linux-kernel - Re: [PATCH 7/7] riscv: remove limit on the size of read-only section for XIP kernel

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Date: Mon, 27 May 2024 14:58:14 +0200
From: Alexandre Ghiti <alex@...ti.fr>
To: Nam Cao <namcao@...utronix.de>, Paul Walmsley <paul.walmsley@...ive.com>,
 Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
 linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc: kernel test robot <lkp@...el.com>
Subject: Re: [PATCH 7/7] riscv: remove limit on the size of read-only section
 for XIP kernel


On 10/05/2024 08:28, Nam Cao wrote:
> XIP_OFFSET is the hard-coded offset of writable data section within the
> kernel.
>
> By hard-coding this value, the read-only section of the kernel (which is
> placed before the writable data section) is restricted in size. This causes
> build failures if the kernel get too big (an example is in Closes:).

s/get/gets

I think you can use:

Closes: https://lore.kernel.org/oe-kbuild-all/202404211031.J6l2AfJk-lkp@intel.com/ [1]

And instead use:

s/an example is in Closes:/[1]


>
> Remove this limit.
>
> Reported-by: kernel test robot <lkp@...el.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202404211031.J6l2AfJk-lkp@intel.com/
> Signed-off-by: Nam Cao <namcao@...utronix.de>
> ---
>   arch/riscv/include/asm/pgtable.h    | 7 -------
>   arch/riscv/kernel/vmlinux-xip.lds.S | 4 ++--
>   2 files changed, 2 insertions(+), 9 deletions(-)
>
> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> index fbf342f4afee..75f4a92ea5bb 100644
> --- a/arch/riscv/include/asm/pgtable.h
> +++ b/arch/riscv/include/asm/pgtable.h
> @@ -104,13 +104,6 @@
>   
>   #endif
>   
> -#ifdef CONFIG_XIP_KERNEL
> -#define XIP_OFFSET		SZ_32M
> -#define XIP_OFFSET_MASK		(SZ_32M - 1)
> -#else
> -#define XIP_OFFSET		0
> -#endif
> -
>   #ifndef __ASSEMBLY__
>   
>   #include <asm/page.h>
> diff --git a/arch/riscv/kernel/vmlinux-xip.lds.S b/arch/riscv/kernel/vmlinux-xip.lds.S
> index 8c3daa1b0531..01f73f2ffecc 100644
> --- a/arch/riscv/kernel/vmlinux-xip.lds.S
> +++ b/arch/riscv/kernel/vmlinux-xip.lds.S
> @@ -65,10 +65,10 @@ SECTIONS
>    * From this point, stuff is considered writable and will be copied to RAM
>    */
>   	__data_loc = ALIGN(PAGE_SIZE);		/* location in file */
> -	. = KERNEL_LINK_ADDR + XIP_OFFSET;	/* location in memory */
> +	. = ALIGN(SZ_2M);			/* location in memory */


You can't use SZ_2M here since it corresponds to PMD_SIZE for rv64 but 
on rv32 (which is allowed to use xip kernels), it's 4MB. Use 
SECTION_ALIGN instead.


>   
>   #undef LOAD_OFFSET
> -#define LOAD_OFFSET (KERNEL_LINK_ADDR + XIP_OFFSET - (__data_loc & XIP_OFFSET_MASK))
> +#define LOAD_OFFSET (KERNEL_LINK_ADDR + _sdata - __data_loc)
>   
>   	_sdata = .;			/* Start of data section */
>   	_data = .;

When the above comment is fixed, you can add:

Reviewed-by: Alexandre Ghiti <alexghiti@...osinc.com>

And many thanks for this big cleanup.

Alex