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Message-ID: <20150906202815.GE9187@lakka.kapsi.fi>
Date: Sun, 6 Sep 2015 23:28:15 +0300
From: Mikko Rapeli <mikko.rapeli@....fi>
To: Ingo Molnar <mingo@...nel.org>
Cc: linux-kernel@...r.kernel.org,
Andy Lutomirski <luto@...capital.net>,
Andrew Morton <akpm@...ux-foundation.org>,
Denys Vlasenko <dvlasenk@...hat.com>,
Brian Gerst <brgerst@...il.com>,
Peter Zijlstra <peterz@...radead.org>,
Borislav Petkov <bp@...en8.de>,
"H. Peter Anvin" <hpa@...or.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Oleg Nesterov <oleg@...hat.com>,
Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 15/15] x86/headers: Remove <asm/sigcontext.h>
On Sun, Sep 06, 2015 at 08:41:45AM +0200, Ingo Molnar wrote:
>
> * Mikko Rapeli <mikko.rapeli@....fi> wrote:
>
> > On Sat, Sep 05, 2015 at 01:59:43PM +0200, Ingo Molnar wrote:
> > >
> > > * Mikko Rapeli <mikko.rapeli@....fi> wrote:
> > >
> > > > > diff --git a/arch/x86/include/uapi/asm/sigcontext32.h b/arch/x86/include/uapi/asm/sigcontext32.h
> > > > > index a92b0f0dc09e..8b870175befa 100644
> > > > > --- a/arch/x86/include/uapi/asm/sigcontext32.h
> > > > > +++ b/arch/x86/include/uapi/asm/sigcontext32.h
> > > > > @@ -3,6 +3,6 @@
> > > > >
> > > > > /* This is a legacy file - all the type definitions are in sigcontext.h: */
> > > > >
> > > > > -#include <asm/sigcontext.h>
> > > > > +#include <uapi/asm/sigcontext.h>
> > > >
> > > > This needs to be without uapi directory in path.
> > >
> > > What do you mean?
> >
> > There is not uapi in path in userspace so it fails to compile:
>
> Ok, I see. So it's not common, but I don't think there's an outright prohibition
> for uapi headers to refer to each other:
>
> arch/hexagon/include/uapi/asm/signal.h:#include <uapi/asm/registers.h>
> arch/mips/include/uapi/asm/siginfo.h:#include <uapi/asm-generic/siginfo.h>
> arch/x86/include/uapi/asm/sigcontext32.h:#include <uapi/asm/sigcontext.h>
>
> There are a couple of solutions:
>
> - copy the uapi/ directory if you take the kernel headers as-is
>
> - adapt the headers to the old user-space layout when you import them.
> (i.e. do a sed -i 's/<uapi/</' on them).
>
> - create a symbolic link from asm/uapi to asm/ in user-space.
>
> The kernel side solutions are uglier:
>
> - We could create a symbolic link from asm/uapi/sigcontext32.h to
> asm/uapi/sigcontext.h, although I'm not sure what the policy for that is in
> the kernel repository - I think it's generally frowned upon.
>
> - We could keep asm/sigcontext.h that includes asm/uapi/sigcontext.h - a
> poor man's symbolic link.
>
> OTOH the last option isn't all that ugly.
Yes, AFAIK it's a common patterns in kernel.
> > This is the fix:
> >
> > --- a/arch/x86/include/uapi/asm/sigcontext32.h
> > +++ b/arch/x86/include/uapi/asm/sigcontext32.h
> > @@ -3,6 +3,6 @@
> >
> > /* This is a legacy file - all the type definitions are in sigcontext.h: */
> >
> > -#include <uapi/asm/sigcontext.h>
> > +#include <asm/sigcontext.h>
>
> There's no asm/sigcontext.h file anymore if you apply my patches - but we could
> reintroduce it to make the copy of UAPI headers to user-space work as-is.
