[v2,1/3] riscv: Add Linux hwprobe syscall support

  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>
---

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       | 30 +++++++++
 .../unix/sysv/linux/riscv/rv32/arch-syscall.h |  1 +
 .../unix/sysv/linux/riscv/rv32/libc.abilist   |  1 +
 .../unix/sysv/linux/riscv/rv64/arch-syscall.h |  1 +
 .../unix/sysv/linux/riscv/rv64/libc.abilist   |  1 +
 sysdeps/unix/sysv/linux/riscv/sys/hwprobe.h   | 67 +++++++++++++++++++
 sysdeps/unix/sysv/linux/syscall-names.list    |  1 +
 9 files changed, 107 insertions(+), 2 deletions(-)
 create mode 100644 sysdeps/unix/sysv/linux/riscv/hwprobe.c
 create mode 100644 sysdeps/unix/sysv/linux/riscv/sys/hwprobe.h
  

On 21/02/23 16:15, 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>
> ---
> 
> 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       | 30 +++++++++
>  .../unix/sysv/linux/riscv/rv32/arch-syscall.h |  1 +
>  .../unix/sysv/linux/riscv/rv32/libc.abilist   |  1 +
>  .../unix/sysv/linux/riscv/rv64/arch-syscall.h |  1 +
>  .../unix/sysv/linux/riscv/rv64/libc.abilist   |  1 +
>  sysdeps/unix/sysv/linux/riscv/sys/hwprobe.h   | 67 +++++++++++++++++++
>  sysdeps/unix/sysv/linux/syscall-names.list    |  1 +
>  9 files changed, 107 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 ($(subdir),misc)
> -sysdep_headers += sys/cachectl.h
> -sysdep_routines += flush-icache
> +sysdep_headers += sys/cachectl.h sys/hwprobe.h
> +sysdep_routines += flush-icache hwprobe
>  endif
>  
>  ifeq ($(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..74f68889ca
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/riscv/hwprobe.c
> @@ -0,0 +1,30 @@
> +/* 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>
> +
> +int
> +__riscv_hwprobe (struct riscv_hwprobe *pairs, long pair_count,
> +  long cpu_count, unsigned long *cpus, unsigned long flags)
> +{
> +  return INLINE_SYSCALL_CALL (riscv_hwprobe, pairs, pair_count,
> +                         cpu_count, cpus, flags);
> +}
> diff --git a/sysdeps/unix/sysv/linux/riscv/rv32/arch-syscall.h b/sysdeps/unix/sysv/linux/riscv/rv32/arch-syscall.h
> index 202520ee25..2416e041c8 100644
> --- a/sysdeps/unix/sysv/linux/riscv/rv32/arch-syscall.h
> +++ b/sysdeps/unix/sysv/linux/riscv/rv32/arch-syscall.h
> @@ -198,6 +198,7 @@
>  #define __NR_request_key 218
>  #define __NR_restart_syscall 128
>  #define __NR_riscv_flush_icache 259
> +#define __NR_riscv_hwprobe 258
>  #define __NR_rseq 293
>  #define __NR_rt_sigaction 134
>  #define __NR_rt_sigpending 136
> diff --git a/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist b/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist
> index 29be561b60..83b7932db7 100644
> --- a/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist
> +++ b/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist
> @@ -2416,3 +2416,4 @@ GLIBC_2.38 __isoc23_wcstoul_l F
>  GLIBC_2.38 __isoc23_wcstoull F
>  GLIBC_2.38 __isoc23_wcstoull_l F
>  GLIBC_2.38 __isoc23_wcstoumax F
> +GLIBC_2.39 __riscv_hwprobe F
> diff --git a/sysdeps/unix/sysv/linux/riscv/rv64/arch-syscall.h b/sysdeps/unix/sysv/linux/riscv/rv64/arch-syscall.h
> index 4e65f337d4..a32bc82f60 100644
> --- a/sysdeps/unix/sysv/linux/riscv/rv64/arch-syscall.h
> +++ b/sysdeps/unix/sysv/linux/riscv/rv64/arch-syscall.h
> @@ -205,6 +205,7 @@
>  #define __NR_request_key 218
>  #define __NR_restart_syscall 128
>  #define __NR_riscv_flush_icache 259
> +#define __NR_riscv_hwprobe 258
>  #define __NR_rseq 293
>  #define __NR_rt_sigaction 134
>  #define __NR_rt_sigpending 136
> diff --git a/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist b/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
> index 506a4e6a65..6ddbcfb131 100644
> --- a/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
> +++ b/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
> @@ -2616,3 +2616,4 @@ GLIBC_2.38 __isoc23_wcstoul_l F
>  GLIBC_2.38 __isoc23_wcstoull F
>  GLIBC_2.38 __isoc23_wcstoull_l F
>  GLIBC_2.38 __isoc23_wcstoumax F
> +GLIBC_2.39 __riscv_hwprobe 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..e619ea43b8
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/riscv/sys/hwprobe.h
> @@ -0,0 +1,67 @@
> +/* 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>
> +#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 key;
> +	unsigned long long value;
> +};

Indentation seems ok here, I think curly brackets should be in the next line.

> +
> +#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_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_MASK		(7 << 0)

Indentation seems off here.

> +
> +#endif // RISCV_HWPROBE_KEY_MVENDORID

No C99/C++ style comments in public headers.

> +
> +__BEGIN_DECLS
> +

Could you add some minimal comment on the how to use this interface, the
exects parameters, etc? 

> +#ifdef __USE_GNU
> +int
> +__riscv_hwprobe (struct riscv_hwprobe *pairs, long pair_count,
> +  long cpu_count, unsigned long *cpus, unsigned long flags);

Add 'extern' (for old -std= modes) and put the function on same line as
return type.

> +#endif
> +
> +__END_DECLS
> +
> +#endif /* sys/hwprobe.h */
> diff --git a/sysdeps/unix/sysv/linux/syscall-names.list b/sysdeps/unix/sysv/linux/syscall-names.list
> index 822498d3e3..4f4a62e91c 100644
> --- a/sysdeps/unix/sysv/linux/syscall-names.list
> +++ b/sysdeps/unix/sysv/linux/syscall-names.list
> @@ -477,6 +477,7 @@ renameat2
>  request_key
>  restart_syscall
>  riscv_flush_icache
> +riscv_hwprobe
>  rmdir
>  rseq
>  rt_sigaction