[PATCH 1/1] drivers/base/cpu: Print kernel arch

[PATCH 1/1] drivers/base/cpu: Print kernel arch

[Petr Vorel]

Print kernel architecture in /sys/devices/system/cpu/arch
using UTS_MACHINE, i.e. member of struct uts_namespace.machine.

This helps people who debug kernel with initramfs with minimal
environment (i.e. without coreutils or even busybox) or allow to open
sysfs file instead of run uname -m in high level languages.

Signed-off-by: Petr Vorel <pvorel@suse.cz>
---
 drivers/base/cpu.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index 4c98849577d4..7c8032e3ff10 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -3,6 +3,7 @@
  * CPU subsystem support
  */
 
+#include <generated/compile.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/init.h>
@@ -232,6 +233,13 @@ static ssize_t print_cpus_kernel_max(struct device *dev,
 }
 static DEVICE_ATTR(kernel_max, 0444, print_cpus_kernel_max, NULL);
 
+static ssize_t print_cpus_arch(struct device *dev,
+				     struct device_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "%s\n", UTS_MACHINE);
+}
+static DEVICE_ATTR(arch, 0444, print_cpus_arch, NULL);
+
 /* arch-optional setting to enable display of offline cpus >= nr_cpu_ids */
 unsigned int total_cpus;
 
@@ -464,6 +472,7 @@ static struct attribute *cpu_root_attrs[] = {
 	&cpu_attrs[1].attr.attr,
 	&cpu_attrs[2].attr.attr,
 	&dev_attr_kernel_max.attr,
+	&dev_attr_arch.attr,
 	&dev_attr_offline.attr,
 	&dev_attr_isolated.attr,
 #ifdef CONFIG_NO_HZ_FULL
-- 
2.37.1

Re: [PATCH 1/1] drivers/base/cpu: Print kernel arch

[Greg Kroah-Hartman]

On Wed, Jul 27, 2022 at 06:11:35PM +0200, Petr Vorel wrote:
> Print kernel architecture in /sys/devices/system/cpu/arch
> using UTS_MACHINE, i.e. member of struct uts_namespace.machine.
> 
> This helps people who debug kernel with initramfs with minimal
> environment (i.e. without coreutils or even busybox) or allow to open
> sysfs file instead of run uname -m in high level languages.
> 
> Signed-off-by: Petr Vorel <pvorel@suse.cz>
> ---
>  drivers/base/cpu.c | 9 +++++++++
>  1 file changed, 9 insertions(+)

You can't add a new sysfs file without a Documentation/ABI/ update as
well.  Please fix that up.


> 
> diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
> index 4c98849577d4..7c8032e3ff10 100644
> --- a/drivers/base/cpu.c
> +++ b/drivers/base/cpu.c
> @@ -3,6 +3,7 @@
>   * CPU subsystem support
>   */
>  
> +#include <generated/compile.h>
>  #include <linux/kernel.h>
>  #include <linux/module.h>
>  #include <linux/init.h>
> @@ -232,6 +233,13 @@ static ssize_t print_cpus_kernel_max(struct device *dev,
>  }
>  static DEVICE_ATTR(kernel_max, 0444, print_cpus_kernel_max, NULL);
>  
> +static ssize_t print_cpus_arch(struct device *dev,
> +				     struct device_attribute *attr, char *buf)
> +{
> +	return sysfs_emit(buf, "%s\n", UTS_MACHINE);
> +}
> +static DEVICE_ATTR(arch, 0444, print_cpus_arch, NULL);

why just UTS_MACHINE?  Doesn't 'uname' show this already?  And I thought
this was in /proc/cpuinfo but odd, it isn't...

Also what about the other things in compile.h?

thanks,

greg k-h

Re: [PATCH 1/1] drivers/base/cpu: Print kernel arch

[Petr Vorel]

Hi Greg,

thanks for your review!

> On Wed, Jul 27, 2022 at 06:11:35PM +0200, Petr Vorel wrote:
> > Print kernel architecture in /sys/devices/system/cpu/arch
> > using UTS_MACHINE, i.e. member of struct uts_namespace.machine.

> > This helps people who debug kernel with initramfs with minimal
> > environment (i.e. without coreutils or even busybox) or allow to open
> > sysfs file instead of run uname -m in high level languages.

> > Signed-off-by: Petr Vorel <pvorel@suse.cz>
> > ---
> >  drivers/base/cpu.c | 9 +++++++++
> >  1 file changed, 9 insertions(+)

> You can't add a new sysfs file without a Documentation/ABI/ update as
> well.  Please fix that up.
I'm sorry. Yes, I realized it later on (once I got offline).
Sure, I'll fix this in v2. But the main question is whether this feature is
acceptable and what is the best place for the file.


> > diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
> > index 4c98849577d4..7c8032e3ff10 100644
> > --- a/drivers/base/cpu.c
> > +++ b/drivers/base/cpu.c
> > @@ -3,6 +3,7 @@
> >   * CPU subsystem support
> >   */

> > +#include <generated/compile.h>
> >  #include <linux/kernel.h>
> >  #include <linux/module.h>
> >  #include <linux/init.h>
> > @@ -232,6 +233,13 @@ static ssize_t print_cpus_kernel_max(struct device *dev,
> >  }
> >  static DEVICE_ATTR(kernel_max, 0444, print_cpus_kernel_max, NULL);

> > +static ssize_t print_cpus_arch(struct device *dev,
> > +				     struct device_attribute *attr, char *buf)
> > +{
> > +	return sysfs_emit(buf, "%s\n", UTS_MACHINE);
> > +}
> > +static DEVICE_ATTR(arch, 0444, print_cpus_arch, NULL);

> why just UTS_MACHINE?  Doesn't 'uname' show this already?  And I thought
> this was in /proc/cpuinfo but odd, it isn't...
Sure, this info is in uname(). But for certain cases is really easier to read
file from /proc or /sys than run create custom C bindings or a binary which
calls uname(2) libc wrapper or run uname binary via execve(2).

Yes, I also expected /proc/cpuinfo would have it but it does not have it. I
don't think it's a good idea to add 'arch  : foo' line to it, but I can do if
there is consensus that it's the best place.

> Also what about the other things in compile.h?
UTS_VERSION is in /proc/version.
LINUX_COMPILE_BY (e.g. "user"), LINUX_COMPILE_HOST (e.g. "host") and
LINUX_COMPILER (e.g. "aarch64-alpine-linux-musl-gcc (Alpine 11.2.1_git20220219)
...") are IMHO useless, but I can add it if you wish.

Well, there is hostname in /proc/sys/kernel/hostname, there are also ostype and
osrelease.. Thinking about it twice /proc/sys/kernel/ looks to me a better place
for arch file than current /sys/devices/system/cpu/. WDYT?

Kind regards,
Petr

> thanks,

> greg k-h

Re: [PATCH 1/1] drivers/base/cpu: Print kernel arch

[Greg Kroah-Hartman]

On Thu, Jul 28, 2022 at 12:22:05AM +0200, Petr Vorel wrote:
> Hi Greg,
> 
> thanks for your review!
> 
> > On Wed, Jul 27, 2022 at 06:11:35PM +0200, Petr Vorel wrote:
> > > Print kernel architecture in /sys/devices/system/cpu/arch
> > > using UTS_MACHINE, i.e. member of struct uts_namespace.machine.
> 
> > > This helps people who debug kernel with initramfs with minimal
> > > environment (i.e. without coreutils or even busybox) or allow to open
> > > sysfs file instead of run uname -m in high level languages.
> 
> > > Signed-off-by: Petr Vorel <pvorel@suse.cz>
> > > ---
> > >  drivers/base/cpu.c | 9 +++++++++
> > >  1 file changed, 9 insertions(+)
> 
> > You can't add a new sysfs file without a Documentation/ABI/ update as
> > well.  Please fix that up.
> I'm sorry. Yes, I realized it later on (once I got offline).
> Sure, I'll fix this in v2. But the main question is whether this feature is
> acceptable and what is the best place for the file.
> 
> 
> > > diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
> > > index 4c98849577d4..7c8032e3ff10 100644
> > > --- a/drivers/base/cpu.c
> > > +++ b/drivers/base/cpu.c
> > > @@ -3,6 +3,7 @@
> > >   * CPU subsystem support
> > >   */
> 
> > > +#include <generated/compile.h>
> > >  #include <linux/kernel.h>
> > >  #include <linux/module.h>
> > >  #include <linux/init.h>
> > > @@ -232,6 +233,13 @@ static ssize_t print_cpus_kernel_max(struct device *dev,
> > >  }
> > >  static DEVICE_ATTR(kernel_max, 0444, print_cpus_kernel_max, NULL);
> 
> > > +static ssize_t print_cpus_arch(struct device *dev,
> > > +				     struct device_attribute *attr, char *buf)
> > > +{
> > > +	return sysfs_emit(buf, "%s\n", UTS_MACHINE);
> > > +}
> > > +static DEVICE_ATTR(arch, 0444, print_cpus_arch, NULL);
> 
> > why just UTS_MACHINE?  Doesn't 'uname' show this already?  And I thought
> > this was in /proc/cpuinfo but odd, it isn't...
> Sure, this info is in uname(). But for certain cases is really easier to read
> file from /proc or /sys than run create custom C bindings or a binary which
> calls uname(2) libc wrapper or run uname binary via execve(2).
> 
> Yes, I also expected /proc/cpuinfo would have it but it does not have it. I
> don't think it's a good idea to add 'arch  : foo' line to it, but I can do if
> there is consensus that it's the best place.
> 
> > Also what about the other things in compile.h?
> UTS_VERSION is in /proc/version.
> LINUX_COMPILE_BY (e.g. "user"), LINUX_COMPILE_HOST (e.g. "host") and
> LINUX_COMPILER (e.g. "aarch64-alpine-linux-musl-gcc (Alpine 11.2.1_git20220219)
> ...") are IMHO useless, but I can add it if you wish.
> 
> Well, there is hostname in /proc/sys/kernel/hostname, there are also ostype and
> osrelease.. Thinking about it twice /proc/sys/kernel/ looks to me a better place
> for arch file than current /sys/devices/system/cpu/. WDYT?

