[PATCH v9 1/6] riscv: Add Linux hwprobe syscall support
Adhemerval Zanella Netto
adhemerval.zanella@linaro.org
Wed Dec 6 17:22:58 GMT 2023
On 30/11/23 15:32, Evan Green wrote:
> Add awareness and a thin wrapper function around a new Linux system call
> that allows callers to get architecture and microarchitecture
> information about the CPUs from the kernel. This can be used to
> do things like dynamically choose a memcpy implementation.
>
> Signed-off-by: Evan Green <evan@rivosinc.com>
> Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>
> ---
>
> Changes in v9:
> - Alphabetize new entries in libc.abilist (to pass checks)
>
> Changes in v8:
> - Fix missed 2.39 in abilists (Joseph)
> - Just return -r (Florian)
>
> Changes in v7:
> - Bumped Versions up to 2.39 (Joseph)
> - Used INTERNAL_SYSCALL_CALL, and return positive errno to match
> pthreads API (Florian).
> - Remove __THROW since it creates a warning in combination with the
> fortified access decorators.
>
> Changes in v6:
> - Prefixed __riscv_hwprobe() parameters names with __ to avoid user
> macro namespace pollution (Joseph)
>
> Changes in v4:
> - Remove __USE_GNU (Florian)
> - __nonnull, __wur, __THROW, and __fortified_attr_access decorations
> (Florian)
> - change long to long int (Florian)
> - Fix comment formatting (Florian)
> - Update backup kernel header content copy.
> - Fix function declaration formatting (Florian)
> - Changed export versions to 2.38
>
> Changes in v3:
> - Update argument types to match v4 kernel interface
>
> Changes in v2:
> - hwprobe.h: Use __has_include and duplicate Linux content to make
> compilation work when Linux headers are absent (Adhemerval)
> - hwprobe.h: Put declaration under __USE_GNU (Adhemerval)
> - Use INLINE_SYSCALL_CALL (Adhemerval)
> - Update versions
> - Update UNALIGNED_MASK to match kernel v3 series.
>
> sysdeps/unix/sysv/linux/riscv/Makefile | 4 +-
> sysdeps/unix/sysv/linux/riscv/Versions | 3 +
> sysdeps/unix/sysv/linux/riscv/hwprobe.c | 36 ++++++++++
> .../unix/sysv/linux/riscv/rv32/libc.abilist | 1 +
> .../unix/sysv/linux/riscv/rv64/libc.abilist | 1 +
> sysdeps/unix/sysv/linux/riscv/sys/hwprobe.h | 72 +++++++++++++++++++
> 6 files changed, 115 insertions(+), 2 deletions(-)
> create mode 100644 sysdeps/unix/sysv/linux/riscv/hwprobe.c
> create mode 100644 sysdeps/unix/sysv/linux/riscv/sys/hwprobe.h
>
> diff --git a/sysdeps/unix/sysv/linux/riscv/Makefile b/sysdeps/unix/sysv/linux/riscv/Makefile
> index 4b6eacb32f..45cc29e40d 100644
> --- a/sysdeps/unix/sysv/linux/riscv/Makefile
> +++ b/sysdeps/unix/sysv/linux/riscv/Makefile
> @@ -1,6 +1,6 @@
> ifeq ($(subdir),misc)
> -sysdep_headers += sys/cachectl.h
> -sysdep_routines += flush-icache
> +sysdep_headers += sys/cachectl.h sys/hwprobe.h
> +sysdep_routines += flush-icache hwprobe
For newer Makefile definitions, add one entr per line:
sysdep_headers += \
sys/cachectl.h \
sys/hwprobe.h \
# sysdep_headers
sysdep_routines += \
flush-icache \
hwprobe \
# sysdep_routines
> endif
>
> ifeq ($(subdir),stdlib)
> diff --git a/sysdeps/unix/sysv/linux/riscv/Versions b/sysdeps/unix/sysv/linux/riscv/Versions
> index 5625d2a0b8..8717b62a4a 100644
> --- a/sysdeps/unix/sysv/linux/riscv/Versions
> +++ b/sysdeps/unix/sysv/linux/riscv/Versions
> @@ -8,4 +8,7 @@ libc {
> GLIBC_2.27 {
> __riscv_flush_icache;
> }
> + GLIBC_2.39 {
> + __riscv_hwprobe;
> + }
> }
> diff --git a/sysdeps/unix/sysv/linux/riscv/hwprobe.c b/sysdeps/unix/sysv/linux/riscv/hwprobe.c
> new file mode 100644
> index 0000000000..e28194e344
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/riscv/hwprobe.c
> @@ -0,0 +1,36 @@
> +/* RISC-V hardware feature probing support on Linux
> + Copyright (C) 2023 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/>. */
> +
> +#include <sys/syscall.h>
> +#include <sys/hwprobe.h>
> +#include <sysdep.h>
> +#include <sysdep-vdso.h>
> +
> +int __riscv_hwprobe (struct riscv_hwprobe *__pairs, size_t __pair_count,
> + size_t __cpu_count, unsigned long int *__cpus,
> + unsigned int __flags)
> +{
> + int r;
> +
> + r = INTERNAL_SYSCALL_CALL (riscv_hwprobe, 5, __pairs, __pair_count,
> + __cpu_count, __cpus, __flags);
You do not need to pass the number of argument with INTERNAL_SYSCALL_CALL
(that why the macro exists). Just issue:
r = INTERNAL_SYSCALL_CALL (riscv_hwprobe, __pairs, __pair_count,
__cpu_count, __cpus, __flags);
The code above will pass '5' as '__pairs' argument and so forth, which
also makes me wonder why it has not failed in your testing.
