linux-kernel - Re: [PATCH] riscv: change XIP's kernel_map.size to be size of the entire kernel

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Date: Wed, 8 May 2024 21:43:11 +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>,
 Alexandre Ghiti <alexghiti@...osinc.com>, linux-riscv@...ts.infradead.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] riscv: change XIP's kernel_map.size to be size of the
 entire kernel

Hi Nam,

On 08/05/2024 21:19, Nam Cao wrote:
> With XIP kernel, kernel_map.size is set to be only the size of data part of
> the kernel. This is inconsistent with "normal" kernel, who sets it to be
> the size of the entire kernel.
>
> More importantly, XIP kernel fails to boot if CONFIG_DEBUG_VIRTUAL is
> enabled, because there are checks on virtual addresses with the assumption
> that kernel_map.size is the size of the entire kernel (these checks are in
> arch/riscv/mm/physaddr.c).
>
> Change XIP's kernel_map.size to be the size of the entire kernel.
>
> Signed-off-by: Nam Cao <namcao@...utronix.de>
> Cc: <stable@...r.kernel.org> # v6.1+
> ---
> I wouldn't consider this inconsistency to be a bug. It only became a
> a problem after kernel_map.size is used to check virtual addresses in
> 5f763b3b5960 ("riscv: Fix DEBUG_VIRTUAL false warnings"). So I will only
> backport this to stable versions that contain this commit: v6.1+
>
>   arch/riscv/mm/init.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index c081e7d349b1..0c0562839899 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -903,7 +903,7 @@ static void __init create_kernel_page_table(pgd_t *pgdir,
>   				   PMD_SIZE, PAGE_KERNEL_EXEC);
>   
>   	/* Map the data in RAM */
> -	end_va = kernel_map.virt_addr + XIP_OFFSET + kernel_map.size;
> +	end_va = kernel_map.virt_addr + kernel_map.size;
>   	for (va = kernel_map.virt_addr + XIP_OFFSET; va < end_va; va += PMD_SIZE)
>   		create_pgd_mapping(pgdir, va,
>   				   kernel_map.phys_addr + (va - (kernel_map.virt_addr + XIP_OFFSET)),
> @@ -1072,7 +1072,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>   
>   	phys_ram_base = CONFIG_PHYS_RAM_BASE;
>   	kernel_map.phys_addr = (uintptr_t)CONFIG_PHYS_RAM_BASE;
> -	kernel_map.size = (uintptr_t)(&_end) - (uintptr_t)(&_sdata);
> +	kernel_map.size = (uintptr_t)(&_end) - (uintptr_t)(&_start);
>   
>   	kernel_map.va_kernel_xip_pa_offset = kernel_map.virt_addr - kernel_map.xiprom;
>   #else


You can add:

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

Thanks,

Alex