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Subject: Re: [PATCH 2/4] Initialize tunable list with the GLIBC_TUNABLES
 environment variable
To: Siddhesh Poyarekar <siddhesh@sourceware.org>, libc-alpha@sourceware.org
References: <1483070938-2308-1-git-send-email-siddhesh@sourceware.org>
 <1483070938-2308-3-git-send-email-siddhesh@sourceware.org>
Cc: carlos@redhat.com
From: Florian Weimer <fweimer@redhat.com>
Message-ID: <3abae843-c36e-171a-b412-2fe1b76685e9@redhat.com>
Date: Fri, 30 Dec 2016 09:50:00 -0000
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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