[PATCH v2] elf: Remove -fno-tree-loop-distribute-patterns usage on dl-support
H.J. Lu
hjl.tools@gmail.com
Wed Aug 10 17:24:36 GMT 2022
On Wed, Aug 10, 2022 at 8:40 AM Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
>
> Besides the option being gcc specific, this approach is still fragile
> and not future proof since we do not if this will be the only
> optimization option gcc will add that transform loops to memset
> (or any libcall).
>
> This patch add a new header dl-symbol-hacks.h that can be used to
> redirect the compiler generated libcalls to port specific string
> implementatation if required (defined by dl-ifunc-generic.h).
>
> Checked on x86_64-linux-gnu and aarch64-linux-gnu.
> ---
> elf/Makefile | 5 ---
> elf/dl-support.c | 1 +
> elf/dl-symbol-hacks.h | 31 ++++++++++++++++
> elf/dl-tunables.c | 1 +
> sysdeps/generic/dl-ifunc-generic.h | 37 +++++++++++++++++++
> .../sysv/linux/aarch64/dl-ifunc-generic.h | 24 ++++++++++++
> .../unix/sysv/linux/i386/dl-ifunc-generic.h | 26 +++++++++++++
> .../sysv/linux/powerpc/dl-ifunc-generic.h | 28 ++++++++++++++
> .../unix/sysv/linux/s390/dl-ifunc-generic.h | 31 ++++++++++++++++
> .../unix/sysv/linux/sparc/dl-ifunc-generic.h | 26 +++++++++++++
> .../unix/sysv/linux/x86_64/dl-ifunc-generic.h | 32 ++++++++++++++++
> 11 files changed, 237 insertions(+), 5 deletions(-)
> create mode 100644 elf/dl-symbol-hacks.h
> create mode 100644 sysdeps/generic/dl-ifunc-generic.h
> create mode 100644 sysdeps/unix/sysv/linux/aarch64/dl-ifunc-generic.h
> create mode 100644 sysdeps/unix/sysv/linux/i386/dl-ifunc-generic.h
> create mode 100644 sysdeps/unix/sysv/linux/powerpc/dl-ifunc-generic.h
> create mode 100644 sysdeps/unix/sysv/linux/s390/dl-ifunc-generic.h
> create mode 100644 sysdeps/unix/sysv/linux/sparc/dl-ifunc-generic.h
> create mode 100644 sysdeps/unix/sysv/linux/x86_64/dl-ifunc-generic.h
>
> diff --git a/elf/Makefile b/elf/Makefile
> index 3386f0ce77..4b992bd348 100644
> --- a/elf/Makefile
> +++ b/elf/Makefile
> @@ -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.
> diff --git a/elf/dl-support.c b/elf/dl-support.c
> index 4af0b5b2ce..6d1996ae6e 100644
> --- a/elf/dl-support.c
> +++ b/elf/dl-support.c
> @@ -44,6 +44,7 @@
> #include <dl-auxv.h>
> #include <dl-find_object.h>
> #include <array_length.h>
> +#include <dl-symbol-hacks.h>
>
> extern char *__progname;
> char **_dl_argv = &__progname; /* This is checked for some error messages. */
> diff --git a/elf/dl-symbol-hacks.h b/elf/dl-symbol-hacks.h
> new file mode 100644
> index 0000000000..6b9d24ed03
> --- /dev/null
> +++ b/elf/dl-symbol-hacks.h
> @@ -0,0 +1,31 @@
> +/* 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_SYMBOL_HACKS_H
> +#define _DL_SYMBOL_HACKS_H
> +
> +#include <dl-ifunc-generic.h>
> +
> +/* Some compiler optimizations may transform loops into memset/memmove
> + calls and without proper redirection it might call PLT throught
> + ifunc without relocations being processed. */
> +#if !IS_IN(rtld) && defined HAVE_MEMSET_IFUNC_GENERIC
> +asm ("memset = " HAVE_MEMSET_IFUNC_GENERIC);
> +#endif
> +
> +#endif
> diff --git a/elf/dl-tunables.c b/elf/dl-tunables.c
> index 8e7ee9df10..c797484522 100644
> --- a/elf/dl-tunables.c
> +++ b/elf/dl-tunables.c
> @@ -32,6 +32,7 @@
> #include <ldsodefs.h>
> #include <array_length.h>
> #include <dl-minimal-malloc.h>
> +#include <dl-symbol-hacks.h>
>
> #define TUNABLES_INTERNAL 1
> #include "dl-tunables.h"
> diff --git a/sysdeps/generic/dl-ifunc-generic.h b/sysdeps/generic/dl-ifunc-generic.h
> new file mode 100644
> index 0000000000..5e1d5c1fd8
> --- /dev/null
> +++ b/sysdeps/generic/dl-ifunc-generic.h
> @@ -0,0 +1,37 @@
> +/* 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 define the following macro to the expected generic
> + implementation if the symbol is provided as iFUNC:
> +
> + HAVE_MEMSET_IFUNC_GENERIC - the generic memset call.
