libc: add {get,set,swap,make}context user context manipulation functions

Add the obsolescent SUSv3 family of user context manipulating functions
for arm, i386, mips, x86_64.

Signed-off-by: Timon ter Braak <timonterbraak@gmail.com>
Signed-off-by: Florian Fainelli <florian@openwrt.org>
Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>
Signed-off-by: Natanael Copa <ncopa@alpinelinux.org>
Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

1 files changed, 188 insertions, 0 deletions

diff --git a/libc/sysdeps/linux/mips/makecontext.S b/libc/sysdeps/linux/mips/makecontext.S
new file mode 100644
index 000000000..6427339a6
--- /dev/null
+++ b/libc/sysdeps/linux/mips/makecontext.S
@@ -0,0 +1,188 @@
+/* Modify saved context.
+   Copyright (C) 2009 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Maciej W. Rozycki <macro@codesourcery.com>.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library.  If not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <sysdep.h>
+#include <sys/asm.h>
+#include <sys/fpregdef.h>
+#include <sys/regdef.h>
+
+#include "ucontext_i.h"
+
+/* int makecontext (ucontext_t *ucp, (void *func) (), int argc, ...) */
+
+	.text
+LOCALSZ = 0
+ARGSZ = 0
+MASK = 0x00000000
+#ifdef __PIC__
+LOCALSZ = 1						/* save gp */
+#endif
+#if _MIPS_SIM != _ABIO32
+ARGSZ = 5						/* save a3-a7 */
+# ifdef __PIC__
+MASK = 0x10000000
+# endif
+#endif
+FRAMESZ = (((ARGSZ + LOCALSZ) * SZREG) + ALSZ) & ALMASK
+GPOFF = FRAMESZ - ((ARGSZ + 1) * SZREG)
+#if _MIPS_SIM != _ABIO32
+A3OFF = FRAMESZ - (5 * SZREG)				/* callee-allocated */
+A4OFF = FRAMESZ - (4 * SZREG)
+A5OFF = FRAMESZ - (3 * SZREG)
+A6OFF = FRAMESZ - (2 * SZREG)
+A7OFF = FRAMESZ - (1 * SZREG)
+NARGREGS = 8
+#else
+A3OFF = FRAMESZ + (3 * SZREG)				/* caller-allocated */
+NARGREGS = 4
+#endif
+
+NESTED (__makecontext, FRAMESZ, ra)
+	.mask	MASK, -(ARGSZ * SZREG)
+	.fmask	0x00000000, 0
+
+98:
+#ifdef __PIC__
+	SETUP_GP
+#endif
+
+	PTR_ADDIU sp, -FRAMESZ
+
+#ifdef __PIC__
+	SETUP_GP64 (GPOFF, __makecontext)
+	SAVE_GP (GPOFF)
+#endif
+
+#ifdef PROF
+	.set	noat
+	move	AT, ra
+	jal	_mcount
+	.set	at
+#endif
+
+	/* Store args to be passed.  */
+	REG_S	a3, A3OFF(sp)
+#if _MIPS_SIM != _ABIO32
+	REG_S	a4, A4OFF(sp)
+	REG_S	a5, A5OFF(sp)
+	REG_S	a6, A6OFF(sp)
+	REG_S	a7, A7OFF(sp)
+#endif
+
+	/* Store a magic flag.  */
+	li	v1, 1
+	REG_S	v1, (0 * SZREG + MCONTEXT_GREGS)(a0)	/* zero */
+
+	/* Set up the stack.  */
+	PTR_L	t0, STACK_SP(a0)
+	PTR_L	t2, STACK_SIZE(a0)
+	PTR_ADDIU t1, sp, A3OFF
+	PTR_ADDU t0, t2
+	and	t0, ALMASK
+	blez	a2, 2f					/* no arguments */
+
+	/* Store register arguments.  */
+	PTR_ADDIU t2, a0, MCONTEXT_GREGS + 4 * SZREG
+	move	t3, zero
+0:
+	addiu	t3, 1
+	REG_L	v1, (t1)
+	PTR_ADDIU t1, SZREG
+	REG_S	v1, (t2)
+	PTR_ADDIU t2, SZREG
+	bgeu	t3, a2, 2f				/* all done */
+	bltu	t3, NARGREGS, 0b			/* next */
+
+	/* Make room for stack arguments.  */
+	PTR_SUBU t2, a2, t3
+	PTR_SLL	t2, 3
+	PTR_SUBU t0, t2
+	and	t0, ALMASK
+
+	/* Store stack arguments.  */
+	move	t2, t0
+1:
+	addiu	t3, 1
+	REG_L	v1, (t1)
+	PTR_ADDIU t1, SZREG
+	REG_S	v1, (t2)
+	PTR_ADDIU t2, SZREG
+	bltu	t3, a2, 1b				/* next */
+
+2:
+#if _MIPS_SIM == _ABIO32
+	/* Make room for a0-a3 storage.  */
+	PTR_ADDIU t0, -(NARGSAVE * SZREG)
+#endif
+	PTR_L	v1, UCONTEXT_LINK(a0)
+#ifdef __PIC__
+	PTR_ADDIU t9, 99f - 98b
+#else
+	PTR_LA	t9, 99f
+#endif
+	REG_S	t0, (29 * SZREG + MCONTEXT_GREGS)(a0)	/* sp */
+	REG_S	v1, (16 * SZREG + MCONTEXT_GREGS)(a0)	/* s0 */
+#ifdef __PIC__
+	REG_S	gp, (17 * SZREG + MCONTEXT_GREGS)(a0)	/* s1 */
+#endif
+	REG_S	t9, (31 * SZREG + MCONTEXT_GREGS)(a0)	/* ra */
+	REG_S	a1, MCONTEXT_PC(a0)
+
+#ifdef __PIC__
+	RESTORE_GP64
+	PTR_ADDIU sp, FRAMESZ
+#endif
+	jr	ra
+
+99:
+#ifdef __PIC__
+	move	gp, s1
+#endif
+	move	a0, zero
+	beqz	s0, 0f
+
+	/* setcontext (ucp) */
+	move	a0, s0
+#ifdef __PIC__
+	PTR_LA	t9, JUMPTARGET (__setcontext)
+	jalr	t9
+# if _MIPS_SIM == _ABIO32
+	move	gp, s1
+# endif
+#else
+	jal	JUMPTARGET (__setcontext)
+#endif
+	move	a0, v0
+
+0:
+	/* exit (a0) */
+#ifdef __PIC__
+	PTR_LA	t9, HIDDEN_JUMPTARGET (exit)
+	jalr	t9
+#else
+	jal	HIDDEN_JUMPTARGET (exit)
+#endif
+
+	/* You don't exist, you won't feel anything.  */
+1:
+	lb	zero, (zero)
+	b	1b
+PSEUDO_END (__makecontext)
+
+weak_alias (__makecontext, makecontext)