S390: Fix backtrace in vdso functions.
Commit Message
Hi,
On s390, GDB fails to show the complete backtrace from within vdso
functions. The macro INTERNAL_VSYSCALL_CALL saves the return address in
r14 to r10 before branching to the vdso function. The branch-instruction
updates r14 in order to let the vdso function return. Then the original
address in r14 is restored from r10. Unfortunately, there are no
cfi-rules and GDB fails.
Furthermore the call of the vdso function does not comply with the s390
ABI as no stack-frame for the vdso-function is generated.
This patch removes the s390 specific macro INTERNAL_VSYSCALL_CALL and
the common implementation in sysdeps/unix/sysv/linux/sysdep-vdso.h is
used. Then the vdso function is called via function-pointer and GCC
generates a new stack-frame and emits all needed cfi-rules.
The defines CLOBBER_[0-6] are removed as they were only used in macro
INTERNAL_VSYSCALL_CALL.
The macro INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK is not used on s390. The
only user is power. Thus it is removed from s390 sysdep.h.
ChangeLog:
* sysdeps/unix/sysv/linux/s390/s390-64/sysdep.h
(INTERNAL_VSYSCALL_CALL, CLOBBER_0, CLOBBER_1, CLOBBER_2,
CLOBBER_3, CLOBBER_4, CLOBBER_5, CLOBBER_6,
INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK): Remove.
* sysdeps/unix/sysv/linux/s390/s390-32/sysdep.h: Likewise.
Comments
On 28/11/2017 10:44, Stefan Liebler wrote:
> Hi,
>
> On s390, GDB fails to show the complete backtrace from within vdso functions. The macro INTERNAL_VSYSCALL_CALL saves the return address in r14 to r10 before branching to the vdso function. The branch-instruction updates r14 in order to let the vdso function return. Then the original address in r14 is restored from r10. Unfortunately, there are no cfi-rules and GDB fails.
>
> Furthermore the call of the vdso function does not comply with the s390 ABI as no stack-frame for the vdso-function is generated.
>
> This patch removes the s390 specific macro INTERNAL_VSYSCALL_CALL and the common implementation in sysdeps/unix/sysv/linux/sysdep-vdso.h is used. Then the vdso function is called via function-pointer and GCC generates a new stack-frame and emits all needed cfi-rules.
>
> The defines CLOBBER_[0-6] are removed as they were only used in macro INTERNAL_VSYSCALL_CALL.
>
> The macro INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK is not used on s390. The only user is power. Thus it is removed from s390 sysdep.h.
I am almost sure we can remove it for powerpc as well (I can't see
no immediate gain on doing a function call using inline assembly
as for INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK on powerpc).
>
> ChangeLog:
>
> * sysdeps/unix/sysv/linux/s390/s390-64/sysdep.h
> (INTERNAL_VSYSCALL_CALL, CLOBBER_0, CLOBBER_1, CLOBBER_2,
> CLOBBER_3, CLOBBER_4, CLOBBER_5, CLOBBER_6,
> INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK): Remove.
> * sysdeps/unix/sysv/linux/s390/s390-32/sysdep.h: Likewise.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
On 11/28/2017 02:09 PM, Adhemerval Zanella wrote:
> I am almost sure we can remove it for powerpc as well (I can't see
> no immediate gain on doing a function call using inline assembly
> as for INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK on powerpc).
Is there another way to obtain the condition code for the error status?
/* The vDSO does not return an error (it clear cr0.so on returning). */
INTERNAL_SYSCALL_DECL (err);
result =
INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK (get_tbfreq, err, uint64_t, 0);
Thanks,
Florian
On 28/11/2017 12:18, Florian Weimer wrote:
> On 11/28/2017 02:09 PM, Adhemerval Zanella wrote:
>> I am almost sure we can remove it for powerpc as well (I can't see
>> no immediate gain on doing a function call using inline assembly
>> as for INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK on powerpc).
>
> Is there another way to obtain the condition code for the error status?
>
> /* The vDSO does not return an error (it clear cr0.so on returning). */
> INTERNAL_SYSCALL_DECL (err);
> result =
> INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK (get_tbfreq, err, uint64_t, 0);
>
> Thanks,
> Florian
I think we can simplify this call in specific since __kernel_get_tbfreq
always succeed if the vDSO is present. The only issue is the symbol
returns an uint64_t even for powerpc32.
On 28/11/2017 13:53, Adhemerval Zanella wrote:
>
>
> On 28/11/2017 12:18, Florian Weimer wrote:
>> On 11/28/2017 02:09 PM, Adhemerval Zanella wrote:
>>> I am almost sure we can remove it for powerpc as well (I can't see
>>> no immediate gain on doing a function call using inline assembly
>>> as for INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK on powerpc).
