[PATCH] x86: Remove ARCH_CET_LEGACY_BITMAP [BZ #25397]

[Florian Weimer]

* H. J. Lu:

> diff --git a/sysdeps/x86/dl-cet.c b/sysdeps/x86/dl-cet.c
> index ca3b5849bc..2be7a3a49f 100644
> --- a/sysdeps/x86/dl-cet.c
> +++ b/sysdeps/x86/dl-cet.c

> +	      /* IBT is enabled only if it is enabled in executable as
> +		 well as all shared objects.  */
> +	      enable_ibt &= (enable_ibt_type == CET_ALWAYS_ON
> +			     || (l->l_cet & lc_ibt) != 0);

As a general comment, I think we should add more logging as to way
processes lose protection.  But that does not need to happen with this
patch.

> +		  /* When IBT is enabled, we can't dlopening a shared
> +		     object without IBT.  */

“we cannot dlopen”

> +		  if (enable_ibt != ibt_enabled)
> +		    _dl_signal_error (EINVAL, l->l_name, "dlopen",
> +				      N_("indirect branch tracking isn't enabled"));

I think the error message should say *where* indirect branch tracking
is not enabled.  I assume this is a property of the loaded object.


> +		  /* When SHSTK is enabled, we can't dlopening a shared
> +		     object without SHSTK.  */
> +		  if (enable_shstk != shstk_enabled)
> +		    _dl_signal_error (EINVAL, l->l_name, "dlopen",
> +				      N_("shadow stack isn't enabled"));

See above.

> diff --git a/sysdeps/x86/tst-cet-legacy-7.c b/sysdeps/x86/tst-cet-legacy-7.c
> new file mode 100644
> index 0000000000..e6f5d6f145
> --- /dev/null
> +++ b/sysdeps/x86/tst-cet-legacy-7.c

> +  funcp = mmap (NULL, 0x1000, PROT_EXEC | PROT_READ | PROT_WRITE,
> +		MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
> +  if (funcp == MAP_FAILED)
> +    FAIL_EXIT1 ("mmap failed (errno=%d)", errno);

You could use xmmap here.

Rest of the patch looks okay to me.