[Minios-devel] [UNIKRAFT PATCH v4 3/5] plat/common: Implement assembly helper for Arm64 thread context switch

[Jia He <justin.he@xxxxxxx>]

From: Wei Chen <wei.chen@xxxxxxx>

Implement assembly helpers for Unikraft schedule APIs.

Signed-off-by: Wei Chen <wei.chen@xxxxxxx>
Signed-off-by: Jianyong Wu <jianyong.wu@xxxxxxx>
Signed-off-by: Jia He <justin.he@xxxxxxx>
---
 plat/common/arm/thread_start64.S | 123 +++++++++++++++++++++++++++++++
 1 file changed, 123 insertions(+)
 create mode 100644 plat/common/arm/thread_start64.S

diff --git a/plat/common/arm/thread_start64.S b/plat/common/arm/thread_start64.S
new file mode 100644
index 0000000..b77463a
--- /dev/null
+++ b/plat/common/arm/thread_start64.S
@@ -0,0 +1,123 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
+/*
+ * Authors: Wei Chen <wei.chen@xxxxxxx>
+ *
+ * Copyright (c) 2018, Arm Ltd. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the copyright holder nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ * THIS HEADER MAY NOT BE EXTRACTED OR MODIFIED IN ANY WAY.
+ */
+#include <sw_ctx.h>
+#include <uk/arch/lcpu.h>
+#include <uk/asm.h>
+
+/*
+ * Thread stack memory layout:
+ *
+ * |-----------------------------| --> SP
+ * |    thread main function     | In init_sp, we have pushed thread main
+ * |-----------------------------| function and arguments to stackfunction
+ * |    arguments                | and arguments to stack.
+ * |-----------------------------| --> ctx->sp = SP - function - arguments
+ * |    Reversed room for Arm64  |
+ * |    Callee saved registers:  |
+ * |    x19 ~ x28                |
+ * |-----------------------------|
+ * |    x29 (frame pointer)      |
+ * |-----------------------------|
+ * |    ...                      |
+ * |    ...                      |
+ * |-----------------------------|
+ * |    thread                   | --> used for uk_thread_current
+ * |-----------------------------|
+ */
+
+/*
+ * This function will jump to thread main function and set up
+ * thread exit handler.
+ */
+ENTRY(asm_thread_starter)
+       mov x2, sp
+       ldp x0, x1, [x2]                /* Load func to x1, args to x0 */
+       ldr x30, =uk_sched_thread_exit  /* Set thread exit handler */
+       br  x1                          /* Jump to thread main function */
+ENDPROC(asm_thread_starter)
+
+/*
+ * x0 = ctx->sp
+ * x1 = ctx->ip = asm_thread_starter
+ *
+ * This function will set the SP to thread's SP and jump to
+ * ctx->ip: asm_thread_starter
+ */
+ENTRY(asm_ctx_start)
+       mov sp, x0      /* set SP */
+       br x1           /* jump to asm_thread_starter */
+ENDPROC(asm_ctx_start)
+
+/*
+ * x0 = prectx
+ * x1 = nextctx
+ * This function will switch to the next thread context
+ */
+ENTRY(asm_sw_ctx_switch)
+       /* Save callee-saved registers to prevctx's stack */
+       sub x2, sp, #__CALLEE_SAVED_SIZE
+       stp x19, x20, [x2, #16 * 0]
+       stp x21, x22, [x2, #16 * 1]
+       stp x23, x24, [x2, #16 * 2]
+       stp x25, x26, [x2, #16 * 3]
+       stp x27, x28, [x2, #16 * 4]
+       stp x29, x30, [x2, #16 * 5]
+
+       /*
+        * Record the restore point for switch out thread to restore
+        * its called-saved registers in next switch to time.
+        */
+       ldr x30, =restore_point
+
+       /* Save sp and restore point to previous context */
+       stp x2, x30, [x0]
+
+       /* Restire sp and restore point from next context */
+       ldp x2, x30, [x1]
+       mov sp, x2
+
+       ret
+
+restore_point:
+       /* Restore the callee-saved registers */
+       ldp x19, x20, [x2, #16 * 0]
+       ldp x21, x22, [x2, #16 * 1]
+       ldp x23, x24, [x2, #16 * 2]
+       ldp x25, x26, [x2, #16 * 3]
+       ldp x27, x28, [x2, #16 * 4]
+       ldp x29, x30, [x2, #16 * 5]
+
+       add sp, x2, #__CALLEE_SAVED_SIZE
+       ret
+ENDPROC(asm_sw_ctx_switch)
-- 
2.17.1


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