From dcc05f2741f62ef9b942adfa8ee88538756c0631 Mon Sep 17 00:00:00 2001
From: Drew Galbraith <dgalbraith33@gmail.com>
Date: Wed, 7 Jun 2023 10:33:10 -0700
Subject: [PATCH] Add a libc skeleton with a primitive malloc.

---
 lib/CMakeLists.txt        |  1 +
 lib/libc/CMakeLists.txt   | 15 +++++++++++++
 lib/libc/include/stddef.h |  5 +++++
 lib/libc/include/stdlib.h |  5 +++++
 lib/libc/src/malloc.cpp   | 44 +++++++++++++++++++++++++++++++++++++++
 sys/CMakeLists.txt        |  1 +
 sys/test2.cpp             |  3 ++-
 7 files changed, 73 insertions(+), 1 deletion(-)
 create mode 100644 lib/libc/CMakeLists.txt
 create mode 100644 lib/libc/include/stddef.h
 create mode 100644 lib/libc/include/stdlib.h
 create mode 100644 lib/libc/src/malloc.cpp

diff --git a/lib/CMakeLists.txt b/lib/CMakeLists.txt
index a9f2ea1..e727efa 100644
--- a/lib/CMakeLists.txt
+++ b/lib/CMakeLists.txt
@@ -1 +1,2 @@
+add_subdirectory(libc)
 add_subdirectory(mammoth)
diff --git a/lib/libc/CMakeLists.txt b/lib/libc/CMakeLists.txt
new file mode 100644
index 0000000..7188b73
--- /dev/null
+++ b/lib/libc/CMakeLists.txt
@@ -0,0 +1,15 @@
+
+add_library(libc STATIC
+  src/malloc.cpp
+  )
+
+target_include_directories(libc
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}
+  PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/include)
+
+target_link_libraries(libc
+  zion_lib
+  )
+
+set_target_properties(libc PROPERTIES
+  COMPILE_FLAGS "${CMAKE_CXX_FLAGS} -ffreestanding -mgeneral-regs-only")
diff --git a/lib/libc/include/stddef.h b/lib/libc/include/stddef.h
new file mode 100644
index 0000000..92a84ac
--- /dev/null
+++ b/lib/libc/include/stddef.h
@@ -0,0 +1,5 @@
+#pragma once
+
+#include <stdint.h>
+
+typedef uint64_t size_t;
diff --git a/lib/libc/include/stdlib.h b/lib/libc/include/stdlib.h
new file mode 100644
index 0000000..3634d1f
--- /dev/null
+++ b/lib/libc/include/stdlib.h
@@ -0,0 +1,5 @@
+#pragma once
+
+#include "stddef.h"
+
+void* malloc(size_t size);
diff --git a/lib/libc/src/malloc.cpp b/lib/libc/src/malloc.cpp
new file mode 100644
index 0000000..fc8393c
--- /dev/null
+++ b/lib/libc/src/malloc.cpp
@@ -0,0 +1,44 @@
+#include <zcall.h>
+
+#include "stdlib.h"
+
+namespace {
+class NaiveAllocator {
+ public:
+  constexpr static uint64_t kSize = 0x4000;
+  NaiveAllocator() {}
+  bool is_init() { return next_addr_ != 0; }
+  void Init() {
+    uint64_t vmmo_cap;
+    uint64_t err = ZMemoryObjectCreate(kSize, &vmmo_cap);
+    if (err != 0) {
+      ZProcessExit(err);
+    }
+    err = ZAddressSpaceMap(Z_INIT_VMAS_SELF, 0, vmmo_cap, &next_addr_);
+    max_addr_ = next_addr_ + kSize;
+  }
+
+  void* Allocate(size_t size) {
+    uint64_t addr = next_addr_;
+    next_addr_ += size;
+    if (next_addr_ >= max_addr_) {
+      return 0;
+    }
+    return reinterpret_cast<void*>(addr);
+  }
+
+ private:
+  uint64_t next_addr_ = 0;
+  uint64_t max_addr_ = 0;
+};
+
+NaiveAllocator gAlloc;
+
+}  // namespace
+
+void* malloc(size_t size) {
+  if (!gAlloc.is_init()) {
+    gAlloc.Init();
+  }
+  return gAlloc.Allocate(size);
+}
diff --git a/sys/CMakeLists.txt b/sys/CMakeLists.txt
index 9a6c0af..adb8d91 100644
--- a/sys/CMakeLists.txt
+++ b/sys/CMakeLists.txt
@@ -20,6 +20,7 @@ add_executable(test2
   test2.cpp)
 
 target_link_libraries(test2
+  libc
   mammoth_lib)
 
 set_target_properties(test2
diff --git a/sys/test2.cpp b/sys/test2.cpp
index 45d3616..d2c8398 100644
--- a/sys/test2.cpp
+++ b/sys/test2.cpp
@@ -1,6 +1,7 @@
 #include <mammoth/channel.h>
 #include <mammoth/debug.h>
 #include <mammoth/thread.h>
+#include <stdlib.h>
 
 void thread_entry(void* a) {
   dbgln("In thread");
@@ -18,7 +19,7 @@ int main(uint64_t bootstrap_cap) {
   Thread t2(thread_entry, b);
 
   uint64_t size = 10;
-  char buff[10];
+  char* buff = (char*)malloc(size);
   Channel c1;
   c1.adopt_cap(bootstrap_cap);
   check(c1.ReadStr(buff, &size));