/*
* 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
