Work on both QEMU and Arty

earth/cpu_mmu.c

@@ -13,12 +13,7 @@
 #include "earth.h"
 #include <stdlib.h>
 
-enum {
- QEMU_PAGE_TABLE,
- ARTY_SOFTWARE_TLB
-};
-
-/* Implementation of Software TLB Translation
+/* Implementation of Software TLB Translation for Arty
  *
  * There are 256 physical frames at the start of the SD card and 28 of
  * them are cached in the memory (more precisely, in the DTIM cache).
@@ -149,7 +144,7 @@ static int cache_write(int frame_no, char* src) {
 }
 
 
-/* Implementation of Page Table Translation
+/* Implementation of Page Table Translation for QEMU
  *
  *
  *
@@ -208,33 +203,39 @@ int qemu_switch(int pid) {
  * Choose the memory translation mechanism accordingly.
  */
 
-static int machine, tmp;
+static int mepc, mstatus;
 void machine_detect(int id) {
- machine = ARTY_SOFTWARE_TLB;
+ earth->platform = ARTY;
  /* Skip the illegal store instruction */
- asm("csrr %0, mepc" : "=r"(tmp));
- asm("csrw mepc, %0" ::"r"(tmp + 4));
+ asm("csrr %0, mepc" : "=r"(mepc));
+ asm("csrw mepc, %0" ::"r"(mepc + 4));
 }
 
 void mmu_init(struct earth* _earth) {
  earth = _earth;
+ earth->platform = QEMU;
  earth->excp_register(machine_detect);
  /* This memory access triggers an exception on Arty, but not QEMU */
  *(int*)(0x1000) = 1;
  earth->excp_register(NULL);
 
- if (machine == ARTY_SOFTWARE_TLB) {
+ if (earth->platform == ARTY) {
  earth->tty_info("Use software translation for Arty");
  earth->mmu_free = arty_free;
  earth->mmu_alloc = arty_alloc;
  earth->mmu_map = arty_map;
  earth->mmu_switch = arty_switch;
+ INFO("Will enter the grass layer with machine mode");
  } else {
  earth->tty_info("Use page table translation for QEMU");
  earth->mmu_free = qemu_free;
  earth->mmu_alloc = qemu_alloc;
  earth->mmu_map = qemu_map;
  earth->mmu_switch = qemu_switch;
+
+ INFO("Will enter the grass layer with supervisor mode");
+ asm("csrr %0, mstatus" : "=r"(mstatus));
+ asm("csrw mstatus, %0" ::"r"((mstatus & ~(3 << 11)) | (1 << 11) ));
  }
 
  curr_vm_pid = -1;

earth/earth.c

@@ -42,12 +42,12 @@ int main() {
  earth_init();
  elf_load(0, grass_read, 0, NULL);
 
- earth->intr_enable();
- int mstatus, mie;
- asm("csrr %0, mstatus" : "=r"(mstatus));
- asm("csrw mstatus, %0" ::"r"((mstatus & ~(3 << 11)) | (1 << 11) ));
-
- INFO("Entering the grass layer with the supervisor mode");
- asm("csrw mepc, %0" ::"r"(GRASS_ENTRY));
- asm("mret");
+ if (earth->platform == QEMU) {
+  earth->intr_enable();
+  asm("csrw mepc, %0" ::"r"(GRASS_ENTRY));
+  asm("mret");
+ } else {
+  void (*grass_entry)() = (void*)GRASS_ENTRY;
+  grass_entry();
+ }
 }

grass/grass.c

@@ -38,6 +38,7 @@ int main() {
  elf_load(GPID_PROCESS, sys_proc_read, 0, 0);
  earth->mmu_switch(GPID_PROCESS);
  timer_reset();
+ if (earth->platform == ARTY) earth->intr_enable();
  void (*sys_proc_entry)() = (void*)APPS_ENTRY;
  sys_proc_entry();
 }

library/egos.h

@@ -1,6 +1,12 @@
 #pragma once
 
 struct earth {
+ /* QEMU or Arty */
+ enum {
+ QEMU,
+ ARTY
+ } platform;
+
  /* CPU interface */
  int (*intr_enable)();
  int (*intr_register)(void (*handler)(int));