>>
>> Is there another way to obtain the condition code for the error status?
>>
>> /* The vDSO does not return an error (it clear cr0.so on returning). */
>> INTERNAL_SYSCALL_DECL (err);
>> result =
>> INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK (get_tbfreq, err, uint64_t, 0);
>>
>> Thanks,
>> Florian
>
> I think we can simplify this call in specific since __kernel_get_tbfreq
> always succeed if the vDSO is present. The only issue is the symbol
> returns an uint64_t even for powerpc32.
>
The problem is for __kernel_clock_getres and __kernel_clock_gettime the
fallback for clocks different than CLOCK_REALTIME or CLOCK_MONOTONIC
is to issue a syscall (and then it requires a mfcr to get the result
value).
On 11/28/2017 02:09 PM, Adhemerval Zanella wrote:
>
>
> On 28/11/2017 10:44, Stefan Liebler wrote:
>> Hi,
>>
>> On s390, GDB fails to show the complete backtrace from within vdso functions. The macro INTERNAL_VSYSCALL_CALL saves the return address in r14 to r10 before branching to the vdso function. The branch-instruction updates r14 in order to let the vdso function return. Then the original address in r14 is restored from r10. Unfortunately, there are no cfi-rules and GDB fails.
>>
>> Furthermore the call of the vdso function does not comply with the s390 ABI as no stack-frame for the vdso-function is generated.
>>
>> This patch removes the s390 specific macro INTERNAL_VSYSCALL_CALL and the common implementation in sysdeps/unix/sysv/linux/sysdep-vdso.h is used. Then the vdso function is called via function-pointer and GCC generates a new stack-frame and emits all needed cfi-rules.
>>
>> The defines CLOBBER_[0-6] are removed as they were only used in macro INTERNAL_VSYSCALL_CALL.
>>
>> The macro INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK is not used on s390. The only user is power. Thus it is removed from s390 sysdep.h.
>
> I am almost sure we can remove it for powerpc as well (I can't see
> no immediate gain on doing a function call using inline assembly
> as for INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK on powerpc).
>
>
>>
>> ChangeLog:
>>
>> * sysdeps/unix/sysv/linux/s390/s390-64/sysdep.h
>> (INTERNAL_VSYSCALL_CALL, CLOBBER_0, CLOBBER_1, CLOBBER_2,
>> CLOBBER_3, CLOBBER_4, CLOBBER_5, CLOBBER_6,
>> INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK): Remove.
>> * sysdeps/unix/sysv/linux/s390/s390-32/sysdep.h: Likewise.
>
> Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
>
If there are no objections regarding the s390 patch, I'll commit.
Adhemerval: Do you keep working on removing
INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK on powerpc?
Bye.
Stefan
On 04/12/2017 05:59, Stefan Liebler wrote:
> On 11/28/2017 02:09 PM, Adhemerval Zanella wrote:
>>
>>
>> On 28/11/2017 10:44, Stefan Liebler wrote:
>>> Hi,
>>>
>>> On s390, GDB fails to show the complete backtrace from within vdso functions. The macro INTERNAL_VSYSCALL_CALL saves the return address in r14 to r10 before branching to the vdso function. The branch-instruction updates r14 in order to let the vdso function return. Then the original address in r14 is restored from r10. Unfortunately, there are no cfi-rules and GDB fails.
>>>
>>> Furthermore the call of the vdso function does not comply with the s390 ABI as no stack-frame for the vdso-function is generated.
>>>
>>> This patch removes the s390 specific macro INTERNAL_VSYSCALL_CALL and the common implementation in sysdeps/unix/sysv/linux/sysdep-vdso.h is used. Then the vdso function is called via function-pointer and GCC generates a new stack-frame and emits all needed cfi-rules.
>>>
>>> The defines CLOBBER_[0-6] are removed as they were only used in macro INTERNAL_VSYSCALL_CALL.
>>>
>>> The macro INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK is not used on s390. The only user is power. Thus it is removed from s390 sysdep.h.
>>
>> I am almost sure we can remove it for powerpc as well (I can't see
>> no immediate gain on doing a function call using inline assembly
>> as for INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK on powerpc).
>>
>>
>>>
>>> ChangeLog:
>>>
>>> * sysdeps/unix/sysv/linux/s390/s390-64/sysdep.h
>>> (INTERNAL_VSYSCALL_CALL, CLOBBER_0, CLOBBER_1, CLOBBER_2,
>>> CLOBBER_3, CLOBBER_4, CLOBBER_5, CLOBBER_6,
>>> INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK): Remove.
>>> * sysdeps/unix/sysv/linux/s390/s390-32/sysdep.h: Likewise.
>>
>> Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
>>
>
> If there are no objections regarding the s390 patch, I'll commit.
