linux-kernel - Re: [PATCH v2 2/4] kexec: add kexec_core flag to control debug printing

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Message-ID: <aQq/2WN8Sqz6m6xc@MiWiFi-R3L-srv>
Date: Wed, 5 Nov 2025 11:09:13 +0800
From: Baoquan He <bhe@...hat.com>
To: Qiang Ma <maqianga@...ontech.com>
Cc: akpm@...ux-foundation.org, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/4] kexec: add kexec_core flag to control debug
 printing

On 11/03/25 at 02:34pm, 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().
> 
> Since kexec_load and kexec_file_load are not triggered
> simultaneously, we can unify the debug flag of kexec and kexec_file
> as kexec_core_dbg_print.

After reconsidering this, I regret calling it kexec_core_dbg_print.
That sounds a printing only happening in kexec_core. Maybe
kexec_dbg_print is better. Because here kexec refers to a generic
concept, but not limited to kexec_load interface only. Just my personal
thinking.

Other than the naming, the whole patch looks good to me. Thanks.

> 
> Next, we need to do four things:
> 
> 1. rename kexec_file_dbg_print to kexec_core_dbg_print
> 2. Add KEXEC_DEBUG
> 3. Initialize kexec_core_dbg_print for kexec
> 4. Set the reset of kexec_file_dbg_print to kimage_free
> 
> Signed-off-by: Qiang Ma <maqianga@...ontech.com>
> ---
>  include/linux/kexec.h      | 9 +++++----
>  include/uapi/linux/kexec.h | 1 +
>  kernel/kexec.c             | 1 +
>  kernel/kexec_core.c        | 4 +++-
>  kernel/kexec_file.c        | 4 +---
>  5 files changed, 11 insertions(+), 8 deletions(-)
> 
> diff --git a/include/linux/kexec.h b/include/linux/kexec.h
> index ff7e231b0485..cad8b5c362af 100644
> --- a/include/linux/kexec.h
> +++ b/include/linux/kexec.h
> @@ -455,10 +455,11 @@ bool kexec_load_permitted(int kexec_image_type);
>  
>  /* List of defined/legal kexec flags */
>  #ifndef CONFIG_KEXEC_JUMP
> -#define KEXEC_FLAGS    (KEXEC_ON_CRASH | KEXEC_UPDATE_ELFCOREHDR | KEXEC_CRASH_HOTPLUG_SUPPORT)
> +#define KEXEC_FLAGS    (KEXEC_ON_CRASH | KEXEC_UPDATE_ELFCOREHDR | KEXEC_CRASH_HOTPLUG_SUPPORT | \
> +			KEXEC_DEBUG)
>  #else
>  #define KEXEC_FLAGS    (KEXEC_ON_CRASH | KEXEC_PRESERVE_CONTEXT | KEXEC_UPDATE_ELFCOREHDR | \
> -			KEXEC_CRASH_HOTPLUG_SUPPORT)
> +			KEXEC_CRASH_HOTPLUG_SUPPORT | KEXEC_DEBUG)
>  #endif
>  
>  /* List of defined/legal kexec file flags */
> @@ -525,10 +526,10 @@ 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/include/uapi/linux/kexec.h b/include/uapi/linux/kexec.h
> index 55749cb0b81d..819c600af125 100644
> --- a/include/uapi/linux/kexec.h
> +++ b/include/uapi/linux/kexec.h
> @@ -14,6 +14,7 @@
>  #define KEXEC_PRESERVE_CONTEXT	0x00000002
>  #define KEXEC_UPDATE_ELFCOREHDR	0x00000004
>  #define KEXEC_CRASH_HOTPLUG_SUPPORT 0x00000008
> +#define KEXEC_DEBUG		0x00000010
>  #define KEXEC_ARCH_MASK		0xffff0000
>  
>  /*
> diff --git a/kernel/kexec.c b/kernel/kexec.c
> index 9bb1f2b6b268..c7a869d32f87 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..865f2b14f23b 100644
> --- a/kernel/kexec_core.c
> +++ b/kernel/kexec_core.c
> @@ -53,7 +53,7 @@ atomic_t __kexec_lock = ATOMIC_INIT(0);
>  /* Flag to indicate we are going to kexec a new kernel */
>  bool kexec_in_progress = false;
>  
> -bool kexec_file_dbg_print;
> +bool kexec_core_dbg_print;
>  
>  /*
>   * When kexec transitions to the new kernel there is a one-to-one
> @@ -576,6 +576,8 @@ void kimage_free(struct kimage *image)
>  	kimage_entry_t *ptr, entry;
>  	kimage_entry_t ind = 0;
>  
> +	kexec_core_dbg_print = false;
> +
>  	if (!image)
>  		return;
>  
> 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
> -- 
> 2.20.1
>