Re: [PATCH 1/7] Apply transparent_union attribute to union semun

2016-09-19 Thread Stafford Horne 



On Mon, 19 Sep 2016, Jonas Bonn wrote:


NAK... this breaks other architectures.

The OpenRISC toolchain is broken with regard to this issue.  Five years ago 
(last I looked) nobody seemed interesting in fixing it. Has anything changed 
here?


Hi Jonas,

This was also pointed out by the automated kbuild system and I replied on 
it. I am currently looking at a possible fix of adding an abi compat layer 
similar to what arm does with 'arch/arm/kernel/sys_oabi-compat.c'.


By toolchain being broken do you mean the openrisc abi spec is broken as 
well?  Last I checked gcc does compile as per the spec.  But it is not a 
very good spec.  There have been discussions to change this as well but no 
progress.


-Stafford


On 09/16/2016 04:42 PM, Stafford Horne wrote:

 ..From: Jonas Bonn 

 The syscall handler for semctl is written under the assumption that the
 toolchain will pass "small" unions as function parameters directly instead
 of by reference.  The union semun is "small" and thus fits this
 description.

 Since it is assumed that the union will be passed directly and not by
 reference, it is safe to access the union members without going via
 get_user.

 The OpenRISC architecture, however, passes all unions by reference, thus
 breaking the above assumption.

 The technically correct fix here is to mark the union as being transparent
 so that the ABI of the union's first element determines the parameter
 passing method and thus make explicit what's already implied in the
 function
 definition.

 Signed-off-by: Jonas Bonn 
 Signed-off-by: Stafford Horne 
 ---
   include/uapi/linux/sem.h | 2 +-
   1 file changed, 1 insertion(+), 1 deletion(-)

 diff --git a/include/uapi/linux/sem.h b/include/uapi/linux/sem.h
 index dd73b90..aabe50f 100644
 --- a/include/uapi/linux/sem.h
 +++ b/include/uapi/linux/sem.h
 @@ -48,7 +48,7 @@ union semun {
unsigned short __user *array;   /* array for GETALL & SETALL */
struct seminfo __user *__buf;   /* buffer for IPC_INFO */
void __user *__pad;
 -};
 +} __attribute__ ((transparent_union));

   struct  seminfo {
int semmap;

Re: [PATCH 1/7] Apply transparent_union attribute to union semun

2016-09-19 Thread Stafford Horne 



On Mon, 19 Sep 2016, Jonas Bonn wrote:


NAK... this breaks other architectures.

The OpenRISC toolchain is broken with regard to this issue.  Five years ago 
(last I looked) nobody seemed interesting in fixing it. Has anything changed 
here?


Hi Jonas,

This was also pointed out by the automated kbuild system and I replied on 
it. I am currently looking at a possible fix of adding an abi compat layer 
similar to what arm does with 'arch/arm/kernel/sys_oabi-compat.c'.


By toolchain being broken do you mean the openrisc abi spec is broken as 
well?  Last I checked gcc does compile as per the spec.  But it is not a 
very good spec.  There have been discussions to change this as well but no 
progress.


-Stafford


On 09/16/2016 04:42 PM, Stafford Horne wrote:

 ..From: Jonas Bonn 

 The syscall handler for semctl is written under the assumption that the
 toolchain will pass "small" unions as function parameters directly instead
 of by reference.  The union semun is "small" and thus fits this
 description.

 Since it is assumed that the union will be passed directly and not by
 reference, it is safe to access the union members without going via
 get_user.

 The OpenRISC architecture, however, passes all unions by reference, thus
 breaking the above assumption.

 The technically correct fix here is to mark the union as being transparent
 so that the ABI of the union's first element determines the parameter
 passing method and thus make explicit what's already implied in the
 function
 definition.

 Signed-off-by: Jonas Bonn 
 Signed-off-by: Stafford Horne 
 ---
   include/uapi/linux/sem.h | 2 +-
   1 file changed, 1 insertion(+), 1 deletion(-)

 diff --git a/include/uapi/linux/sem.h b/include/uapi/linux/sem.h
 index dd73b90..aabe50f 100644
 --- a/include/uapi/linux/sem.h
 +++ b/include/uapi/linux/sem.h
 @@ -48,7 +48,7 @@ union semun {
unsigned short __user *array;   /* array for GETALL & SETALL */
struct seminfo __user *__buf;   /* buffer for IPC_INFO */
void __user *__pad;
 -};
 +} __attribute__ ((transparent_union));

   struct  seminfo {
int semmap;

Re: [PATCH 1/7] Apply transparent_union attribute to union semun

2016-09-19 Thread Jonas Bonn 

NAK... this breaks other architectures.

