start with assignment 4.4

report-2/week_1.4.md

@@ -170,3 +170,47 @@ and when the 'malicious' code is removed, it functions as normal.
 
 > Tasks are no longer able to access the SysTick peripheral. It is time to implement a system call using the SVC interrupt mechanism. The `taskYield()` function would also classify as a system call. Write a system call function that will allow a task to change the SysTick period to a value between 1 and 10 ms . The system call should utilize the SVC mechanism by passing a different number than the `taskYield()` call. Make sure both calls keep working! Within the SVC interrupt service routine you will have to find the used SVC instruction using the PC value and look at the LSB to determine the system call number. You can also utilize the tasks’ stack to find the passed SysTick period parameter. When this parameter is invalid the system call should simply return.
 
+### user
+```
+instrucion: 0x08000600 -> 00060008
+SP:         0x20000484
+```
+
+### kernel
+
+```
+psp:        0x20000460
+
+0x20000400 : 0x20000400 <Hex>
+  Address   0 - 3     4 - 7     8 - B     C - F
+  20000430  04000000  05000000  06000000  74040020
+  20000440  08000000  09000000  0A000000  0B000000
+  20000450  1F030000  01000000  1F030000  B0000020
+  20000460  1F030000  01000000  1F030000  B0000020
+  20000470  0C000000  F1060008  62060008  00020001
+  20000480  88040020  88040020  07000000  FDFFFFFF
+  20000490  807505D0  022C0CBF  4FF40075  4FF44075
+  200004A0  082815D1  CB4C2068  20F44070  20602068
+  200004B0  28432060  206840F0  04002060  206840F4
+  200004C0  80302060  00F040F9  216821F0  04012160
+  200004D0  F0000020  00000000  00000000  14050020
+
+PSP+(8*4): 88040020 -> 20000488
+
+0x20000400 : 0x20000400 <Hex>
+  Address   0 - 3     4 - 7     8 - B     C - F
+  20000440  08000000  09000000  0A000000  0B000000
+  20000450  1F030000  01000000  1F030000  B0000020
+  20000460  1F030000  01000000  1F030000  B0000020
+  20000470  0C000000  F1060008  62060008  00020001
+  20000480  88040020  88040020  07000000  FDFFFFFF
+  20000490  807505D0  022C0CBF  4FF40075  4FF44075
+  200004A0  082815D1  CB4C2068  20F44070  20602068
+  200004B0  28432060  206840F0  04002060  206840F4
+  200004C0  80302060  00F040F9  216821F0  04012160
+  200004D0  F0000020  00000000  00000000  14050020
+  200004E0  00000000  00000000  00000000  00000000
+
+
+```
+

report-2/week_1.4/assignment_4.4/VersdOS.c

@@ -37,6 +37,7 @@ void writePSP(void * ptr);
 void returnToPSP(void);
 void returnToMSP(void);
 void toUnprivileged(void);
+uint32_t* getStackpointer(void);
 
 #define TASK_MASK MAX_TASKS-1
 #define IDLE_TASK MAX_TASKS
@@ -250,8 +251,27 @@ void PendSV_Handler(void)
 
 void SVC_Handler(void)
 {
+	uint32_t* sp = getStackpointer();
+	
+
+
+	uint8_t svc_id = 1;
+
+	switch (svc_id)
+	{
+		case 1: // taskYield
 			taskToExecute = schedule();
 			SCB->ICSR |= (1<<28);
+			break;
+
+		case 2: // setSysTick_10ms
+			SysTick->LOAD = 10 * CLOCK_FREQ_IN_KHz - 1;
+			break;
+
+		case 3: // setSysTick_1ms
+			SysTick->LOAD = 1 * CLOCK_FREQ_IN_KHz - 1;
+			break;
+	}
 }
 
 //Call Super Visor
@@ -267,4 +287,12 @@ void delay(uint32_t ticks)
 	taskYield();
 }
 
+void setSysTick_10ms(void)
+{
+	asm("	svc #2");
+}
 
+void setSysTick_1ms(void)
+{
+	asm("	svc #3");
+}

report-2/week_1.4/assignment_4.4/VersdOS.h

@@ -23,5 +23,7 @@ void addTaskToList(void(*function)(void), uint32_t stackSize, int8_t priority);
 void startVersdOS(uint16_t sysTickPeriodIn_ms);
 
 void delay(uint32_t ticks);
+void setSysTick_10ms(void);
+void setSysTick_1ms(void);
 
 #endif /* VERSDOS_H_ */

report-2/week_1.4/assignment_4.4/VersdOS_ll.s

@@ -13,6 +13,7 @@
         .global returnToPSP
         .global returnToMSP
         .global toUnprivileged
+        .global getStackpointer
        // .global SVC_Handler
 		
 pushRegistersToCurrentPSP:
@@ -51,3 +52,7 @@ toUnprivileged:
 		ORR     R0, R0, #1     // clear bit 0 (nPRIV)
 		msr     CONTROL, R0    // copy R0 to control register
 		bx	    lr
+
+getStackpointer:
+		mov     R0, SP
+		bx	    lr

report-2/week_1.4/assignment_4.4/main.c

@@ -56,6 +56,10 @@ void toggleBlue(void)
     {
     	GPIOD->ODR ^= 1 << BLUE;
     	delay(800-1);
+		setSysTick_10ms();
+    	GPIOD->ODR ^= 1 << BLUE;
+    	delay(800-1);
+		setSysTick_1ms();
     }
 }