>
> Adhemerval: Do you keep working on removing INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK on powerpc?
Different than s390 where the an error is indicate through a negative value,
powerpc signals an error through CR0.SO. And __kernel_clock_getres and
__kernel_clock_gettime fallback to a syscall call in case the timers are
not supported through vDSO, which requires we check CR0.SO value. I do
not a reliable way to check it after a function call on GCC (we can issue
a volatile assembly after it, but I think it is still fragile and it
would require a arch-specific wrapper anyway).
There is also the issue with __kernel_get_tbfreq which returns a 64 bit
value for powercp32, so we need another wrapper that does expect the return
code as long int.
On 12/04/2017 11:47 AM, Adhemerval Zanella wrote:
>
>
> On 04/12/2017 05:59, Stefan Liebler wrote:
>> On 11/28/2017 02:09 PM, Adhemerval Zanella wrote:
>>>
>>>
>>> On 28/11/2017 10:44, Stefan Liebler wrote:
>>>> Hi,
>>>>
>>>> On s390, GDB fails to show the complete backtrace from within vdso functions. The macro INTERNAL_VSYSCALL_CALL saves the return address in r14 to r10 before branching to the vdso function. The branch-instruction updates r14 in order to let the vdso function return. Then the original address in r14 is restored from r10. Unfortunately, there are no cfi-rules and GDB fails.
>>>>
>>>> Furthermore the call of the vdso function does not comply with the s390 ABI as no stack-frame for the vdso-function is generated.
>>>>
>>>> This patch removes the s390 specific macro INTERNAL_VSYSCALL_CALL and the common implementation in sysdeps/unix/sysv/linux/sysdep-vdso.h is used. Then the vdso function is called via function-pointer and GCC generates a new stack-frame and emits all needed cfi-rules.
>>>>
>>>> The defines CLOBBER_[0-6] are removed as they were only used in macro INTERNAL_VSYSCALL_CALL.
>>>>
>>>> The macro INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK is not used on s390. The only user is power. Thus it is removed from s390 sysdep.h.
>>>
>>> I am almost sure we can remove it for powerpc as well (I can't see
>>> no immediate gain on doing a function call using inline assembly
>>> as for INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK on powerpc).
>>>
>>>
>>>>
>>>> ChangeLog:
>>>>
>>>> * sysdeps/unix/sysv/linux/s390/s390-64/sysdep.h
>>>> (INTERNAL_VSYSCALL_CALL, CLOBBER_0, CLOBBER_1, CLOBBER_2,
>>>> CLOBBER_3, CLOBBER_4, CLOBBER_5, CLOBBER_6,
>>>> INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK): Remove.
>>>> * sysdeps/unix/sysv/linux/s390/s390-32/sysdep.h: Likewise.
>>>
>>> Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
>>>
>>
>> If there are no objections regarding the s390 patch, I'll commit.
>>
>> Adhemerval: Do you keep working on removing INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK on powerpc?
>
> Different than s390 where the an error is indicate through a negative value,
> powerpc signals an error through CR0.SO. And __kernel_clock_getres and
> __kernel_clock_gettime fallback to a syscall call in case the timers are
> not supported through vDSO, which requires we check CR0.SO value. I do
> not a reliable way to check it after a function call on GCC (we can issue
> a volatile assembly after it, but I think it is still fragile and it
> would require a arch-specific wrapper anyway).
>
> There is also the issue with __kernel_get_tbfreq which returns a 64 bit
> value for powercp32, so we need another wrapper that does expect the return
> code as long int.
>
Okay.
Then I've just committed this patch.
commit a1000218276c4cfb9a72e53f17b144b137faf334
Author: Stefan Liebler <stli@linux.vnet.ibm.com>
Date: Mon Nov 27 11:24:45 2017 +0100
S390: Fix backtrace in vdso functions.
On s390, GDB fails to show the complete backtrace from within vdso functions.
The macro INTERNAL_VSYSCALL_CALL saves the return address in r14 to r10
before branching to the vdso function. The branch-instruction updates r14
in order to let the vdso function return. Then the original address in r14 is
restored from r10. Unfortunately, there are no cfi-rules and GDB fails.
Furthermore the call of the vdso function does not comply with the s390 ABI
as no stack-frame for the vdso-function is generated.
This patch removes the s390 specific macro INTERNAL_VSYSCALL_CALL
and the common implementation in sysdeps/unix/sysv/linux/sysdep-vdso.h is used.
Then the vdso function is called via function-pointer and GCC generates a
new stack-frame and emits all needed cfi-rules.
The defines CLOBBER_[0-6] are removed as they were only used in macro
INTERNAL_VSYSCALL_CALL.
The macro INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK is not used on s390.
