Spawn Processes using memory primitives rather than and elf loader.

This allows us to remove the temporary syscall for that style of process
spawn.

lib/mammoth/src/debug.cpp

@@ -1,5 +1,31 @@
 #include "include/mammoth/debug.h"
 
 #include <zcall.h>
+#include <zerrors.h>
 
-void dbgln(const char* str) { ZDebug(str); }
+void dbgln(const char* str) {
+  // Safe to ignore the result since right now this doesn't throw.
+  uint64_t _ = ZDebug(str);
+}
+
+void check(uint64_t code) {
+  switch (code) {
+    case Z_OK:
+      return;
+    case ZE_NOT_FOUND:
+      dbgln("crash: NOT_FOUND");
+      break;
+    case ZE_INVALID:
+      dbgln("crash: INVALID");
+      break;
+    case ZE_DENIED:
+      dbgln("crash: DENIED");
+      break;
+    case ZE_UNIMPLEMENTED:
+      dbgln("crash: UNIMPLEMENTED");
+    default:
+      dbgln("Unhandled code");
+      break;
+  }
+  ZProcessExit(code);
+}

lib/mammoth/src/process.cpp

@@ -0,0 +1,97 @@
+#include "include/mammoth/process.h"
+
+#include <zcall.h>
+
+#include "include/mammoth/debug.h"
+
+namespace {
+
+typedef struct {
+  char ident[16];
+  uint16_t type;
+  uint16_t machine;
+  uint32_t version;
+  uint64_t entry;
+  uint64_t phoff;
+  uint64_t shoff;
+  uint32_t flags;
+  uint16_t ehsize;
+  uint16_t phentsize;
+  uint16_t phnum;
+  uint16_t shentsize;
+  uint16_t shnum;
+  uint16_t shstrndx;
+} Elf64Header;
+
+typedef struct {
+  uint32_t name;
+  uint32_t type;
+  uint64_t flags;
+  uint64_t addr;
+  uint64_t offset;
+  uint64_t size;
+  uint32_t link;
+  uint32_t info;
+  uint64_t addralign;
+  uint64_t entsize;
+} Elf64SectionHeader;
+
+typedef struct {
+  uint32_t type;
+  uint32_t flags;
+  uint64_t offset;
+  uint64_t vaddr;
+  uint64_t paddr;
+  uint64_t filesz;
+  uint64_t memsz;
+  uint64_t align;
+} Elf64ProgramHeader;
+
+void memcpy(uint64_t base, uint64_t len, uint64_t dest) {
+  uint8_t* srcptr = reinterpret_cast<uint8_t*>(base);
+  uint8_t* destptr = reinterpret_cast<uint8_t*>(dest);
+  for (uint64_t i = 0; i < len; i++) {
+    destptr[i] = srcptr[i];
+  }
+}
+
+uint64_t LoadElfProgram(uint64_t base, uint64_t as_cap) {
+  Elf64Header* header = reinterpret_cast<Elf64Header*>(base);
+  Elf64ProgramHeader* programs =
+      reinterpret_cast<Elf64ProgramHeader*>(base + header->phoff);
+  for (uint64_t i = 0; i < header->phnum; i++) {
+    Elf64ProgramHeader& program = programs[i];
+    dbgln("Create mem object");
+    uint64_t mem_cap;
+    uint64_t size = program.filesz;
+    check(ZMemoryObjectCreate(size, &mem_cap));
+
+    dbgln("Map Local");
+    uint64_t vaddr;
+    check(ZAddressSpaceMap(Z_INIT_AS_SELF, 0, mem_cap, &vaddr));
+
+    dbgln("Copy");
+    memcpy(base + program.offset, program.filesz, vaddr);
+
+    dbgln("Map Foreign");
+    check(ZAddressSpaceMap(as_cap, program.vaddr, mem_cap, &vaddr));
+  }
+  return header->entry;
+}
+
+}  // namespace
+
+uint64_t SpawnProcessFromElfRegion(uint64_t program) {
+  dbgln("Spawn");
+  uint64_t proc_cap;
+  uint64_t as_cap;
+  check(ZProcessSpawn(Z_INIT_PROC_SELF, &proc_cap, &as_cap));
+
+  uint64_t entry_point = LoadElfProgram(program, as_cap);
+  dbgln("Thread Create");
+  uint64_t thread_cap;
+  check(ZThreadCreate(proc_cap, &thread_cap));
+
+  dbgln("Thread start");
+  check(ZThreadStart(thread_cap, entry_point, 0, 0));
+}