| Message ID | ead922fd-1eb9-3781-345d-6a2ea63ecd01@linux.vnet.ibm.com |
|---|---|
| State | New |
| Headers | show |
| Series | S390: Fix backtrace in vdso functions. | expand |
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.
diff --git a/sysdeps/unix/sysv/linux/s390/s390-32/sysdep.h b/sysdeps/unix/sysv/linux/s390/s390-32/sysdep.h
index e56fc32..644b83c 100644
--- a/sysdeps/unix/sysv/linux/s390/s390-32/sysdep.h
+++ b/sysdeps/unix/sysv/linux/s390/s390-32/sysdep.h
@@ -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
diff --git a/sysdeps/unix/sysv/linux/s390/s390-64/sysdep.h b/sysdeps/unix/sysv/linux/s390/s390-64/sysdep.h
index 622991d..18ed339 100644
--- a/sysdeps/unix/sysv/linux/s390/s390-64/sysdep.h
+++ b/sysdeps/unix/sysv/linux/s390/s390-64/sysdep.h
@@ -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