[PATCH] LoongArch: Use the generic shmlab.h.

[Adhemerval Zanella Netto]

On 09/09/25 04:03, caiyinyu wrote:
> The shmlba.h file related to the LoongArch architecture was introduced
> in commit 3eed5f3a1ee to address the mismatch in the SHMLBA definition
> between glibc and the kernel. See [1].  The SHMLBA definition was later
> updated in commit d23b77953f5a. See [2].  Now, we adopt the definition
> from the common layer.
> 
> [1]:
> commit 3eed5f3a1ee356969afb403a1cf18d06f8d2d98a
> Author: caiyinyu <caiyinyu@loongson.cn>
> Date:   Thu May 25 17:01:11 2023 +0800
> 
>     LoongArch: Fix inconsistency in SHMLBA macro values between glibc and kernel
> 
>     The LoongArch glibc was using the value of the SHMLBA macro from common code,
>     which is __getpagesize() (16k), but this was inconsistent with the value of
>     the SHMLBA macro in the kernel, which is SZ_64K (64k). This caused several
>     shmat-related tests in LTP (Linux Test Project) to fail. This commit fixes
>     the issue by ensuring that the glibc's SHMLBA macro value matches the value
>     used in the kernel like other architectures.
> 
> [2]:
> commit d23b77953f5a4fbf94c05157b186aac2a247ae32
> Author: Huacai Chen <chenhuacai@kernel.org>
> Date:   Wed Jan 17 12:43:08 2024 +0800
> 
>     LoongArch: Change SHMLBA from SZ_64K to PAGE_SIZE
> 
>     LoongArch has hardware page coloring for L1 Cache, so we don't have
>     cache aliases. But SFB (Store Fill Buffer) still has aliases. So we
>     define SHMLBA to SZ_64K previously. But there are losts of applications
>     use PAGE_SIZE rather than SHMLBA to mmap() file pages and shared pages.
>     Of course we can fix them one by one, but not easy.
> 
>     On the other hand, we can simply disable SFB for 4KB page size to fix
>     cache alias (there will be performance decrease, but acceptable), and
>     in future we will fix SFB in hardware. So we can safely define SHMLBA to
>     PAGE_SIZE (use the generic shmparam.h) to make life easier.
> 
> Signed-off-by: caiyinyu <caiyinyu@loongson.cn>
> Reported-by: lixing <lixing@loongson.cn>

LGTM, thanks. 

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

> ---
>  .../unix/sysv/linux/loongarch/bits/shmlba.h   | 24 -------------------
>  1 file changed, 24 deletions(-)
>  delete mode 100644 sysdeps/unix/sysv/linux/loongarch/bits/shmlba.h
> 
> diff --git a/sysdeps/unix/sysv/linux/loongarch/bits/shmlba.h b/sysdeps/unix/sysv/linux/loongarch/bits/shmlba.h
> deleted file mode 100644
> index e74644d460..0000000000
> --- a/sysdeps/unix/sysv/linux/loongarch/bits/shmlba.h
> +++ /dev/null
> @@ -1,24 +0,0 @@
> -/* Define SHMLBA.  LoongArch version.
> -   Copyright (C) 2023-2025 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_SHM_H
> -# error "Never use <bits/shmlba.h> directly; include <sys/shm.h> instead."
> -#endif
> -
> -/* Segment low boundary address multiple.  */
> -#define SHMLBA		0x10000