linux-kernel - Re: [PATCH] kexec: print out debugging message if required for kexec

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Message-ID: <2D19268A448AA783+4e165a7d-fdf1-48e8-a651-63d9a77dc823@uniontech.com>
Date: Fri, 31 Oct 2025 16:49:09 +0800
From: Qiang Ma <maqianga@...ontech.com>
To: Baoquan He <bhe@...hat.com>
Cc: akpm@...ux-foundation.org, kexec@...ts.infradead.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kexec: print out debugging message if required for
 kexec_load


在 2025/10/31 16:14, Baoquan He 写道:
> On 10/31/25 at 10:40am, Qiang Ma wrote:
>> 在 2025/10/30 21:58, Baoquan He 写道:
>>> On 10/30/25 at 07:41pm, Qiang Ma wrote:
>>>> 在 2025/10/30 17:42, Baoquan He 写道:
>>>>> On 10/30/25 at 03:33pm, Qiang Ma wrote:
>>>>>> The commit a85ee18c7900 ("kexec_file: print out debugging message
>>>>>> if required") has added general code printing in kexec_file_load(),
>>>>>> but not in kexec_load().
>>>>>>
>>>>>> Especially in the RISC-V architecture, kexec_image_info() has been
>>>>>> removed(commit eb7622d908a0 ("kexec_file, riscv: print out debugging
>>>>>> message if required")). As a result, when using '-d' for the kexec_load
>>>>>> interface, print nothing in the kernel space. This might be helpful for
>>>>>> verifying the accuracy of the data passed to the kernel. Therefore, refer to
>>>>>> this commit a85ee18c7900 ("kexec_file: print out debugging message
>>>>>> if required"), debug print information has been added.
>>>>> kexec_file_dbg_print setting when CONFIG_KEXEC_FILE is set. I doubt it
>>>>> doesn't work when you unset CONFIG_KEXEC_FILE.
>>>> Yes, I just actually tested it and it really doesn't work when unset
>>>> CONFIG_KEXEC_FILE.
>>>>
>>>> In the next version, I can add a KEXEC_DEBUG for the kernel and kexec-tools.
>>> Hold on please, it may not need that highweight change. I will reply to
>>> you tomorrow if I have other idea.
>> Ok. My current idea is to refer to kexec_file, define a kexec_dbg_print,
>> initialize it in the kimage_alloc_init(), modify KEXEC_FLAGS and
>> kexec_dprintk,
>> and add the judgment of kexec_debug.
> Maybe we can unify it because kexec_file_dbg_print is declared and
> defined in CONFIG_KEXEC_CORE scope. Rename it to kexec_core_dbg_print
> and initialize it in do_kimage_alloc_init() for both, or in
> kimage_alloc_init() for kexec, and kimage_file_alloc_init() for
> kexec_file. It needs a new flag for kexec. What do you think?
I think it's okay.

I had also considered unifying a flag before, but I thought there was a 
possibility that
kexec_load and kexec_file_load could be executed simultaneously, so I 
gave up.
Later, after looking at the kexec-tools code, I found that 
kexec_file_load would be executed first.
So, it would be better to unify them into one flag.
>
> Please feel free to take it as reference, or you can go in other ways
> you have better one.
OK.
>
> diff --git a/include/linux/kexec.h b/include/linux/kexec.h
> index ff7e231b0485..df33a0dd5780 100644
> --- a/include/linux/kexec.h
> +++ b/include/linux/kexec.h
> @@ -525,10 +525,10 @@ static inline int arch_kexec_post_alloc_pages(void *vaddr, unsigned int pages, g
>   static inline void arch_kexec_pre_free_pages(void *vaddr, unsigned int pages) { }
>   #endif
>   
> -extern bool kexec_file_dbg_print;
> +extern bool kexec_core_dbg_print;
>   
>   #define kexec_dprintk(fmt, arg...) \
> -        do { if (kexec_file_dbg_print) pr_info(fmt, ##arg); } while (0)
> +        do { if (kexec_core_dbg_print) pr_info(fmt, ##arg); } while (0)
>   
>   extern void *kimage_map_segment(struct kimage *image, unsigned long addr, unsigned long size);
>   extern void kimage_unmap_segment(void *buffer);
> diff --git a/kernel/kexec.c b/kernel/kexec.c
> index 28008e3d462e..570adb845662 100644
> --- a/kernel/kexec.c
> +++ b/kernel/kexec.c
> @@ -42,6 +42,7 @@ static int kimage_alloc_init(struct kimage **rimage, unsigned long entry,
>   	if (!image)
>   		return -ENOMEM;
>   
> +	kexec_core_dbg_print = !!(flags & KEXEC_DEBUG);
>   	image->start = entry;
>   	image->nr_segments = nr_segments;
>   	memcpy(image->segment, segments, nr_segments * sizeof(*segments));
> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
> index fa00b239c5d9..3af3ba77a3bd 100644
> --- a/kernel/kexec_core.c
> +++ b/kernel/kexec_core.c
> @@ -619,6 +619,7 @@ void kimage_free(struct kimage *image)
>   	if (image->file_mode)
>   		kimage_file_post_load_cleanup(image);
>   
> +	kexec_core_dbg_print = false;
>   	kfree(image);
>   }
>   
> diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
> index eb62a9794242..4a24aadbad02 100644
> --- a/kernel/kexec_file.c
> +++ b/kernel/kexec_file.c
> @@ -138,8 +138,6 @@ void kimage_file_post_load_cleanup(struct kimage *image)
>   	 */
>   	kfree(image->image_loader_data);
>   	image->image_loader_data = NULL;
> -
> -	kexec_file_dbg_print = false;
>   }
>   
>   #ifdef CONFIG_KEXEC_SIG
> @@ -314,7 +312,7 @@ kimage_file_alloc_init(struct kimage **rimage, int kernel_fd,
>   	if (!image)
>   		return -ENOMEM;
>   
> -	kexec_file_dbg_print = !!(flags & KEXEC_FILE_DEBUG);
> +	kexec_core_dbg_print = !!(flags & KEXEC_FILE_DEBUG);
>   	image->file_mode = 1;
>   
>   #ifdef CONFIG_CRASH_DUMP
>
>