
  if ( ((get_cpu_info()->current_vcpu))->domain )
    ptr[0] =3D ~ptr[0];
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~=
~=