On a kernel trap, print a stacktrace from the RSP when the trap was raised

cb005b88 · Silas Boyd-Wickizer · fc7e1de6 · cb005b88 · cb005b88 · cb005b88
--- a/console.c
+++ b/console.c
@@ -147,23 +147,44 @@ stacktrace(void)
 #undef PRINT_RET
 }
-void __attribute__((noreturn))
+void __noret__
+kerneltrap(struct trapframe *tf)
+{
+  extern void sys_halt();
+  uptr pc[10];
+  int i;
+  cli();
+  cons.locking = 0;
+  cprintf("unexpected trap %d from cpu %d rip %lx (cr2=0x%lx)\n",
+          tf->trapno, mycpu()->id, tf->rip, rcr2());
+  getcallerpcs((void*)tf->rbp, pc);
+  for (i = 0; i < NELEM(pc) && pc[i] != 0; i++)
+    cprintf("  %p\n", pc[i]);
+  panicked = 1;
+  acquire(&cons.lock);
+  sys_halt();
+  for(;;)
+    ;
+}
+void __noret__
 panic(const char *s)
 {
  extern void sys_halt();
  cli();
  cons.locking = 0;
  cprintf("cpu%d: panic: ", mycpu()->id);
  cprintf(s);
  cprintf("\n");
  stacktrace();
  panicked = 1;
  acquire(&cons.lock);
-  // Never release cons.lock
  sys_halt();
  for(;;)
    ;

--- a/kernel.h
+++ b/kernel.h
@@ -45,7 +45,8 @@ void            cv_tick(void);
 // console.c
 void            cprintf(const char*, ...);
-void            panic(const char*) __attribute__((noreturn));
+void            panic(const char*) __noret__;
+void            kerneltrap(struct trapframe *tf) __noret__;
 void            snprintf(char *buf, u32 n, char *fmt, ...);
 void            consoleintr(int(*)(void));
@@ -237,7 +238,7 @@ int             growproc(int);
 int             kill(int);
 void            pinit(void);
 void            procdumpall(void);
-void            scheduler(void) __attribute__((noreturn));
+void            scheduler(void) __noret__;
 void            sched(void);
 void            userinit(void);
 int             wait(void);

--- a/trap.c
+++ b/trap.c
@@ -115,12 +115,8 @@ trap(struct trapframe *tf)
      break;
    }
-    if(myproc() == 0 || (tf->cs&3) == 0){
+    if (myproc() == 0 || (tf->cs&3) == 0)
-      // In kernel, it must be our mistake.
+      kerneltrap(tf);
-      cprintf("unexpected trap %d from cpu %d rip %lx (cr2=0x%lx)\n",
-              tf->trapno, mycpu()->id, tf->rip, rcr2());
-      panic("trap");
-    }
    if(tf->trapno == T_PGFLT){
      uptr addr = rcr2();