Re: [PATCH v2 3/4] kexec: print out debugging message if required for kexec_load

[Qiang Ma]

在 2025/11/5 15:53, Baoquan He 写道:
On 11/05/25 at 11:41am, Qiang Ma wrote:
在 2025/11/5 11:01, Baoquan He 写道:
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().

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.

Signed-off-by: Qiang Ma <maqia...@uniontech.com>
Reported-by: kernel test robot <l...@intel.com>
Closes: 
https://lore.kernel.org/oe-kbuild-all/202510310332.6xrle70k-...@intel.com/
---
   kernel/kexec.c | 11 +++++++++++
   1 file changed, 11 insertions(+)

diff --git a/kernel/kexec.c b/kernel/kexec.c
index c7a869d32f87..9b433b972cc1 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -154,7 +154,15 @@ static int do_kexec_load(unsigned long entry, unsigned 
long nr_segments,
        if (ret)
                goto out;
+       kexec_dprintk("nr_segments = %lu\n", nr_segments);
        for (i = 0; i < nr_segments; i++) {
+               struct kexec_segment *ksegment;
+
+               ksegment = &image->segment[i];
+               kexec_dprintk("segment[%lu]: buf=0x%p bufsz=0x%zx mem=0x%lx 
memsz=0x%zx\n",
+                             i, ksegment->buf, ksegment->bufsz, ksegment->mem,
+                             ksegment->memsz);
There has already been a print_segments() in kexec-tools/kexec/kexec.c,
you will get duplicated printing. That sounds not good. Have you tested
this?
I have tested it, kexec-tools is the debug message printed
in user space, while kexec_dprintk is printed
in kernel space.

This might be helpful for verifying the accuracy of
the data passed to the kernel.
Hmm, that's not necessary with a debug printing to verify value passed
in kernel. We should only add debug pringing when we need but lack it.
I didn't check it carefully, if you add the debug printing only for
verifying accuracy, that doesn't justify the code change.

Also, adding these prints here is helpful for debugging the 
kimage_load_segment().
+
                ret = kimage_load_segment(image, i);
                if (ret)
                        goto out;
@@ -166,6 +174,9 @@ static int do_kexec_load(unsigned long entry, unsigned long 
nr_segments,
        if (ret)
                goto out;
+       kexec_dprintk("kexec_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