Re: [PATCH 2/4] Initialize tunable list with the GLIBC_TUNABLES environment variable

[Florian Weimer <fweimer at redhat dot com>]

On 12/30/2016 05:08 AM, Siddhesh Poyarekar wrote:
> +  /* Bare mmap system call to avoid setting errno which may not be available
> +     yet.  */
> +  INTERNAL_SYSCALL_DECL (err);
> +  char *out = (char *) INTERNAL_SYSCALL_CALL (mmap, err, NULL, i, PROT_READ | PROT_WRITE,
> +				     MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
> +  if (INTERNAL_SYSCALL_ERROR_P (out, err))
> +    return NULL;

INTERNAL_SYSCALL is not available in generic code.

You should use sbrk (like the TCB allocation in the startup code; it 
would also reduce wasted memory), or mmap with a comment indicating that 
this will crash if mmap updates errno.  (I believe the comment in the 
startup code about mmap is wrong.)

Thanks,
Florian