sh: Move over sh64 switch_to and stack unwinder.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

1 files changed, 198 insertions, 0 deletions

diff --git a/arch/sh/kernel/cpu/sh5/switchto.S b/arch/sh/kernel/cpu/sh5/switchto.S
new file mode 100644
index 000000000000..45b2d90eed7d
--- /dev/null
+++ b/arch/sh/kernel/cpu/sh5/switchto.S
@@ -0,0 +1,198 @@
+/*
+ * arch/sh64/kernel/switchto.S
+ *
+ * sh64 context switch
+ *
+ * Copyright (C) 2004  Richard Curnow
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+*/
+
+	.section .text..SHmedia32,"ax"
+	.little
+
+	.balign 32
+
+	.type sh64_switch_to,@function
+	.global sh64_switch_to
+	.global __sh64_switch_to_end
+sh64_switch_to:
+
+/* Incoming args
+   r2 - prev
+   r3 - &prev->thread
+   r4 - next
+   r5 - &next->thread
+
+   Outgoing results
+   r2 - last (=prev) : this just stays in r2 throughout
+
+   Want to create a full (struct pt_regs) on the stack to allow backtracing
+   functions to work.  However, we only need to populate the callee-save
+   register slots in this structure; since we're a function our ancestors must
+   have themselves preserved all caller saved state in the stack.  This saves
+   some wasted effort since we won't need to look at the values.
+
+   In particular, all caller-save registers are immediately available for
+   scratch use.
+
+*/
+
+#define FRAME_SIZE (76*8 + 8)
+
+	movi	FRAME_SIZE, r0
+	sub.l	r15, r0, r15
+	! Do normal-style register save to support backtrace
+
+	st.l	r15,   0, r18	! save link reg
+	st.l	r15,   4, r14	! save fp
+	add.l	r15, r63, r14	! setup frame pointer
+
+	! hopefully this looks normal to the backtrace now.
+
+	addi.l	r15,   8, r1    ! base of pt_regs
+	addi.l	r1,   24, r0    ! base of pt_regs.regs
+	addi.l	r0, (63*8), r8	! base of pt_regs.trregs
+
+	/* Note : to be fixed?
+	   struct pt_regs is really designed for holding the state on entry
+	   to an exception, i.e. pc,sr,regs etc.  However, for the context
+	   switch state, some of this is not required.  But the unwinder takes
+	   struct pt_regs * as an arg so we have to build this structure
+	   to allow unwinding switched tasks in show_state() */
+
+	st.q	r0, ( 9*8), r9
+	st.q	r0, (10*8), r10
+	st.q	r0, (11*8), r11
+	st.q	r0, (12*8), r12
+	st.q	r0, (13*8), r13
+	st.q	r0, (14*8), r14 ! for unwind, want to look as though we took a trap at
+	! the point where the process is left in suspended animation, i.e. current
+	! fp here, not the saved one.
+	st.q	r0, (16*8), r16
+
+	st.q	r0, (24*8), r24
+	st.q	r0, (25*8), r25
+	st.q	r0, (26*8), r26
+	st.q	r0, (27*8), r27
+	st.q	r0, (28*8), r28
+	st.q	r0, (29*8), r29
+	st.q	r0, (30*8), r30
+	st.q	r0, (31*8), r31
+	st.q	r0, (32*8), r32
+	st.q	r0, (33*8), r33
+	st.q	r0, (34*8), r34
+	st.q	r0, (35*8), r35
+
+	st.q	r0, (44*8), r44
+	st.q	r0, (45*8), r45
+	st.q	r0, (46*8), r46
+	st.q	r0, (47*8), r47
+	st.q	r0, (48*8), r48
+	st.q	r0, (49*8), r49
+	st.q	r0, (50*8), r50
+	st.q	r0, (51*8), r51
+	st.q	r0, (52*8), r52
+	st.q	r0, (53*8), r53
+	st.q	r0, (54*8), r54
+	st.q	r0, (55*8), r55
+	st.q	r0, (56*8), r56
+	st.q	r0, (57*8), r57
+	st.q	r0, (58*8), r58
+	st.q	r0, (59*8), r59
+
+	! do this early as pta->gettr has no pipeline forwarding (=> 5 cycle latency)
+	! Use a local label to avoid creating a symbol that will confuse the !
