linux-kernel - [RFC PATCH v2 2/3] thread_local_abi: wire up x86 32/64 system call

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Date:	Tue, 22 Dec 2015 13:02:12 -0500
From:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:	Paul Turner <pjt@...gle.com>, Andrew Hunter <ahh@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	Russell King <linux@....linux.org.uk>
Cc:	linux-kernel@...r.kernel.org,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Peter Zijlstra <peterz@...radead.org>,
	Andy Lutomirski <luto@...capital.net>,
	Andi Kleen <andi@...stfloor.org>,
	Dave Watson <davejwatson@...com>, Chris Lameter <cl@...ux.com>,
	Ingo Molnar <mingo@...hat.com>, Ben Maurer <bmaurer@...com>,
	Steven Rostedt <rostedt@...dmis.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Josh Triplett <josh@...htriplett.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-api@...r.kernel.org
Subject: [RFC PATCH v2 2/3] thread_local_abi: wire up x86 32/64 system call

Wire up the thread local ABI on x86 32/64. Call the
thread_local_abi_handle_notify_resume() function on return to
userspace if TIF_NOTIFY_RESUME thread flag is set.

This provides an ABI improving the speed of a getcpu operation
on x86 by removing the need to perform a function call, "lsl"
instruction, or system call on the fast path.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
CC: Russell King <linux@....linux.org.uk>
CC: Catalin Marinas <catalin.marinas@....com>
CC: Will Deacon <will.deacon@....com>
CC: Thomas Gleixner <tglx@...utronix.de>
CC: Paul Turner <pjt@...gle.com>
CC: Andrew Hunter <ahh@...gle.com>
CC: Peter Zijlstra <peterz@...radead.org>
CC: Andy Lutomirski <luto@...capital.net>
CC: Andi Kleen <andi@...stfloor.org>
CC: Dave Watson <davejwatson@...com>
CC: Chris Lameter <cl@...ux.com>
CC: Ingo Molnar <mingo@...hat.com>
CC: Ben Maurer <bmaurer@...com>
CC: Steven Rostedt <rostedt@...dmis.org>
CC: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
CC: Josh Triplett <josh@...htriplett.org>
CC: Linus Torvalds <torvalds@...ux-foundation.org>
CC: Andrew Morton <akpm@...ux-foundation.org>
CC: Thomas Gleixner <tglx@...utronix.de>
CC: linux-api@...r.kernel.org
---
 arch/x86/entry/common.c                | 2 ++
 arch/x86/entry/syscalls/syscall_32.tbl | 1 +
 arch/x86/entry/syscalls/syscall_64.tbl | 1 +
 3 files changed, 4 insertions(+)

diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index a89fdbc..222cacf 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -249,6 +249,8 @@ static void exit_to_usermode_loop(struct pt_regs *regs, u32 cached_flags)
 		if (cached_flags & _TIF_NOTIFY_RESUME) {
 			clear_thread_flag(TIF_NOTIFY_RESUME);
 			tracehook_notify_resume(regs);
+			if (thread_local_abi_active(current))
+				thread_local_abi_handle_notify_resume(current);
 		}
 
 		if (cached_flags & _TIF_USER_RETURN_NOTIFY)
diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
index f17705e..c6c385e 100644
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl
@@ -383,3 +383,4 @@
 374	i386	userfaultfd		sys_userfaultfd
 375	i386	membarrier		sys_membarrier
 376	i386	mlock2			sys_mlock2
+377	i386	thread_local_abi	sys_thread_local_abi
diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
index 314a90b..748aee3 100644
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -332,6 +332,7 @@
 323	common	userfaultfd		sys_userfaultfd
 324	common	membarrier		sys_membarrier
 325	common	mlock2			sys_mlock2
+326	common	thread_local_abi	sys_thread_local_abi
 
 #
 # x32-specific system call numbers start at 512 to avoid cache impact
-- 
2.1.4

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