linux-kernel - Re: [PATCH] tools/nolibc: remove LINUX_REBOOT

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Date:   Tue, 2 May 2023 08:47:15 +0200
From:   Thomas Weißschuh <thomas@...ch.de>
To:     Willy Tarreau <w@....eu>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tools/nolibc: remove LINUX_REBOOT_ constants

On 2023-05-02 08:32:15+0200, Willy Tarreau wrote:
> On Fri, Apr 28, 2023 at 05:52:11PM +0200, Thomas Weißschuh wrote:
> > The same constants and some more have been exposed to userspace via
> > linux/reboot.h for a long time.
> > 
> > To avoid conflicts and trim down nolibc a bit drop the custom
> > definitions.
> 
> For me it breaks the build when including nolibc directly, so most
> likely we need to include certain files:

Indeed, sorry no idea how I missed that.

>   In file included from /g/public/linux/master/tools/include/nolibc/nolibc.h:99,
>                    from <command-line>:
>   /g/public/linux/master/tools/include/nolibc/sys.h: In function 'reboot':
>   /g/public/linux/master/tools/include/nolibc/sys.h:972:30: error: 'LINUX_REBOOT_MAGIC1' undeclared (first use in this function)
>     972 |         int ret = sys_reboot(LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2, cmd, 0);
>         |                              ^~~~~~~~~~~~~~~~~~~
>   /g/public/linux/master/tools/include/nolibc/sys.h:972:30: note: each undeclared identifier is reported only once for each function it appears in
> 
> I suspect it might be like the S_* macros for stat() that we had to
> guard against. What build conflict did you meet ? I would like as well
> to redefine the least possible and if we can make sure to fix the
> conflict efficiently without breaking code, that would be better.

The conflict looks like this:

    In file included from nolibc-test.c:18:
    sysroot/x86/include/linux/reboot.h:10: warning: "LINUX_REBOOT_MAGIC2" redefined
       10 | #define LINUX_REBOOT_MAGIC2     672274793
          | 
    In file included from sysroot/x86/include/nolibc.h:98,
                     from sysroot/x86/include/errno.h:26,
                     from sysroot/x86/include/stdio.h:14,
                     from nolibc-test.c:15:
    ... and all the other ones.



The following trivial fix on top of my patch would fix the problem:

diff --git a/tools/include/nolibc/sys.h b/tools/include/nolibc/sys.h
index 5d624dc63a42..9d27131c224e 100644
--- a/tools/include/nolibc/sys.h
+++ b/tools/include/nolibc/sys.h
@@ -21,6 +21,7 @@
 #include <linux/auxvec.h>
 #include <linux/fcntl.h> // for O_* and AT_*
 #include <linux/stat.h>  // for statx()
+#include <linux/reboot.h> // for LINUX_REBOOT_*
 
 #include "arch.h"
 #include "errno.h"


Want me to send a v2 or will you fix it up on your side?