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Re: [PATCH] i386: Add _startup_sbrk and _startup_fatal [BZ #21913]



On 06/08/2017 19:26, H.J. Lu wrote:
[..]
> diff --git a/sysdeps/generic/startup.h b/sysdeps/generic/startup.h
> new file mode 100644
> index 0000000000..aa63b31181
> --- /dev/null
> +++ b/sysdeps/generic/startup.h
> @@ -0,0 +1,30 @@
> +/* Generic definitions of functions used by static libc main startup.
> +   Copyright (C) 2017 Free Software Foundation, Inc.
> +   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
> +   <http://www.gnu.org/licenses/>.  */
> +
> +static inline void *
> +_startup_sbrk (intptr_t __delta)
> +{
> +  return __sbrk (__delta);
> +}
> +
> +__attribute__ ((__noreturn__))
> +static inline void
> +_startup_fatal (const char *__message)
> +{
> +  __libc_fatal (__message);
> +}

I think there is no need of underlying prefixes for inline functions.

> diff --git a/sysdeps/unix/sysv/linux/i386/Makefile b/sysdeps/unix/sysv/linux/i386/Makefile
> index 4080b8c966..cefa1511f6 100644
> --- a/sysdeps/unix/sysv/linux/i386/Makefile
> +++ b/sysdeps/unix/sysv/linux/i386/Makefile
> @@ -31,6 +31,10 @@ sysdep_routines += divdi3
>  shared-only-routines += divdi3
>  CPPFLAGS-divdi3.c = -Din_divdi3_c
>  endif
> +ifneq (,$(pic-default))
> +sysdep_routines += startup_sbrk
> +static-only-routines += startup_sbrk
> +endif
>  endif
>  
>  ifeq ($(subdir),nptl)
> diff --git a/sysdeps/unix/sysv/linux/i386/startup.h b/sysdeps/unix/sysv/linux/i386/startup.h
> new file mode 100644
> index 0000000000..ccfba45153
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/i386/startup.h
> @@ -0,0 +1,38 @@
> +/* Linux/i386 definitions of functions used by static libc main startup.
> +   Copyright (C) 2017 Free Software Foundation, Inc.
> +   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
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#if defined PIC && !defined SHARED

We already check and set build-pie-default on configure/make.in, wouldn't
be useful if we also define a BUILD_PIE as well?

> +# include <abort-instr.h>
> +
> +/* Can't use "call *%gs:SYSINFO_OFFSET" during statup in static PIE.  */
> +# define I386_USE_SYSENTER 0
> +
> +extern void * _startup_sbrk (intptr_t) attribute_hidden;
> +
> +__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 ();
> +}

Maybe also provide a __writev using 'int $0x80' so it can use _dl_debug_printf?

> +#else
> +# include_next <startup.h>
> +#endif
> diff --git a/sysdeps/unix/sysv/linux/i386/startup_sbrk.c b/sysdeps/unix/sysv/linux/i386/startup_sbrk.c
> new file mode 100644
> index 0000000000..8239938ddf
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/i386/startup_sbrk.c

I am not very found of replicating generic code, but for this case it seems
that i386 version seems to have too many specific cases that I am not sure
if it worth trying to consolidate it.

> @@ -0,0 +1,67 @@
> +/* Linux/i386 definitions of _startup_sbrk.
> +   Copyright (C) 2017 Free Software Foundation, Inc.
> +   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
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#include <unistd.h>
> +#include <startup.h>
> +#include <errno.h>
> +#include <sysdep.h>
> +
> +/* Defined in brk.c.  */
> +extern void *__curbrk attribute_hidden;
> +
> +static int
> +startup_brk (void *addr)
> +{
> +  INTERNAL_SYSCALL_DECL (err);
> +  void *newbrk = (void *) INTERNAL_SYSCALL_CALL (brk, err, addr);
> +  __curbrk = newbrk;
> +  if (newbrk < addr)
> +    _startup_fatal (NULL);
> +  return 0;
> +}
> +
> +/* Extend the process's data space by INCREMENT.  If INCREMENT is negative,
> +   shrink data space by - INCREMENT.  Return start of new space allocated,
> +   or call _startup_fatal for errors.  */
> +
> +void *
> +_startup_sbrk (intptr_t increment)
> +{
> +  void *oldbrk;
> +
> +  /* Update __curbrk from the kernel's brk value.  That way two separate
> +     instances of __brk and __sbrk can share the heap, returning
> +     interleaved pieces of it.  */
> +  if (__curbrk == NULL)
> +    if (startup_brk (0) < 0)		/* Initialize the break.  */
> +      _startup_fatal (NULL);
> +
> +  if (increment == 0)
> +    return __curbrk;
> +
> +  oldbrk = __curbrk;
> +  if (increment > 0
> +      ? ((uintptr_t) oldbrk + (uintptr_t) increment < (uintptr_t) oldbrk)
> +      : ((uintptr_t) oldbrk < (uintptr_t) -increment))
> +    _startup_fatal (NULL);
> +
> +  if (startup_brk (oldbrk + increment) < 0)
> +    _startup_fatal (NULL);
> +
> +  return oldbrk;
> +}
> 


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