Jiri reported that the current kexec_dprintk() always prints out
debugging message whenever kexec/kdmmp loading is triggered. That is
not wanted. The debugging message is supposed to be printed out when
'kexec -s -d' is specified for kexec/kdump loading.
After investigating, the reason is the current kexec_dprintk() takes
printk(KERN_INFO) or printk(KERN_DEBUG) depending on whether '-d' is
specified. However, distros usually have defaulg log level like below:
[~]# cat /proc/sys/kernel/printk
7 4 1 7
So, even though '-d' is not specified, printk(KERN_DEBUG) also always
prints out. I thought printk(KERN_DEBUG) is equal to pr_debug(), it's
not.
Fix it by changing to use pr_info() instead which are expected to work.
Fixes: cbc2fe9d9cb2 ("kexec_file: add kexec_file flag to control debug printing")
Signed-off-by: Baoquan He <[email protected]>
Reported-by: Jiri Slaby <[email protected]>
Closes: https://lore.kernel.org/all/[email protected]
---
v1->v2:
- Change to use pr_info() only when "kexec -s -d" is specified. With
this change, those debugging message for "kexec -c -d" of kexec_load
will be missed. We'll see if we need add them for kexec_load too, if
someone explicitly requests it.
include/linux/kexec.h | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index 060835bb82d5..f31bd304df45 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -461,10 +461,8 @@ static inline void arch_kexec_pre_free_pages(void *vaddr, unsigned int pages) {
extern bool kexec_file_dbg_print;
-#define kexec_dprintk(fmt, ...) \
- printk("%s" fmt, \
- kexec_file_dbg_print ? KERN_INFO : KERN_DEBUG, \
- ##__VA_ARGS__)
+#define kexec_dprintk(fmt, arg...) \
+ do { if (kexec_file_dbg_print) pr_info(fmt, ##arg); } while (0)
#else /* !CONFIG_KEXEC_CORE */
struct pt_regs;
--
2.41.0
On Tue, 9 Apr 2024 at 12:23, Baoquan He <[email protected]> wrote:
>
> Jiri reported that the current kexec_dprintk() always prints out
> debugging message whenever kexec/kdmmp loading is triggered. That is
> not wanted. The debugging message is supposed to be printed out when
> 'kexec -s -d' is specified for kexec/kdump loading.
>
> After investigating, the reason is the current kexec_dprintk() takes
> printk(KERN_INFO) or printk(KERN_DEBUG) depending on whether '-d' is
> specified. However, distros usually have defaulg log level like below:
>
> [~]# cat /proc/sys/kernel/printk
> 7 4 1 7
>
> So, even though '-d' is not specified, printk(KERN_DEBUG) also always
> prints out. I thought printk(KERN_DEBUG) is equal to pr_debug(), it's
> not.
>
> Fix it by changing to use pr_info() instead which are expected to work.
Could you also update the kernel/crash_core.c and
kernel/crash_reserve.c to include the filename prefix?
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
Otherwise:
Reviewed-by: Dave Young <[email protected]>
>
> Fixes: cbc2fe9d9cb2 ("kexec_file: add kexec_file flag to control debug printing")
> Signed-off-by: Baoquan He <[email protected]>
> Reported-by: Jiri Slaby <[email protected]>
> Closes: https://lore.kernel.org/all/[email protected]
> ---
> v1->v2:
> - Change to use pr_info() only when "kexec -s -d" is specified. With
> this change, those debugging message for "kexec -c -d" of kexec_load
> will be missed. We'll see if we need add them for kexec_load too, if
> someone explicitly requests it.
