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Re: [PATCH] i386: Add _startup_sbrk and _startup_fatal [BZ #21913]
- From: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
- To: libc-alpha at sourceware dot org
- Date: Mon, 7 Aug 2017 10:34:46 -0300
- Subject: Re: [PATCH] i386: Add _startup_sbrk and _startup_fatal [BZ #21913]
- Authentication-results: sourceware.org; auth=none
- References: <20170806222606.GA13700@gmail.com>
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;
> +}
>