The OpenRISC toolchain is broken with regard to this issue.  Five years 
ago (last I looked) nobody seemed interesting in fixing it. Has anything 
changed here?


/Jonas

On 09/16/2016 04:42 PM, Stafford Horne wrote:

..From: Jonas Bonn 

The syscall handler for semctl is written under the assumption that the
toolchain will pass "small" unions as function parameters directly instead
of by reference.  The union semun is "small" and thus fits this description.

Since it is assumed that the union will be passed directly and not by
reference, it is safe to access the union members without going via
get_user.

The OpenRISC architecture, however, passes all unions by reference, thus
breaking the above assumption.

The technically correct fix here is to mark the union as being transparent
so that the ABI of the union's first element determines the parameter
passing method and thus make explicit what's already implied in the function
definition.

Signed-off-by: Jonas Bonn 
Signed-off-by: Stafford Horne 
---
  include/uapi/linux/sem.h | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/uapi/linux/sem.h b/include/uapi/linux/sem.h
index dd73b90..aabe50f 100644
--- a/include/uapi/linux/sem.h
+++ b/include/uapi/linux/sem.h
@@ -48,7 +48,7 @@ union semun {
unsigned short __user *array;   /* array for GETALL & SETALL */
struct seminfo __user *__buf;   /* buffer for IPC_INFO */
void __user *__pad;
-};
+} __attribute__ ((transparent_union));
  
  struct  seminfo {

int semmap;

Re: [PATCH 1/7] Apply transparent_union attribute to union semun

2016-09-19 Thread Jonas Bonn 

NAK... this breaks other architectures.

The OpenRISC toolchain is broken with regard to this issue.  Five years 
ago (last I looked) nobody seemed interesting in fixing it. Has anything 
changed here?


/Jonas

On 09/16/2016 04:42 PM, Stafford Horne wrote:

..From: Jonas Bonn 

The syscall handler for semctl is written under the assumption that the
toolchain will pass "small" unions as function parameters directly instead
of by reference.  The union semun is "small" and thus fits this description.

Since it is assumed that the union will be passed directly and not by
reference, it is safe to access the union members without going via
get_user.

The OpenRISC architecture, however, passes all unions by reference, thus
breaking the above assumption.

The technically correct fix here is to mark the union as being transparent
so that the ABI of the union's first element determines the parameter
passing method and thus make explicit what's already implied in the function
definition.

Signed-off-by: Jonas Bonn 
Signed-off-by: Stafford Horne 
---
  include/uapi/linux/sem.h | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/uapi/linux/sem.h b/include/uapi/linux/sem.h
index dd73b90..aabe50f 100644
--- a/include/uapi/linux/sem.h
+++ b/include/uapi/linux/sem.h
@@ -48,7 +48,7 @@ union semun {
unsigned short __user *array;   /* array for GETALL & SETALL */
struct seminfo __user *__buf;   /* buffer for IPC_INFO */
void __user *__pad;
-};
+} __attribute__ ((transparent_union));
  
  struct  seminfo {

int semmap;

Re: [PATCH 1/7] Apply transparent_union attribute to union semun

2016-09-16 Thread Stafford Horne 



On Sat, 17 Sep 2016, kbuild test robot wrote:


Hi Jonas,

[auto build test ERROR on linus/master]
[also build test ERROR on v4.8-rc6 next-20160916]
[if your patch is applied to the wrong git tree, please drop us a note to help 
improve the system]
[Suggest to use git(>=2.9.0) format-patch --base= (or --base=auto for 
convenience) to record what (public, well-known) commit your patch series was built on]
[Check https://git-scm.com/docs/git-format-patch for more information]

url:
https://github.com/0day-ci/linux/commits/Stafford-Horne/openrisc-Misc-fixes-from-backlog/20160916-230114
config: x86_64-randconfig-b0-09170504 (attached as .config)
compiler: gcc-4.4 (Debian 4.4.7-8) 4.4.7
reproduce:
   # save the attached .config to linux build tree
   make ARCH=x86_64

All errors (new ones prefixed by >>):

  cc1: warnings being treated as errors
  In file included from include/linux/sem.h:7,
   from include/linux/sched.h:35,
   from include/linux/kasan.h:4,
   from include/linux/slab.h:118,
   from include/linux/resource_ext.h:19,
   from include/linux/acpi.h:26,
   from drivers/gpu/drm/i915/i915_drv.c:30:

include/uapi/linux/sem.h:51: error: union cannot be made transparent


Thanks for catching this.  I missed that this would break non openrisc 
architectures.


