[PATCH 3/3] xtensa: fix _Unwind_GetCFA

[PATCH 3/3] xtensa: fix _Unwind_GetCFA

[Max Filippov]

Returning context->cfa in _Unwind_GetCFA makes CFA point one stack frame
higher than what was actually used by code at context->ra. This results
in invalid CFA value in signal frames and premature unwinding completion
in forced unwinding used by uClibc NPTL thread cancellation.
Returning context->sp from _Unwind_GetCFA makes all CFA values valid and
matching code that used them.

2015-08-18  Max Filippov  <jcmvbkbc@gmail.com>
libgcc/
	* config/xtensa/unwind-dw2-xtensa.c (_Unwind_GetCFA): Return
	context->sp instead of context->cfa.
---
 libgcc/config/xtensa/unwind-dw2-xtensa.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libgcc/config/xtensa/unwind-dw2-xtensa.c b/libgcc/config/xtensa/unwind-dw2-xtensa.c
index 82b0e63..8e579c7 100644
--- a/libgcc/config/xtensa/unwind-dw2-xtensa.c
+++ b/libgcc/config/xtensa/unwind-dw2-xtensa.c
@@ -130,7 +130,7 @@ _Unwind_GetGR (struct _Unwind_Context *context, int index)
 _Unwind_Word
 _Unwind_GetCFA (struct _Unwind_Context *context)
 {
-  return (_Unwind_Ptr) context->cfa;
+  return (_Unwind_Ptr) context->sp;
 }
 
 /* Overwrite the saved value for register INDEX in CONTEXT with VAL.  */
-- 
1.8.1.4

[PATCH 1/3] xtensa: reimplement register spilling

[Max Filippov]

Spilling windowed registers in userspace is much easier, more portable,
less error-prone and equally effective as in kernel. Now that register
spilling syscall is considered obsolete in the xtensa linux kernel
replace it with CALL12 followed by series of ENTRY in libgcc.

2015-08-18  Max Filippov  <jcmvbkbc@gmail.com>
libgcc/
	* config/xtensa/lib2funcs.S (__xtensa_libgcc_window_spill): Use
	CALL12 followed by series of ENTRY to spill windowed registers.
	(__xtensa_nonlocal_goto): Call __xtensa_libgcc_window_spill
	instead of making linux spill syscall.
---
 libgcc/config/xtensa/lib2funcs.S | 30 +++++++++++++++++++++++-------
 1 file changed, 23 insertions(+), 7 deletions(-)

diff --git a/libgcc/config/xtensa/lib2funcs.S b/libgcc/config/xtensa/lib2funcs.S
index 4d451c8..ef0703f 100644
--- a/libgcc/config/xtensa/lib2funcs.S
+++ b/libgcc/config/xtensa/lib2funcs.S
@@ -34,10 +34,29 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 	.global	__xtensa_libgcc_window_spill
 	.type	__xtensa_libgcc_window_spill,@function
 __xtensa_libgcc_window_spill:
-	entry	sp, 32
-	movi	a2, 0
-	syscall
+	entry	sp, 48
+#if XCHAL_NUM_AREGS > 16
+	call12	1f
+	retw
+	.align	4
+1:
+	.rept	(XCHAL_NUM_AREGS - 24) / 12
+	_entry	sp, 48
+	mov	a12, a0
+	.endr
+	_entry	sp, 16
+#if XCHAL_NUM_AREGS % 12 == 0
+	mov	a4, a4
+#elif XCHAL_NUM_AREGS % 12 == 4
+	mov	a8, a8
+#elif XCHAL_NUM_AREGS % 12 == 8
+	mov	a12, a12
+#endif
 	retw
+#else
+	mov	a8, a8
+	retw
+#endif
 	.size	__xtensa_libgcc_window_spill, .-__xtensa_libgcc_window_spill
 #endif
 
@@ -61,10 +80,7 @@ __xtensa_nonlocal_goto:
 	entry	sp, 32
 
 	/* Flush registers.  */
-	mov	a5, a2
-	movi	a2, 0
-	syscall
-	mov	a2, a5
+	call8	__xtensa_libgcc_window_spill
 
 	/* Because the save area for a0-a3 is stored one frame below
 	   the one identified by a2, the only way to restore those
-- 
1.8.1.4

[PATCH 0/3] xtensa: libgcc: fixes for stack unwinding

[Max Filippov]

Hi Sterling,

these three patches fix bits of xtensa libgcc related to stack unwinding.
They fix a number of uClibc-ng NPTL thread cancellation and cleanup tests,
particularly uClibc-ng 1.0.5 tests
  nptl/tst-cancelx4,
  nptl/tst-cancelx16,
  nptl/tst-cancelx18,
  nptl/tst-cancelx20,
  nptl/tst-cancelx21,
  nptl/tst-cleanupx1,
  nptl/tst-cleanupx3,
  nptl/tst-oncex3,
  nptl/tst-oncex4.

