[PATCH v3] elf: Extend glibc.rtld.execstack tunable to force executable stack (BZ 32653)

[Florian Weimer]

* Adhemerval Zanella:

> --- a/manual/tunables.texi
> +++ b/manual/tunables.texi
> @@ -365,8 +365,11 @@ change the main stack permission if kernel starts with a non-executable stack.
>  The @code{glibc.rtld.execstack} can be used to control whether an executable
>  stack is allowed from the main program.  Setting the value to @code{0} disables
>  the ABI auto-negotiation (meaning no executable stacks even if the ABI or ELF
> -header requires it), while @code{1} enables auto-negotiation (although the
> -program might not need an executable stack).
> +header requires it), @code{1} enables auto-negotiation (although the program
> +might not need an executable stack), while @code{2} forces and executable

forces an[] executable

> +stack during initialization (this is provide for compatibility reasons, where

stack [at process start].  [T]his is provide[d] for compatibility[], [when]

> +the program requires to dynamically load modules with executable stacks with
> +@code{dlopen}).

the program dynamically loads modules with @code{dlopen} which require
an executable stack.

>  When executable stacks are not allowed, and if the main program requires it,
>  the loader will fail with an error message.
> @@ -380,7 +383,8 @@ of hardware capabilities and kernel configuration.
>  @strong{NB:} Trying to load a dynamic shared library with @code{dlopen} or
>  @code{dlmopen} that requires an executable stack will always fail if the
>  main program does not require an executable stack at loading time.  This
> -is enforced regardless of the tunable value.
> +can be disable by setting the tunable to @code{2}, where the stack is

can be [worked around]

> +always executable.
>  @end deftp

> diff --git a/sysdeps/unix/sysv/linux/dl-execstack.c b/sysdeps/unix/sysv/linux/dl-execstack.c
> index 9791b339ca..338c642040 100644
> --- a/sysdeps/unix/sysv/linux/dl-execstack.c
> +++ b/sysdeps/unix/sysv/linux/dl-execstack.c
> @@ -17,6 +17,7 @@
>     <https://www.gnu.org/licenses/>.  */
>  
>  #include <ldsodefs.h>
> +#include <dl-tunables.h>
>  
>  int
>  _dl_make_stack_executable (void **stack_endp)

Is this steal needed?

Thanks,
Florian