>
> include/linux/kexec.h | 6 ++----
> 1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/kexec.h b/include/linux/kexec.h
> index 060835bb82d5..f31bd304df45 100644
> --- a/include/linux/kexec.h
> +++ b/include/linux/kexec.h
> @@ -461,10 +461,8 @@ static inline void arch_kexec_pre_free_pages(void *vaddr, unsigned int pages) {
>
> extern bool kexec_file_dbg_print;
>
> -#define kexec_dprintk(fmt, ...) \
> - printk("%s" fmt, \
> - kexec_file_dbg_print ? KERN_INFO : KERN_DEBUG, \
> - ##__VA_ARGS__)
> +#define kexec_dprintk(fmt, arg...) \
> + do { if (kexec_file_dbg_print) pr_info(fmt, ##arg); } while (0)
>
> #else /* !CONFIG_KEXEC_CORE */
> struct pt_regs;
> --
> 2.41.0
>
>
On 04/12/24 at 03:28pm, Dave Young wrote:
> On Tue, 9 Apr 2024 at 12:23, Baoquan He <[email protected]> wrote:
> >
> > Jiri reported that the current kexec_dprintk() always prints out
> > debugging message whenever kexec/kdmmp loading is triggered. That is
> > not wanted. The debugging message is supposed to be printed out when
> > 'kexec -s -d' is specified for kexec/kdump loading.
> >
> > After investigating, the reason is the current kexec_dprintk() takes
> > printk(KERN_INFO) or printk(KERN_DEBUG) depending on whether '-d' is
> > specified. However, distros usually have defaulg log level like below:
> >
> > [~]# cat /proc/sys/kernel/printk
> > 7 4 1 7
> >
> > So, even though '-d' is not specified, printk(KERN_DEBUG) also always
> > prints out. I thought printk(KERN_DEBUG) is equal to pr_debug(), it's
> > not.
> >
> > Fix it by changing to use pr_info() instead which are expected to work.
>
> Could you also update the kernel/crash_core.c and
> kernel/crash_reserve.c to include the filename prefix?
> #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
OK, thanks for testing and spotting this.
When I tested this patch, I only did test kexec reboot functionality.
So the line of printing in kernel/crash_core.c is missed. While there
seems to be no kexec_dprintk() in kernel/crash_reserve.c. Anyway,
adding pr_fmt() is a good idea for debug printing in that file. I will
post a standalone patch to add these.
>
> Otherwise:
> Reviewed-by: Dave Young <[email protected]>
Thanks again.
>
> >
> > Fixes: cbc2fe9d9cb2 ("kexec_file: add kexec_file flag to control debug printing")
> > Signed-off-by: Baoquan He <[email protected]>
> > Reported-by: Jiri Slaby <[email protected]>
> > Closes: https://lore.kernel.org/all/[email protected]
> > ---
> > v1->v2:
> > - Change to use pr_info() only when "kexec -s -d" is specified. With
> > this change, those debugging message for "kexec -c -d" of kexec_load
> > will be missed. We'll see if we need add them for kexec_load too, if
> > someone explicitly requests it.
> >
> > include/linux/kexec.h | 6 ++----
> > 1 file changed, 2 insertions(+), 4 deletions(-)
> >
> > diff --git a/include/linux/kexec.h b/include/linux/kexec.h
> > index 060835bb82d5..f31bd304df45 100644
> > --- a/include/linux/kexec.h
> > +++ b/include/linux/kexec.h
> > @@ -461,10 +461,8 @@ static inline void arch_kexec_pre_free_pages(void *vaddr, unsigned int pages) {
> >
> > extern bool kexec_file_dbg_print;
> >
> > -#define kexec_dprintk(fmt, ...) \
> > - printk("%s" fmt, \
> > - kexec_file_dbg_print ? KERN_INFO : KERN_DEBUG, \
> > - ##__VA_ARGS__)
> > +#define kexec_dprintk(fmt, arg...) \
> > + do { if (kexec_file_dbg_print) pr_info(fmt, ##arg); } while (0)
> >
> > #else /* !CONFIG_KEXEC_CORE */
> > struct pt_regs;
> > --
> > 2.41.0
> >
> >
>
Hi Dave,
On 04/12/24 at 03:28pm, Dave Young wrote:
> On Tue, 9 Apr 2024 at 12:23, Baoquan He <[email protected]> wrote:
> >
> > Jiri reported that the current kexec_dprintk() always prints out
> > debugging message whenever kexec/kdmmp loading is triggered. That is
> > not wanted. The debugging message is supposed to be printed out when
> > 'kexec -s -d' is specified for kexec/kdump loading.
