[v9,1/6] 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>
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
  

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 */
  

On 06/12/23 14:22, Adhemerval Zanella Netto wrote:

> 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.

In the next patch you replaced with INTERNAL_VSYSCALL_CALL, so it answers
why it has not failed in your tests.