RE: Linux 4.4.256

[David Laight <David.Laight@ACULAB.COM>]

From: David Laight
> Sent: 08 February 2021 09:10
> 
> From: Willy Tarreau
> > Sent: 06 February 2021 13:23
> >
> > On Sat, Feb 06, 2021 at 02:11:13PM +0100, Willy Tarreau wrote:
> > > Something like this looks more robust to me, it will use SUBLEVEL for
> > > values 0 to 255 and 255 for any larger value:
> >
> > diff --git a/Makefile b/Makefile
> > index 7d86ad6ad36c..9b91b8815b40 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -1252,7 +1252,7 @@ endef
> >
> >  define filechk_version.h
> >  	echo \#define LINUX_VERSION_CODE $(shell                         \
> > -	expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + 0$(SUBLEVEL)); \
> > +	expr $(VERSION) \* 65536 + 0$(PATCHLEVEL) \* 256 + 255 \* \( 0$(SUBLEVEL) \> 255 \) +
> > 0$(SUBLEVEL) \* \( 0$(SUBLEVEL) \<= 255 \) ); \
> >  	echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))'
> >  endef
> 
> Why not:
> 	$(shell echo $$(($(VERSION)<<16 + $(PATCHLEVEL)<<8 + ($(SUBVERSION) < 255 ? $(SUBVERSION) :
> 255))))
> Untested, but I think only the one $ needs any kind of escape.
> The extra leading zeros do have to go - $((...)) does octal :-(

Or probably even better:

echo '#define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + ((c) > 255 ? 255 : (c)))'
echo '#define LINUX_VERSION_CODE KERNEL_VERSION($(VERSION), $(PATCHLEVEL)+0, $(SUBLEVEL)+0)'

Which gets rid of the $(shell) as well.

	David

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