> >
> > After investigating, the reason is the current kexec_dprintk() takes
> > printk(KERN_INFO) or printk(KERN_DEBUG) depending on whether '-d' is
> > specified. However, distros usually have defaulg log level like below:
> >
> > [~]# cat /proc/sys/kernel/printk
> > 7 4 1 7
> >
> > So, even though '-d' is not specified, printk(KERN_DEBUG) also always
> > prints out. I thought printk(KERN_DEBUG) is equal to pr_debug(), it's
> > not.
> >
> > Fix it by changing to use pr_info() instead which are expected to work.
>
> Could you also update the kernel/crash_core.c and
> kernel/crash_reserve.c to include the filename prefix?
> #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
When I added pr_fmt() to kernel/crash_reserve.c and tested code, the
printed boot log about crashkernel reservation is changed as below:
[ +0.000000] crash_reserve: crashkernel reserved: 0x000000007d000000 - 0x0000000095000000 (384 MB)
When I looked around, I noticed all other lines around don't have the
module name printed out. Seems it's not appropriate to add one for
crashkernel alone. And the kexec_dprintk() doesn't exist in
kernel/crash_reserve.c. Furthermore, the kexec_dprintk() is added to
enable debugging printing for kexec_file_load when loading kexec/kdump
kernel. This crashkernel reservation may not be related. Combinbed these
all, I would suggest not adding pr_fmt() for kernel/crash_reserve.c for
now, let's add pr_fmt() for kernel/crash_core.c, what do you think?
>
> >
> > Fixes: cbc2fe9d9cb2 ("kexec_file: add kexec_file flag to control debug printing")
> > Signed-off-by: Baoquan He <[email protected]>
> > Reported-by: Jiri Slaby <[email protected]>
> > Closes: https://lore.kernel.org/all/[email protected]
> > ---
> > v1->v2:
> > - Change to use pr_info() only when "kexec -s -d" is specified. With
> > this change, those debugging message for "kexec -c -d" of kexec_load
> > will be missed. We'll see if we need add them for kexec_load too, if
> > someone explicitly requests it.
> >
> > include/linux/kexec.h | 6 ++----
> > 1 file changed, 2 insertions(+), 4 deletions(-)
> >
> > diff --git a/include/linux/kexec.h b/include/linux/kexec.h
> > index 060835bb82d5..f31bd304df45 100644
> > --- a/include/linux/kexec.h
> > +++ b/include/linux/kexec.h
> > @@ -461,10 +461,8 @@ static inline void arch_kexec_pre_free_pages(void *vaddr, unsigned int pages) {
> >
> > extern bool kexec_file_dbg_print;
> >
> > -#define kexec_dprintk(fmt, ...) \
> > - printk("%s" fmt, \
> > - kexec_file_dbg_print ? KERN_INFO : KERN_DEBUG, \
> > - ##__VA_ARGS__)
> > +#define kexec_dprintk(fmt, arg...) \
> > + do { if (kexec_file_dbg_print) pr_info(fmt, ##arg); } while (0)
> >
> > #else /* !CONFIG_KEXEC_CORE */
> > struct pt_regs;
> > --
> > 2.41.0
> >
> >
>
On Sun, 14 Apr 2024 at 10:54, Baoquan He <[email protected]> wrote:
>
> Hi Dave,
>
> On 04/12/24 at 03:28pm, Dave Young wrote:
> > On Tue, 9 Apr 2024 at 12:23, Baoquan He <[email protected]> wrote:
> > >
> > > Jiri reported that the current kexec_dprintk() always prints out
> > > debugging message whenever kexec/kdmmp loading is triggered. That is
> > > not wanted. The debugging message is supposed to be printed out when
> > > 'kexec -s -d' is specified for kexec/kdump loading.
