[kernel] Add test mode, controlled by manifest

The manifest can now supply a list of boot flags, including "test".
Those get turned into the bootproto::args::flags field by the
bootloader. The kernel takes those and uses the test flag to control
enabling syscalls with the new "test" attribute, like the new
test_finish syscall, which lets automated tests call back to the kernel
to shut down the system.

src/boot/bootconfig.cpp

@@ -41,7 +41,8 @@ bootconfig::bootconfig(util::buffer data, uefi::boot_services *bs)
     data += 1; // reserved byte
     uint16_t num_programs = *util::read<uint16_t>(data);
     uint16_t num_data = *util::read<uint16_t>(data);
-    data += 2; // reserved short
+
+    m_flags = *util::read<uint16_t>(data);
 
     read_descriptor(m_kernel, data);
     read_descriptor(m_init, data);

src/boot/bootconfig.h

@@ -28,12 +28,14 @@ public:
     /// Constructor. Loads bootconfig from the given buffer.
     bootconfig(util::buffer data, uefi::boot_services *bs);
 
-    inline const descriptor & kernel() { return m_kernel; }
-    inline const descriptor & init() { return m_init; }
+    inline uint16_t flags() const { return m_flags; }
+    inline const descriptor & kernel() const { return m_kernel; }
+    inline const descriptor & init() const { return m_init; }
     descriptors programs() { return m_programs; }
     descriptors data() { return m_data; }
 
 private:
+    uint16_t m_flags;
     descriptor m_kernel;
     descriptor m_init;
     descriptors m_programs;

src/boot/main.cpp

@@ -77,6 +77,7 @@ load_resources(bootproto::args *args, video::screen *screen, uefi::handle image,
 
     args->kernel = loader::load_program(disk, bc.kernel(), true);
     args->init = loader::load_program(disk, bc.init());
+    args->flags = static_cast<bootproto::boot_flags>(bc.flags());
 
     namespace bits = util::bits;
     using bootproto::desc_flags;

src/kernel/cpu.cpp

@@ -98,8 +98,6 @@ bsp_late_init()
     asm ("mov %%cr4, %0" : "=r"(cr4));
     uint64_t efer = rdmsr(msr::ia32_efer);
     log::debug(logs::boot, "Control regs: cr0:%lx cr4:%lx efer:%lx", cr0, cr4, efer);
-
-    syscall_initialize();
 }
 
 cpu_data *

src/kernel/main.cpp

@@ -18,6 +18,7 @@
 #include "objects/vm_area.h"
 #include "scheduler.h"
 #include "smp.h"
+#include "syscall.h"
 #include "sysconf.h"
 
 extern "C" {
@@ -55,6 +56,10 @@ kernel_main(bootproto::args *args)
 
     bsp_late_init();
 
+    using bootproto::boot_flags;
+    bool enable_test = util::bits::has(args->flags, boot_flags::test);
+    syscall_initialize(enable_test);
+
     device_manager &devices = device_manager::get();
     devices.parse_acpi(args->acpi_table);
 

src/kernel/syscall.cpp.cog

@@ -66,7 +66,7 @@ syscall_invalid(uint64_t call)
 }
 
 void
-syscall_initialize()
+syscall_initialize(bool enable_test)
 {
     memset(&syscall_registry, 0, sizeof(syscall_registry));
 
@@ -77,8 +77,17 @@ syscall_initialize()
         else:
             name = method.name
 
-        cog.outl(f"syscall_registry[{id}] = reinterpret_cast<uintptr_t>(syscalls::_syscall_verify_{name});")
-        cog.outl(f"""log::debug(logs::syscall, "Enabling syscall {id:02x} as {name}");""")
+        indent = ""
+        if "test" in method.options:
+            cog.outl("if (enable_test) {")
+            indent = "    "
+
+        cog.outl(f"{indent}syscall_registry[{id}] = reinterpret_cast<uintptr_t>(syscalls::_syscall_verify_{name});")
+        cog.outl(f"""{indent}log::debug(logs::syscall, "Enabling syscall {id:02x} as {name}");""")
+
+        if "test" in method.options:
+            cog.outl("}")
+
         cog.outl("")
     ]]]*/
     //[[[end]]]

src/kernel/syscall.h.cog

@@ -17,5 +17,5 @@ cog.outl(f"constexpr size_t num_syscalls = {len(syscalls.methods)};")
 ]]]*/
 /// [[[end]]]
 
-void syscall_initialize();
+void syscall_initialize(bool enable_test);
 extern "C" void syscall_enable();

src/kernel/syscalls/system.cpp

@@ -36,6 +36,14 @@ noop()
     return j6_status_ok;
 }
 
+[[ noreturn ]] j6_status_t
+test_finish(uint32_t exit_code)
+{
+    // Tell QEMU to exit
+    asm ( "out %0, %1" :: "a"(exit_code), "Nd"(0xf4) );
+    while (1) asm ("hlt");
+}
+
 j6_status_t
 system_get_log(system *self, void *buffer, size_t *buffer_len)
 {

src/libraries/bootproto/include/bootproto/kernel.h

@@ -114,8 +114,10 @@ struct frame_block
 
 enum class boot_flags : uint16_t {
     none  = 0x0000,
-    debug = 0x0001
+    debug = 0x0001,
+    test  = 0x0002,
 };
+is_bitfield(boot_flags);
 
 struct args
 {