| 1 | /* SPDX-License-Identifier: GPL-2.0-only */ |
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| 2 | /* |
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| 3 | * Context switch support for Hexagon |
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| 4 | * |
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| 5 | * Copyright (c) 2010-2011, The Linux Foundation. All rights reserved. |
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| 6 | */ |
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| 7 | |
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| 8 | #include <asm/asm-offsets.h> |
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| 9 | |
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| 10 | .text |
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| 11 | |
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| 12 | /* |
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| 13 | * The register used as a fast-path thread information pointer |
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| 14 | * is determined as a kernel configuration option. If it happens |
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| 15 | * to be a callee-save register, we're going to be saving and |
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| 16 | * restoring it twice here. |
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| 17 | * |
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| 18 | * This code anticipates a revised ABI where R20-23 are added |
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| 19 | * to the set of callee-save registers, but this should be |
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| 20 | * backward compatible to legacy tools. |
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| 21 | */ |
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| 22 | |
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| 23 | |
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| 24 | /* |
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| 25 | * void switch_to(struct task_struct *prev, |
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| 26 | * struct task_struct *next, struct task_struct *last); |
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| 27 | */ |
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| 28 | .p2align 2 |
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| 29 | .globl __switch_to |
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| 30 | .type __switch_to, @function |
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| 31 | |
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| 32 | /* |
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| 33 | * When we exit the wormhole, we need to store the previous task |
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| 34 | * in the new R0's pointer. Technically it should be R2, but they should |
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| 35 | * be the same; seems like a legacy thing. In short, don't butcher |
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| 36 | * R0, let it go back out unmolested. |
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| 37 | */ |
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| 38 | |
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| 39 | __switch_to: |
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| 40 | /* |
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| 41 | * Push callee-saves onto "prev" stack. |
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| 42 | * Here, we're sneaky because the LR and FP |
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| 43 | * storage of the thread_stack structure |
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| 44 | * is automagically allocated by allocframe, |
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| 45 | * so we pass struct size less 8. |
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| 46 | */ |
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| 47 | allocframe(#(_SWITCH_STACK_SIZE - 8)); |
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| 48 | memd(R29+#(_SWITCH_R2726))=R27:26; |
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| 49 | memd(R29+#(_SWITCH_R2524))=R25:24; |
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| 50 | memd(R29+#(_SWITCH_R2322))=R23:22; |
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| 51 | memd(R29+#(_SWITCH_R2120))=R21:20; |
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| 52 | memd(R29+#(_SWITCH_R1918))=R19:18; |
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| 53 | memd(R29+#(_SWITCH_R1716))=R17:16; |
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| 54 | /* Stash thread_info pointer in task_struct */ |
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| 55 | memw(R0+#_TASK_THREAD_INFO) = THREADINFO_REG; |
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| 56 | memw(R0 +#(_TASK_STRUCT_THREAD + _THREAD_STRUCT_SWITCH_SP)) = R29; |
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| 57 | /* Switch to "next" stack and restore callee saves from there */ |
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| 58 | R29 = memw(R1 + #(_TASK_STRUCT_THREAD + _THREAD_STRUCT_SWITCH_SP)); |
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| 59 | { |
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| 60 | R27:26 = memd(R29+#(_SWITCH_R2726)); |
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| 61 | R25:24 = memd(R29+#(_SWITCH_R2524)); |
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| 62 | } |
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| 63 | { |
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| 64 | R23:22 = memd(R29+#(_SWITCH_R2322)); |
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| 65 | R21:20 = memd(R29+#(_SWITCH_R2120)); |
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| 66 | } |
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| 67 | { |
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| 68 | R19:18 = memd(R29+#(_SWITCH_R1918)); |
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| 69 | R17:16 = memd(R29+#(_SWITCH_R1716)); |
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| 70 | } |
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| 71 | { |
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| 72 | /* THREADINFO_REG is currently one of the callee-saved regs |
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| 73 | * above, and so be sure to re-load it last. |
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| 74 | */ |
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| 75 | THREADINFO_REG = memw(R1 + #_TASK_THREAD_INFO); |
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| 76 | R31:30 = memd(R29+#_SWITCH_FP); |
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| 77 | } |
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| 78 | { |
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| 79 | R29 = add(R29,#_SWITCH_STACK_SIZE); |
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| 80 | jumpr R31; |
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| 81 | } |
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| 82 | .size __switch_to, .-__switch_to |
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| 83 | |
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