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Date:   Fri, 2 Mar 2018 16:16:45 +0900
From:   AKASHI Takahiro <takahiro.akashi@linaro.org>
To:     Dave Young <dyoung@redhat.com>
Cc:     vgoyal@redhat.com, bhe@redhat.com, mpe@ellerman.id.au,
        bauerman@linux.vnet.ibm.com, prudo@linux.vnet.ibm.com,
        kexec@lists.infradead.org, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org
Subject: Re: [PATCH 2/7] kexec_file,x86,powerpc: factor out kexec_file_ops
 functions
Message-ID: <20180302071644.GS6019@linaro.org>
Mail-Followup-To: AKASHI Takahiro <takahiro.akashi@linaro.org>,
        Dave Young <dyoung@redhat.com>, vgoyal@redhat.com, bhe@redhat.com,
        mpe@ellerman.id.au, bauerman@linux.vnet.ibm.com,
        prudo@linux.vnet.ibm.com, kexec@lists.infradead.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-s390@vger.kernel.org
References: <20180227044814.24808-1-takahiro.akashi@linaro.org>
 <20180227044814.24808-3-takahiro.akashi@linaro.org>
 <20180302050426.GA2952@dhcp-128-65.nay.redhat.com>
 <20180302052444.GN6019@linaro.org>
 <20180302055306.GE2952@dhcp-128-65.nay.redhat.com>
 <20180302060857.GD15422@dhcp-128-65.nay.redhat.com>
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On Fri, Mar 02, 2018 at 02:08:57PM +0800, Dave Young wrote:
> On 03/02/18 at 01:53pm, Dave Young wrote:
> > On 03/02/18 at 02:24pm, AKASHI Takahiro wrote:
> > > On Fri, Mar 02, 2018 at 01:04:26PM +0800, Dave Young wrote:
> > > > On 02/27/18 at 01:48pm, AKASHI Takahiro wrote:
> > > > > As arch_kexec_kernel_image_{probe,load}(),
> > > > > arch_kimage_file_post_load_cleanup() and arch_kexec_kernel_verify_sig()
> > > > > are almost duplicated among architectures, they can be commonalized with
> > > > > an architecture-defined kexec_file_ops array. So let's factor them out.
> > > > > 
> > > > > Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
> > > > > Cc: Dave Young <dyoung@redhat.com>
> > > > > Cc: Vivek Goyal <vgoyal@redhat.com>
> > > > > Cc: Baoquan He <bhe@redhat.com>
> > > > > Cc: Michael Ellerman <mpe@ellerman.id.au>
> > > > > Cc: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
> > > > > ---
> > > > >  arch/powerpc/include/asm/kexec.h            |  2 +-
> > > > >  arch/powerpc/kernel/kexec_elf_64.c          |  2 +-
> > > > >  arch/powerpc/kernel/machine_kexec_file_64.c | 39 ++------------------
> > > > >  arch/x86/include/asm/kexec-bzimage64.h      |  2 +-
> > > > >  arch/x86/kernel/kexec-bzimage64.c           |  2 +-
> > > > >  arch/x86/kernel/machine_kexec_64.c          | 45 ++---------------------
> > > > >  include/linux/kexec.h                       | 17 +++++----
> > > > >  kernel/kexec_file.c                         | 55 ++++++++++++++++++++++++++---
> > > > >  8 files changed, 70 insertions(+), 94 deletions(-)
> > > > > 
> > > > > diff --git a/arch/powerpc/include/asm/kexec.h b/arch/powerpc/include/asm/kexec.h
> > > > > index d8b1e8e7e035..4a585cba1787 100644
> > > > > --- a/arch/powerpc/include/asm/kexec.h
> > > > > +++ b/arch/powerpc/include/asm/kexec.h
