added implementation for armv7a

10 files changed, 124 insertions, 2 deletions

diff --git a/.github/workflows/check.yml b/.github/workflows/check.yml
index 1d7dfa4..e8278d7 100644
--- a/.github/workflows/check.yml
+++ b/.github/workflows/check.yml
@@ -15,7 +15,7 @@ jobs:
           docker/build.sh matcha-box
     - name: Run examples
       run: |
-          for arch in x86_64 arm64; do
+          for arch in x86_64 arm64 arm; do
               echo -e "\e[1;32m==> check ARCH=$arch\e0m"
               docker run                 \
                   --rm                   \
diff --git a/Makefile b/Makefile
index 0681880..08d4494 100644
--- a/Makefile
+++ b/Makefile
@@ -4,6 +4,8 @@ ARCH ?= x86_64
 
 ifeq ($(ARCH),arm64)
 PREFIX := aarch64-linux-gnu-
+else ifeq ($(ARCH),arm)
+PREFIX := arm-linux-gnueabi-
 endif
 
 CXX      := $(PREFIX)g++
@@ -28,6 +30,11 @@ ifeq ($(ARCH),arm64)
 	    -L /usr/aarch64-linux-gnu                     \
 	    -E LD_LIBRARY_PATH=/usr/aarch64-linux-gnu/lib \
 	    $<
+else ifeq ($(ARCH),arm)
+	qemu-arm                                          \
+	    -L /usr/arm-linux-gnueabi                     \
+	    -E LD_LIBRARY_PATH=/usr/arm-linux-gnueabi/lib \
+	    $<
 else
 	$<
 endif
@@ -40,6 +47,13 @@ ifeq ($(ARCH),arm64)
 	    -g 1234                                       \
 	    $< &
 	gdb-multiarch -ex 'target remote :1234' -ex 'b main' -ex 'c' $<
+else ifeq ($(ARCH),arm)
+	qemu-arm                                          \
+	    -L /usr/arm-linux-gnueabi                     \
+	    -E LD_LIBRARY_PATH=/usr/arm-linux-gnueabi/lib \
+	    -g 1234                                       \
+	    $< &
+	gdb-multiarch -ex 'target remote :1234' -ex 'b main' -ex 'c' $<
 else
 	which cgdb && cgdb --ex 'start' $< \
 	           ||  gdb --ex 'start' $<
diff --git a/docker/Dockerfile b/docker/Dockerfile
index 7a41480..703ee7a 100644
--- a/docker/Dockerfile
+++ b/docker/Dockerfile
@@ -11,11 +11,13 @@ RUN apt update                     \
       g++                          \
       gcc-aarch64-linux-gnu        \
       g++-aarch64-linux-gnu        \
+      gcc-arm-linux-gnueabi        \
+      g++-arm-linux-gnueabi        \
       gdb-multiarch                \
       qemu-user                    \
  && rm -rf /var/lib/apt/lists/*    \
  && apt-get clean                  \
  # Remove expensive qemu emulators which are currently not used.
- && rm -f $(find /usr/bin -name 'qemu-*' | grep -v 'qemu-aarch64$')
+ && rm -f $(find /usr/bin -name 'qemu-*' | grep -v 'qemu-aarch64$\|qemu-arm$')
 
 WORKDIR /develop
diff --git a/lib/Makefile b/lib/Makefile
index 24fe7bd..c85d450 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -4,6 +4,8 @@ ARCH ?= x86_64
 
 ifeq ($(ARCH),arm64)
 PREFIX := aarch64-linux-gnu-
+else ifeq ($(ARCH),arm)
+PREFIX := arm-linux-gnueabi-
 endif
 