Max Filippov (3):
  xtensa: reimplement register spilling
  xtensa: use unwind-dw2-fde-dip instead of unwind-dw2-fde
  xtensa: fix _Unwind_GetCFA

 libgcc/config/xtensa/lib2funcs.S         | 30 +++++++++++++++++++++++-------
 libgcc/config/xtensa/t-windowed          |  2 +-
 libgcc/config/xtensa/unwind-dw2-xtensa.c |  2 +-
 3 files changed, 25 insertions(+), 9 deletions(-)

-- 
1.8.1.4

[PATCH 2/3] xtensa: use unwind-dw2-fde-dip instead of unwind-dw2-fde

[Max Filippov]

This allows having exception cleanup code in binaries that don't
register their unwind tables.

2015-08-18  Max Filippov  <jcmvbkbc@gmail.com>
libgcc/
	* config/xtensa/t-windowed (LIB2ADDEH): Replace unwind-dw2-fde
	with unwind-dw2-fde-dip.
---
 libgcc/config/xtensa/t-windowed | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libgcc/config/xtensa/t-windowed b/libgcc/config/xtensa/t-windowed
index 7d9e9db..a99156c 100644
--- a/libgcc/config/xtensa/t-windowed
+++ b/libgcc/config/xtensa/t-windowed
@@ -1,2 +1,2 @@
 LIB2ADDEH = $(srcdir)/config/xtensa/unwind-dw2-xtensa.c \
-   $(srcdir)/unwind-dw2-fde.c $(srcdir)/unwind-sjlj.c $(srcdir)/unwind-c.c
+   $(srcdir)/unwind-dw2-fde-dip.c $(srcdir)/unwind-sjlj.c $(srcdir)/unwind-c.c
-- 
1.8.1.4

Re: [PATCH 1/3] xtensa: reimplement register spilling

[augustine.sterling]

On Mon, Aug 17, 2015 at 2:59 PM, Max Filippov <jcmvbkbc@gmail.com> wrote:
> 2015-08-18  Max Filippov  <jcmvbkbc@gmail.com>
> libgcc/
>         * config/xtensa/lib2funcs.S (__xtensa_libgcc_window_spill): Use
>         CALL12 followed by series of ENTRY to spill windowed registers.
>         (__xtensa_nonlocal_goto): Call __xtensa_libgcc_window_spill
>         instead of making linux spill syscall.

Approved.

Re: [PATCH 2/3] xtensa: use unwind-dw2-fde-dip instead of unwind-dw2-fde

[augustine.sterling]

On Mon, Aug 17, 2015 at 2:59 PM, Max Filippov <jcmvbkbc@gmail.com> wrote:
> This allows having exception cleanup code in binaries that don't
> register their unwind tables.
>
> 2015-08-18  Max Filippov  <jcmvbkbc@gmail.com>
> libgcc/
>         * config/xtensa/t-windowed (LIB2ADDEH): Replace unwind-dw2-fde
>         with unwind-dw2-fde-dip.

Approved.

Re: [PATCH 3/3] xtensa: fix _Unwind_GetCFA

[augustine.sterling]

On Mon, Aug 17, 2015 at 2:59 PM, Max Filippov <jcmvbkbc@gmail.com> wrote:
> 2015-08-18  Max Filippov  <jcmvbkbc@gmail.com>
> libgcc/
>         * config/xtensa/unwind-dw2-xtensa.c (_Unwind_GetCFA): Return
>         context->sp instead of context->cfa.

Approved.

Re: [PATCH 1/3] xtensa: reimplement register spilling

[Max Filippov]

On Tue, Aug 18, 2015 at 3:50 AM, augustine.sterling@gmail.com
<augustine.sterling@gmail.com> wrote:
> On Mon, Aug 17, 2015 at 2:59 PM, Max Filippov <jcmvbkbc@gmail.com> wrote:
>> 2015-08-18  Max Filippov  <jcmvbkbc@gmail.com>
>> libgcc/
>>         * config/xtensa/lib2funcs.S (__xtensa_libgcc_window_spill): Use
>>         CALL12 followed by series of ENTRY to spill windowed registers.
>>         (__xtensa_nonlocal_goto): Call __xtensa_libgcc_window_spill
>>         instead of making linux spill syscall.
>
> Approved.

Applied whole series to trunk. Thank you!

-- Max