The default COMMAND_LINE_SIZE of 512, inherited from asm-generic, is
too small for modern use cases. For example, kdump configurations or
extensive debugging parameters can easily exceed this limit.

Therefore, increase the command line size to 4096 bytes, aligning
LoongArch with the MIPS architecture. This change follows a broader
trend among architectures to raise this limit to support modern needs;
for instance, PowerPC increased its value for similar reasons in
commit a5980d064fe2 ("powerpc: Bump COMMAND_LINE_SIZE to 2048").

Similar to the change made for RISC-V in commit 61fc1ee8be26
("riscv: Bump COMMAND_LINE_SIZE value to 1024"), this is considered
a safe change. The broader kernel community has reached a consensus
that modifying COMMAND_LINE_SIZE from UAPI headers does not
constitute a uABI breakage, as well-behaved userspace applications
should not rely on this macro.

Suggested-by: Huang Cun <cunhuang@tencent.com>
Signed-off-by: Ming Wang <wangming01@loongson.cn>
---
 arch/loongarch/include/uapi/asm/setup.h | 8 ++++++++
 1 file changed, 8 insertions(+)
 create mode 100644 arch/loongarch/include/uapi/asm/setup.h

diff --git a/arch/loongarch/include/uapi/asm/setup.h b/arch/loongarch/include/uapi/asm/setup.h
new file mode 100644
index 000000000000..d46363ce3e02
--- /dev/null
+++ b/arch/loongarch/include/uapi/asm/setup.h
@@ -0,0 +1,8 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+
+#ifndef _UAPI_ASM_LOONGARCH_SETUP_H
+#define _UAPI_ASM_LOONGARCH_SETUP_H
+
+#define COMMAND_LINE_SIZE	4096
+
+#endif /* _UAPI_ASM_LOONGARCH_SETUP_H */
-- 
2.43.0

Applied, thanks.

Huacai

On Tue, Aug 12, 2025 at 8:20 PM Ming Wang <wangming01@loongson.cn> wrote:
>
> The default COMMAND_LINE_SIZE of 512, inherited from asm-generic, is
> too small for modern use cases. For example, kdump configurations or
> extensive debugging parameters can easily exceed this limit.
>
> Therefore, increase the command line size to 4096 bytes, aligning
> LoongArch with the MIPS architecture. This change follows a broader
> trend among architectures to raise this limit to support modern needs;
> for instance, PowerPC increased its value for similar reasons in
> commit a5980d064fe2 ("powerpc: Bump COMMAND_LINE_SIZE to 2048").
>
> Similar to the change made for RISC-V in commit 61fc1ee8be26
> ("riscv: Bump COMMAND_LINE_SIZE value to 1024"), this is considered
> a safe change. The broader kernel community has reached a consensus
> that modifying COMMAND_LINE_SIZE from UAPI headers does not
> constitute a uABI breakage, as well-behaved userspace applications
> should not rely on this macro.
>
> Suggested-by: Huang Cun <cunhuang@tencent.com>
> Signed-off-by: Ming Wang <wangming01@loongson.cn>
> ---
>  arch/loongarch/include/uapi/asm/setup.h | 8 ++++++++
>  1 file changed, 8 insertions(+)
>  create mode 100644 arch/loongarch/include/uapi/asm/setup.h
>
> diff --git a/arch/loongarch/include/uapi/asm/setup.h b/arch/loongarch/include/uapi/asm/setup.h
> new file mode 100644
> index 000000000000..d46363ce3e02
> --- /dev/null
> +++ b/arch/loongarch/include/uapi/asm/setup.h
> @@ -0,0 +1,8 @@
> +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
> +
> +#ifndef _UAPI_ASM_LOONGARCH_SETUP_H
> +#define _UAPI_ASM_LOONGARCH_SETUP_H
> +
> +#define COMMAND_LINE_SIZE      4096
> +
> +#endif /* _UAPI_ASM_LOONGARCH_SETUP_H */
> --
> 2.43.0
>
>