From: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
To: Carlos O'Donell <carlos@redhat.com>
Cc: libc-alpha@sourceware.org, "H . J . Lu" <hjl.tools@gmail.com>
Subject: Re: [PATCH v4] elf: Remove -fno-tree-loop-distribute-patterns usage on dl-support
Date: Thu, 6 Oct 2022 12:25:35 -0300 [thread overview]
Message-ID: <356e0256-23db-80f1-8112-7a27cdbe5d74@linaro.org> (raw)
In-Reply-To: <YzxbxKIfS0QwXa4j@fedora>
On 04/10/22 13:13, Carlos O'Donell wrote:
> On Thu, Aug 11, 2022 at 09:19:09AM -0300, Adhemerval Zanella via Libc-alpha 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
>
> s/do not/do not know/g
>
Ok.
>> optimization option gcc will add that transform loops to memset
>
> s/transform/transforms/g
>
>> (or any libcall).
>>
>> This patch add a new header dl-symbol-hacks.h that can be used to
>
> s/add/adds/g
> s/dl-symbol-hacks.h/, dl-symbol-hacks.h,/g
Ack.
>
>> 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 ++++++++++++++++
>> sysdeps/aarch64/multiarch/dl-ifunc-generic.h | 24 ++++++++++++
>> sysdeps/generic/dl-ifunc-generic.h | 37 +++++++++++++++++++
>> .../i386/i686/multiarch/dl-ifunc-generic.h | 24 ++++++++++++
>> .../powerpc64/le/multiarch/dl-ifunc-generic.h | 24 ++++++++++++
>> sysdeps/s390/multiarch/dl-ifunc-generic.h | 29 +++++++++++++++
>> .../sparcv9/multiarch/dl-ifunc-generic.h | 24 ++++++++++++
>> .../sparc64/multiarch/dl-ifunc-generic.h | 24 ++++++++++++
>> sysdeps/x86_64/multiarch/dl-ifunc-generic.h | 32 ++++++++++++++++
>> 11 files changed, 250 insertions(+), 5 deletions(-)
>> create mode 100644 elf/dl-symbol-hacks.h
>> create mode 100644 sysdeps/aarch64/multiarch/dl-ifunc-generic.h
>> create mode 100644 sysdeps/generic/dl-ifunc-generic.h
>> create mode 100644 sysdeps/i386/i686/multiarch/dl-ifunc-generic.h
>> create mode 100644 sysdeps/powerpc/powerpc64/le/multiarch/dl-ifunc-generic.h
>> create mode 100644 sysdeps/s390/multiarch/dl-ifunc-generic.h
>> create mode 100644 sysdeps/sparc/sparc32/sparcv9/multiarch/dl-ifunc-generic.h
>> create mode 100644 sysdeps/sparc/sparc64/multiarch/dl-ifunc-generic.h
>> create mode 100644 sysdeps/x86_64/multiarch/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
>> -
>
> OK.
>
>> # 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>
>
> OK.
>
>>
>> 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..1b83b284dd
>> --- /dev/null
>> +++ b/elf/dl-symbol-hacks.h
>
> Bikeshed. Call it "dl-symbol-redir.h" since that's what it does.
Ack.
>
> Can we get rid of this?
>
> Can we flatten the headers out?
>
> At the very least I think we want to remove the typo-prone macro
> API and always define the macros.
>
>> @@ -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
>
> s/PLT throught/through the PLT via an/g
Ack.
>
>> + ifunc without relocations being processed. */
>> +#ifdef HAVE_MEMSET_IFUNC_GENERIC
>
> Typo unsafe macro API.
>
> Can we always define this? Use a generic definition?
The typo unsafe is done on purpose, since it is only an issue for ABI that
provides memset through ifunc. For other architectures there is no need
to use it (it will be "memset = memset").
Using a generic definition would require to replicate the asm logic on
each header. I think it should be ok.
>
>> +asm ("memset = " HAVE_MEMSET_IFUNC_GENERIC);
>> +#endif
>> +
>> +#endif
>> diff --git a/sysdeps/aarch64/multiarch/dl-ifunc-generic.h b/sysdeps/aarch64/multiarch/dl-ifunc-generic.h
>> new file mode 100644
>> index 0000000000..1278a06ff0
>> --- /dev/null
>> +++ b/sysdeps/aarch64/multiarch/dl-ifunc-generic.h
>
> Call it "dl-symbol-redir-ifunc.h"?
