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

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Message-ID: <aQRv1JCoeYY4u7OX@MiWiFi-R3L-srv>
Date: Fri, 31 Oct 2025 16:14:12 +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] kexec: print out debugging message if required for
 kexec_load

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?

Please feel free to take it as reference, or you can go in other ways
you have better one.

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