> + */
> +
> +#endif
> diff --git a/sysdeps/unix/sysv/linux/aarch64/dl-ifunc-generic.h b/sysdeps/unix/sysv/linux/aarch64/dl-ifunc-generic.h
> new file mode 100644
> index 0000000000..1278a06ff0
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/aarch64/dl-ifunc-generic.h
> @@ -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
> +
> +#define HAVE_MEMSET_IFUNC_GENERIC "__memset_generic"
> +
> +#endif
> diff --git a/sysdeps/unix/sysv/linux/i386/dl-ifunc-generic.h b/sysdeps/unix/sysv/linux/i386/dl-ifunc-generic.h
> new file mode 100644
> index 0000000000..c8e294b3c9
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/i386/dl-ifunc-generic.h
> @@ -0,0 +1,26 @@
> +/* 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
> +
> +#ifdef USE_MULTIARCH
> +# define HAVE_MEMSET_IFUNC_GENERIC "__memset_ia32"
> +#endif
> +
> +#endif
This file should be in sysdeps/i386/i686/multiarch.
> diff --git a/sysdeps/unix/sysv/linux/powerpc/dl-ifunc-generic.h b/sysdeps/unix/sysv/linux/powerpc/dl-ifunc-generic.h
> new file mode 100644
> index 0000000000..b0f9401670
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/powerpc/dl-ifunc-generic.h
> @@ -0,0 +1,28 @@
> +/* 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
> +
> +/* powerpc and powerpc64 provides the default memset as 'memset', so
> + no need to redirect it. */
> +#if defined USE_MULTIARCH && defined __powerpc64__ && _CALL_ELF != 2
> +# define HAVE_MEMSET_IFUNC_GENERIC "__memset_power8"
> +#endif
> +
> +#endif
> diff --git a/sysdeps/unix/sysv/linux/s390/dl-ifunc-generic.h b/sysdeps/unix/sysv/linux/s390/dl-ifunc-generic.h
> new file mode 100644
> index 0000000000..f664ac07a7
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/s390/dl-ifunc-generic.h
> @@ -0,0 +1,31 @@
> +/* 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
> +
> +#ifdef USE_MULTIARCH
> +# include <ifunc-memset.h>
> +
> +# define IFUNC_SYMBOL_STR1(s) #s
> +# define IFUNC_SYMBOL_STR(s) IFUNC_SYMBOL_STR1(s)
> +
> +# define HAVE_MEMSET_IFUNC_GENERIC IFUNC_SYMBOL_STR(MEMSET_DEFAULT)
> +#endif
> +
> +#endif
> diff --git a/sysdeps/unix/sysv/linux/sparc/dl-ifunc-generic.h b/sysdeps/unix/sysv/linux/sparc/dl-ifunc-generic.h
> new file mode 100644
> index 0000000000..86815317a9
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/sparc/dl-ifunc-generic.h
> @@ -0,0 +1,26 @@
> +/* 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
> +
> +#ifdef USE_MULTIARCH
> +# define HAVE_MEMSET_IFUNC_GENERIC "__memset_ultra1"
> +#endif
> +
> +#endif
> diff --git a/sysdeps/unix/sysv/linux/x86_64/dl-ifunc-generic.h b/sysdeps/unix/sysv/linux/x86_64/dl-ifunc-generic.h
> new file mode 100644
> index 0000000000..7b7cf1c3d6
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/x86_64/dl-ifunc-generic.h
> @@ -0,0 +1,32 @@
> +/* 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
> +
> +#endif
> --
> 2.34.1
>
This file should be in sysdeps/x86_64/multiarch and the generic
memset should follow sysdeps/x86_64/memset.S:
#define DEFAULT_IMPL_V1 "multiarch/memset-sse2-unaligned-erms.S"
#define DEFAULT_IMPL_V3 "multiarch/memset-avx2-unaligned-erms.S"
#define DEFAULT_IMPL_V4 "multiarch/memset-evex-unaligned-erms.S"
--
H.J.
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