>
> This is not generic, it is aarch64 specific.
Ack.
>
>> @@ -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/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
>
> Call it "dl-symbol-redir-ifunc.h"?
Ack.
>
>> @@ -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.
>> + */
>> +
>
> Define the macro by default.
>
>> +#endif
>> diff --git a/sysdeps/i386/i686/multiarch/dl-ifunc-generic.h b/sysdeps/i386/i686/multiarch/dl-ifunc-generic.h
>> new file mode 100644
>> index 0000000000..a538931c03
>> --- /dev/null
>> +++ b/sysdeps/i386/i686/multiarch/dl-ifunc-generic.h
>
> Call it "dl-symbol-redir-ifunc.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_ia32"
>
> OK.
>
>> +
>> +#endif
>> diff --git a/sysdeps/powerpc/powerpc64/le/multiarch/dl-ifunc-generic.h b/sysdeps/powerpc/powerpc64/le/multiarch/dl-ifunc-generic.h
>> new file mode 100644
>> index 0000000000..1bf516494d
>> --- /dev/null
>> +++ b/sysdeps/powerpc/powerpc64/le/multiarch/dl-ifunc-generic.h
>
> Call it "dl-symbol-redir-ifunc.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_power8"
>
> OK.
>
>> +
>> +#endif
>> diff --git a/sysdeps/s390/multiarch/dl-ifunc-generic.h b/sysdeps/s390/multiarch/dl-ifunc-generic.h
>> new file mode 100644
>> index 0000000000..b0e5ed23aa
>> --- /dev/null
>> +++ b/sysdeps/s390/multiarch/dl-ifunc-generic.h
>
> Call it "dl-symbol-redir-ifunc.h"?
>
>> @@ -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)
>> +
>> +#define HAVE_MEMSET_IFUNC_GENERIC IFUNC_SYMBOL_STR(MEMSET_DEFAULT)
>
> OK. Ugh.
>
>> +
>> +#endif
>> diff --git a/sysdeps/sparc/sparc32/sparcv9/multiarch/dl-ifunc-generic.h b/sysdeps/sparc/sparc32/sparcv9/multiarch/dl-ifunc-generic.h
>> new file mode 100644
>> index 0000000000..417b24d2c1
>> --- /dev/null
>> +++ b/sysdeps/sparc/sparc32/sparcv9/multiarch/dl-ifunc-generic.h
>
> Call it "dl-symbol-redir-ifunc.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_ultra1"
>
> OK.
>
>> +
>> +#endif
>> diff --git a/sysdeps/sparc/sparc64/multiarch/dl-ifunc-generic.h b/sysdeps/sparc/sparc64/multiarch/dl-ifunc-generic.h
>> new file mode 100644
>> index 0000000000..417b24d2c1
>> --- /dev/null
>> +++ b/sysdeps/sparc/sparc64/multiarch/dl-ifunc-generic.h
>
> Call it "dl-symbol-redir-ifunc.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_ultra1"
>
> OK.
>
>> +
>> +#endif
>> diff --git a/sysdeps/x86_64/multiarch/dl-ifunc-generic.h b/sysdeps/x86_64/multiarch/dl-ifunc-generic.h
>> new file mode 100644
>> index 0000000000..7b7cf1c3d6
>> --- /dev/null
>> +++ b/sysdeps/x86_64/multiarch/dl-ifunc-generic.h
>
> Call it "dl-symbol-redir-ifunc.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
>
> OK.
>
>> +
>> +#endif
>> --
>> 2.34.1
>>
>
prev parent reply other threads:[~2022-10-06 15:25 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-11 12:19 Adhemerval Zanella
2022-08-11 14:32 ` Andreas Schwab
2022-08-11 15:48 ` Adhemerval Zanella Netto
2022-08-11 14:33 ` Andreas Schwab
2022-08-22 13:55 ` Adhemerval Zanella Netto
2022-09-20 19:06 ` Adhemerval Zanella Netto
2022-10-04 16:13 ` Carlos O'Donell
2022-10-06 15:25 ` Adhemerval Zanella Netto [this message]
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