Yeah, I think /proc/sys/kernel/ makes sense, good idea.

greg k-h

Re: [PATCH 1/1] drivers/base/cpu: Print kernel arch

[Petr Vorel]

> On Thu, Jul 28, 2022 at 12:22:05AM +0200, Petr Vorel wrote:
> > Hi Greg,

> > thanks for your review!

> > > On Wed, Jul 27, 2022 at 06:11:35PM +0200, Petr Vorel wrote:
> > > > Print kernel architecture in /sys/devices/system/cpu/arch
> > > > using UTS_MACHINE, i.e. member of struct uts_namespace.machine.

> > > > This helps people who debug kernel with initramfs with minimal
> > > > environment (i.e. without coreutils or even busybox) or allow to open
> > > > sysfs file instead of run uname -m in high level languages.

> > > > Signed-off-by: Petr Vorel <pvorel@suse.cz>
> > > > ---
> > > >  drivers/base/cpu.c | 9 +++++++++
> > > >  1 file changed, 9 insertions(+)

> > > You can't add a new sysfs file without a Documentation/ABI/ update as
> > > well.  Please fix that up.
> > I'm sorry. Yes, I realized it later on (once I got offline).
> > Sure, I'll fix this in v2. But the main question is whether this feature is
> > acceptable and what is the best place for the file.


> > > > diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
> > > > index 4c98849577d4..7c8032e3ff10 100644
> > > > --- a/drivers/base/cpu.c
> > > > +++ b/drivers/base/cpu.c
> > > > @@ -3,6 +3,7 @@
> > > >   * CPU subsystem support
> > > >   */

> > > > +#include <generated/compile.h>
> > > >  #include <linux/kernel.h>
> > > >  #include <linux/module.h>
> > > >  #include <linux/init.h>
> > > > @@ -232,6 +233,13 @@ static ssize_t print_cpus_kernel_max(struct device *dev,
> > > >  }
> > > >  static DEVICE_ATTR(kernel_max, 0444, print_cpus_kernel_max, NULL);

> > > > +static ssize_t print_cpus_arch(struct device *dev,
> > > > +				     struct device_attribute *attr, char *buf)
> > > > +{
> > > > +	return sysfs_emit(buf, "%s\n", UTS_MACHINE);
> > > > +}
> > > > +static DEVICE_ATTR(arch, 0444, print_cpus_arch, NULL);

> > > why just UTS_MACHINE?  Doesn't 'uname' show this already?  And I thought
> > > this was in /proc/cpuinfo but odd, it isn't...
> > Sure, this info is in uname(). But for certain cases is really easier to read
> > file from /proc or /sys than run create custom C bindings or a binary which
> > calls uname(2) libc wrapper or run uname binary via execve(2).

> > Yes, I also expected /proc/cpuinfo would have it but it does not have it. I
> > don't think it's a good idea to add 'arch  : foo' line to it, but I can do if
> > there is consensus that it's the best place.

> > > Also what about the other things in compile.h?
> > UTS_VERSION is in /proc/version.
> > LINUX_COMPILE_BY (e.g. "user"), LINUX_COMPILE_HOST (e.g. "host") and
> > LINUX_COMPILER (e.g. "aarch64-alpine-linux-musl-gcc (Alpine 11.2.1_git20220219)
> > ...") are IMHO useless, but I can add it if you wish.

> > Well, there is hostname in /proc/sys/kernel/hostname, there are also ostype and
> > osrelease.. Thinking about it twice /proc/sys/kernel/ looks to me a better place
> > for arch file than current /sys/devices/system/cpu/. WDYT?

> Yeah, I think /proc/sys/kernel/ makes sense, good idea.
Thanks for info, I'll send v2 shortly.

Kind regards,
Petr

> greg k-h