started properly implementing syscall structure

kernel.c

@@ -2,20 +2,23 @@
 #include "ecall.h"
 #include "sched.h"
 
-void thread_1();
+void create_processes_from_bin_table();
 
 extern ProcessControlBlock processes[PROCESS_COUNT];
 
 loaded_binary binary_table[NUM_BINARIES];
 
-static int idx = 0;
-
 extern void init()
 {
-    for (int i = 0; i < 100; i++) {
+    init_ecall_table();
-        idx += binary_table[i].entrypoint + 4;
+
-    }
+    create_processes_from_bin_table();
 
     scheduler_run_next();   
 }
 
+void create_processes_from_bin_table()
+{
+
+}
+

kinclude/boot.S

@@ -88,6 +88,10 @@ trap_vector:
             mv      a0,  t6             // save struct address to already saved register
             csrrw   t6,  mscratch, t6   // load original t6 register from mscratch
             sw      t6,  120(a0)        // save original t6 register
+            // save mepc to pc field in pcb
+            csrr    t6,  mepc
+            sw      t6,  -4(a0)
+            // load mcause and mtval values in the correct registers for call to trap_handle function
             csrr    a1,  mcause
             srli    a0,  a1, 31
             slli    a1,  a1, 1

kinclude/ecall.c

@@ -2,36 +2,71 @@
 #include "sched.h"
 #include "csr.h"
 
-void ecall_handle_spawn(void* entry, void* args)
+typedef int (*ecall_handler)(int*,ProcessControlBlock*);
+
+ecall_handler ecall_table[ECALL_TABLE_LEN] = { 0 };
+
+int ecall_handle_spawn_thread(int* args_ptr, ProcessControlBlock* pcb)
 {
+    void* entry = (void*) args_ptr[0];
+    void* args  = (void*) args_ptr[1];
 
+    return EINVAL;
+// void* entry, void* args
 }
 
-void ecall_handle_sleep(int until)
+int ecall_handle_sleep(int* args, ProcessControlBlock* pcb)
 {
+    int len = *args;
+    if (len < 0) {
+        return EINVAL;
+    }
+
+    pcb->asleep_until = read_time() + len;
+    pcb->status = PROC_WAIT_SLEEP;
 
+    return 0;
 }
 
-void ecall_handle_join(int pid, int timeout)
+int ecall_handle_join(int* args, ProcessControlBlock* pcb)
 {
-
+    return EINVAL;
 }
 
-void ecall_handle_kill(int pid)
+int ecall_handle_kill(int* args, ProcessControlBlock* pcb)
 {
+    return EINVAL;
 
 }
 
-void ecall_handle_exit(int status)
+int ecall_handle_exit(int* args, ProcessControlBlock* pcb)
 {
+    pcb->status = PROC_DEAD;
+    pcb->exit_code = *args;
 
+    return 0;
 }
 
 void trap_handle_ecall() {
-    int *regs = get_current_process_registers();
+    ProcessControlBlock* pcb = get_current_process();
+    int *regs = pcb->regs;
     int code = regs[16];
-    __asm__("ebreak");
+
-    HALT(18);
+    // check if the code is too large/small or if the handler is zero
+    if (code < 0 || code > ECALL_TABLE_LEN || ecall_table[code] == 0) {
+        regs[9] = ENOCODE;
+        __asm__("ebreak");
+    } else {
+        // get the corresponding ecall handler
+        ecall_handler handler = ecall_table[code];
+        regs[9] = handler(&regs[9], pcb);
+    }
+
+    // increment pc of this process
+    pcb->pc += 4;
+
+    // try to reschedule 
+    scheduler_try_return_to(pcb);
 }
 
 void trap_handle(int interrupt_bit, int code, int mtval) 
@@ -58,3 +93,12 @@ void trap_handle(int interrupt_bit, int code, int mtval)
     HALT(1);
     __builtin_unreachable();
 }
+
+void init_ecall_table() 
+{
+    ecall_table[ECALL_SPAWN] = ecall_handle_spawn_thread;
+    ecall_table[ECALL_SLEEP] = ecall_handle_sleep;
+    ecall_table[ECALL_JOIN]  = ecall_handle_join;
+    ecall_table[ECALL_KILL]  = ecall_handle_kill;
+    ecall_table[ECALL_EXIT]  = ecall_handle_exit;
+}

kinclude/ecall.h

@@ -1,6 +1,8 @@
 #ifndef H_ECALL
 #define H_ECALL
 
+#include "sched.h"
+
 /* ecall codes are defined here
  *
  *
@@ -13,12 +15,23 @@ enum ecall_codes {
     ECALL_EXIT  = 5,
 };
 
+#define ECALL_TABLE_LEN 16
+
+enum ecall_errors {
+    ENOCODE = -1,   // invalid syscall code
+    EINVAL  = -2,   // invalid argument value
+    ENOMEM  = -3,   // not enough memory
+};
+
+// initializer for ecall lookup table
+void init_ecall_table();
+
 // syscall handlers, are setup in the mtvec csr
-void ecall_handle_spawn(void* entry, void* args);
+int ecall_handle_spawn(int*, ProcessControlBlock*);
-void ecall_handle_sleep(int until);
+int ecall_handle_sleep(int*, ProcessControlBlock*);
-void ecall_handle_join(int pid, int timeout);
+int ecall_handle_join(int*, ProcessControlBlock*);
-void ecall_handle_kill(int pid);
+int ecall_handle_kill(int*, ProcessControlBlock*);
-void ecall_handle_exit(int status);
+int ecall_handle_exit(int*, ProcessControlBlock*);
 
 
 void __attribute__((__noreturn__)) trap_handle(int interrupt_bit, int code, int mtval);

kinclude/sched.c

@@ -16,9 +16,22 @@ void scheduler_run_next ()
     scheduler_switch_to(current_process_index);
 }
 
+void scheduler_try_return_to(ProcessControlBlock* pcb)
+{
+    if (pcb->status != PROC_RDY) {
+        scheduler_run_next();
+    } else {
+        current_process_index = scheduler_index_from_pid(pcb->pid);
+        //FIXME: this refreshes the processes time slice which we actually don't want!
+        unsigned long long int mtimecmp = read_time() + TIME_SLICE_LEN;
+        write_mtimecmp(mtimecmp);
+        scheduler_switch_to(current_process_index);
+    }
+}
+
 int  scheduler_select_free() 
 {
-    long long int mtime;
+    unsigned long long int mtime;
     int i;
     int timeout_available = false; // note if a timeout is available
 

kinclude/sched.h

@@ -16,6 +16,7 @@ struct ProcessControlBlock {
     int pid;
     int pc;
     int regs[31];
+    int exit_code;
     // scheduling information
     enum process_status status;
     ProcessControlBlock *waiting_for_process;
@@ -29,6 +30,7 @@ extern ProcessControlBlock processes[PROCESS_COUNT];
 int  scheduler_select_free();
 int  scheduler_create_process(int binid);
 void __attribute__((noreturn)) scheduler_run_next();
+void __attribute__((noreturn)) scheduler_try_return_to(ProcessControlBlock*);
 void __attribute__((noreturn)) scheduler_switch_to(int proc_index);
 int  scheduler_index_from_pid(int pid);
 int* get_current_process_registers();