This issue is that "
All members of the union must have the same machine representation; this 
is necessary for this argument passing to work properly.

"

Definitely int and * will not always be the same.  Investingating what we 
can do on in arch/openrisc side without breaking the build/backcompat for

others.

Any other idea's welcome.

-Stafford


vim +51 include/uapi/linux/sem.h

   45   union semun {
   46   int val;/* value for SETVAL */
   47   struct semid_ds __user *buf;/* buffer for IPC_STAT & 
IPC_SET */
   48   unsigned short __user *array;   /* array for GETALL & SETALL */
   49   struct seminfo __user *__buf;   /* buffer for IPC_INFO */
   50   void __user *__pad;
 > 51} __attribute__ ((transparent_union));
   52
   53   struct  seminfo {
   54   int semmap;

---
0-DAY kernel test infrastructureOpen Source Technology Center
https://lists.01.org/pipermail/kbuild-all   Intel Corporation

Re: [PATCH 1/7] Apply transparent_union attribute to union semun

2016-09-16 Thread Stafford Horne 



On Sat, 17 Sep 2016, kbuild test robot wrote:


Hi Jonas,

[auto build test ERROR on linus/master]
[also build test ERROR on v4.8-rc6 next-20160916]
[if your patch is applied to the wrong git tree, please drop us a note to help 
improve the system]
[Suggest to use git(>=2.9.0) format-patch --base= (or --base=auto for 
convenience) to record what (public, well-known) commit your patch series was built on]
[Check https://git-scm.com/docs/git-format-patch for more information]

url:
https://github.com/0day-ci/linux/commits/Stafford-Horne/openrisc-Misc-fixes-from-backlog/20160916-230114
config: x86_64-randconfig-b0-09170504 (attached as .config)
compiler: gcc-4.4 (Debian 4.4.7-8) 4.4.7
reproduce:
   # save the attached .config to linux build tree
   make ARCH=x86_64

All errors (new ones prefixed by >>):

  cc1: warnings being treated as errors
  In file included from include/linux/sem.h:7,
   from include/linux/sched.h:35,
   from include/linux/kasan.h:4,
   from include/linux/slab.h:118,
   from include/linux/resource_ext.h:19,
   from include/linux/acpi.h:26,
   from drivers/gpu/drm/i915/i915_drv.c:30:

include/uapi/linux/sem.h:51: error: union cannot be made transparent


Thanks for catching this.  I missed that this would break non openrisc 
architectures.


This issue is that "
All members of the union must have the same machine representation; this 
is necessary for this argument passing to work properly.

"

Definitely int and * will not always be the same.  Investingating what we 
can do on in arch/openrisc side without breaking the build/backcompat for

others.

Any other idea's welcome.

-Stafford


vim +51 include/uapi/linux/sem.h

   45   union semun {
   46   int val;/* value for SETVAL */
   47   struct semid_ds __user *buf;/* buffer for IPC_STAT & 
IPC_SET */
   48   unsigned short __user *array;   /* array for GETALL & SETALL */
   49   struct seminfo __user *__buf;   /* buffer for IPC_INFO */
   50   void __user *__pad;
 > 51} __attribute__ ((transparent_union));
   52
   53   struct  seminfo {
   54   int semmap;

---
0-DAY kernel test infrastructureOpen Source Technology Center
https://lists.01.org/pipermail/kbuild-all   Intel Corporation

Re: [PATCH 1/7] Apply transparent_union attribute to union semun

2016-09-16 Thread kbuild test robot 
Hi Jonas,

[auto build test ERROR on linus/master]
[also build test ERROR on v4.8-rc6 next-20160916]
[if your patch is applied to the wrong git tree, please drop us a note to help 
improve the system]
[Suggest to use git(>=2.9.0) format-patch --base= (or --base=auto for 
convenience) to record what (public, well-known) commit your patch series was 
built on]
[Check https://git-scm.com/docs/git-format-patch for more information]

url:
https://github.com/0day-ci/linux/commits/Stafford-Horne/openrisc-Misc-fixes-from-backlog/20160916-230114
config: x86_64-randconfig-b0-09170504 (attached as .config)
compiler: gcc-4.4 (Debian 4.4.7-8) 4.4.7
reproduce:
# save the attached .config to linux build tree
make ARCH=x86_64 

