Re: [PATCHv2 1/6] kexec: Change the image probe's prototype

[Simon Horman <horms@kernel.org>]

On Tue, May 16, 2023 at 03:31:19PM +0800, Pingfan Liu wrote:
> As more complicated kernel format occurs such as zboot, where the
> compressed kernel is stored as a payload. The straight forward
> decompression can not meet the demand.
> 
> A new image probe method is expected to read in the kernel file and decide
> how to unfold the content by itself.
> 
> This patch aims to change the image probe's prototype from
>             typedef int (probe_t)(const char *kernel_buf, off_t kernel_size);
> to
>             typedef int (probe_t)(const char *kernel_buf, off_t kernel_size, struct kexec_info *info);
> 
> Later, info can be used to return both the file descriptor and the
> parsed kernel buffer.
> 
> In case your are curious, the remaing part of the log describes the
> process of the substitution of the new prototype, which can be divided
> into three groups.
> 
> 1. change function pointer and its callsites:
>   sed -i 's/(probe_t)(const char \*kernel_buf, off_t kernel_size);/(probe_t)(const char \*kernel, off_t kernel_size, struct kexec_info \*info);/g' kexec/kexec.h
>   sed -i 's/\.probe(\([^,]*\), \([^)]*\))/\.probe(\1, \2, NULL)/g' kexec/kexec.c
> 
> 2. change the function declaration and definition of each 'probe'
>    instance by coccinelle because they may cross lines
> 
> The cocci file looks like:
> 
> @ rule1 @
> identifier fn =~ "_probe";
> identifier buf, size;
> typedef off_t;
> @@
> 
> -int fn(const char *buf, off_t size)
> +int fn(const char *buf, off_t size, struct kexec_info *info)
> {
>         ...
> }
> 
> @ rule2 @
> identifier fn =~ "_probe";
> identifier buf, size;
> typedef off_t;
> @@
> 
> +int fn(const char *buf, off_t size, struct kexec_info *info);
> -int fn(const char *buf, off_t size);
> 
> Then running the command
> spatch --sp-file cocci/define.cocci --dir kexec --include-headers > ../define.patch
> git apply --directory=kexec ../define.patch
> 
> 3. change the direct calls to the probe instances
> 
> Originally I planned to achieve this by coccinelle, but failed similar
> to [1]. I have tried using "-I and --include" option for coccinelle, but it
> still did not work.
> 
> Checking the direct callsite by "git grep "_probe(" | grep -v const"
> Fortunatelly, it turns out that only a few direct callsites exist, which
> lies in i386, and easy to be amended manually.
> 
> Anyway, just FYI, the cocci file looks like:
> @ rule1 @
> identifier fn =~ "_probe";
> identifier buf, size;
> identifier info;
> typedef off_t;
> @@
> 
> int fn(const char *buf, off_t size, struct kexec_info *info);
> 
> /* change the direct callsite of any probe */
> @ rule2 @
> identifier rule1.fn;
> expression E1, E2;
> @@
> 
>  fn(E1, E2
> +  ,NULL
>    )
> 
> Then running the command:
> spatch --sp-file cocci/direct.cocci --dir kexec --include-headers
> 
> [1]: https://lore.kernel.org/all/alpine.DEB.2.22.394.2202280705080.3112@hadrien/T/
> 
> Signed-off-by: Pingfan Liu <piliu@redhat.com>
> To: kexec@lists.infradead.org
> Cc: horms@verge.net.au
> Cc: ardb@kernel.org
> Cc: jeremy.linton@arm.com

Unfortunately I am seeing a build failure on (at least) sh4 with this change:

 ../../kexec/arch/sh/kexec-zImage-sh.c:54:5: error: conflicting types for ‘zImage_sh_probe’
    54 | int zImage_sh_probe(const char *buf, off_t UNUSED(len))
       |     ^~~~~~~~~~~~~~~
 In file included from ../../kexec/arch/sh/kexec-zImage-sh.c:27:
 ../../kexec/arch/sh/kexec-sh.h:11:5: note: previous declaration of ‘zImage_sh_probe’ was here
    11 | int zImage_sh_probe(const char *buf, off_t len, struct kexec_info *info);
       |     ^~~~~~~~~~~~~~~
 ../../kexec/arch/sh/kexec-zImage-sh.c:29:18: warning: ‘probe_debug’ defined but not used [-Wunused-const-variable=]
    29 | static const int probe_debug = 0;
       |                  ^~~~~~~~~~~
 make[1]: *** [Makefile:124: kexec/arch/sh/kexec-zImage-sh.o] Error 1
 make[1]: *** Waiting for unfinished jobs....
 ../../kexec/arch/sh/kexec-netbsd-sh.c:28:18: warning: ‘probe_debug’ defined but not used [-Wunused-const-variable=]
    28 | static const int probe_debug = 0;
       |                  ^~~~~~~~~~~

Link: https://github.com/horms/kexec-tools/actions/runs/5068250493/jobs/9100319093#step:5:215

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