--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/arm.c	Fri May 26 23:11:05 2017 +0900
@@ -0,0 +1,127 @@
+// BSP support routine
+#include "types.h"
+#include "defs.h"
+#include "param.h"
+#include "memlayout.h"
+#include "proc.h"
+#include "arm.h"
+#include "mmu.h"
+
+void cli (void)
+{
+    uint val;
+
+    // ok, enable paging using read/modify/write
+    asm("MRS %[v], cpsr": [v]"=r" (val)::);
+    val |= DIS_INT;
+    asm("MSR cpsr_cxsf, %[v]": :[v]"r" (val):);
+}
+
+void sti (void)
+{
+    uint val;
+
+    // ok, enable paging using read/modify/write
+    asm("MRS %[v], cpsr": [v]"=r" (val)::);
+    val &= ~DIS_INT;
+    asm("MSR cpsr_cxsf, %[v]": :[v]"r" (val):);
+}
+
+// return the cpsr used for user program
+uint spsr_usr ()
+{
+    uint val;
+
+    // ok, enable paging using read/modify/write
+    asm("MRS %[v], cpsr": [v]"=r" (val)::);
+    val &= ~MODE_MASK;
+    val |= USR_MODE;
+
+    return val;
+}
+
+// return whether interrupt is currently enabled
+int int_enabled ()
+{
+    uint val;
+
+    // ok, enable paging using read/modify/write
+    asm("MRS %[v], cpsr": [v]"=r" (val)::);
+
+    return !(val & DIS_INT);
+}
+
+// Pushcli/popcli are like cli/sti except that they are matched:
+// it takes two popcli to undo two pushcli.  Also, if interrupts
+// are off, then pushcli, popcli leaves them off.
+
+void pushcli (void)
+{
+    int enabled;
+
+    enabled = int_enabled();
+
+    cli();
+
+    if (cpu->ncli++ == 0) {
+        cpu->intena = enabled;
+    }
+}
+
+void popcli (void)
+{
+    if (int_enabled()) {
+        panic("popcli - interruptible");
+    }
+
+    if (--cpu->ncli < 0) {
+        cprintf("cpu (%d)->ncli: %d\n", cpu, cpu->ncli);
+        panic("popcli -- ncli < 0");
+    }
+
+    if ((cpu->ncli == 0) && cpu->intena) {
+        sti();
+    }
+}
+
+// Record the current call stack in pcs[] by following the call chain.
+// In ARM ABI, the function prologue is as:
+//		push	{fp, lr}
+//		add		fp, sp, #4
+// so, fp points to lr, the return address
+void getcallerpcs (void * v, uint pcs[])
+{
+    uint *fp;
+    int i;
+
+    fp = (uint*) v;
+
+    for (i = 0; i < N_CALLSTK; i++) {
+        if ((fp == 0) || (fp < (uint*) KERNBASE) || (fp == (uint*) 0xffffffff)) {
+            break;
+        }
+
+        fp = fp - 1;			// points fp to the saved fp
+        pcs[i] = fp[1];     // saved lr
+        fp = (uint*) fp[0];	// saved fp
+    }
+
+    for (; i < N_CALLSTK; i++) {
+        pcs[i] = 0;
+    }
+}
+
+void show_callstk (char *s)
+{
+    int i;
+    uint pcs[N_CALLSTK];
+
+    cprintf("%s\n", s);
+
+    getcallerpcs(get_fp(), pcs);
+
+    for (i = N_CALLSTK - 1; i >= 0; i--) {
+        cprintf("%d: 0x%x\n", i + 1, pcs[i]);
+    }
+
+}