UEFI: add support for tasks scheduler and make it default

compileopts/config.go

@@ -482,7 +482,11 @@ func (c *Config) LinkerFlavor() string {
 // ExtraFiles returns the list of extra files to be built and linked with the
 // executable. This can include extra C and assembly files.
 func (c *Config) ExtraFiles() []string {
-	return c.Target.ExtraFiles
+	files := append([]string(nil), c.Target.ExtraFiles...)
+	if c.Scheduler() == "tasks" && c.GOARCH() == "amd64" && slices.Contains(c.Target.BuildTags, "uefi") {
+		files = append(files, "src/internal/task/task_stack_amd64_windows.S")
+	}
+	return files
 }
 
 // DumpSSA returns whether to dump Go SSA while compiling (-dumpssa flag). Only

src/internal/task/task_stack_amd64.go

@@ -1,4 +1,4 @@
-//go:build scheduler.tasks && amd64 && !windows
+//go:build scheduler.tasks && amd64 && !windows && !uefi
 
 package task
 

src/internal/task/task_stack_amd64_winabi.go

@@ -0,0 +1,58 @@
+//go:build scheduler.tasks && amd64 && uefi
+
+package task
+
+// This is almost the same as task_stack_amd64.go, but with the extra rdi and
+// rsi registers saved: UEFI on amd64 uses the Win64 ABI.
+
+import "unsafe"
+
+var systemStack uintptr
+
+// calleeSavedRegs is the list of registers that must be saved and restored when
+// switching between tasks. Also see task_stack_amd64_windows.S that relies on
+// the exact layout of this struct.
+type calleeSavedRegs struct {
+	// rbx is placed here so the stack is correctly aligned when saving XMM regs.
+	rbx   uintptr
+	xmm15 [2]uint64
+	xmm14 [2]uint64
+	xmm13 [2]uint64
+	xmm12 [2]uint64
+	xmm11 [2]uint64
+	xmm10 [2]uint64
+	xmm9  [2]uint64
+	xmm8  [2]uint64
+	xmm7  [2]uint64
+	xmm6  [2]uint64
+	rbp   uintptr
+	rdi   uintptr
+	rsi   uintptr
+	r12   uintptr
+	r13   uintptr
+	r14   uintptr
+	r15   uintptr
+
+	pc uintptr
+}
+
+func (s *state) archInit(r *calleeSavedRegs, fn uintptr, args unsafe.Pointer) {
+	s.sp = uintptr(unsafe.Pointer(r))
+	r.pc = uintptr(unsafe.Pointer(&startTask))
+	r.r12 = fn
+	r.r13 = uintptr(args)
+}
+
+func (s *state) resume() {
+	swapTask(s.sp, &systemStack)
+}
+
+func (s *state) pause() {
+	newStack := systemStack
+	systemStack = 0
+	swapTask(newStack, &s.sp)
+}
+
+func SystemStack() uintptr {
+	return systemStack
+}

src/runtime/sleep_custom_uefi.go

@@ -0,0 +1,14 @@
+//go:build scheduler.tasks && uefi
+
+package runtime
+
+//go:linkname gosched runtime.Gosched
+func gosched()
+
+func schedulerSleepCustom(duration int64) bool {
+	deadline := ticks() + nanosecondsToTicks(duration)
+	for ticks() < deadline {
+		gosched()
+	}
+	return true
+}

targets/uefi-amd64.json

@@ -6,7 +6,7 @@
   "goos": "linux",
   "goarch": "amd64",
   "gc": "leaking",
-  "scheduler": "none",
+  "scheduler": "tasks",
   "linker": "ld.lld",
   "linker-flavor": "coff",
   "libc": "picolibc",