Re: [PATCH 1/5] Linux: Implement a useful version of _startup_fatal

["H.J. Lu" <hjl.tools@gmail.com>]

On Mon, May 2, 2022 at 12:16 PM Florian Weimer via Libc-alpha
<libc-alpha@sourceware.org> wrote:
>
> ---
>  sysdeps/unix/sysv/linux/i386/startup.h | 17 ++----------
>  sysdeps/unix/sysv/linux/startup.h      | 38 ++++++++++++++++++++++++++
>  2 files changed, 40 insertions(+), 15 deletions(-)
>  create mode 100644 sysdeps/unix/sysv/linux/startup.h
>
> diff --git a/sysdeps/unix/sysv/linux/i386/startup.h b/sysdeps/unix/sysv/linux/i386/startup.h
> index 67c9310f3a..694d6cf4e7 100644
> --- a/sysdeps/unix/sysv/linux/i386/startup.h
> +++ b/sysdeps/unix/sysv/linux/i386/startup.h
> @@ -19,19 +19,6 @@
>  #if BUILD_PIE_DEFAULT
>  /* Can't use "call *%gs:SYSINFO_OFFSET" during statup in static PIE.  */
>  # define I386_USE_SYSENTER 0
> -
> -# include <sysdep.h>
> -# include <abort-instr.h>
> -
> -__attribute__ ((__noreturn__))
> -static inline void
> -_startup_fatal (const char *message __attribute__ ((unused)))
> -{
> -  /* This is only called very early during startup in static PIE.
> -     FIXME: How can it be improved?  */
> -  ABORT_INSTRUCTION;
> -  __builtin_unreachable ();
> -}
> -#else
> -# include_next <startup.h>
>  #endif
> +
> +#include_next <startup.h>
> diff --git a/sysdeps/unix/sysv/linux/startup.h b/sysdeps/unix/sysv/linux/startup.h
> new file mode 100644
> index 0000000000..a5de941759
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/startup.h
> @@ -0,0 +1,38 @@
> +/* Linux definitions of functions used by static libc main startup.
> +   Copyright (C) 2017-2022 Free Software Foundation, Inc.
                             Shouldn't it just be 2022?
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#ifdef SHARED
> +# include_next <startup.h>
> +#else
> +# include <sysdep.h>
> +
> +/* Avoid a run-time invocation of strlen.  */
> +#define _startup_fatal(message)                                         \

Is this needed only for static PIE?

> +  do                                                                    \
> +    {                                                                   \
> +      size_t message_length = __builtin_strlen (message);               \
> +      if (! __builtin_constant_p (message_length))                      \
> +        {                                                               \
> +          extern void _startup_fatal_not_constant (void);               \
> +          _startup_fatal_not_constant ();                               \
> +        }                                                               \
> +      INTERNAL_SYSCALL_CALL (write, STDERR_FILENO, message, message_length); \
> +      INTERNAL_SYSCALL_CALL (exit_group, 127);                          \
> +    }                                                                   \
> +  while (0)
> +#endif  /* !SHARED */
> --
> 2.35.1
>
>


-- 
H.J.