> > > > > @@ -95,7 +95,7 @@ static inline bool kdump_in_progress(void)
> > > > >  }
> > > > >  
> > > > >  #ifdef CONFIG_KEXEC_FILE
> > > > > -extern struct kexec_file_ops kexec_elf64_ops;
> > > > > +extern const struct kexec_file_ops kexec_elf64_ops;
> > > > >  
> > > > >  #ifdef CONFIG_IMA_KEXEC
> > > > >  #define ARCH_HAS_KIMAGE_ARCH
> > > > > diff --git a/arch/powerpc/kernel/kexec_elf_64.c b/arch/powerpc/kernel/kexec_elf_64.c
> > > > > index 9a42309b091a..6c78c11c7faf 100644
> > > > > --- a/arch/powerpc/kernel/kexec_elf_64.c
> > > > > +++ b/arch/powerpc/kernel/kexec_elf_64.c
> > > > > @@ -657,7 +657,7 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
> > > > >  	return ret ? ERR_PTR(ret) : fdt;
> > > > >  }
> > > > >  
> > > > > -struct kexec_file_ops kexec_elf64_ops = {
> > > > > +const struct kexec_file_ops kexec_elf64_ops = {
> > > > >  	.probe = elf64_probe,
> > > > >  	.load = elf64_load,
> > > > >  };
> > > > > diff --git a/arch/powerpc/kernel/machine_kexec_file_64.c b/arch/powerpc/kernel/machine_kexec_file_64.c
> > > > > index e4395f937d63..a27ec647350c 100644
> > > > > --- a/arch/powerpc/kernel/machine_kexec_file_64.c
> > > > > +++ b/arch/powerpc/kernel/machine_kexec_file_64.c
> > > > > @@ -31,52 +31,19 @@
> > > > >  
> > > > >  #define SLAVE_CODE_SIZE		256
> > > > >  
> > > > > -static struct kexec_file_ops *kexec_file_loaders[] = {
> > > > > +const struct kexec_file_ops * const kexec_file_loaders[] = {
> > > > >  	&kexec_elf64_ops,
> > > > > +	NULL
> > > > >  };
> > > > >  
> > > > >  int arch_kexec_kernel_image_probe(struct kimage *image, void *buf,
> > > > >  				  unsigned long buf_len)
> > > > >  {
> > > > > -	int i, ret = -ENOEXEC;
> > > > > -	struct kexec_file_ops *fops;
> > > > > -
> > > > >  	/* We don't support crash kernels yet. */
> > > > >  	if (image->type == KEXEC_TYPE_CRASH)
> > > > >  		return -ENOTSUPP;
> > > > >  
> > > > > -	for (i = 0; i < ARRAY_SIZE(kexec_file_loaders); i++) {
> > > > > -		fops = kexec_file_loaders[i];
> > > > > -		if (!fops || !fops->probe)
> > > > > -			continue;
> > > > > -
> > > > > -		ret = fops->probe(buf, buf_len);
> > > > > -		if (!ret) {
> > > > > -			image->fops = fops;
> > > > > -			return ret;
> > > > > -		}
> > > > > -	}
> > > > > -
> > > > > -	return ret;
> > > > > -}
> > > > > -
> > > > > -void *arch_kexec_kernel_image_load(struct kimage *image)
> > > > > -{
> > > > > -	if (!image->fops || !image->fops->load)
> > > > > -		return ERR_PTR(-ENOEXEC);
> > > > > -
> > > > > -	return image->fops->load(image, image->kernel_buf,
> > > > > -				 image->kernel_buf_len, image->initrd_buf,
> > > > > -				 image->initrd_buf_len, image->cmdline_buf,
> > > > > -				 image->cmdline_buf_len);
> > > > > -}
> > > > > -
> > > > > -int arch_kimage_file_post_load_cleanup(struct kimage *image)
> > > > > -{
> > > > > -	if (!image->fops || !image->fops->cleanup)
> > > > > -		return 0;
> > > > > -
> > > > > -	return image->fops->cleanup(image->image_loader_data);
> > > > > +	return _kexec_kernel_image_probe(image, buf, buf_len);
