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