Cleanup

earth/cpu_mmu.c

@@ -83,7 +83,9 @@ int soft_tlb_switch(int pid) {
 #define FLAG_VALID_RWX 0xF
 #define FLAG_NEXT_LEVEL 0x1
 static unsigned int frame_id, *root, *leaf;
-static unsigned int* pid_to_pagetable_base[MAX_NPROCESS];
+
+#define MAX_ROOT_PAGE_TABLES 32 /* A number large enough for demo purpose */
+static unsigned int* pid_to_pagetable_base[MAX_ROOT_PAGE_TABLES];
 
 void setup_identity_region(int pid, unsigned int addr, int npages) {
  /* Allocate the leaf page table */
@@ -118,7 +120,8 @@ void pagetable_identity_mapping(int pid) {
 }
 
 int page_table_map(int pid, int page_no, int frame_id) {
- if (pid >= MAX_NPROCESS) FATAL("page_table_map: too many processes");
+ if (pid >= MAX_ROOT_PAGE_TABLES)
+ FATAL("page_table_map: too many page table allocations");
 
  /* Student's code goes here (page table translation). */
 

grass/grass.c

@@ -27,6 +27,7 @@ int main() {
  grass->proc_alloc = proc_alloc;
  grass->proc_free = proc_free;
  grass->proc_set_ready = proc_set_ready;
+ grass->proc_save_stack_paddr = proc_save_stack_paddr;
 
  grass->sys_exit = sys_exit;
  grass->sys_send = sys_send;

grass/process.c

@@ -79,6 +79,11 @@ void proc_free(int pid) {
  }
 }
 
+void proc_save_stack_paddr(int pid, void* paddr) {
+ for (int i = 0; i < MAX_NPROCESS; i++)
+ if (proc_set[i].pid == pid) proc_set[i].stack_paddr = paddr;
+}
+
 void proc_set_ready(int pid) { proc_set_status(pid, PROC_READY); }
 void proc_set_running(int pid) { proc_set_status(pid, PROC_RUNNING); }
 void proc_set_runnable(int pid) { proc_set_status(pid, PROC_RUNNABLE); }

grass/process.h

@@ -6,12 +6,14 @@
 struct process{
  int pid;
  int status;
- int receiver_pid; /* used when process is waiting to send a message */
+ int receiver_pid;  /* used when waiting to send a message */
 
- void *mepc; /* machine exception program counter (mepc) */
- void *sp_vaddr; /* used for switching stack between user / kernel */
+ void *mepc; /* machine exception program counter (mepc) */
+ void *sp_vaddr; /* used to switch between user and kernel stacks */
+ void *stack_paddr; /* used in the page table translation project */
 };
 
+#define MAX_NPROCESS 16
 extern int proc_curr_idx;
 extern struct process proc_set[MAX_NPROCESS];
 #define curr_pid proc_set[proc_curr_idx].pid
@@ -36,6 +38,7 @@ void proc_free(int);
 void proc_set_ready (int);
 void proc_set_running (int);
 void proc_set_runnable (int);
+void proc_save_stack_paddr(int, void*);
 
 void ctx_entry(void);
 void ctx_start(void** old_sp, void* new_sp);

grass/scheduler.c

@@ -53,30 +53,20 @@ void intr_entry(int id) {
 }
 
 void ctx_entry() {
- /* Switched to the kernel stack */
+ /* Now on the kernel stack */
  int mepc, tmp;
  asm("csrr %0, mepc" : "=r"(mepc));
  proc_set[proc_curr_idx].mepc = (void*) mepc;
 
  /* Student's code goes here (page table translation). */
-
- /* Save the interrupt stack
- * Copy 0x400 bytes from sp_vaddr of the current process
- * to grass->stack_paddr of the current process
- */
-
+ /* Save the interrupt stack */
  /* Student's code ends here. */
 
  /* kernel_entry() is either proc_yield() or proc_syscall() */
  kernel_entry();
 
  /* Student's code goes here (page table translation). */
-
- /* Restore the interrupt stack
- * Copy 0x400 bytes from grass->stack_paddr of the current process
- * to sp_vaddr of the current process
- */
-
+ /* Restore the interrupt stack */
  /* Student's code ends here. */
 
  /* Switch back to the user application stack */
@@ -139,12 +129,12 @@ static void proc_send(struct syscall *sc) {
  } else {
  /* Copy message from sender to kernel stack */
  struct sys_msg tmp;
+ earth->mmu_switch(curr_pid);
  memcpy(&tmp, &sc->msg, sizeof(tmp));
 
  /* Copy message from kernel stack to receiver */
  earth->mmu_switch(receiver);
  memcpy(&sc->msg, &tmp, sizeof(tmp));
- earth->mmu_switch(curr_pid);
 
  /* Set receiver process as runnable */
  proc_set_runnable(receiver);

library/egos.h

@@ -30,12 +30,12 @@ struct earth {
  enum { PAGE_TABLE, SOFT_TLB } translation;
 };
 
-#define MAX_NPROCESS 16
 struct grass {
  /* Process control interface */
  int (*proc_alloc)();
  void (*proc_free)(int pid);
  void (*proc_set_ready)(int pid);
+ void (*proc_save_stack_paddr)(int pid, void* paddr);
 
  /* System call interface */
  void (*sys_exit)(int status);
@@ -45,9 +45,6 @@ struct grass {
  /* Shell environment variables */
  int workdir_ino;
  char workdir[128];
-
- /* Physical address of process stack, used in the page table project */
- void* stack_paddr[MAX_NPROCESS];
 };
 
 extern struct earth *earth;

library/elf/elf.c

@@ -64,7 +64,7 @@ static void load_app(int pid, elf_reader reader,
  /* Setup two pages for argc, argv and stack */
  earth->mmu_alloc(&frame_no, &base);
  earth->mmu_map(pid, stack_start++, frame_no);
- grass->stack_paddr[pid] = (void*)(FRAME_CACHE_START + frame_no * PAGE_SIZE);
+ grass->proc_save_stack_paddr(pid, (void*)(FRAME_CACHE_START + frame_no * PAGE_SIZE));
 
  int* argc_addr = (int*)base;
  int* argv_addr = argc_addr + 1;