James Devine
7 years ago
parent
4159eb0665
commit
c39a6b3b36
@ -0,0 +1,293 @@
|
||||
; The MIT License (MIT)
|
||||
|
||||
; Copyright (c) 2016 British Broadcasting Corporation.
|
||||
; This software is provided by Lancaster University by arrangement with the BBC.
|
||||
|
||||
; Permission is hereby granted, free of charge, to any person obtaining a
|
||||
; copy of this software and associated documentation files (the "Software"),
|
||||
; to deal in the Software without restriction, including without limitation
|
||||
; the rights to use, copy, modify, merge, publish, distribute, sublicense,
|
||||
; and/or sell copies of the Software, and to permit persons to whom the
|
||||
; Software is furnished to do so, subject to the following conditions:
|
||||
|
||||
; The above copyright notice and this permission notice shall be included in
|
||||
; all copies or substantial portions of the Software.
|
||||
|
||||
; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
|
||||
; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
|
||||
; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
|
||||
; THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
|
||||
; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
|
||||
; FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
|
||||
; DEALINGS IN THE SOFTWARE.
|
||||
|
||||
AREA asm_func, CODE, READONLY
|
||||
|
||||
; Export our context switching subroutine as a C function for use in mbed
|
||||
EXPORT swap_context
|
||||
EXPORT save_context
|
||||
EXPORT save_register_context
|
||||
EXPORT restore_register_context
|
||||
|
||||
ALIGN
|
||||
|
||||
; R0 Contains a pointer to the TCB of the fibre being scheduled out.
|
||||
; R1 Contains a pointer to the TCB of the fibre being scheduled in.
|
||||
; R2 Contains a pointer to the base of the stack of the fibre being scheduled out.
|
||||
; R3 Contains a pointer to the base of the stack of the fibre being scheduled in.
|
||||
|
||||
swap_context
|
||||
|
||||
; Write our core registers into the TCB
|
||||
; First, store the general registers
|
||||
|
||||
; Skip this is we're given a NULL parameter for the TCB
|
||||
CMP R0, #0
|
||||
BEQ store_context_complete
|
||||
|
||||
STR R0, [R0,#0]
|
||||
STR R1, [R0,#4]
|
||||
STR R2, [R0,#8]
|
||||
STR R3, [R0,#12]
|
||||
STR R4, [R0,#16]
|
||||
STR R5, [R0,#20]
|
||||
STR R6, [R0,#24]
|
||||
STR R7, [R0,#28]
|
||||
|
||||
; Now the high general purpose registers
|
||||
MOV R4, R8
|
||||
STR R4, [R0,#32]
|
||||
MOV R4, R9
|
||||
STR R4, [R0,#36]
|
||||
MOV R4, R10
|
||||
STR R4, [R0,#40]
|
||||
MOV R4, R11
|
||||
STR R4, [R0,#44]
|
||||
MOV R4, R12
|
||||
STR R4, [R0,#48]
|
||||
|
||||
; Now the Stack and Link Register.
|
||||
; As this context is only intended for use with a fiber scheduler,
|
||||
; we don't need the PC.
|
||||
MOV R6, SP
|
||||
STR R6, [R0,#52]
|
||||
MOV R4, LR
|
||||
STR R4, [R0,#56]
|
||||
|
||||
store_context_complete
|
||||
; Finally, Copy the stack. We do this to reduce RAM footprint, as stack is usually very small at the point
|
||||
; of scheduling, but we need a lot of capacity for interrupt handling and other functions.
|
||||
|
||||
; Skip this is we're given a NULL parameter for the stack.
|
||||
CMP R2, #0
|
||||
BEQ store_stack_complete
|
||||
|
||||
LDR R4, [R0,#60] ; Load R4 with the fiber's defined stack_base.
|
||||
store_stack
|
||||
SUBS R4, #4
|
||||
SUBS R2, #4
|
||||
|
||||
LDR R5, [R4]
|
||||
STR R5, [R2]
|
||||
|
||||
CMP R4, R6
|
||||
BNE store_stack
|
||||
|
||||
store_stack_complete
|
||||
|
||||
;
|
||||
; Now page in the new context.
|
||||
; Update all registers except the PC. We can also safely ignore the STATUS register, as we're just a fiber scheduler.
|
||||
;
|
||||
LDR R4, [R1, #56]
|
||||
MOV LR, R4
|
||||
LDR R6, [R1, #52]
|
||||
MOV SP, R6
|
||||
|
||||
; Copy the stack in.
|
||||
; n.b. we do this after setting the SP to make comparisons easier.
|
||||
|
||||
; Skip this is we're given a NULL parameter for the stack.
|
||||
CMP R3, #0
|
||||
BEQ restore_stack_complete
|
||||
|
||||
LDR R4, [R1,#60] ; Load R4 with the fiber's defined stack_base.
|
||||
|
||||
restore_stack
|
||||
SUBS R4, #4
|
||||
SUBS R3, #4
|
||||
|
||||
LDR R5, [R3]
|
||||
STR R5, [R4]
|
||||
|
||||
CMP R4, R6
|
||||
BNE restore_stack
|
||||
|
||||
restore_stack_complete
|
||||
LDR R4, [R1, #48]
|
||||
MOV R12, R4
|
||||
LDR R4, [R1, #44]
|
||||
MOV R11, R4
|
||||
LDR R4, [R1, #40]
|
||||
MOV R10, R4
|
||||
LDR R4, [R1, #36]
|
||||
MOV R9, R4
|
||||
LDR R4, [R1, #32]
|
||||
MOV R8, R4
|
||||
|
||||
LDR R7, [R1, #28]
|
||||
LDR R6, [R1, #24]
|
||||
LDR R5, [R1, #20]
|
||||
LDR R4, [R1, #16]
|
||||
LDR R3, [R1, #12]
|
||||
LDR R2, [R1, #8]
|
||||
LDR R0, [R1, #0]
|
||||
LDR R1, [R1, #4]
|
||||
|
||||
; Return to caller (scheduler).