 AS       := $(PREFIX)gcc
diff --git a/lib/arch.h b/lib/arch.h
index bb58576..524d401 100644
--- a/lib/arch.h
+++ b/lib/arch.h
@@ -10,6 +10,8 @@ static_assert(false, "Matcha Threads only supported on Linux!");
 #    include "arch/x86_64/api.h"
 #elif defined(__aarch64__)
 #    include "arch/arm64/api.h"
+#elif defined(__arm__)
+#    include "arch/arm/api.h"
 #else
 static_assert(false, "Unsupported architecture!");
 #endif
diff --git a/lib/arch/arm/README.md b/lib/arch/arm/README.md
new file mode 100644
index 0000000..8631c93
--- /dev/null
+++ b/lib/arch/arm/README.md
@@ -0,0 +1,9 @@
+# Procedure Call Standard ARM64
+
+- Integer/pointer arguments via `r0`-`r3`
+- Integer/pointer return values via `r0`
+- Callee saved registers `r4`-`r11`, `sp`, `lr`, `fp`
+
+## Reference
+- [johannst armv7 notes](https://johannst.github.io/notes/arch/armv7.html)
+
diff --git a/lib/arch/arm/api.h b/lib/arch/arm/api.h
new file mode 100644
index 0000000..c7a688d
--- /dev/null
+++ b/lib/arch/arm/api.h
@@ -0,0 +1,6 @@
+/* Copyright (c) 2021 Johannes Stoelp */
+
+#pragma once
+
+extern "C" void yield(const void* new_stack, void** old_stack);
+void* init_stack(void* stack_ptr, void (*entry)(void*), const void* ctx);
diff --git a/lib/arch/arm/init_stack.cc b/lib/arch/arm/init_stack.cc
new file mode 100644
index 0000000..422be64
--- /dev/null
+++ b/lib/arch/arm/init_stack.cc
@@ -0,0 +1,35 @@
+#include <cassert>
+#include <cstdint>  // uintN_t
+
+extern "C" void thread_create();
+
+void* init_stack(void* stack_ptr, void (*entry)(void*), const void* ctx) {
+    static_assert(sizeof(uint32_t) == sizeof(std::uintptr_t), "Pointer must be 32bit!");
+
+    // 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.
+
+    uint32_t* stack = static_cast<uint32_t*>(stack_ptr);
+    // Arguments for `thread_create`.
+    *(--stack) = reinterpret_cast<uint32_t>(ctx);
+    *(--stack) = reinterpret_cast<uint32_t>(entry);
+
+    // Yield epilogue.
+    *(--stack) = reinterpret_cast<uint32_t>(thread_create);  // r15 (PC)
+    *(--stack) = static_cast<uint32_t>(0);                   // r11 (FP)
+
+    // Callee saved registers.
+    *(--stack) = static_cast<uint32_t>(0);  // r11
+    *(--stack) = static_cast<uint32_t>(0);  // r10
+    *(--stack) = static_cast<uint32_t>(0);  // r9
+    *(--stack) = static_cast<uint32_t>(0);  // r8
+    *(--stack) = static_cast<uint32_t>(0);  // r7
+    *(--stack) = static_cast<uint32_t>(0);  // r6
+    *(--stack) = static_cast<uint32_t>(0);  // r5
+    *(--stack) = static_cast<uint32_t>(0);  // r4
+
+    assert((reinterpret_cast<std::uintptr_t>(stack) & 0x7) == 0);  // 8byte aligned
+    return static_cast<void*>(stack);
+}
diff --git a/lib/arch/arm/thread_create.s b/lib/arch/arm/thread_create.s
new file mode 100644
index 0000000..7231c3e
--- /dev/null
+++ b/lib/arch/arm/thread_create.s
@@ -0,0 +1,20 @@
+# Copyright (c) 2021 Johannes Stoelp
+
+    .arch armv7-a
+    .section .text, "ax", %progbits
+
+     # extern "C" void thread_create();
+    .global thread_create
+    .type   thread_create, %function
+thread_create:
+    .cfi_startproc
+    ldr r0, [sp, #0x4]
+    ldr r1, [sp]
+
+    blx r1
+
+    # FIXME: no return from thread after user fn finished.
+1:
+    b 1b
+    .cfi_endproc
+    .size thread_create, .-thread_create
diff --git a/lib/arch/arm/yield.s b/lib/arch/arm/yield.s
new file mode 100644
index 0000000..de9d604
--- /dev/null
+++ b/lib/arch/arm/yield.s
@@ -0,0 +1,32 @@
+# Copyright (c) 2021 Johannes Stoelp
+
+    .arch armv7-a
+    .section .text, "ax", %progbits
+
+    # extern "C" void yield(const void* new_stack, void** old_stack);
+    #                                   ^^^^^^^^^         ^^^^^^^^^
+    #                                   x0                x1
+    .global yield
+    .type   yield, %function
+yield:
+    .cfi_startproc
+    // prologue
+    push {fp, lr}
+    mov fp, sp
+
+    // push callee saved registers
+    push {r4-r11}
+
+    // arg0: r0 holds new stack
+    // arg1: r1 holds addr to location current stack must be saved
+    mov r2, sp
+    str r2, [r1]  // save current stack ptr
+    mov sp, r0    // switch to new stack ptr
+
+    // pop callee saved registers
+    pop {r4-r11}
+
+    // epilogue
+    pop {fp, pc}
+    .cfi_endproc
+    .size yield, .-yield