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 14:33:26 +0900
From:   AKASHI Takahiro <takahiro.akashi@...aro.org>
To:     Dave Young <dyoung@...hat.com>
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 Fri, Mar 02, 2018 at 01:19:56PM +0800, Dave Young wrote:
> 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

Yeah, for now.
What I thought of is that we might want to extend its functionality
in the future as I did here for kernel_map without changing its interface.
But I'd defer to you.

-Takahiro AKASHI

> >  	if (ret)
> >  		goto out;
> >  
> 
> Thanks
> Dave
> > -- 
> > 2.16.2
> >