> > > > >  }
> > > > >  
> > > > >  /**
> > > > > diff --git a/arch/x86/include/asm/kexec-bzimage64.h b/arch/x86/include/asm/kexec-bzimage64.h
> > > > > index 9f07cff43705..df89ee7d3e9e 100644
> > > > > --- a/arch/x86/include/asm/kexec-bzimage64.h
> > > > > +++ b/arch/x86/include/asm/kexec-bzimage64.h
> > > > > @@ -2,6 +2,6 @@
> > > > >  #ifndef _ASM_KEXEC_BZIMAGE64_H
> > > > >  #define _ASM_KEXEC_BZIMAGE64_H
> > > > >  
> > > > > -extern struct kexec_file_ops kexec_bzImage64_ops;
> > > > > +extern const struct kexec_file_ops kexec_bzImage64_ops;
> > > > >  
> > > > >  #endif  /* _ASM_KEXE_BZIMAGE64_H */
> > > > > diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c
> > > > > index fb095ba0c02f..705654776c0c 100644
> > > > > --- a/arch/x86/kernel/kexec-bzimage64.c
> > > > > +++ b/arch/x86/kernel/kexec-bzimage64.c
> > > > > @@ -538,7 +538,7 @@ static int bzImage64_verify_sig(const char *kernel, unsigned long kernel_len)
> > > > >  }
> > > > >  #endif
> > > > >  
> > > > > -struct kexec_file_ops kexec_bzImage64_ops = {
> > > > > +const struct kexec_file_ops kexec_bzImage64_ops = {
> > > > >  	.probe = bzImage64_probe,
> > > > >  	.load = bzImage64_load,
> > > > >  	.cleanup = bzImage64_cleanup,
> > > > > diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
> > > > > index 1f790cf9d38f..2cdd29d64181 100644
> > > > > --- a/arch/x86/kernel/machine_kexec_64.c
> > > > > +++ b/arch/x86/kernel/machine_kexec_64.c
> > > > > @@ -30,8 +30,9 @@
> > > > >  #include <asm/set_memory.h>
> > > > >  
> > > > >  #ifdef CONFIG_KEXEC_FILE
> > > > > -static struct kexec_file_ops *kexec_file_loaders[] = {
> > > > > +const struct kexec_file_ops * const kexec_file_loaders[] = {
> > > > >  		&kexec_bzImage64_ops,
> > > > > +		NULL
> > > > >  };
> > > > >  #endif
> > > > >  
> > > > > @@ -363,27 +364,6 @@ void arch_crash_save_vmcoreinfo(void)
> > > > >  /* arch-dependent functionality related to kexec file-based syscall */
> > > > >  
> > > > >  #ifdef CONFIG_KEXEC_FILE
> > > > > -int arch_kexec_kernel_image_probe(struct kimage *image, void *buf,
> > > > > -				  unsigned long buf_len)
> > > > > -{
> > > > > -	int i, ret = -ENOEXEC;
> > > > > -	struct kexec_file_ops *fops;
> > > > > -
> > > > > -	for (i = 0; i < ARRAY_SIZE(kexec_file_loaders); i++) {
> > > > > -		fops = kexec_file_loaders[i];
> > > > > -		if (!fops || !fops->probe)
> > > > > -			continue;
> > > > > -
> > > > > -		ret = fops->probe(buf, buf_len);
> > > > > -		if (!ret) {
> > > > > -			image->fops = fops;
> > > > > -			return ret;
> > > > > -		}
> > > > > -	}
> > > > > -
> > > > > -	return ret;
> > > > > -}
> > > > > -
> > > > >  void *arch_kexec_kernel_image_load(struct kimage *image)
> > > > >  {
> > > > >  	vfree(image->arch.elf_headers);
> > > > > @@ -398,27 +378,6 @@ void *arch_kexec_kernel_image_load(struct kimage *image)
> > > > >  				 image->cmdline_buf_len);
> > > > >  }
> > > > >  
> > > > > -int arch_kimage_file_post_load_cleanup(struct kimage *image)
> > > > > -{
> > > > > -	if (!image->fops || !image->fops->cleanup)
