"TLS-lite": add kernel support for a per-thread userspace pointer,

for pointing to the thread-control-block.  Support for mapping this
to the correct hardware register can be added as it's finished;
start with support for amd64, sparc, and sparc64.  Includes syscalls
for getting and setting it (for a portable __errno implementation) as
well as creating a new thread with an initial value for it.

discussed with miod@, kettenis@, deraadt@; committing to get the syscalls
in with the impending libc bump and do further refinements in tree

2 files changed, 61 insertions, 3 deletions

diff --git a/sys/arch/amd64/include/proc.h b/sys/arch/amd64/include/proc.h
index b56cdb7e50f..733c93ea5cc 100644
--- a/sys/arch/amd64/include/proc.h
+++ b/sys/arch/amd64/include/proc.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: proc.h,v 1.6 2011/03/23 16:54:34 pirofti Exp $	*/
+/*	$OpenBSD: proc.h,v 1.7 2011/10/15 23:35:29 guenther Exp $	*/
 /*	$NetBSD: proc.h,v 1.1 2003/04/26 18:39:46 fvdl Exp $	*/
 
 /*
@@ -35,11 +35,10 @@
 #ifndef _MACHINE_PROC_H_
 #define _MACHINE_PROC_H_
 
-#include <machine/frame.h>
-
 /*
  * Machine-dependent part of the proc structure for amd64.
  */
+struct trapframe;
 struct mdproc {
 	struct	trapframe *md_regs;	/* registers on current frame */
 	int	md_flags;
@@ -49,5 +48,8 @@ struct mdproc {
 /* md_flags */
 #define	MDP_USEDFPU	0x0001	/* has used the FPU */
 #define MDP_IRET	0x0002	/* return via iret, not sysret */
+				/* (iret can restore r11 and rcx) */
+
+#define __HAVE_MD_TCB
 
 #endif /* _MACHINE_PROC_H_ */
diff --git a/sys/arch/amd64/include/tcb.h b/sys/arch/amd64/include/tcb.h
new file mode 100644
index 00000000000..f6a0ed87a7f
--- /dev/null
+++ b/sys/arch/amd64/include/tcb.h
@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2011 Philip Guenther <guenther@openbsd.org>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#ifndef _MACHINE_TCB_H_
+#define _MACHINE_TCB_H_
+
+#ifdef _KERNEL
+
+#include <machine/pcb.h>
+
+#define TCB_GET(p)		\
+	((void *)((struct pcb *)(p)->p_addr)->pcb_fsbase)
+#define TCB_SET(p, addr)	\
+	(((struct pcb *)(p)->p_addr)->pcb_fsbase = (u_int64_t)(addr))
+
+#else /* _KERNEL */
+
+#include <stddef.h>		/* for offsetof */
+
+/* ELF TLS ABI calls for big TCB, with static TLS data at negative offsets */
+#define TLS_VARIANT	2
+
+/* Read a slot from the TCB */
+static inline void *
+__amd64_read_tcb(long offset)
+{
+	void	*val;
+	__asm__ ("movq %%fs:(%1),%0" : "=r" (val) : "r" (offset));
+	return val;
+}
+
+/* Get a pointer to the TCB itself */
+#define TCB_GET()		__amd64_read_tcb(0)
+
+/* Get the value of a specific member in the TCB */
+#define TCB_GET_MEMBER(member)	\
+	__amd64_read_tcb(offsetof(struct thread_control_block, member))
+
+/* Setting the TCB pointer can only be done via syscall, so no TCB_SET() */
+
+#endif /* _KERNEL */
+
+#endif /* _MACHINE_TCB_H_ */