From 7303e30ec1d8fb5ca1f07c92d069241c32b2ee1b Mon Sep 17 00:00:00 2001
From: Dominik Brodowski <linux@dominikbrodowski.net>
Date: Thu, 5 Apr 2018 11:53:03 +0200
Subject: syscalls/core: Prepare CONFIG_ARCH_HAS_SYSCALL_WRAPPER=y for compat
 syscalls

It may be useful for an architecture to override the definitions of the
COMPAT_SYSCALL_DEFINE0() and __COMPAT_SYSCALL_DEFINEx() macros in
<linux/compat.h>, in particular to use a different calling convention
for syscalls. This patch provides a mechanism to do so, based on the
previously introduced CONFIG_ARCH_HAS_SYSCALL_WRAPPER. If it is enabled,
<asm/sycall_wrapper.h> is included in <linux/compat.h> and may be used
to define the macros mentioned above. Moreover, as the syscall calling
convention may be different if CONFIG_ARCH_HAS_SYSCALL_WRAPPER is set,
the compat syscall function prototypes in <linux/compat.h> are #ifndef'd
out in that case.

As some of the syscalls and/or compat syscalls may not be present,
the COND_SYSCALL() and COND_SYSCALL_COMPAT() macros in kernel/sys_ni.c
as well as the SYS_NI() and COMPAT_SYS_NI() macros in
kernel/time/posix-stubs.c can be re-defined in <asm/syscall_wrapper.h> iff
CONFIG_ARCH_HAS_SYSCALL_WRAPPER is enabled.

Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20180405095307.3730-5-linux@dominikbrodowski.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 init/Kconfig | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

(limited to 'init')

diff --git a/init/Kconfig b/init/Kconfig
index 068eb6c3bbf7..2dbc88051bde 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1925,8 +1925,11 @@ config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
 	bool
 
 # It may be useful for an architecture to override the definitions of the
-# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>,
-# in particular to use a different calling convention for syscalls.
+# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>
+# and the COMPAT_ variants in <linux/compat.h>, in particular to use a
+# different calling convention for syscalls. They can also override the
+# macros for not-implemented syscalls in kernel/sys_ni.c and
+# kernel/time/posix-stubs.c. All these overrides need to be available in
+# <asm/syscall_wrapper.h>.
 config ARCH_HAS_SYSCALL_WRAPPER
 	def_bool n
-	depends on !COMPAT
-- 
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