linux-kernel - Re: [PATCH] MIPS: relocatable: Provide kaslr

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Date:   Mon, 1 Feb 2021 13:50:28 +0100
From:   Thomas Bogendoerfer <tsbogend@...ha.franken.de>
To:     Jinyang He <hejinyang@...ngson.cn>
Cc:     Huacai Chen <chenhuacai@...nel.org>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] MIPS: relocatable: Provide kaslr_offset() to get the
 kernel offset

On Wed, Jan 27, 2021 at 12:12:25PM +0800, Jinyang He wrote:
> Use kimage_vaddr to indicate kernel start address. Provide kaslr_offset()
> to get the kernel offset when KASLR is enabled. Error may occur before
> update_kimage_vaddr(), so put it at the end of the offset branch.
> 
> Fixes: a307a4ce9ecd ("MIPS: Loongson64: Add KASLR support")
> Reported-by: kernel test robot <lkp@...el.com>
> Signed-off-by: Jinyang He <hejinyang@...ngson.cn>
> ---
>  arch/mips/include/asm/page.h |  6 ++++++
>  arch/mips/kernel/relocate.c  | 12 ++++++++++++
>  arch/mips/kernel/setup.c     |  3 +++
>  3 files changed, 21 insertions(+)
> 
> diff --git a/arch/mips/include/asm/page.h b/arch/mips/include/asm/page.h
> index 6a77bc4..9429520 100644
> --- a/arch/mips/include/asm/page.h
> +++ b/arch/mips/include/asm/page.h
> @@ -255,6 +255,12 @@ extern bool __virt_addr_valid(const volatile void *kaddr);
>  
>  #define VM_DATA_DEFAULT_FLAGS	VM_DATA_FLAGS_TSK_EXEC
>  
> +extern unsigned long kimage_vaddr;
> +static inline unsigned long kaslr_offset(void)
> +{
> +	return kimage_vaddr - VMLINUX_LOAD_ADDRESS;
> +}

this breaks for 32bit kernels:

<command-line>:0:22: error: large integer implicitly truncated to unsigned type [-Werror=overflow]
/local/tbogendoerfer/korg/linux/arch/mips/kernel/setup.c:87:41: note: in expansion of macro ‘VMLINUX_LOAD_ADDRESS’
 unsigned long kimage_vaddr __initdata = VMLINUX_LOAD_ADDRESS;
                                         ^~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors

-- 
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