|
||||
BX LR
|
||||
|
||||
|
||||
; R0 Contains a pointer to the TCB of the fibre to snapshot
|
||||
; R1 Contains a pointer to the base of the stack of the fibre being snapshotted
|
||||
|
||||
save_context
|
||||
|
||||
; Write our core registers into the TCB
|
||||
; First, store the general registers
|
||||
|
||||
STR R0, [R0,#0]
|
||||
STR R1, [R0,#4]
|
||||
STR R2, [R0,#8]
|
||||
STR R3, [R0,#12]
|
||||
STR R4, [R0,#16]
|
||||
STR R5, [R0,#20]
|
||||
STR R6, [R0,#24]
|
||||
STR R7, [R0,#28]
|
||||
|
||||
; Now the high general purpose registers
|
||||
MOV R4, R8
|
||||
STR R4, [R0,#32]
|
||||
MOV R4, R9
|
||||
STR R4, [R0,#36]
|
||||
MOV R4, R10
|
||||
STR R4, [R0,#40]
|
||||
MOV R4, R11
|
||||
STR R4, [R0,#44]
|
||||
MOV R4, R12
|
||||
STR R4, [R0,#48]
|
||||
|
||||
; Now the Stack and Link Register.
|
||||
; As this context is only intended for use with a fiber scheduler,
|
||||
; we don't need the PC.
|
||||
MOV R6, SP
|
||||
STR R6, [R0,#52]
|
||||
MOV R4, LR
|
||||
STR R4, [R0,#56]
|
||||
|
||||
; Finally, Copy the stack. We do this to reduce RAM footprint, as stackis usually very small at the point
|
||||
; of sceduling, but we need a lot of capacity for interrupt handling and other functions.
|
||||
|
||||
LDR R4, [R0,#60] ; Load R4 with the fiber's defined stack_base.
|
||||
|
||||
store_stack1
|
||||
SUBS R4, #4
|
||||
SUBS R1, #4
|
||||
|
||||
LDR R5, [R4]
|
||||
STR R5, [R1]
|
||||
|
||||
CMP R4, R6
|
||||
BNE store_stack1
|
||||
|
||||
; Restore scratch registers.
|
||||
|
||||
LDR R7, [R0, #28]
|
||||
LDR R6, [R0, #24]
|
||||
LDR R5, [R0, #20]
|
||||
LDR R4, [R0, #16]
|
||||
|
||||
; Return to caller (scheduler).
|
||||
BX LR
|
||||
|
||||
|
||||
; R0 Contains a pointer to the TCB of the fiber to snapshot
|
||||
save_register_context
|
||||
|
||||
; Write our core registers into the TCB
|
||||
; First, store the general registers
|
||||
|
||||
STR R0, [R0,#0]
|
||||
STR R1, [R0,#4]
|
||||
STR R2, [R0,#8]
|
||||
STR R3, [R0,#12]
|
||||
STR R4, [R0,#16]
|
||||
STR R5, [R0,#20]
|
||||
STR R6, [R0,#24]
|
||||
STR R7, [R0,#28]
|
||||
|
||||
; Now the high general purpose registers
|
||||
MOV R4, R8
|
||||
STR R4, [R0,#32]
|
||||
MOV R4, R9
|
||||
STR R4, [R0,#36]
|
||||
MOV R4, R10
|
||||
STR R4, [R0,#40]
|
||||
MOV R4, R11
|
||||
STR R4, [R0,#44]
|
||||
MOV R4, R12
|
||||
STR R4, [R0,#48]
|
||||
|
||||
; Now the Stack Pointer and Link Register.
|
||||
; As this context is only intended for use with a fiber scheduler,
|
||||
; we don't need the PC.
|
||||
MOV R4, SP
|
||||
STR R4, [R0,#52]
|
||||
MOV R4, LR
|
||||
STR R4, [R0,#56]
|
||||
|
||||
; Restore scratch registers.
|
||||
LDR R4, [R0, #16]
|
||||
|
||||
; Return to caller (scheduler).
|
||||
BX LR
|
||||
|
||||
|
||||
restore_register_context
|
||||
|
||||
;
|
||||
; Now page in the new context.
|
||||
; Update all registers except the PC. We can also safely ignore the STATUS register, as we're just a fiber scheduler.
|
||||
;
|
||||
LDR R4, [R0, #56]
|
||||
MOV LR, R4
|
||||
LDR R4, [R0, #52]
|
||||
MOV SP, R4
|
||||
|
||||
; High registers...
|
||||
LDR R4, [R0, #48]
|
||||
MOV R12, R4
|
||||
LDR R4, [R0, #44]
|
||||
MOV R11, R4
|
||||
LDR R4, [R0, #40]
|
||||
MOV R10, R4
|
||||
LDR R4, [R0, #36]
|
||||
MOV R9, R4
|
||||
LDR R4, [R0, #32]
|
||||
MOV R8, R4
|
||||
|
||||
; Low registers...
|
||||
LDR R7, [R0, #28]
|
||||
LDR R6, [R0, #24]
|
||||
LDR R5, [R0, #20]
|
||||
LDR R4, [R0, #16]
|
||||
LDR R3, [R0, #12]
|
||||
LDR R2, [R0, #8]
|
||||
LDR R0, [R0, #0]
|
||||
LDR R1, [R0, #4]
|
||||
|
||||
; Return to caller (normally the scheduler).
|
||||
BX LR
|
||||
|
||||
ALIGN
|
||||
END
|
||||
Loading…
Reference in new issue