sparc64: Make global reg dumping even more useful.

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>

3 files changed, 40 insertions, 11 deletions

diff --git a/arch/sparc/include/asm/ptrace_64.h b/arch/sparc/include/asm/ptrace_64.h
index ec6d45c84cd0..390d92ac67cf 100644
--- a/arch/sparc/include/asm/ptrace_64.h
+++ b/arch/sparc/include/asm/ptrace_64.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
@@ -315,9 +315,9 @@ 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__  */
 
diff --git a/arch/sparc64/kernel/process.c b/arch/sparc64/kernel/process.c
index 0f60547c24d9..fc8137a21ced 100644
--- a/arch/sparc64/kernel/process.c
+++ b/arch/sparc64/kernel/process.c
@@ -304,6 +304,19 @@ 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)
 {
@@ -315,14 +328,22 @@ 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;
 }
 
@@ -375,13 +396,14 @@ static void sysrq_handle_globreg(int key, struct tty_struct *tty)
                        ((tp && tp->task) ? tp->task->pid : -1));
 
                 if (gp->tstate & TSTATE_PRIV) {
-                        printk("             TPC[%pS] O7[%pS] I7[%pS]\n",
+                        printk("             TPC[%pS] O7[%pS] I7[%pS] RPC[%pS]\n",
                                (void *) gp->tpc,
                                (void *) gp->o7,
-                               (void *) gp->i7);
+                               (void *) gp->i7,
+                               (void *) gp->rpc);
                 } else {
-                        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);
                 }
         }
 
diff --git a/arch/sparc64/mm/ultra.S b/arch/sparc64/mm/ultra.S
index 4c8ca131ffaf..77ba88597cc5 100644
--- a/arch/sparc64/mm/ultra.S
+++ b/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