> > >
> > > After investigating, the reason is the current kexec_dprintk() takes
> > > printk(KERN_INFO) or printk(KERN_DEBUG) depending on whether '-d' is
> > > specified. However, distros usually have defaulg log level like below:
> > >
> > > [~]# cat /proc/sys/kernel/printk
> > > 7 4 1 7
> > >
> > > So, even though '-d' is not specified, printk(KERN_DEBUG) also always
> > > prints out. I thought printk(KERN_DEBUG) is equal to pr_debug(), it's
> > > not.
> > >
> > > Fix it by changing to use pr_info() instead which are expected to work.
> >
> > Could you also update the kernel/crash_core.c and
> > kernel/crash_reserve.c to include the filename prefix?
> > #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
>
> When I added pr_fmt() to kernel/crash_reserve.c and tested code, the
> printed boot log about crashkernel reservation is changed as below:
>
> [ +0.000000] crash_reserve: crashkernel reserved: 0x000000007d000000 - 0x0000000095000000 (384 MB)
>
> When I looked around, I noticed all other lines around don't have the
> module name printed out. Seems it's not appropriate to add one for
> crashkernel alone. And the kexec_dprintk() doesn't exist in
> kernel/crash_reserve.c. Furthermore, the kexec_dprintk() is added to
> enable debugging printing for kexec_file_load when loading kexec/kdump
> kernel. This crashkernel reservation may not be related. Combinbed these
> all, I would suggest not adding pr_fmt() for kernel/crash_reserve.c for
> now, let's add pr_fmt() for kernel/crash_core.c, what do you think?
Hi Baoquan, I'm fine with it.
But adding pr_fmt is always good as all the pr_* will have a prefix
instead of manually add "crashkernel:" in every pr_warn etc. There
are indeed a few without any prefix in this file though. But it can
be done separately, not necessary to be done here together with the
debug print though.
Thanks
Dave
>
> >
> > >
> > > Fixes: cbc2fe9d9cb2 ("kexec_file: add kexec_file flag to control debug printing")
> > > Signed-off-by: Baoquan He <[email protected]>
> > > Reported-by: Jiri Slaby <[email protected]>
> > > Closes: https://lore.kernel.org/all/[email protected]
> > > ---
> > > v1->v2:
> > > - Change to use pr_info() only when "kexec -s -d" is specified. With
> > > this change, those debugging message for "kexec -c -d" of kexec_load
> > > will be missed. We'll see if we need add them for kexec_load too, if
> > > someone explicitly requests it.
> > >
> > > include/linux/kexec.h | 6 ++----
> > > 1 file changed, 2 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/include/linux/kexec.h b/include/linux/kexec.h
> > > index 060835bb82d5..f31bd304df45 100644
> > > --- a/include/linux/kexec.h
> > > +++ b/include/linux/kexec.h
> > > @@ -461,10 +461,8 @@ static inline void arch_kexec_pre_free_pages(void *vaddr, unsigned int pages) {
> > >
> > > extern bool kexec_file_dbg_print;
> > >
> > > -#define kexec_dprintk(fmt, ...) \
> > > - printk("%s" fmt, \
> > > - kexec_file_dbg_print ? KERN_INFO : KERN_DEBUG, \
> > > - ##__VA_ARGS__)
> > > +#define kexec_dprintk(fmt, arg...) \
> > > + do { if (kexec_file_dbg_print) pr_info(fmt, ##arg); } while (0)
> > >
> > > #else /* !CONFIG_KEXEC_CORE */
> > > struct pt_regs;
> > > --
> > > 2.41.0
> > >
> > >
> >
>