Adding support for Xen for x86 (32bit and 64bit)

Author: amd-asahoo

portable/GCC/XEN_x86/IA32/ISR_Support.h

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+/*
+ * FreeRTOS Kernel <DEVELOPMENT BRANCH>
+ * Copyright (C) 2021 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ * 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.
+ *
+ * https://www.FreeRTOS.org
+ * https://github.com/FreeRTOS
+ *
+ */
+
+    .extern ulTopOfSystemStack
+    .extern ulInterruptNesting
+
+/*-----------------------------------------------------------*/
+
+.macro portFREERTOS_INTERRUPT_ENTRY
+
+    /* Save general purpose registers. */
+    pusha
+
+    /* If ulInterruptNesting is zero the rest of the task context will need
+    saving and a stack switch might be required. */
+    movl    ulInterruptNesting, %eax
+    test    %eax, %eax
+    jne     2f
+
+    /* Interrupts are not nested, so save the rest of the task context. */
+    .if configSUPPORT_FPU == 1
+
+        /* If the task has a buffer allocated to save the FPU context then
+        save the FPU context now. */
+        movl    pucPortTaskFPUContextBuffer, %eax
+        test    %eax, %eax
+        je      1f
+        fnsave  ( %eax ) /* Save FLOP context into ucTempFPUBuffer array. */
+        fwait
+
+        1:
+        /* Save the address of the FPU context, if any. */
+        push    pucPortTaskFPUContextBuffer
+
+    .endif /* configSUPPORT_FPU */
+
+    /* Find the TCB. */
+    movl    pxCurrentTCB, %eax
+
+    /* Stack location is first item in the TCB. */
+    movl    %esp, (%eax)
+
+    /* Switch stacks. */
+    movl    ulTopOfSystemStack, %esp
+    movl    %esp, %ebp
+
+    2:
+    /* Increment nesting count. */
+    add     $1, ulInterruptNesting
+
+.endm
+/*-----------------------------------------------------------*/
+
+.macro portINTERRUPT_EPILOGUE
+
+    cli
+    sub     $1, ulInterruptNesting
+
+    /* If the nesting has unwound to zero. */
+    movl    ulInterruptNesting, %eax
+    test    %eax, %eax
+    jne     2f
+
+    /* If a yield was requested then select a new TCB now. */
+    movl    ulPortYieldPending, %eax
+    test    %eax, %eax
+    je      1f
+    movl    $0, ulPortYieldPending
+    call    vTaskSwitchContext
+
+    1:
+    /* Stack location is first item in the TCB. */
+    movl    pxCurrentTCB, %eax
+    movl    (%eax), %esp
+
+    .if configSUPPORT_FPU == 1
+
+        /* Restore address of task's FPU context buffer. */
+        pop     pucPortTaskFPUContextBuffer
+
+        /* If the task has a buffer allocated in which its FPU context is saved,
+        then restore it now. */
+        movl    pucPortTaskFPUContextBuffer, %eax
+        test    %eax, %eax
+        je      1f
+        frstor  ( %eax )
+        1:
+    .endif
+
+    2:
+    popa
+
+.endm
+/*-----------------------------------------------------------*/
+
+.macro portFREERTOS_INTERRUPT_EXIT
+
+    portINTERRUPT_EPILOGUE
+    /* EOI. */
+    movl    $0x00, (0xFEE000B0)
+    iret
+
+.endm

portable/GCC/XEN_x86/IA32/README.md

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+# Description
+This folder contain source for FreeRTOS port for x86_32.