sparc64: Make global reg dumping even more useful.

[ Upstream commit 5afe2738 ]

Record one more level of stack frame program counter.

Particularly when lockdep and all sorts of spinlock debugging is
enabled, figuring out the caller of spin_lock() is difficult when the
cpu is stuck on the lock.
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

arch/sparc64/kernel/process.c

@@ -305,6 +305,19 @@ void show_regs(struct pt_regs *regs)
 struct global_reg_snapshot global_reg_snapshot[NR_CPUS];
 static DEFINE_SPINLOCK(global_reg_snapshot_lock);
 
+static bool kstack_valid(struct thread_info *tp, struct reg_window *rw)
+{
+	unsigned long thread_base, fp;
+
+	thread_base = (unsigned long) tp;
+	fp = (unsigned long) rw;
+
+	if (fp < (thread_base + sizeof(struct thread_info)) ||
+	    fp >= (thread_base + THREAD_SIZE))
+		return false;
+	return true;
+}
+
 static void __global_reg_self(struct thread_info *tp, struct pt_regs *regs,
 			      int this_cpu)
 {
@@ -316,14 +329,22 @@ static void __global_reg_self(struct thread_info *tp, struct pt_regs *regs,
 	global_reg_snapshot[this_cpu].o7 = regs->u_regs[UREG_I7];
 
 	if (regs->tstate & TSTATE_PRIV) {
+		struct thread_info *tp = current_thread_info();
 		struct reg_window *rw;
 
 		rw = (struct reg_window *)
 			(regs->u_regs[UREG_FP] + STACK_BIAS);
-		global_reg_snapshot[this_cpu].i7 = rw->ins[7];
-	} else
+		if (kstack_valid(tp, rw)) {
+			global_reg_snapshot[this_cpu].i7 = rw->ins[7];
+			rw = (struct reg_window *)
+				(rw->ins[6] + STACK_BIAS);
+			if (kstack_valid(tp, rw))
+				global_reg_snapshot[this_cpu].rpc = rw->ins[7];
+		}
+	} else {
 		global_reg_snapshot[this_cpu].i7 = 0;
-
+		global_reg_snapshot[this_cpu].rpc = 0;
+	}
 	global_reg_snapshot[this_cpu].thread = tp;
 }
 
@@ -384,12 +405,14 @@ static void sysrq_handle_globreg(int key, struct tty_struct *tty)
 			sprint_symbol(buffer, gp->o7);
 			printk("O7[%s] ", buffer);
 			sprint_symbol(buffer, gp->i7);
-			printk("I7[%s]\n", buffer);
+			printk("I7[%s] ", buffer);
+			sprint_symbol(buffer, gp->rpc);
+			printk("RPC[%s]\n", buffer);
 		} else
 #endif
 		{
-			printk("             TPC[%lx] O7[%lx] I7[%lx]\n",
-			       gp->tpc, gp->o7, gp->i7);
+			printk("             TPC[%lx] O7[%lx] I7[%lx] RPC[%lx]\n",
+			       gp->tpc, gp->o7, gp->i7, gp->rpc);
 		}
 	}
 

arch/sparc64/mm/ultra.S

@@ -531,6 +531,13 @@ xcall_fetch_glob_regs:
 	stx		%g7, [%g1 + GR_SNAP_TNPC]
 	stx		%o7, [%g1 + GR_SNAP_O7]
 	stx		%i7, [%g1 + GR_SNAP_I7]
+	/* Don't try this at home kids... */
+	rdpr		%cwp, %g2
+	sub		%g2, 1, %g7
+	wrpr		%g7, %cwp
+	mov		%i7, %g7
+	wrpr		%g2, %cwp
+	stx		%g7, [%g1 + GR_SNAP_RPC]
 	sethi		%hi(trap_block), %g7
 	or		%g7, %lo(trap_block), %g7
 	sllx		%g2, TRAP_BLOCK_SZ_SHIFT, %g2

include/asm-sparc64/ptrace.h

@@ -134,9 +134,9 @@ struct global_reg_snapshot {
 	unsigned long		tnpc;
 	unsigned long		o7;
 	unsigned long		i7;
+	unsigned long		rpc;
 	struct thread_info	*thread;
 	unsigned long		pad1;
-	unsigned long		pad2;
 };
 
 #define __ARCH_WANT_COMPAT_SYS_PTRACE
@@ -314,9 +314,9 @@ extern void __show_regs(struct pt_regs *);
 #define GR_SNAP_TNPC	0x10
 #define GR_SNAP_O7	0x18
 #define GR_SNAP_I7	0x20
-#define GR_SNAP_THREAD	0x28
-#define GR_SNAP_PAD1	0x30
-#define GR_SNAP_PAD2	0x38
+#define GR_SNAP_RPC	0x28
+#define GR_SNAP_THREAD	0x30
+#define GR_SNAP_PAD1	0x38
 
 #endif  /*  __KERNEL__  */