All errors (new ones prefixed by >>):

   cc1: warnings being treated as errors
   In file included from include/linux/sem.h:7,
from include/linux/sched.h:35,
from include/linux/kasan.h:4,
from include/linux/slab.h:118,
from include/linux/resource_ext.h:19,
from include/linux/acpi.h:26,
from drivers/gpu/drm/i915/i915_drv.c:30:
>> include/uapi/linux/sem.h:51: error: union cannot be made transparent

vim +51 include/uapi/linux/sem.h

45  union semun {
46  int val;/* value for SETVAL */
47  struct semid_ds __user *buf;/* buffer for IPC_STAT & 
IPC_SET */
48  unsigned short __user *array;   /* array for GETALL & SETALL */
49  struct seminfo __user *__buf;   /* buffer for IPC_INFO */
50  void __user *__pad;
  > 51  } __attribute__ ((transparent_union));
52  
53  struct  seminfo {
54  int semmap;

---
0-DAY kernel test infrastructureOpen Source Technology Center
https://lists.01.org/pipermail/kbuild-all   Intel Corporation


.config.gz
Description: application/gzip

Re: [PATCH 1/7] Apply transparent_union attribute to union semun

2016-09-16 Thread kbuild test robot 
Hi Jonas,

[auto build test ERROR on linus/master]
[also build test ERROR on v4.8-rc6 next-20160916]
[if your patch is applied to the wrong git tree, please drop us a note to help 
improve the system]
[Suggest to use git(>=2.9.0) format-patch --base= (or --base=auto for 
convenience) to record what (public, well-known) commit your patch series was 
built on]
[Check https://git-scm.com/docs/git-format-patch for more information]

url:
https://github.com/0day-ci/linux/commits/Stafford-Horne/openrisc-Misc-fixes-from-backlog/20160916-230114
config: x86_64-randconfig-b0-09170504 (attached as .config)
compiler: gcc-4.4 (Debian 4.4.7-8) 4.4.7
reproduce:
# save the attached .config to linux build tree
make ARCH=x86_64 

All errors (new ones prefixed by >>):

   cc1: warnings being treated as errors
   In file included from include/linux/sem.h:7,
from include/linux/sched.h:35,
from include/linux/kasan.h:4,
from include/linux/slab.h:118,
from include/linux/resource_ext.h:19,
from include/linux/acpi.h:26,
from drivers/gpu/drm/i915/i915_drv.c:30:
>> include/uapi/linux/sem.h:51: error: union cannot be made transparent

vim +51 include/uapi/linux/sem.h

45  union semun {
46  int val;/* value for SETVAL */
47  struct semid_ds __user *buf;/* buffer for IPC_STAT & 
IPC_SET */
48  unsigned short __user *array;   /* array for GETALL & SETALL */
49  struct seminfo __user *__buf;   /* buffer for IPC_INFO */
50  void __user *__pad;
  > 51  } __attribute__ ((transparent_union));
52  
53  struct  seminfo {
54  int semmap;

---
0-DAY kernel test infrastructureOpen Source Technology Center
https://lists.01.org/pipermail/kbuild-all   Intel Corporation


.config.gz
Description: application/gzip

Re: [PATCH 1/7] Apply transparent_union attribute to union semun

2016-09-16 Thread kbuild test robot 
Hi Jonas,

[auto build test WARNING on linus/master]
[also build test WARNING on v4.8-rc6 next-20160916]
[if your patch is applied to the wrong git tree, please drop us a note to help 
improve the system]
[Suggest to use git(>=2.9.0) format-patch --base= (or --base=auto for 
convenience) to record what (public, well-known) commit your patch series was 
built on]
[Check https://git-scm.com/docs/git-format-patch for more information]

url:
https://github.com/0day-ci/linux/commits/Stafford-Horne/openrisc-Misc-fixes-from-backlog/20160916-230114
config: x86_64-randconfig-x011-09161116 (attached as .config)
compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901
reproduce:
# save the attached .config to linux build tree
make ARCH=x86_64 