Actually there is, in user space :)
$ git show -s --pretty=one HEAD
bea04c5252803fa53dcc5366ae32357a0ab07b44 x86/headers: Remove <asm/sigcontext.h>
$ make headers_install
...
$ ls usr/include/asm/sigcontext.h
usr/include/asm/sigcontext.h
$ diff -up arch/x86/include/uapi/asm/sigcontext.h usr/include/asm/sigcontext.h
--- arch/x86/include/uapi/asm/sigcontext.h 2015-09-06 22:10:54.918303649 +0200
+++ usr/include/asm/sigcontext.h 2015-09-06 22:11:18.214835356 +0200
@@ -1,5 +1,5 @@
-#ifndef _UAPI_ASM_X86_SIGCONTEXT_H
-#define _UAPI_ASM_X86_SIGCONTEXT_H
+#ifndef _ASM_X86_SIGCONTEXT_H
+#define _ASM_X86_SIGCONTEXT_H
/*
* Linux signal context definitions. The sigcontext includes a complex hierarchy of CPU
@@ -14,7 +14,7 @@
* to grow new quirks for quite some time. Promise!
*/
-#include <linux/compiler.h>
+
#include <linux/types.h>
#define FP_XSTATE_MAGIC1 0x46505853U
@@ -271,20 +271,12 @@ struct sigcontext_64 {
/*
* Create the real 'struct sigcontext' type:
*/
-#ifdef __KERNEL__
-# ifdef __i386__
-# define sigcontext sigcontext_32
-# else
-# define sigcontext sigcontext_64
-# endif
-#endif
/*
* The old user-space sigcontext definition, just in case user-space still
* relies on it. The kernel definition (in asm/sigcontext.h) has unified
* field names but otherwise the same layout.
*/
-#ifndef __KERNEL__
#define _fpstate_ia32 _fpstate_32
#define sigcontext_ia32 sigcontext_32
@@ -311,7 +303,7 @@ struct sigcontext {
__u32 eflags;
__u32 esp_at_signal;
__u16 ss, __ssh;
- struct _fpstate __user *fpstate;
+ struct _fpstate *fpstate;
__u32 oldmask;
__u32 cr2;
};
@@ -343,13 +335,12 @@ struct sigcontext {
__u64 trapno;
__u64 oldmask;
__u64 cr2;
- struct _fpstate __user *fpstate; /* Zero when no FPU context */
+ struct _fpstate *fpstate; /* Zero when no FPU context */
# ifdef __ILP32__
__u32 __fpstate_pad;
# endif
__u64 reserved1[8];
};
# endif /* __x86_64__ */
-#endif /* !__KERNEL__ */
-#endif /* _UAPI_ASM_X86_SIGCONTEXT_H */
+#endif /* _ASM_X86_SIGCONTEXT_H */
So that's what changes when the file is exported for userspace together with
the path from which uapi is removed. So if, like you said kernel side has
problems with
--- a/arch/x86/include/uapi/asm/sigcontext32.h
+++ b/arch/x86/include/uapi/asm/sigcontext32.h
@@ -3,6 +3,6 @@
/* This is a legacy file - all the type definitions are in sigcontext.h: */
-#include <uapi/asm/sigcontext.h>
+#include <asm/sigcontext.h>
#endif /* _ASM_X86_SIGCONTEXT32_H */
Then a nice solution would be for the kernel side wrapper to do like you
said (on top of your changes on master):
--- /dev/null
+++ b/arch/x86/include/asm/sigcontext.h
@@ -0,0 +1,6 @@
+#ifndef _ASM_X86_SIGCONTEXT_H
+#define _ASM_X86_SIGCONTEXT_H
+
+#include <uapi/asm/sigcontext.h>
+
+#endif /* _ASM_X86_SIGCONTEXT_H */
And I guess logically this belongs to commit "x86/headers: Remove
<asm/sigcontext.h>".
-Mikko
--
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