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

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Date:	Tue, 25 Aug 2009 14:47:34 -0400
From:	Jason Baron <jbaron@...hat.com>
To:	Steven Rostedt <rostedt@...dmis.org>
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, Aug 25, 2009 at 09:40:05AM -0400, Jason Baron wrote:
> > > On Mon, Aug 24, 2009 at 05:40:18PM -0400, Jason Baron wrote:
> > > > Add a dynamic definition of NR_syscalls for x86_64. This is used in the 
> > > > syscall events tracing code.
> > > > 
> > > > Signed-off-by: Jason Baron <jbaron@...hat.com>
> > > > 
> > > > ---
> > > >  include/linux/ftrace.h |    5 +++++
> > > >  1 files changed, 5 insertions(+), 0 deletions(-)
> > > > 
> > > > diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> > > > index dc3b132..3bd94ee 100644
> > > > --- a/include/linux/ftrace.h
> > > > +++ b/include/linux/ftrace.h
> > > > @@ -14,6 +14,11 @@
> > > >  
> > > >  #include <asm/ftrace.h>
> > > >  
> > > > +#ifdef CONFIG_X86_64
> > > > +#include <asm/asm-offsets.h>
> > > > +#define NR_syscalls (__NR_syscall_max + 1)
> > > > +#endif
> > > > +
> > > 
> > > 
> > > I'd rather see this in arch/x86/include/unistd_64.h, since
> > > NR_syscalls seems to be the defined in unistd.h in all archs.
> > > 
> > > That also makes a unified way to retrieve this number for
> > > other users.
> > > 
> > 
> > Yes, NR_syscalls should be included there.
> > 
> > -- Steve
> 
> 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
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)
 




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