WIP add stack overflow check in yield

Author: salkinium

examples/generic/fiber_overflow/main.cpp

@@ -0,0 +1,49 @@
+/*
+ * Copyright (c) 2024, Niklas Hauser
+ *
+ * This file is part of the modm project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+// ----------------------------------------------------------------------------
+
+#include <modm/board.hpp>
+#include <modm/processing.hpp>
+
+using namespace Board;
+using namespace std::chrono_literals;
+
+// modm::Fiber<> blinky([]
+// {
+// 	while(1)
+// 	{
+// 		Board::Leds::toggle();
+// 		modm::this_fiber::sleep_for(0.5s);
+// 	}
+// });
+
+modm::Fiber<> bad_fiber([]
+{
+
+	MODM_LOG_INFO << "\nReboot!\nPush the button to overflow the stack!" << modm::endl;
+
+	while(1)
+	{
+		// cause stack overflow on button push
+		if (Button::read()) asm volatile ("push {r0-r7}");
+		modm::this_fiber::yield();
+	}
+});
+
+int
+main()
+{
+	Board::initialize();
+	Board::Leds::setOutput();
+
+	modm::fiber::Scheduler::run();
+
+	return 0;
+}

examples/generic/fiber_overflow/project.xml

@@ -0,0 +1,11 @@
+<library>
+  <!-- <extends>modm:nucleo-u575zi-q</extends> -->
+  <extends>modm:nucleo-g071rb</extends>
+  <options>
+    <option name="modm:build:build.path">../../../build/generic/fiber_overflow</option>
+  </options>
+  <modules>
+    <module>modm:build:scons</module>
+    <module>modm:processing:fiber</module>
+  </modules>
+</library>

examples/nucleo_u575zi-q/fiber_overflow/project.xml

@@ -64,7 +64,7 @@ modm_context_reset(modm_context_t *ctx);
  * Switches control from the main context to the fiber context. This initializes
  * the hardware and then jumps from the caller context into the `to` fiber.
  */
-void
+uintptr_t
 modm_context_start(modm_context_t *to);
 
 /**
@@ -80,7 +80,7 @@ modm_context_jump(modm_context_t *from, modm_context_t *to) asm("modm_context_ju
  * `modm_context_start()` function.
  */
 void modm_noreturn
-modm_context_end();
+modm_context_end(uintptr_t retval);
 
 /**
  * Zeros the register file and watermarks the rest of the stack.

src/modm/processing/fiber/context.h

@@ -142,7 +142,7 @@ modm_context_stack_usage(const modm_context_t *ctx)
 bool
 modm_context_stack_overflow(const modm_context_t *ctx)
 {
-	return *ctx->bottom != StackWatermark;
+	return ctx->sp >= ctx->bottom and *ctx->bottom != StackWatermark;
 }
 
 #define MODM_PUSH_CONTEXT() \
@@ -173,7 +173,7 @@ modm_context_stack_overflow(const modm_context_t *ctx)
 		"pop {r4-r11, pc}	\n\t"
 %% endif
 %#
-void modm_naked
+uintptr_t modm_naked
 modm_context_start(modm_context_t*)
 {
 	asm volatile
@@ -211,41 +211,57 @@ modm_context_jump(modm_context_t*, modm_context_t*)
 	(
 		MODM_PUSH_CONTEXT()
 %#
+%% if not with_psplim
+		"ldr r3, [r0, #4]		\n\t"	// Load from->bottom
+%% endif
 %% if is_cm0
-		"mov r2,  sp		\n\t"
-		"str r2, [r0]		\n\t"	// Store the SP in from->sp
+		"mov r2,  sp			\n\t"
+		"str r2, [r0]			\n\t"	// Store the SP in from->sp
+%#
+		"cmp r2, r3				\n\t"	// Compare SP to from->bottom
 %% else
-		"str sp, [r0]		\n\t"	// Store the SP in from->sp
+		"str sp, [r0]			\n\t"	// Store the SP in from->sp
+%% if not with_psplim
+%#
+		"cmp sp, r3				\n\t"	// Compare SP to from->bottom
+%% endif
+%% endif
+%% if not with_psplim
+		"ble modm_context_end	\n\t"	// If SP <= bottom, stack overflow
+		"ldr r3, [r3]			\n\t"	// Load stack bottom
+		"ldr r2, =0xf00dcafe	\n\t"	// Load StackWatermark value
+		"cmp r2, r3				\n\t"	// Check if stack watermark is still at the bottom
+		"bne modm_context_end	\n\t"	// If not, stack overflow
 %% endif
 %#
 %% if is_cm0
-		"ldr r2, [r1]		\n\t"
-		"mov sp,  r2		\n\t"	// Restore SP from to->sp
+		"ldr r2, [r1]			\n\t"
+		"mov sp,  r2			\n\t"	// Restore SP from to->sp
 %% elif with_psplim
-		"ldm r1, {r1-r2}	\n\t"
-		"msr psplim, r2		\n\t"	// Set PSPLIM to ctx->bottom
-		"mov sp, r1			\n\t"	// Set PSP to ctx->sp
+		"ldm r1, {r1-r2}		\n\t"
+		"msr psplim, r2			\n\t"	// Set PSPLIM to ctx->bottom
+		"mov sp, r1				\n\t"	// Set PSP to ctx->sp
 %% else
-		"ldr sp, [r1]		\n\t"	// Restore SP from to->sp
+		"ldr sp, [r1]			\n\t"	// Restore SP from to->sp
 %% endif
 %#
 		MODM_POP_CONTEXT()
 	);
 }
 
