[fiber] Add support for ARM64 targets

src/modm/processing/fiber/context_arm64.cpp

@@ -0,0 +1,127 @@
+/*
+ * Copyright (c) 2020, Erik Henriksson
+ * Copyright (c) 2021, 2023, Niklas Hauser
+ *
+ * This file is part of the modm project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+// ----------------------------------------------------------------------------
+
+#include "context.h"
+#include <modm/architecture/detect.hpp>
+
+/* Stack layout (growing downwards):
+ *
+ * Permanent Storage:
+ * Fiber Function
+ * Fiber Function Argument
+ *
+ * Temporary Prepare:
+ * Entry Function
+ *
+ * Register file:
+ * LR
+ * FP
+ * x28
+ * x27
+ * x26
+ * x25
+ * x24
+ * x23
+ * x22
+ * x21
+ * x20
+ * x19
+ * d15
+ * d14
+ * d13
+ * d12
+ * d11
+ * d10
+ * d9
+ * d8
+ */
+
+namespace
+{
+
+constexpr size_t StackWordsReset = 1;
+constexpr size_t StackWordsStorage = 2;
+constexpr size_t StackWordsRegisters = 20;
+constexpr size_t StackWordsAll = StackWordsStorage + StackWordsRegisters;
+constexpr size_t StackSizeWord = sizeof(uintptr_t);
+constexpr uintptr_t StackWatermark = 0xc0ffee'f00d'facade;
+
+}
+
+extern "C" void modm_context_entry();
+
+void
+modm_context_init(modm_context_t *ctx,
+				  uintptr_t *bottom, uintptr_t *top,
+				  uintptr_t fn, uintptr_t fn_arg)
+{
+	ctx->bottom = bottom;
+	ctx->top = top;
+
+	ctx->sp = top;
+	*--ctx->sp = fn;
+	*--ctx->sp = fn_arg;
+}
+
+void
+modm_context_reset(modm_context_t *ctx)
+{
+	*ctx->bottom = StackWatermark;
+
+	ctx->sp = ctx->top - StackWordsStorage;
+	*--ctx->sp = (uintptr_t) modm_context_entry;
+	ctx->sp -= StackWordsRegisters - StackWordsReset;
+}
+
+void
+modm_context_watermark(modm_context_t *ctx)
+{
+	// clear the register file on the stack
+	for (auto *word = ctx->top - StackWordsAll;
+		 word < ctx->top - StackWordsStorage - StackWordsReset; word++)
+		*word = 0;
+
+	// then color the whole stack *below* the register file
+	for (auto *word = ctx->bottom; word < ctx->top - StackWordsAll; word++)
+		*word = StackWatermark;
+}
+
+size_t
+modm_context_stack_usage(const modm_context_t *ctx)
+{
+	for (auto *word = ctx->bottom; word < ctx->top; word++)
+		if (StackWatermark != *word)
+			return (ctx->top - word) * StackSizeWord;
+	return 0;
+}
+
+bool
+modm_context_stack_overflow(const modm_context_t *ctx)
+{
+	return *ctx->bottom != StackWatermark;
+}
+
+static modm_context_t main_context;
+
+void
+modm_context_start(modm_context_t *to)
+{
+	modm_context_jump(&main_context, to);
+}
+
+void
+modm_context_end()
+{
+	modm_context_t dummy;
+	modm_context_jump(&dummy, &main_context);
+	__builtin_unreachable();
+}

src/modm/processing/fiber/context_arm64_asm.S.in

@@ -0,0 +1,83 @@
+/*
+ * Copyright (c) 2023, Niklas Hauser
+ *
+ * This file is part of the modm project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+; ----------------------------------------------------------------------------
+
+.text
+.globl _modm_context_entry
+.balign 16
+_modm_context_entry:
+
+ldr x0, [sp]		; Load closure data pointer
+ldr x1, [sp, #8]	; Jump to closure function
+br x1
+
+
+/*
+The assembly code below is adapted from the Boost Context library to work
+for Windows, Linux and macOS.
+See https://github.com/boostorg/context/tree/develop/src/asm
+- Windows: jump_arm64_aapcs_pe_armasm.asm
+- Linux: jump_arm64_aapcs_elf_gas.S
+- macOS: jump_arm64_aapcs_macho_gas.S
+
+			Copyright Oliver Kowalke 2009.
+   Distributed under the Boost Software License, Version 1.0.
+	  (See accompanying file LICENSE_1_0.txt or copy at
+			http://www.boost.org/LICENSE_1_0.txt)
+*/
+
+.text
+.globl _modm_context_jump
+.balign 16
+_modm_context_jump:
+
+; move stack pointer down
+sub sp,  sp,  #0xa0
+
+; save d8 - d15
+stp d8,  d9,  [sp, #0x00]
+stp d10, d11, [sp, #0x10]
+stp d12, d13, [sp, #0x20]
+stp d14, d15, [sp, #0x30]
+
+; save x19-x30
+stp x19, x20, [sp, #0x40]
+stp x21, x22, [sp, #0x50]
+stp x23, x24, [sp, #0x60]
+stp x25, x26, [sp, #0x70]
+stp x27, x28, [sp, #0x80]
+stp fp,  lr,  [sp, #0x90]
+
+; Store the SP in from->sp
+mov x19, sp
+str x19, [x0]
+
+; Restore SP from to->sp
+ldr x19, [x1]
+mov sp,  x19
+
+; load d8 - d15
+ldp d8,  d9,  [sp, #0x00]
+ldp d10, d11, [sp, #0x10]
+ldp d12, d13, [sp, #0x20]
+ldp d14, d15, [sp, #0x30]
+
+; load x19-x30
+ldp x19, x20, [sp, #0x40]
+ldp x21, x22, [sp, #0x50]
+ldp x23, x24, [sp, #0x60]
+ldp x25, x26, [sp, #0x70]
+ldp x27, x28, [sp, #0x80]
+ldp fp,  lr,  [sp, #0x90]
+
+; restore stack from GP + FPU
+add sp,  sp,  #0xa0
+
+ret

src/modm/processing/fiber/module.lb

@@ -26,8 +26,7 @@ def prepare(module, options):
     module.add_query(
         EnvironmentQuery(name="__enabled", factory=is_enabled))
 
-    # No ARM64 support yet!
-    return "arm64" not in options[":target"].get_driver("core")["type"]
+    return True
 
 
 def build(env):
@@ -64,6 +63,12 @@ def build(env):
         env.substitutions["default_stack_size"] = 2**20 # 1MB
         env.template("context_x86_64.cpp.in")
 
+    elif "arm64" in core:
+        env.substitutions["stack_minimum"] = (20 + 2) * 8
+        env.substitutions["default_stack_size"] = 2**20 # 1MB
+        env.copy("context_arm64.cpp")
+        env.template("context_arm64_asm.S.in")
+
     env.template("context.h.in")
     env.template("stack.hpp.in")
     env.template("scheduler.hpp.in")