tile: improve stack backtrace

This commit fixes a number of issues with the tile backtrace code.

- Don't try to identify userspace shared object or executable paths
  if we are doing a backtrace from an interrupt; it's not legal,
  and also unlikely to be interesting.  Likewise, don't try to do
  it for other address spaces, since d_path() assumes it is being
  called in "current" context.

- Move "in_backtrace" from thread_struct to thread_info.
  This way we can access it even if our stack thread_info has been
  clobbered, which makes backtracing more robust.

- Avoid using "current" directly when testing for is_sigreturn().
  Since "current" may be corrupt, we're better off using kbt->task
  explicitly to look up the vdso_base for the current task.
  Conveniently, this simplifies the internal APIs (we only need
  one is_sigreturn() function now).

- Avoid bogus "Odd fault" warning when pc/sp/ex1 are all zero,
  as is true for kernel threads above the last frame.

- Hook into Tejun Heo's dump_stack() framework in lib/dump_stack.c.

- Write last entry in save_stack_trace() as ULONG_MAX, not zero,
  since ftrace (at least) relies on finding that marker.

- Implement save_stack_trace_regs() and save_strack_trace_user(),
  and set CONFIG_USER_STACKTRACE_SUPPORT.

Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>

1 files changed, 23 insertions, 13 deletions

diff --git a/arch/tile/kernel/process.c b/arch/tile/kernel/process.c
index 96ea75e04582..a45213781ad0 100644
--- a/arch/tile/kernel/process.c
+++ b/arch/tile/kernel/process.c
@@ -546,33 +546,43 @@ void exit_thread(void)
 #endif
 }
 
-void show_regs(struct pt_regs *regs)
+void tile_show_regs(struct pt_regs *regs)
 {
-	struct task_struct *tsk = validate_current();
 	int i;
-
-	if (tsk != &corrupt_current)
-		show_regs_print_info(KERN_ERR);
 #ifdef __tilegx__
 	for (i = 0; i < 17; i++)
-		pr_err(" r%-2d: " REGFMT " r%-2d: " REGFMT " r%-2d: " REGFMT "\n",
+		pr_err(" r%-2d: "REGFMT" r%-2d: "REGFMT" r%-2d: "REGFMT"\n",
 		       i, regs->regs[i], i+18, regs->regs[i+18],
 		       i+36, regs->regs[i+36]);
-	pr_err(" r17: " REGFMT " r35: " REGFMT " tp : " REGFMT "\n",
+	pr_err(" r17: "REGFMT" r35: "REGFMT" tp : "REGFMT"\n",
 	       regs->regs[17], regs->regs[35], regs->tp);
-	pr_err(" sp : " REGFMT " lr : " REGFMT "\n", regs->sp, regs->lr);
+	pr_err(" sp : "REGFMT" lr : "REGFMT"\n", regs->sp, regs->lr);
 #else
 	for (i = 0; i < 13; i++)
-		pr_err(" r%-2d: " REGFMT " r%-2d: " REGFMT " r%-2d: " REGFMT " r%-2d: " REGFMT "\n",
+		pr_err(" r%-2d: "REGFMT" r%-2d: "REGFMT
+		       " r%-2d: "REGFMT" r%-2d: "REGFMT"\n",
 		       i, regs->regs[i], i+14, regs->regs[i+14],
 		       i+27, regs->regs[i+27], i+40, regs->regs[i+40]);
-	pr_err(" r13: " REGFMT " tp : " REGFMT " sp : " REGFMT " lr : " REGFMT "\n",
+	pr_err(" r13: "REGFMT" tp : "REGFMT" sp : "REGFMT" lr : "REGFMT"\n",
 	       regs->regs[13], regs->tp, regs->sp, regs->lr);
 #endif
-	pr_err(" pc : " REGFMT " ex1: %ld     faultnum: %ld\n",
-	       regs->pc, regs->ex1, regs->faultnum);
+	pr_err(" pc : "REGFMT" ex1: %ld     faultnum: %ld flags:%s%s%s%s\n",
+	       regs->pc, regs->ex1, regs->faultnum,
+	       is_compat_task() ? " compat" : "",
+	       (regs->flags & PT_FLAGS_DISABLE_IRQ) ? " noirq" : "",
+	       !(regs->flags & PT_FLAGS_CALLER_SAVES) ? " nocallersave" : "",
+	       (regs->flags & PT_FLAGS_RESTORE_REGS) ? " restoreregs" : "");
+}
+
+void show_regs(struct pt_regs *regs)
+{
+	struct KBacktraceIterator kbt;
+
+	show_regs_print_info(KERN_DEFAULT);
+	tile_show_regs(regs);
 
-	dump_stack_regs(regs);
+	KBacktraceIterator_init(&kbt, NULL, regs);
+	tile_show_stack(&kbt);
 }
 
 /* To ensure stack dump on tiles occurs one by one. */