Also, there is no need to double underscore in the implementation itself.
> +
> + /* Negate negative errno values to match pthreads API. */
> + return -r;
> +}
> diff --git a/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist b/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist
> index a13c484582..6c96e25552 100644
> --- a/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist
> +++ b/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist
> @@ -2436,6 +2436,7 @@ GLIBC_2.38 strlcat F
> GLIBC_2.38 strlcpy F
> GLIBC_2.38 wcslcat F
> GLIBC_2.38 wcslcpy F
> +GLIBC_2.39 __riscv_hwprobe F
> GLIBC_2.39 pidfd_getpid F
> GLIBC_2.39 pidfd_spawn F
> GLIBC_2.39 pidfd_spawnp F
> diff --git a/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist b/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
> index cf65d8d6d4..225278807b 100644
> --- a/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
> +++ b/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
> @@ -2636,6 +2636,7 @@ GLIBC_2.38 strlcat F
> GLIBC_2.38 strlcpy F
> GLIBC_2.38 wcslcat F
> GLIBC_2.38 wcslcpy F
> +GLIBC_2.39 __riscv_hwprobe F
> GLIBC_2.39 pidfd_getpid F
> GLIBC_2.39 pidfd_spawn F
> GLIBC_2.39 pidfd_spawnp F
> diff --git a/sysdeps/unix/sysv/linux/riscv/sys/hwprobe.h b/sysdeps/unix/sysv/linux/riscv/sys/hwprobe.h
> new file mode 100644
> index 0000000000..aa189a4818
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/riscv/sys/hwprobe.h
> @@ -0,0 +1,72 @@
> +/* RISC-V architecture probe interface
> + Copyright (C) 2023 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 _SYS_HWPROBE_H
> +#define _SYS_HWPROBE_H 1
> +
> +#include <features.h>
> +#include <stddef.h>
> +#ifdef __has_include
> +# if __has_include (<asm/hwprobe.h>)
> +# include <asm/hwprobe.h>
> +# endif
> +#endif
> +
> +/* Define a (probably stale) version of the interface if the Linux headers
> + aren't present. */
> +#ifndef RISCV_HWPROBE_KEY_MVENDORID
> +struct riscv_hwprobe {
> + signed long long int key;
> + unsigned long long int value;
> +};
> +
> +#define RISCV_HWPROBE_KEY_MVENDORID 0
> +#define RISCV_HWPROBE_KEY_MARCHID 1
> +#define RISCV_HWPROBE_KEY_MIMPID 2
> +#define RISCV_HWPROBE_KEY_BASE_BEHAVIOR 3
> +#define RISCV_HWPROBE_BASE_BEHAVIOR_IMA (1 << 0)
> +#define RISCV_HWPROBE_KEY_IMA_EXT_0 4
> +#define RISCV_HWPROBE_IMA_FD (1 << 0)
> +#define RISCV_HWPROBE_IMA_C (1 << 1)
> +#define RISCV_HWPROBE_IMA_V (1 << 2)
> +#define RISCV_HWPROBE_EXT_ZBA (1 << 3)
> +#define RISCV_HWPROBE_EXT_ZBB (1 << 4)
> +#define RISCV_HWPROBE_EXT_ZBS (1 << 5)
> +#define RISCV_HWPROBE_KEY_CPUPERF_0 5
> +#define RISCV_HWPROBE_MISALIGNED_UNKNOWN (0 << 0)
> +#define RISCV_HWPROBE_MISALIGNED_EMULATED (1 << 0)
> +#define RISCV_HWPROBE_MISALIGNED_SLOW (2 << 0)
> +#define RISCV_HWPROBE_MISALIGNED_FAST (3 << 0)
> +#define RISCV_HWPROBE_MISALIGNED_UNSUPPORTED (4 << 0)
> +#define RISCV_HWPROBE_MISALIGNED_MASK (7 << 0)
It has some inconsistent space/tab usage, I would recoment to just use
spaces in macro definitions.
> +
> +#endif /* RISCV_HWPROBE_KEY_MVENDORID */
> +
> +__BEGIN_DECLS
> +
> +extern int __riscv_hwprobe (struct riscv_hwprobe *__pairs, size_t __pair_count,
> + size_t __cpu_count, unsigned long int *__cpus,
> + unsigned int __flags)
> + __nonnull ((1)) __wur
> + __fortified_attr_access (__read_write__, 1, 2)
> + __fortified_attr_access (__read_only__, 4, 3);
> +
> +__END_DECLS
> +
> +#endif /* sys/hwprobe.h */
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