fix TLS again;

still not quite but a lot better.

proc.c

@@ -70,12 +70,13 @@ ksegment(void)
   c = &cpus[cpunum()];
   c->gdt[SEG_KCODE] = SEG(STA_X|STA_R, 0, 0x100000 + 64*1024-1, 0);
   c->gdt[SEG_KDATA] = SEG(STA_W, 0, 0xffffffff, 0);
-  c->gdt[SEG_KCPU] = SEG(STA_W, (uint)(&c->tls+1), 0xffffffff, 0);
+  c->gdt[SEG_KCPU] = SEG(STA_W, &c->tlsstruct, 0xffffffff, 0);
   lgdt(c->gdt, sizeof(c->gdt));
   loadfsgs(SEG_KCPU << 3);
   
-  // Initialize cpu-local variables.
+  // Initialize cpu-local storage.
   c->tlsstruct = &c->tlsstruct;
+  asm volatile("");  // Do not let gcc reorder across this line.
   cpu = c;
   proc = 0;
 }

proc.h

@@ -58,7 +58,10 @@ struct cpu {
   volatile uint booted;        // Has the CPU started?
   int ncli;                    // Depth of pushcli nesting.
   int intena;                  // Were interrupts enabled before pushcli?
-  void *tls[2];
+  
+  // "Thread"-local storage variables
+  struct cpu *cpu;
+  struct proc *proc;
   void *tlsstruct;
 };