 void modm_naked
-modm_context_end()
+modm_context_end(uintptr_t)
 {
 	asm volatile
 	(
-		"mrs r0, control	\n\t"
+		"mrs r1, control	\n\t"
 %% if is_cm0
-		"mov r1, #2			\n\t"
-		"bic r0, r0, r1		\n\t"	// Unset SPSEL
+		"mov r2, #2			\n\t"
+		"bic r1, r1, r2		\n\t"	// Unset SPSEL
 %% else
-		"bic r0, r0, #2		\n\t"	// Unset SPSEL
+		"bic r1, r1, #2		\n\t"	// Unset SPSEL
 %% endif
-		"msr control, r0	\n\t"
+		"msr control, r1	\n\t"
 
 		MODM_POP_CONTEXT()
 	);

src/modm/processing/fiber/context_arm_m.cpp.in

@@ -21,7 +21,7 @@ def is_enabled(env):
         not env.has_module(":processing:protothread")
 
 def prepare(module, options):
-    module.depends(":architecture:clock", ":architecture:atomic")
+    module.depends(":architecture:clock", ":architecture:atomic", ":architecture:assert")
 
     module.add_query(
         EnvironmentQuery(name="__enabled", factory=is_enabled))
@@ -56,7 +56,7 @@ def build(env):
 
     if core.startswith("cortex-m"):
         env.substitutions["stack_minimum"] = (2 + 9 + (16 if with_fpu else 0)) * 4
-        env.substitutions["default_stack_size"] = 512
+        env.substitutions["default_stack_size"] = 1024
         env.template("context_arm_m.cpp.in")
 
     elif core.startswith("avr"):
@@ -77,7 +77,7 @@ def build(env):
     env.copy("context.h")
     env.template("stack.hpp.in")
     env.template("scheduler.hpp.in")
-    env.copy("scheduler.cpp")
+    env.template("scheduler.cpp.in")
     env.copy("task.hpp")
     env.copy("task_impl.hpp")
     env.copy("functions.hpp")

src/modm/processing/fiber/module.lb

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2024, Niklas Hauser
+ * Copyright (c) 2023, Niklas Hauser
  *
  * This file is part of the modm project.
  *
@@ -9,34 +9,27 @@
  */
 // ----------------------------------------------------------------------------
 
-#include <modm/board.hpp>
-#include <modm/processing.hpp>
+#include "scheduler.hpp"
 
-using namespace Board;
-using namespace std::chrono_literals;
-
-modm::Fiber<> blinky([]
+/// @cond
+namespace modm::this_fiber
 {
-	while(1)
-	{
-		Board::LedBlue::toggle();
-		modm::this_fiber::sleep_for(0.5s);
-	}
-});
 
-modm::Fiber<> bad_fiber([]
+void
+yield()
 {
+	modm::fiber::Scheduler::instance().yield();
+}
 
-	MODM_LOG_INFO << "\nReboot!\nPush the button to overflow the stack!" << modm::endl;
+modm::fiber::id
+get_id()
+{
+	return modm::fiber::Scheduler::instance().get_id();
+}
 
-	while(1)
-	{
-		// cause stack overflow on button push
-		if (Button::read()) asm volatile ("push {r0-r7}");
-		modm::this_fiber::yield();
-	}
-});
+} // namespace modm::this_fiber
 
+%% if with_psplim
 // On fiber stack overflow this handler will be called
 extern "C" void
 UsageFault_Handler()
@@ -51,15 +44,6 @@ UsageFault_Handler()
 	}
 	else HardFault_Handler();
 }
+%% endif
 
-int
-main()
-{
-	Board::initialize();
-	// Enable the UsageFault handler
-	SCB->SHCSR |= SCB_SHCSR_USGFAULTENA_Msk;
-
-	modm::fiber::Scheduler::run();
-
-	return 0;
-}
+/// @endcond

src/modm/processing/fiber/scheduler.cpp

@@ -15,6 +15,7 @@
 #define MODM_FIBER_SCHEDULER_HPP
 
 #include "task.hpp"
+#include <modm/architecture/interface/assert.hpp>
 %% if multicore
 #include <modm/platform/core/multicore.hpp>
 %% endif
@@ -109,7 +110,13 @@ protected:
 	{
 		if (current == nullptr) return;
 		Task* next = current->next;
-		if (next == current) return;
+		if (next == current) {
+%% if not with_psplim
+			if (modm_context_stack_overflow(&current->ctx))
+				modm_context_end((uintptr_t) current);
+%% endif
+			return;
+		}
 		last = current;
 		jump(*next);
 	}
@@ -123,7 +130,7 @@ protected:
 		if (empty())
 		{
 			current = nullptr;
-			modm_context_end();
+			modm_context_end(0);
 		}
 		jump(*next);
 		__builtin_unreachable();
@@ -147,7 +154,14 @@ protected:
 	{
 		if (empty()) return false;
 		current = last->next;
+%% if with_psplim
+		// Enable the UsageFault handler
+		SCB->SHCSR |= SCB_SHCSR_USGFAULTENA_Msk;
 		modm_context_start(&current->ctx);
+%% else
+		const auto overflow = (Task *) modm_context_start(&current->ctx);
+		modm_assert(not overflow, "fbr.stkof", "Fiber stack overflow", overflow);
+%% endif
 		return true;
 	}