linux-kernel - Re: [PATCH 2/4] Add NR_syscalls for x86

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Message-ID: <alpine.DEB.2.00.0908252223310.28127@gandalf.stny.rr.com>
Date:	Tue, 25 Aug 2009 22:25:52 -0400 (EDT)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Jason Baron <jbaron@...hat.com>
cc:	Frederic Weisbecker <fweisbec@...il.com>,
	linux-kernel@...r.kernel.org, x86@...nel.org, lethal@...ux-sh.org,
	mingo@...e.hu, laijs@...fujitsu.com, peterz@...radead.org,
	mathieu.desnoyers@...ymtl.ca, jiayingz@...gle.com,
	mbligh@...gle.com, lizf@...fujitsu.com, jistone@...hat.com,
	tglx@...utronix.de, hpa@...or.com
Subject: Re: [PATCH 2/4] Add NR_syscalls for x86_64


On Tue, 25 Aug 2009, Jason Baron wrote:

> On Tue, Aug 25, 2009 at 09:40:05AM -0400, Jason Baron wrote:
> > 
> > right, for x86_64, unistd.h is included to generate __NR_syscall_max
> > which is then used for NR_syscalls. So I did initially try it there, but
> > there were dependency problems. I'll see what I can come up with...
> > 
> > thanks,
> > 
> > -Jason
> 
> ok, since unistd_64.h is used to generate offsets.c, which eventually
> generates, asm/asm-offsets.h, which defines, __NR_syscall_max, we can't
> just put #define of NR_syscalls in unistd_64.h. However, it seems the

Why not? A define is not a problem until it is used. Is something in 
asm-offsets.c using NR_syscalls?

> only point in time that unistd_64.h can not depend upon __NR_syscall_max,
> is before asm/asm-offsets.h is defined. Thus, the patch below passes in
> a '-DCREATE_OFFSETS' during the creation of asm/asm-offsets.h, so that
> we do not include it before it exists. The patch is hacky but works.
> thoughts?
> 
> Signed-off-by: Jason Baron <jbaron@...hat.com>
> 
> ---
> 
>  Kbuild                           |    2 +-
>  arch/x86/include/asm/unistd_64.h |    6 ++++++
>  scripts/Makefile.build           |    4 ++++
>  3 files changed, 11 insertions(+), 1 deletions(-)
> 
> 
> diff --git a/Kbuild b/Kbuild
> index f056b4f..5f43d4d 100644
> --- a/Kbuild
> +++ b/Kbuild
> @@ -78,7 +78,7 @@ endef
>  arch/$(SRCARCH)/kernel/asm-offsets.s: arch/$(SRCARCH)/kernel/asm-offsets.c \
>                                        $(obj)/$(bounds-file) FORCE
>  	$(Q)mkdir -p $(dir $@)
> -	$(call if_changed_dep,cc_s_c)
> +	$(call if_changed_dep,cc_s_c_define_offset)
>  
>  $(obj)/$(offsets-file): arch/$(SRCARCH)/kernel/asm-offsets.s Kbuild
>  	$(call cmd,offsets)
> diff --git a/arch/x86/include/asm/unistd_64.h b/arch/x86/include/asm/unistd_64.h
> index 900e161..70c0c3d 100644
> --- a/arch/x86/include/asm/unistd_64.h
> +++ b/arch/x86/include/asm/unistd_64.h
> @@ -688,6 +688,12 @@ __SYSCALL(__NR_perf_counter_open, sys_perf_counter_open)
>  #endif	/* __NO_STUBS */
>  
>  #ifdef __KERNEL__
> +
> +#ifndef CREATE_OFFSETS
> +#include <asm/asm-offsets.h>
> +#define NR_syscalls (__NR_syscall_max + 1)
> +#endif
> +
>  /*
>   * "Conditional" syscalls
>   *
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index 5c4b7a4..4177858 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -145,6 +145,10 @@ $(multi-objs-y:.o=.lst) : modname = $(modname-multi)
>  quiet_cmd_cc_s_c = CC $(quiet_modtag)  $@
>  cmd_cc_s_c       = $(CC) $(c_flags) -fverbose-asm -S -o $@ $<
>  
> +quiet_cmd_cc_s_c_define_offset = CC $(quiet_modtag)  $@
> +cmd_cc_s_c_define_offset       = $(CC) $(c_flags) -DCREATE_OFFSETS \
> +					-fverbose-asm -S -o $@ $<
> +
>  $(obj)/%.s: $(src)/%.c FORCE
>  	$(call if_changed_dep,cc_s_c)


Ug, yuck yuck yuck. Sometimes "it works" is not good enough ;-)

How about just adding in asm/unistd.h

 #ifdef __KERNEL__
 # ifdef CONFIG_X86_32
 #  include "unistd_32.h"
 # else
 #  include "unistd_64.h"
+#  define NR_syscalls (__NR_syscall_max + 1)
 # endif
 #else
 # ifdef __i386__
 #  include "unistd_32.h"
 # else
 #  include "unistd_64.h"
 # endif
 #endif

And if this is a problem because asm-offset_64.c includes asm/unistd.h, 
then make it just include unistd_64.h.

Or am I missing something?

-- Steve


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