From: Rusty Russell <rusty@rustcorp•com.au>
To: Al Viro <viro@zeniv•linux.org.uk>
Cc: Michal Marek <mmarek@suse•cz>,
Andrew Morton <akpm@linux-foundation•org>,
Guenter Roeck <linux@roeck-us•net>,
Jean Delvare <khali@linux-fr•org>,
linux-kbuild@vger•kernel.org, linux-kernel@vger•kernel.org,
Mike Frysinger <vapier@gentoo•org>,
uclinux-dist-devel@blackfin•uclinux.org,
linux-next@vger•kernel.org, James Hogan <james.hogan@imgtec•com>
Subject: Re: [RFC -next] linux/linkage.h: fix symbol prefix handling
Date: Fri, 08 Mar 2013 11:03:13 +1100 [thread overview]
Message-ID: <87sj46wyf2.fsf@rustcorp.com.au> (raw)
In-Reply-To: <1362656642-2693-1-git-send-email-james.hogan@imgtec.com>
James Hogan <james.hogan@imgtec•com> writes:
> The commit "consolidate cond_syscall and SYSCALL_ALIAS declarations"
> broke the build on blackfin and metag due to the following code:
>
> #ifndef SYMBOL_NAME
> #ifdef CONFIG_SYMBOL_PREFIX
> #define SYMBOL_NAME(x) CONFIG_SYMBOL_PREFIX ## x
> #else
> #define SYMBOL_NAME(x) x
> #endif
> #endif
> #define __SYMBOL_NAME(x) __stringify(SYMBOL_NAME(x))
>
> __stringify literally stringifies CONFIG_SYMBOL_PREFIX ##x, so you get
> lines like this in the assembly output:
>
> .weak CONFIG_SYMBOL_PREFIXsys_quotactl
> .set
> CONFIG_SYMBOL_PREFIXsys_quotactl,CONFIG_SYMBOL_PREFIXsys_ni_syscall
>
> This is fixed by defining SYMBOL_PREFIX from the command line for c
> files in addition to assembly for architectures that set
> CONFIG_SYMBOL_PREFIX (scripts/Makefile.lib), and defining __SYMBOL_NAME
> as:
>
> #define __SYMBOL_NAME(x) __stringify(SYMBOL_PREFIX) #x
>
> We first have to ensure SYMBOL_PREFIX is defined (which avoids polluting
> the command lines for architectures that don't use symbol prefixes).
> Also the definition of SYMBOL_PREFIX in <linux/kernel.h> is removed as
> it conflicts, isn't used anywhere, and is defined as a string so differs
> from the assembly definition.
So now, if CONFIG_SYMBOL_PREFIX, SYMBOL_PREFIX is defined on the cmdline
as a string. Otherwise it's empty (not the empty string?):
> +/* This helps us to avoid #ifdef SYMBOL_PREFIX */
> +#ifndef SYMBOL_PREFIX
> +#define SYMBOL_PREFIX
> #endif
> -#define __SYMBOL_NAME(x) __stringify(SYMBOL_NAME(x))
> +
> +#define __SYMBOL_NAME(x) __stringify(SYMBOL_PREFIX) #x
And why are you __stringify()ing a string?
> #ifndef cond_syscall
> #define cond_syscall(x) asm(".weak\t" __SYMBOL_NAME(x) \
> diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
> index 07125e6..f1cce6a 100644
> --- a/scripts/Makefile.lib
> +++ b/scripts/Makefile.lib
> @@ -123,6 +123,7 @@ ifdef CONFIG_SYMBOL_PREFIX
> _sym_flags = -DSYMBOL_PREFIX=$(patsubst "%",%,$(CONFIG_SYMBOL_PREFIX))
> _cpp_flags += $(_sym_flags)
> _a_flags += $(_sym_flags)
> +_c_flags += $(_sym_flags)
> endif
Confused,
Rusty.
next prev parent reply other threads:[~2013-03-08 0:03 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-07 11:44 [RFC -next] linux/linkage.h: fix symbol prefix handling James Hogan
2013-03-08 0:03 ` Rusty Russell [this message]
2013-03-08 9:15 ` James Hogan
2013-03-11 6:35 ` Rusty Russell
2013-03-11 12:07 ` Stephen Rothwell
2013-03-12 4:48 ` Rusty Russell
2013-03-12 12:33 ` Stephen Rothwell
2013-03-13 0:00 ` Rusty Russell
2013-03-13 6:31 ` Sam Ravnborg
2013-03-13 9:21 ` James Hogan
2013-03-13 18:15 ` Sam Ravnborg
2013-03-14 4:00 ` Rusty Russell
2013-03-14 10:49 ` James Hogan
2013-03-15 4:37 ` Rusty Russell
2013-03-12 12:36 ` James Hogan
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