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, 0 insertions, 1 deletions

diff --git a/arch/tile/lib/exports.c b/arch/tile/lib/exports.c
index 16326f288177..9d171ca4302c 100644
--- a/arch/tile/lib/exports.c
+++ b/arch/tile/lib/exports.c
@@ -26,7 +26,6 @@ EXPORT_SYMBOL(finv_user_asm);
 #include <linux/kernel.h>
 #include <asm/processor.h>
 EXPORT_SYMBOL(current_text_addr);
-EXPORT_SYMBOL(dump_stack);
 
 /* arch/tile/kernel/head.S */
 EXPORT_SYMBOL(empty_zero_page);