Added Semihosting call to exit with an arbitrary exit code, this should

make panic exit codes more obvious.

kernel/src/common/include/interrupt.h

@@ -81,17 +81,19 @@ enum SemihostingSWI {
     BreakPoint          = 0x20020,
     WatchPoint          = 0x20021,
     StepComplete        = 0x20022,
-    RunTimeErrorUnknown = 0x20023,
-    InternalError       = 0x20024,
-    UserInterruption    = 0x20025,
+    RunTimeErrorUnknown = 0x20023, // Qemu exits with 1
+    InternalError       = 0x20024, // Qemu exits with 1
+    UserInterruption    = 0x20025, // Qemu exits with 1
     ApplicationExit     = 0x20026, // Qemu exits with 0
-    StackOverflow       = 0x20027,
-    DivisionByZero      = 0x20028,
+    StackOverflow       = 0x20027, // Qemu exits with 1
+    DivisionByZero      = 0x20028, // Qemu exits with 1
     OSSpecific          = 0x20029, // Qemu exits with 1
 };
 
 void SemihostingCall(enum SemihostingSWI mode);
 
+void SemihostingOSExit(int code) __attribute__ ((noreturn));;
+
 typedef enum {
     IRQ,		// (this is bit 0x8 on the CPSR)
     FIQ,		// (this is bit 0x4 on the CPSR)

kernel/src/common/interrupt.c

@@ -267,6 +267,29 @@ void __attribute__((always_inline)) inline SemihostingCall(enum SemihostingSWI m
     );
 }
 
+
+/// Uses the ExtendedExit Semihosting call
+/// ARM Docs: https://developer.arm.com/docs/100863/0200/semihosting-operations/sys_exit_extended-0x20
+void __attribute__((always_inline)) inline SemihostingOSExit(int code) {
+    struct {
+        uint32_t field1;
+        uint32_t field2;
+    } parameters;
+
+    parameters.field1 = ApplicationExit;
+    parameters.field2 = code;
+
+    asm volatile (
+        "MOV r0, #0x20\n"
+        "mov r1, %[in0]\n"
+        "svc 0x00123456\n"
+        ::
+        [in0] "r" (&parameters)
+    );
+
+    __builtin_unreachable();
+}
+
 /* enable IRQ and/or FIQ */
 void enable_interrupt(InterruptType mask) {
     INFO("Enabling interrupts with mask %i", mask);

kernel/src/klibc/klibc.c

@@ -51,10 +51,10 @@ void panic() {
     kprintf("|_ ((_)((_|()\\  )\\ ) /((_)   (_)) )(_)) )\\ |(_) )\\  \n");
     kprintf("| |/ (_))  ((_)_(_/((_))| |  | _ ((_)_ _(_/((_)((_) \n");
     kprintf("  ' </ -_)| '_| ' \\)) -_) |  |  _/ _` | ' \\)) / _|  \n");
-    kprintf(" _|\\_\\___||_| |_||_|\\___|_|  |_| \\__,_|_||_||_\\__|  ");
-    SemihostingCall(OSSpecific);
+    kprintf(" _|\\_\\___||_| |_||_|\\___|_|  |_| \\__,_|_||_||_\\__|\n");
+
+    SemihostingOSExit(-1);
     SLEEP;
-    __builtin_unreachable();
 }
 
 void splash() {