140 lines
5.5 KiB
C
Executable file
140 lines
5.5 KiB
C
Executable file
// overlay_os_asm.h -- Overlay manager assembly macros for OS use.
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// $Id$
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// Copyright (c) 2013 Tensilica Inc.
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//
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// Permission is hereby granted, free of charge, to any person obtaining
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// a copy of this software and associated documentation files (the
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// "Software"), to deal in the Software without restriction, including
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// without limitation the rights to use, copy, modify, merge, publish,
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// distribute, sublicense, and/or sell copies of the Software, and to
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// permit persons to whom the Software is furnished to do so, subject to
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// the following conditions:
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//
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// The above copyright notice and this permission notice shall be included
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// in all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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// IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
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// CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
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// TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
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// SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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#ifndef OVERLAY_OS_ASM_H
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#define OVERLAY_OS_ASM_H
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// The macros in here are intended to be used by RTOS task switch code
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// to check overlay status. Such code is usually in assembly and cannot
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// call C code without penalty. For C code usage, it is best to use the
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// corresponding C functions from the library.
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// Inline assembly version of xt_overlay_get_state(). The arguments are
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// three AR registers (a0-a15):
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//
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// "pcreg" - should contain the outgoing task's PC, i.e. the point at
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// which the task got interrupted. The return value is also
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// returned in this register.
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// "sr1/2" - Scratch registers. These must be distinct from "pcreg".
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//
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// The return value is a 32-bit result that should be saved with the
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// task context and passed as-is to xt_overlay_check_map.
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.macro _xt_overlay_get_state pcreg sr1 sr2
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movi \sr1, _mapping_id
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movi \sr2, _ovly_id
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l16si \sr1, \sr1, 0
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l16ui \sr2, \sr2, 0
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slli \sr1, \sr1, 16
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or \pcreg, \sr1, \sr2
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.endm
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// Inline assembly version of xt_overlay_check_map(). It requires 5 AR
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// registers (a0-a15) as arguments.
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//
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// "pcreg" - should contain the interrupted task's PC, i.e. the point
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// at which the task got interrupted. This will be adjusted
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// if required.
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// "psreg" - should contain the interrupted task's PS. This will be
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// adjusted if required.
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// "ovreg" - should contain the overlay state on entry. Contents may
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// be clobbered.
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// "spreg" - should contain the tasks stack pointer on entry.
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// "sr1" - Scratch register. Must be distinct from any of the above.
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//
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// The return values are "pcreg" and "psreg" and these must be used
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// to update the task's PC and PS.
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// Note that this macro may store data below the "spreg" pointer. If
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// it does, then it will also disable interrupts via the PS, so that
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// the task resumes with all interrupts disabled (to avoid corrupting
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// this data).
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//
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// (SP - 24) Overlay ID to restore
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// (SP - 28) Task PC
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// (SP - 32) Task PS
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.macro _xt_overlay_check_map pcreg psreg ovreg spreg sr1
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// There are four cases to deal with:
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//
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// _ovly_id = -1, _mapping_id = -1
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// No overlay is mapped or mapping, nothing to do.
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//
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// _ovly_id >= 0, _mapping_id = -1
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// An overlay was mapped, check PC to see if we need a restore.
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//
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// _ovly_id = -1, _mapping_id >= 0
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// An overlay is being mapped. Either it belongs to this task, which
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// implies that the PC is in the mapping function, or it does not
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// belong to this task. Either way there is nothing to do.
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//
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// _ovly_id >= 0, _mapping_id >= 0
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// Illegal, cannot happen by design. Don't need to handle this.
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//
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// So, the logic is to check _ovly_id first. If this is >= 0, then
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// we check the task PC. If the PC is in the regions of interest then
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// we'll patch the return PC to invoke xt_overlay_restore.
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.L1:
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extui \sr1, \ovreg, 0, 16 // Extract _ovly_id
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bbsi.l \sr1, 15, .Lno // If -1 then we're done
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mov \ovreg, \sr1 // Restore this one
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// Next check the PC to see if it falls within the ranges of interest.
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.L2:
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movi \sr1, _overlay_vma // Is PC < VMA range ?
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bltu \pcreg, \sr1, .L3
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movi \sr1, _overlay_vma_end // Is PC > VMA range ?
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bgeu \pcreg, \sr1, .L3
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j .L4 // PC is in VMA range
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.L3:
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movi \sr1, _overlay_call_stubs_start // Is PC < call stubs range ?
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bltu \pcreg, \sr1, .Lno
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movi \sr1, _overlay_call_stubs_end // Is PC > call stubs range ?
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bgeu \pcreg, \sr1, .Lno
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// If we get here then a restore is needed. Save the overlay ID, PC and PS.
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// Return modified PC and PS so that xt_overlay_restore() will execute in
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// the context of the task when resumed. Note that the OS resumption code
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// may expect PS.EXCM to be set so we leave it as is in the return value.
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.L4:
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s32e \ovreg, \spreg, -24 // Save overlay ID
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s32e \pcreg, \spreg, -28 // Save task PC
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s32e \psreg, \spreg, -32 // Save task PS
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movi \pcreg, xt_overlay_restore // Adjust resumption PC
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movi \sr1, 15
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or \psreg, \psreg, \sr1 // Set intlevel to highest
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.Lno:
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.endm
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#endif // OVERLAY_OS_ASM_H
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