linux-kernel - RE: Linux 4.4.256

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Date:   Mon, 8 Feb 2021 09:09:32 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Willy Tarreau' <w@....eu>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:     Guenter Roeck <linux@...ck-us.net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "lwn@....net" <lwn@....net>, "jslaby@...e.cz" <jslaby@...e.cz>,
        "shuah@...nel.org" <shuah@...nel.org>,
        "patches@...nelci.org" <patches@...nelci.org>,
        "lkft-triage@...ts.linaro.org" <lkft-triage@...ts.linaro.org>,
        "pavel@...x.de" <pavel@...x.de>,
        "jonathanh@...dia.com" <jonathanh@...dia.com>
Subject: RE: Linux 4.4.256

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 :-(

	David

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