> > > > > -		return 0;
> > > > > -
> > > > > -	return image->fops->cleanup(image->image_loader_data);
> > > > > -}
> > > > > -
> > > > > -#ifdef CONFIG_KEXEC_VERIFY_SIG
> > > > > -int arch_kexec_kernel_verify_sig(struct kimage *image, void *kernel,
> > > > > -				 unsigned long kernel_len)
> > > > > -{
> > > > > -	if (!image->fops || !image->fops->verify_sig) {
> > > > > -		pr_debug("kernel loader does not support signature verification.");
> > > > > -		return -EKEYREJECTED;
> > > > > -	}
> > > > > -
> > > > > -	return image->fops->verify_sig(kernel, kernel_len);
> > > > > -}
> > > > > -#endif
> > > > > -
> > > > >  /*
> > > > >   * Apply purgatory relocations.
> > > > >   *
> > > > > diff --git a/include/linux/kexec.h b/include/linux/kexec.h
> > > > > index f16f6ceb3875..2e095c3b4537 100644
> > > > > --- a/include/linux/kexec.h
> > > > > +++ b/include/linux/kexec.h
> > > > > @@ -159,6 +159,15 @@ struct kexec_buf {
> > > > >  	bool top_down;
> > > > >  };
> > > > >  
> > > > > +extern const struct kexec_file_ops * const kexec_file_loaders[];
> > > > > +
> > > > > +int _kexec_kernel_image_probe(struct kimage *image, void *buf,
> > > > > +			      unsigned long buf_len);
> > > > > +void *_kexec_kernel_image_load(struct kimage *image);
> > > > > +int _kimage_file_post_load_cleanup(struct kimage *image);
> > > > > +int _kexec_kernel_verify_sig(struct kimage *image, void *buf,
> > > > > +			     unsigned long buf_len);
> > > > 
> > > > AKASHI, since the above 3 functions nobody else used, suppose it is for
> > > > future use, they can be made static for now.  Later if someone needs
> > > > they can remove the static easily.
> > > 
> > > OK.
> > > May I change those names, for example, to kexec_kernel_image_probe_default()
> > > and so on? I don't like to export _XYZ as a global symbol.
> > 
> > Hmm, if so it is becoming even longer, maybe something shorter eg. below
> > 
> > kexec_image_probe
> > kexec_image_load
> > kexec_image_post_load_cleanup
> > kexec_image_verify_sig

OK.

> > and for the sub routine maybe then add _default suffix, they still look
> > not very good, but I can not think of any better names.

Me, neither. Then, the resulting code looks like:

__weak arch_kexec_(kernel_)image_probe() {
        return kexec_image_probe_default();
}

Should we preserve "kernel_" so as not to change the existing names?


> BTW, there can be a short code comment to explain why they are needed to
> be separate functions so that less confusion while reading code.

Sure

-Takahiro AKASHI


> > 
> > 
> > > 
> > > -Takahiro AKASHI
> > >       
> > > 
> > > 
> > > > > +}
> > > > > +
> > > > >  int __weak arch_kexec_kernel_verify_sig(struct kimage *image, void *buf,
> > > > >  					unsigned long buf_len)
> > > > >  {
> > > > > -	return -EKEYREJECTED;
> > > > > +	return _kexec_kernel_verify_sig(image, buf, buf_len);
> > > > >  }
> > > > >  #endif
> > > > >  
> > > > > -- 
> > > > > 2.16.2
> > > > > 
> > > > 
> > > > Thanks
> > > > Dave
> > 
> > Thanks
> > Dave