From 533a9e57de8cb74594499f625810ad812359d3fb Mon Sep 17 00:00:00 2001
From: johannst <johannes.stoelp@gmail.com>
Date: Tue, 29 Sep 2020 04:31:51 +0200
Subject: added basic arm64 support

---
 lib/arch/arm64/api.h           |  6 ++++++
 lib/arch/arm64/init_stack.cc   | 37 +++++++++++++++++++++++++++++++++++++
 lib/arch/arm64/thread_create.s | 20 ++++++++++++++++++++
 lib/arch/arm64/yield.s         | 42 ++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 105 insertions(+)
 create mode 100644 lib/arch/arm64/api.h
 create mode 100644 lib/arch/arm64/init_stack.cc
 create mode 100644 lib/arch/arm64/thread_create.s
 create mode 100644 lib/arch/arm64/yield.s

(limited to 'lib/arch')

diff --git a/lib/arch/arm64/api.h b/lib/arch/arm64/api.h
new file mode 100644
index 0000000..b2babc9
--- /dev/null
+++ b/lib/arch/arm64/api.h
@@ -0,0 +1,6 @@
+/* Copyright (c) 2020 Johannes Stoelp */
+
+#pragma once
+
+extern "C" void yield(const void* new_stack, void* const* old_stack);
+void* init_stack(void* stack_ptr, void (*entry)(void*), void* ctx);
diff --git a/lib/arch/arm64/init_stack.cc b/lib/arch/arm64/init_stack.cc
new file mode 100644
index 0000000..b28d957
--- /dev/null
+++ b/lib/arch/arm64/init_stack.cc
@@ -0,0 +1,37 @@
+#include <cassert>
+#include <cstdint>  // uintN_t
+
+extern "C" void thread_create();
+
+void* init_stack(void* stack_ptr, void (*entry)(void*), void* ctx) {
+    static_assert(sizeof(uint64_t) == sizeof(std::uintptr_t), "Pointer must be 64bit!");
+
+    // Setup initial stack frame which will be popped when yielding
+    // first time into the thread.
+    // Basic idea is to yield into Thread::entry() function which will
+    // then call the user function.
+
+    uint64_t* stack = static_cast<uint64_t*>(stack_ptr);
+    // Arguments for `thread_create`.
+    *(--stack) = reinterpret_cast<uint64_t>(ctx);
+    *(--stack) = reinterpret_cast<uint64_t>(entry);
+
+    // Yield epilogue.
+    *(--stack) = reinterpret_cast<uint64_t>(thread_create);  // x30 (LR)
+    *(--stack) = static_cast<uint64_t>(0);                   // x29 (FP)
+
+    // Callee saved registers.
+    *(--stack) = static_cast<uint64_t>(0);  // x28
+    *(--stack) = static_cast<uint64_t>(0);  // x27
+    *(--stack) = static_cast<uint64_t>(0);  // x26
+    *(--stack) = static_cast<uint64_t>(0);  // x25
+    *(--stack) = static_cast<uint64_t>(0);  // x24
+    *(--stack) = static_cast<uint64_t>(0);  // x23
+    *(--stack) = static_cast<uint64_t>(0);  // x22
+    *(--stack) = static_cast<uint64_t>(0);  // x21
+    *(--stack) = static_cast<uint64_t>(0);  // x20
+    *(--stack) = static_cast<uint64_t>(0);  // x19
+
+    assert((reinterpret_cast<std::uintptr_t>(stack) & 0xf) == 0);  // 16byte aligned
+    return static_cast<void*>(stack);
+}
diff --git a/lib/arch/arm64/thread_create.s b/lib/arch/arm64/thread_create.s
new file mode 100644
index 0000000..dc6fae2
--- /dev/null
+++ b/lib/arch/arm64/thread_create.s
@@ -0,0 +1,20 @@
+# Copyright (c) 2020 Johannes Stoelp
+
+    .arch armv8-a
+    .section .text, "ax", @progbits
+
+     # extern "C" void thread_create();
+    .global thread_create
+    .type   thread_create, @function
+thread_create:
+    .cfi_startproc
+    ldr x0, [sp, 0x8]
+    ldr x1, [sp]
+
+    blr x1
+
+    # FIXME: no return from thread after user fn finished.
+1:
+    b 1b
+    .cfi_endproc
+    .size thread_create, .-thread_create
diff --git a/lib/arch/arm64/yield.s b/lib/arch/arm64/yield.s
new file mode 100644
index 0000000..63a4051
--- /dev/null
+++ b/lib/arch/arm64/yield.s
@@ -0,0 +1,42 @@
+# Copyright (c) 2020 Johannes Stoelp
+
+    .arch armv8-a
+    .section .text, "ax", @progbits
+
+    # extern "C" void yield(const void* new_stack, void* const* old_stack);
+    #                                   ^^^^^^^^^               ^^^^^^^^^
+    #                                   rdi                     rsi
+    .global yield
+    .type   yield, @function
+yield:
+    .cfi_startproc
+    // prologue
+    stp x29, x30, [sp, -16]!
+    mov x29, sp
+
+    // push callee saved registers
+    stp x27, x28, [sp, -16]!
+    stp x25, x26, [sp, -16]!
+    stp x23, x24, [sp, -16]!
+    stp x21, x22, [sp, -16]!
+    stp x19, x20, [sp, -16]!
+
+    // arg0: x0 holds new stack
+    // arg1: x1 holds addr to location current stack must be saved
+    mov x2, sp
+    str x2, [x1]  // save current stack ptr
+    mov sp, x0    // switch to new stack ptr
+
+    // pop callee saved registers
+    ldp x19, x20, [sp], 16
+    ldp x21, x22, [sp], 16
+    ldp x23, x24, [sp], 16
+    ldp x25, x26, [sp], 16
+    ldp x27, x28, [sp], 16
+
+    // epilogue
+    ldp x29, x30, [sp], 16
+
+    ret
+    .cfi_endproc
+    .size yield, .-yield
-- 
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