linux-kernel - Re: [PATCH 4/7] x86: kexec_file: remove X86_64 dependency from prepare_elf64

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Date:   Fri, 2 Mar 2018 13:19:56 +0800
From:   Dave Young <dyoung@...hat.com>
To:     AKASHI Takahiro <takahiro.akashi@...aro.org>
Cc:     vgoyal@...hat.com, bhe@...hat.com, mpe@...erman.id.au,
        bauerman@...ux.vnet.ibm.com, prudo@...ux.vnet.ibm.com,
        kexec@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org
Subject: Re: [PATCH 4/7] x86: kexec_file: remove X86_64 dependency from
 prepare_elf64_headers()

On 02/27/18 at 01:48pm, AKASHI Takahiro wrote:
> The code guarded by CONFIG_X86_64 is necessary on some architectures
> which have a dedicated kernel mapping outside of linear memory mapping.
> (arm64 is among those.)
> 
> In this patch, an additional argument, kernel_map, is added to enable/
> disable the code removing #ifdef.
> 
> Signed-off-by: AKASHI Takahiro <takahiro.akashi@...aro.org>
> Cc: Dave Young <dyoung@...hat.com>
> Cc: Vivek Goyal <vgoyal@...hat.com>
> Cc: Baoquan He <bhe@...hat.com>
> ---
>  arch/x86/kernel/crash.c | 25 +++++++++++++------------
>  1 file changed, 13 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
> index 2123fa0efc17..913fd8021f8a 100644
> --- a/arch/x86/kernel/crash.c
> +++ b/arch/x86/kernel/crash.c
> @@ -347,7 +347,7 @@ static int prepare_elf64_ram_headers_callback(struct resource *res, void *arg)
>  	return 0;
>  }
>  
> -static int prepare_elf64_headers(struct crash_elf_data *ced,
> +static int prepare_elf64_headers(struct crash_elf_data *ced, int kernel_map,
>  		void **addr, unsigned long *sz)
>  {
>  	Elf64_Ehdr *ehdr;
> @@ -414,17 +414,17 @@ static int prepare_elf64_headers(struct crash_elf_data *ced,
>  	phdr->p_filesz = phdr->p_memsz = VMCOREINFO_NOTE_SIZE;
>  	(ehdr->e_phnum)++;
>  
> -#ifdef CONFIG_X86_64
>  	/* Prepare PT_LOAD type program header for kernel text region */
> -	phdr = (Elf64_Phdr *)bufp;
> -	bufp += sizeof(Elf64_Phdr);
> -	phdr->p_type = PT_LOAD;
> -	phdr->p_flags = PF_R|PF_W|PF_X;
> -	phdr->p_vaddr = (Elf64_Addr)_text;
> -	phdr->p_filesz = phdr->p_memsz = _end - _text;
> -	phdr->p_offset = phdr->p_paddr = __pa_symbol(_text);
> -	(ehdr->e_phnum)++;
> -#endif
> +	if (kernel_map) {
> +		phdr = (Elf64_Phdr *)bufp;
> +		bufp += sizeof(Elf64_Phdr);
> +		phdr->p_type = PT_LOAD;
> +		phdr->p_flags = PF_R|PF_W|PF_X;
> +		phdr->p_vaddr = (Elf64_Addr)_text;
> +		phdr->p_filesz = phdr->p_memsz = _end - _text;
> +		phdr->p_offset = phdr->p_paddr = __pa_symbol(_text);
> +		(ehdr->e_phnum)++;
> +	}
>  
>  	/* Go through all the ranges in cmem->ranges[] and prepare phdr */
>  	for (i = 0; i < cmem->nr_ranges; i++) {
> @@ -477,7 +477,8 @@ static int prepare_elf_headers(struct kimage *image, void **addr,
>  		goto out;
>  
>  	/* By default prepare 64bit headers */
> -	ret =  prepare_elf64_headers(ced, addr, sz);
> +	ret =  prepare_elf64_headers(ced,
> +				(int)IS_ENABLED(CONFIG_X86_64), addr, sz);

A bool would be enough for kernel_map

>  	if (ret)
>  		goto out;
>  

Thanks
Dave
> -- 
> 2.16.2
>