The only user is power. Thus it is removed from s390 sysdep.h.
ChangeLog:
* sysdeps/unix/sysv/linux/s390/s390-64/sysdep.h
(INTERNAL_VSYSCALL_CALL, CLOBBER_0, CLOBBER_1, CLOBBER_2,
CLOBBER_3, CLOBBER_4, CLOBBER_5, CLOBBER_6,
INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK): Remove.
* sysdeps/unix/sysv/linux/s390/s390-32/sysdep.h: Likewise.
@@ -271,48 +271,12 @@
#define ASMFMT_5 , "0" (gpr2), "d" (gpr3), "d" (gpr4), "d" (gpr5), "d" (gpr6)
#define ASMFMT_6 , "0" (gpr2), "d" (gpr3), "d" (gpr4), "d" (gpr5), "d" (gpr6), "d" (gpr7)
-#define CLOBBER_0 , "3", "4", "5"
-#define CLOBBER_1 , "3", "4", "5"
-#define CLOBBER_2 , "4", "5"
-#define CLOBBER_3 , "5"
-#define CLOBBER_4
-#define CLOBBER_5
-#define CLOBBER_6
-
/* List of system calls which are supported as vsyscalls. */
#define HAVE_CLOCK_GETRES_VSYSCALL 1
#define HAVE_CLOCK_GETTIME_VSYSCALL 1
#define HAVE_GETTIMEOFDAY_VSYSCALL 1
#define HAVE_GETCPU_VSYSCALL 1
-/* This version is for internal uses when there is no desire
- to set errno */
-#define INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK(name, err, nr, args...) \
- ({ \
- long int _ret = ENOSYS; \
- \
- __typeof (__vdso_##name) vdsop = __vdso_##name; \
- PTR_DEMANGLE (vdsop); \
- if (vdsop != NULL) \
- _ret = INTERNAL_VSYSCALL_CALL (vdsop, err, nr, ##args); \
- else \
- err = 1 << 28; \
- _ret; \
- })
-
-#define INTERNAL_VSYSCALL_CALL(fn, err, nr, args...) \
- ({ \
- DECLARGS_##nr(args) \
- register long _ret __asm__("2"); \
- __asm__ __volatile__ ( \
- "lr 10,14\n\t" \
- "basr 14,%1\n\t" \
- "lr 14,10\n\t" \
- : "=d" (_ret) \
- : "d" (fn) ASMFMT_##nr \
- : "cc", "memory", "0", "1", "10" CLOBBER_##nr); \
- _ret; })
-
/* Pointer mangling support. */
#if IS_IN (rtld)
/* We cannot use the thread descriptor because in ld.so we use setjmp
@@ -277,14 +277,6 @@
#define ASMFMT_5 , "0" (gpr2), "d" (gpr3), "d" (gpr4), "d" (gpr5), "d" (gpr6)
#define ASMFMT_6 , "0" (gpr2), "d" (gpr3), "d" (gpr4), "d" (gpr5), "d" (gpr6), "d" (gpr7)
-#define CLOBBER_0 , "3", "4", "5"
-#define CLOBBER_1 , "3", "4", "5"
-#define CLOBBER_2 , "4", "5"
-#define CLOBBER_3 , "5"
-#define CLOBBER_4
-#define CLOBBER_5
-#define CLOBBER_6
-
/* List of system calls which are supported as vsyscalls. */
#define HAVE_CLOCK_GETRES_VSYSCALL 1
#define HAVE_CLOCK_GETTIME_VSYSCALL 1
@@ -293,34 +285,6 @@
#define SINGLE_THREAD_BY_GLOBAL 1
-/* This version is for internal uses when there is no desire
- to set errno */
-#define INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK(name, err, nr, args...) \
- ({ \
- long int _ret = ENOSYS; \
- \
- __typeof (__vdso_##name) vdsop = __vdso_##name; \
- PTR_DEMANGLE (vdsop); \
- if (vdsop != NULL) \
- _ret = INTERNAL_VSYSCALL_CALL (vdsop, err, nr, ##args); \
- else \
- err = 1 << 28; \
- _ret; \
- })
-
-#define INTERNAL_VSYSCALL_CALL(fn, err, nr, args...) \
- ({ \
- DECLARGS_##nr(args) \
- register long _ret __asm__("2"); \
- __asm__ __volatile__ ( \
- "lgr 10,14\n\t" \
- "basr 14,%1\n\t" \
- "lgr 14,10\n\t" \
- : "=d" (_ret) \
- : "a" (fn) ASMFMT_##nr \
- : "cc", "memory", "0", "1", "10" CLOBBER_##nr); \
- _ret; })
-
/* Pointer mangling support. */
#if IS_IN (rtld)
/* We cannot use the thread descriptor because in ld.so we use setjmp