+	! backtrace
+	pta	.Lsave_pc, tr0
+
+	gettr	tr5, r45
+	gettr	tr6, r46
+	gettr	tr7, r47
+	st.q	r8, (5*8), r45
+	st.q	r8, (6*8), r46
+	st.q	r8, (7*8), r47
+
+	! Now switch context
+	gettr	tr0, r9
+	st.l	r3, 0, r15	! prev->thread.sp
+	st.l	r3, 8, r1	! prev->thread.kregs
+	st.l	r3, 4, r9	! prev->thread.pc
+	st.q	r1, 0, r9	! save prev->thread.pc into pt_regs->pc
+
+	! Load PC for next task (init value or save_pc later)
+	ld.l	r5, 4, r18	! next->thread.pc
+	! Switch stacks
+	ld.l	r5, 0, r15	! next->thread.sp
+	ptabs	r18, tr0
+
+	! Update current
+	ld.l	r4, 4, r9	! next->thread_info (2nd element of next task_struct)
+	putcon	r9, kcr0	! current = next->thread_info
+
+	! go to save_pc for a reschedule, or the initial thread.pc for a new process
+	blink	tr0, r63
+
+	! Restore (when we come back to a previously saved task)
+.Lsave_pc:
+	addi.l	r15, 32, r0	! r0 = next's regs
+	addi.l	r0, (63*8), r8	! r8 = next's tr_regs
+
+	ld.q	r8, (5*8), r45
+	ld.q	r8, (6*8), r46
+	ld.q	r8, (7*8), r47
+	ptabs	r45, tr5
+	ptabs	r46, tr6
+	ptabs	r47, tr7
+
+	ld.q	r0, ( 9*8), r9
+	ld.q	r0, (10*8), r10
+	ld.q	r0, (11*8), r11
+	ld.q	r0, (12*8), r12
+	ld.q	r0, (13*8), r13
+	ld.q	r0, (14*8), r14
+	ld.q	r0, (16*8), r16
+
+	ld.q	r0, (24*8), r24
+	ld.q	r0, (25*8), r25
+	ld.q	r0, (26*8), r26
+	ld.q	r0, (27*8), r27
+	ld.q	r0, (28*8), r28
+	ld.q	r0, (29*8), r29
+	ld.q	r0, (30*8), r30
+	ld.q	r0, (31*8), r31
+	ld.q	r0, (32*8), r32
+	ld.q	r0, (33*8), r33
+	ld.q	r0, (34*8), r34
+	ld.q	r0, (35*8), r35
+
+	ld.q	r0, (44*8), r44
+	ld.q	r0, (45*8), r45
+	ld.q	r0, (46*8), r46
+	ld.q	r0, (47*8), r47
+	ld.q	r0, (48*8), r48
+	ld.q	r0, (49*8), r49
+	ld.q	r0, (50*8), r50
+	ld.q	r0, (51*8), r51
+	ld.q	r0, (52*8), r52
+	ld.q	r0, (53*8), r53
+	ld.q	r0, (54*8), r54
+	ld.q	r0, (55*8), r55
+	ld.q	r0, (56*8), r56
+	ld.q	r0, (57*8), r57
+	ld.q	r0, (58*8), r58
+	ld.q	r0, (59*8), r59
+
+	! epilogue
+	ld.l	r15, 0, r18
+	ld.l	r15, 4, r14
+	ptabs	r18, tr0
+	movi	FRAME_SIZE, r0
+	add	r15, r0, r15
+	blink	tr0, r63
+__sh64_switch_to_end:
+.LFE1:
+	.size	sh64_switch_to,.LFE1-sh64_switch_to
+