elf: Remove -fno-tree-loop-distribute-patterns usage on dl-support

Besides the option being gcc specific, this approach is still fragile
and not future proof since we do not know if this will be the only
optimization option gcc will add that transforms loops to memset
(or any libcall).

This patch adds a new header, dl-symbol-redir-ifunc.h, that can b
used to redirect the compiler generated libcalls to port the generic
memset implementation if required.

Checked on x86_64-linux-gnu and aarch64-linux-gnu.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
This commit is contained in:
Adhemerval Zanella 2022-10-06 12:35:35 -03:00
parent c15318bfc5
commit 5355f9ca7b
10 changed files with 222 additions and 5 deletions

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@ -162,11 +162,6 @@ ifeq (yes,$(have-loop-to-function))
CFLAGS-rtld.c += -fno-tree-loop-distribute-patterns
endif
ifeq (yes,$(have-loop-to-function))
# Likewise, during static library startup, memset is not yet available.
CFLAGS-dl-support.c = -fno-tree-loop-distribute-patterns
endif
# Compile rtld itself without stack protection.
# Also compile all routines in the static library that are elided from
# the shared libc because they are in libc.a in the same way.

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@ -44,6 +44,7 @@
#include <dl-auxv.h>
#include <dl-find_object.h>
#include <array_length.h>
#include <dl-symbol-redir-ifunc.h>
extern char *__progname;
char **_dl_argv = &__progname; /* This is checked for some error messages. */

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@ -0,0 +1,24 @@
/* Symbol rediretion for loader/static initialization code.
Copyright (C) 2022 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
<https://www.gnu.org/licenses/>. */
#ifndef _DL_IFUNC_GENERIC_H
#define _DL_IFUNC_GENERIC_H
asm ("memset = __memset_generic");
#endif

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@ -0,0 +1,38 @@
/* Symbol rediretion for loader/static initialization code.
Copyright (C) 2022 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
<https://www.gnu.org/licenses/>. */
#ifndef _DL_IFUNC_GENERIC_H
#define _DL_IFUNC_GENERIC_H
/* The compiler might optimize loops or other constructs to library calls even
in freestanding mode. Although it is safe in most scenarios, on program
loading and static startup, iFUNC resolution might require other dynamic
relocation that are not yet done.
Instead of adding per-file compiler flags to avoid the libcall generation,
this header defines generic symbols that will be routed instead of the
default symbols name.
Each port can then make the required redirection to the expected generic
implementation if the symbol is provided as iFUNC, with a global definition
such as:
asm ("memset = __memset_generic");
*/
#endif

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@ -0,0 +1,24 @@
/* Symbol rediretion for loader/static initialization code.
Copyright (C) 2022 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
<https://www.gnu.org/licenses/>. */
#ifndef _DL_IFUNC_GENERIC_H
#define _DL_IFUNC_GENERIC_H
asm ("memset = __memset_ia32");
#endif

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@ -0,0 +1,24 @@
/* Symbol rediretion for loader/static initialization code.
Copyright (C) 2022 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
<https://www.gnu.org/licenses/>. */
#ifndef _DL_IFUNC_GENERIC_H
#define _DL_IFUNC_GENERIC_H
asm ("memset = __memset_power8");
#endif

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@ -0,0 +1,29 @@
/* Symbol rediretion for loader/static initialization code.
Copyright (C) 2022 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
<https://www.gnu.org/licenses/>. */
#ifndef _DL_IFUNC_GENERIC_H
#define _DL_IFUNC_GENERIC_H
#include <ifunc-memset.h>
#define IFUNC_SYMBOL_STR1(s) #s
#define IFUNC_SYMBOL_STR(s) IFUNC_SYMBOL_STR1(s)
asm ("memset = " IFUNC_SYMBOL_STR(MEMSET_DEFAULT));
#endif

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@ -0,0 +1,24 @@
/* Symbol rediretion for loader/static initialization code.
Copyright (C) 2022 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
<https://www.gnu.org/licenses/>. */
#ifndef _DL_IFUNC_GENERIC_H
#define _DL_IFUNC_GENERIC_H
asm ("memset = __memset_ultra1");
#endif

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@ -0,0 +1,24 @@
/* Symbol rediretion for loader/static initialization code.
Copyright (C) 2022 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
<https://www.gnu.org/licenses/>. */
#ifndef _DL_IFUNC_GENERIC_H
#define _DL_IFUNC_GENERIC_H
asm ("memset = __memset_ultra1");
#endif

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@ -0,0 +1,34 @@
/* Symbol rediretion for loader/static initialization code.
Copyright (C) 2022 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
<https://www.gnu.org/licenses/>. */
#ifndef _DL_IFUNC_GENERIC_H
#define _DL_IFUNC_GENERIC_H
#include <isa-level.h>
#if MINIMUM_X86_ISA_LEVEL >= 4
# define HAVE_MEMSET_IFUNC_GENERIC "__memset_evex_unaligned"
#elif MINIMUM_X86_ISA_LEVEL == 3
# define HAVE_MEMSET_IFUNC_GENERIC "__memset_avx2_unaligned"
#else
# define HAVE_MEMSET_IFUNC_GENERIC "__memset_sse2_unaligned"
#endif
asm ("memset = " HAVE_MEMSET_IFUNC_GENERIC);
#endif