Initial commit: Schunix as it stands before the SchOS rename

An x86-64 operating system built from xv6, now largely rewritten: SMP,
a copy-on-write root filesystem (SchFS), PCI/USB/virtio drivers, a TTF
rasteriser, and a Linux-numbered syscall ABI.

No history before this point -- the tree was never under version control.
This commit exists so the rename that follows has something to undo to.

kernel/core/spinlock.c

@@ -0,0 +1,115 @@
+#include "types.h"
+#include "defs.h"
+#include "param.h"
+#include "x86.h"
+#include "memlayout.h"
+#include "mmu.h"
+#include "proc.h"
+#include "spinlock.h"
+
+void
+initlock(struct spinlock *lk, char *name)
+{
+  lk->name = name;
+  lk->locked = 0;
+  lk->cpu = 0;
+}
+
+void
+acquire(struct spinlock *lk)
+{
+  pushcli();
+  if(holding(lk))
+    panic("acquire");
+
+  {
+    uint64 spins = 0;
+    while(xchg(&lk->locked, 1) != 0){
+      if(++spins == 200000000ULL){
+        cprintf("acquire: stuck on \"%s\" held by cpu=%p pcs0=%p pcs1=%p pcs2=%p, acquirer cpu=%p\n",
+                lk->name, lk->cpu, lk->pcs[0], lk->pcs[1], lk->pcs[2], mycpu());
+        panic("acquire: deadlock");
+      }
+    }
+  }
+
+  __sync_synchronize();
+
+  lk->cpu = mycpu();
+  getcallerpcs(&lk, lk->pcs);
+}
+
+void
+release(struct spinlock *lk)
+{
+  if(!holding(lk))
+    panic("release");
+
+  lk->pcs[0] = 0;
+  lk->cpu = 0;
+
+  __sync_synchronize();
+
+  asm volatile("movq $0, %0" : "+m" (lk->locked) : );
+
+  popcli();
+}
+
+void
+getcallerpcs(void *v, addr_t pcs[])
+{
+  addr_t *rbp;
+
+  asm volatile("mov %%rbp, %0" : "=r" (rbp));
+  getstackpcs(rbp, pcs);
+}
+
+void
+getstackpcs(addr_t *rbp, addr_t pcs[])
+{
+  int i;
+
+  for(i = 0; i < 10; i++){
+    if(rbp == 0 || rbp < (addr_t*)KERNBASE || rbp == (addr_t*)0xffffffff)
+      break;
+    pcs[i] = rbp[1];
+    rbp = (addr_t*)rbp[0];
+  }
+  for(; i < 10; i++)
+    pcs[i] = 0;
+}
+
+int
+holding(struct spinlock *lock)
+{
+  return lock->locked && lock->cpu == mycpu();
+}
+
+void
+pushcli(void)
+{
+  int eflags;
+
+  eflags = readeflags();
+  cli();
+  if(mycpu() == 0){
+    extern uint64 kernel_fs_base;
+    cprintf("pushcli: cpu==NULL cs=0x%p kernel_fs_base=0x%p actual_fs_base=0x%p\n",
+            readcs(), kernel_fs_base, rdmsr(0xC0000100));
+    panic("pushcli: cpu is NULL");
+  }
+  if(mycpu()->ncli == 0)
+    mycpu()->intena = eflags & FL_IF;
+  mycpu()->ncli += 1;
+}
+
+void
+popcli(void)
+{
+  if(readeflags()&FL_IF)
+    panic("popcli - interruptible");
+  if(--mycpu()->ncli < 0)
+    panic("popcli");
+  if(mycpu()->ncli == 0 && mycpu()->intena)
+    sti();
+}