All warnings (new ones prefixed by >>):

   In file included from include/linux/sem.h:7:0,
from include/linux/sched.h:35,
from include/linux/utsname.h:5,
from init/version.c:12:
>> include/uapi/linux/sem.h:45:7: warning: union cannot be made transparent
union semun {
  ^
--
   In file included from include/linux/sem.h:7:0,
from include/linux/sched.h:35,
from include/linux/kasan.h:4,
from kernel/sched/core.c:29:
>> include/uapi/linux/sem.h:45:7: warning: union cannot be made transparent
union semun {
  ^
   In file included from include/linux/perf_event.h:47:0,
from kernel/sched/core.c:42:
   include/linux/ftrace.h: In function 'preempt_schedule_common':
   include/linux/ftrace.h:703:36: warning: calling '__builtin_return_address' 
with a nonzero argument is unsafe [-Wframe-address]
#  define ftrace_return_address(n) __builtin_return_address(n)
   ^~~
   include/linux/ftrace.h:710:38: note: in expansion of macro 
'ftrace_return_address'
#define CALLER_ADDR1 ((unsigned long)ftrace_return_address(1))
 ^
   include/linux/ftrace.h:723:9: note: in expansion of macro 'CALLER_ADDR1'
 addr = CALLER_ADDR1;
^~~~
   include/linux/ftrace.h:703:36: warning: calling '__builtin_return_address' 
with a nonzero argument is unsafe [-Wframe-address]
#  define ftrace_return_address(n) __builtin_return_address(n)
   ^~~
   include/linux/ftrace.h:711:38: note: in expansion of macro 
'ftrace_return_address'
#define CALLER_ADDR2 ((unsigned long)ftrace_return_address(2))
 ^
   include/linux/ftrace.h:726:9: note: in expansion of macro 'CALLER_ADDR2'
 return CALLER_ADDR2;
^~~~
   include/linux/ftrace.h: In function 'preempt_count_add':
   include/linux/ftrace.h:703:36: warning: calling '__builtin_return_address' 
with a nonzero argument is unsafe [-Wframe-address]
#  define ftrace_return_address(n) __builtin_return_address(n)
   ^~~
   include/linux/ftrace.h:710:38: note: in expansion of macro 
'ftrace_return_address'
#define CALLER_ADDR1 ((unsigned long)ftrace_return_address(1))
 ^
   include/linux/ftrace.h:723:9: note: in expansion of macro 'CALLER_ADDR1'
 addr = CALLER_ADDR1;
^~~~
   include/linux/ftrace.h:703:36: warning: calling '__builtin_return_address' 
with a nonzero argument is unsafe [-Wframe-address]
#  define ftrace_return_address(n) __builtin_return_address(n)
   ^~~
   include/linux/ftrace.h:711:38: note: in expansion of macro 
'ftrace_return_address'
#define CALLER_ADDR2 ((unsigned long)ftrace_return_address(2))
 ^
   include/linux/ftrace.h:726:9: note: in expansion of macro 'CALLER_ADDR2'
 return CALLER_ADDR2;
^~~~
   include/linux/ftrace.h: In function 'preempt_schedule_notrace':
   include/linux/ftrace.h:703:36: warning: calling '__builtin_return_address' 
with a nonzero argument is unsafe [-Wframe-address]
#  define ftrace_return_address(n) __builtin_return_address(n)
   ^~~
   include/linux/ftrace.h:710:38: note: in expansion of macro 
'ftrace_return_address'
#define CALLER_ADDR1 ((unsigned long)ftrace_return_address(1))
 ^
   include/linux/ftrace.h:723:9: note: in expansion of macro 'CALLER_ADDR1'
 addr = CALLER_ADDR1;
^~~~
   include/linux/ftrace.h:703:36: warning: calling '__builtin_return_address' 
with a nonzero argument is unsafe [-Wframe-address]
#  define ftrace_return_address(n) __builtin_return_address(n)

