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

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Message-ID: <aQNvHdZcVzletjdi@MiWiFi-R3L-srv>
Date: Thu, 30 Oct 2025 21:58:53 +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 10/30/25 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.

> 
> > > Signed-off-by: Qiang Ma <maqianga@...ontech.com>
> > > ---
> > >   kernel/kexec.c | 11 +++++++++++
> > >   1 file changed, 11 insertions(+)
> > > 
> > > diff --git a/kernel/kexec.c b/kernel/kexec.c
> > > index 28008e3d462e..02845a7499e9 100644
> > > --- a/kernel/kexec.c
> > > +++ b/kernel/kexec.c
> > > @@ -151,7 +151,15 @@ static int do_kexec_load(unsigned long entry, unsigned long nr_segments,
> > >   	if (ret)
> > >   		goto out;
> > > +	kexec_dprintk("nr_segments = %lu\n", image->nr_segments);
> > >   	for (i = 0; i < nr_segments; i++) {
> > > +		struct kexec_segment *ksegment;
> > > +
> > > +		ksegment = &image->segment[i];
> > > +		kexec_dprintk("segment[%d]: buf=0x%p bufsz=0x%zx mem=0x%lx memsz=0x%zx\n",
> > > +			      i, ksegment->buf, ksegment->bufsz, ksegment->mem,
> > > +			      ksegment->memsz);
> > > +
> > >   		ret = kimage_load_segment(image, i);
> > >   		if (ret)
> > >   			goto out;
> > > @@ -163,6 +171,9 @@ static int do_kexec_load(unsigned long entry, unsigned long nr_segments,
> > >   	if (ret)
> > >   		goto out;
> > > +	kexec_dprintk("kexec_file_load: type:%u, start:0x%lx head:0x%lx flags:0x%lx\n",
> > > +		      image->type, image->start, image->head, flags);
> > > +
> > >   	/* Install the new kernel and uninstall the old */
> > >   	image = xchg(dest_image, image);
> > > -- 
> > > 2.20.1
> > > 
> > > 
> > 
>