[Mesa-dev] [PATCH] Disable the code that allocates W|X memory on OpenBSD

[Emil Velikov]

On 1 September 2016 at 18:23, Jonathan Gray <jsg at jsg.id.au> wrote:
> OpenBSD now has strict W^X enforcement.  Processes that violate
> the policy get killed by the kernel.  Don't attempt to use
> executable memory on OpenBSD to avoid this.
>
> Patch from Mark Kettenis.
>

> --- a/src/gallium/auxiliary/rtasm/rtasm_execmem.c
> +++ b/src/gallium/auxiliary/rtasm/rtasm_execmem.c
> @@ -69,6 +69,16 @@ static struct mem_block *exec_heap = NULL;
>  static unsigned char *exec_mem = NULL;
>
>
> +#ifdef __OpenBSD__
> +
> +static int
> +init_heap(void)
> +{
> +   return 0;
> +}
Afaict this is equivalent to using the #else path in translate_see.c.
In general I'm wondering if we can/should not have a configure toggle
for this. Then again please look below.


> --- a/src/mapi/u_execmem.c
> +++ b/src/mapi/u_execmem.c
> @@ -45,8 +45,15 @@ static unsigned int head = 0;
>
>  static unsigned char *exec_mem = (unsigned char *)0;
>
> +#if defined(__OpenBSD__)
>
> -#if defined(__linux__) || defined(__OpenBSD__) || defined(_NetBSD__) || defined(__sun) || defined(__HAIKU__)
> +static int
> +init_map(void)
> +{
> +  return 0;
> +}
> +
And this one to --disable-glx-tls and/or --disable-asm. Which reminds
me of - have you guys tried enabling either/both of them. Has there
been (m)any issues ?

For a long while the intent has been to use --enable-glx-tls by
default and kill off the other codepaths. But with the write xor
execute policy, it's going to be (close to) impossible.

Have you guys considered a way to disable the restriction for usecases
that need the behaviour ?


Thanks
Emil