Re: [PATCH 1/7] Apply transparent_union attribute to union semun

2016-09-16 Thread kbuild test robot 
Hi Jonas,

[auto build test WARNING on linus/master]
[also build test WARNING on v4.8-rc6 next-20160916]
[if your patch is applied to the wrong git tree, please drop us a note to help 
improve the system]
[Suggest to use git(>=2.9.0) format-patch --base= (or --base=auto for 
convenience) to record what (public, well-known) commit your patch series was 
built on]
[Check https://git-scm.com/docs/git-format-patch for more information]

url:
https://github.com/0day-ci/linux/commits/Stafford-Horne/openrisc-Misc-fixes-from-backlog/20160916-230114
config: x86_64-randconfig-x011-09161116 (attached as .config)
compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901
reproduce:
# save the attached .config to linux build tree
make ARCH=x86_64 

All warnings (new ones prefixed by >>):

   In file included from include/linux/sem.h:7:0,
from include/linux/sched.h:35,
from include/linux/utsname.h:5,
from init/version.c:12:
>> include/uapi/linux/sem.h:45:7: warning: union cannot be made transparent
union semun {
  ^
--
   In file included from include/linux/sem.h:7:0,
from include/linux/sched.h:35,
from include/linux/kasan.h:4,
from kernel/sched/core.c:29:
>> include/uapi/linux/sem.h:45:7: warning: union cannot be made transparent
union semun {
  ^
   In file included from include/linux/perf_event.h:47:0,
from kernel/sched/core.c:42:
   include/linux/ftrace.h: In function 'preempt_schedule_common':
   include/linux/ftrace.h:703:36: warning: calling '__builtin_return_address' 
with a nonzero argument is unsafe [-Wframe-address]
#  define ftrace_return_address(n) __builtin_return_address(n)
   ^~~
   include/linux/ftrace.h:710:38: note: in expansion of macro 
'ftrace_return_address'
#define CALLER_ADDR1 ((unsigned long)ftrace_return_address(1))
 ^
   include/linux/ftrace.h:723:9: note: in expansion of macro 'CALLER_ADDR1'
 addr = CALLER_ADDR1;
^~~~
   include/linux/ftrace.h:703:36: warning: calling '__builtin_return_address' 
with a nonzero argument is unsafe [-Wframe-address]
#  define ftrace_return_address(n) __builtin_return_address(n)
   ^~~
   include/linux/ftrace.h:711:38: note: in expansion of macro 
'ftrace_return_address'
#define CALLER_ADDR2 ((unsigned long)ftrace_return_address(2))
 ^
   include/linux/ftrace.h:726:9: note: in expansion of macro 'CALLER_ADDR2'
 return CALLER_ADDR2;
^~~~
   include/linux/ftrace.h: In function 'preempt_count_add':
   include/linux/ftrace.h:703:36: warning: calling '__builtin_return_address' 
with a nonzero argument is unsafe [-Wframe-address]
#  define ftrace_return_address(n) __builtin_return_address(n)
   ^~~
   include/linux/ftrace.h:710:38: note: in expansion of macro 
'ftrace_return_address'
#define CALLER_ADDR1 ((unsigned long)ftrace_return_address(1))
 ^
   include/linux/ftrace.h:723:9: note: in expansion of macro 'CALLER_ADDR1'
 addr = CALLER_ADDR1;
^~~~
   include/linux/ftrace.h:703:36: warning: calling '__builtin_return_address' 
with a nonzero argument is unsafe [-Wframe-address]
#  define ftrace_return_address(n) __builtin_return_address(n)
   ^~~
   include/linux/ftrace.h:711:38: note: in expansion of macro 
'ftrace_return_address'
#define CALLER_ADDR2 ((unsigned long)ftrace_return_address(2))
 ^
   include/linux/ftrace.h:726:9: note: in expansion of macro 'CALLER_ADDR2'
 return CALLER_ADDR2;
^~~~
   include/linux/ftrace.h: In function 'preempt_schedule_notrace':
   include/linux/ftrace.h:703:36: warning: calling '__builtin_return_address' 
with a nonzero argument is unsafe [-Wframe-address]
#  define ftrace_return_address(n) __builtin_return_address(n)
   ^~~
   include/linux/ftrace.h:710:38: note: in expansion of macro 
'ftrace_return_address'
#define CALLER_ADDR1 ((unsigned long)ftrace_return_address(1))
 ^
   include/linux/ftrace.h:723:9: note: in expansion of macro 'CALLER_ADDR1'
 addr = CALLER_ADDR1;
^~~~
   include/linux/ftrace.h:703:36: warning: calling '__builtin_return_address' 
with a nonzero argument is unsafe [-Wframe-address]
#  define ftrace_return_address(n) __builtin_return_address(n)