[merge] Build failure selftest/powerpc/mm/pkey_exec_prot
Michael Ellerman
mpe at ellerman.id.au
Tue Aug 4 22:23:24 AEST 2020
Sandipan Das <sandipan at linux.ibm.com> writes:
> On 04/08/20 6:38 am, Michael Ellerman wrote:
>> Sandipan Das <sandipan at linux.ibm.com> writes:
>>> On 03/08/20 4:32 pm, Michael Ellerman wrote:
>>>> Sachin Sant <sachinp at linux.vnet.ibm.com> writes:
>>>>>> On 02-Aug-2020, at 10:58 PM, Sandipan Das <sandipan at linux.ibm.com> wrote:
>>>>>> On 02/08/20 4:45 pm, Sachin Sant wrote:
>>>>>>> pkey_exec_prot test from linuxppc merge branch (3f68564f1f5a) fails to
>>>>>>> build due to following error:
>>>>>>>
>>>>>>> gcc -std=gnu99 -O2 -Wall -Werror -DGIT_VERSION='"v5.8-rc7-1276-g3f68564f1f5a"' -I/home/sachin/linux/tools/testing/selftests/powerpc/include -m64 pkey_exec_prot.c /home/sachin/linux/tools/testing/selftests/kselftest_harness.h /home/sachin/linux/tools/testing/selftests/kselftest.h ../harness.c ../utils.c -o /home/sachin/linux/tools/testing/selftests/powerpc/mm/pkey_exec_prot
>>>>>>> In file included from pkey_exec_prot.c:18:
>>>>>>> /home/sachin/linux/tools/testing/selftests/powerpc/include/pkeys.h:34: error: "SYS_pkey_mprotect" redefined [-Werror]
>>>>>>> #define SYS_pkey_mprotect 386
>>>>>>>
>>>>>>> In file included from /usr/include/sys/syscall.h:31,
>>>>>>> from /home/sachin/linux/tools/testing/selftests/powerpc/include/utils.h:47,
>>>>>>> from /home/sachin/linux/tools/testing/selftests/powerpc/include/pkeys.h:12,
>>>>>>> from pkey_exec_prot.c:18:
>>>>>>> /usr/include/bits/syscall.h:1583: note: this is the location of the previous definition
>>>>>>> # define SYS_pkey_mprotect __NR_pkey_mprotect
>>>>>>>
>>>>>>> commit 128d3d021007 introduced this error.
>>>>>>> selftests/powerpc: Move pkey helpers to headers
>>>>>>>
>>>>>>> Possibly the # defines for sys calls can be retained in pkey_exec_prot.c or
>>>>>>>
>>>>>>
>>>>>> I am unable to reproduce this on the latest merge branch (HEAD at f59195f7faa4).
>>>>>> I don't see any redefinitions in pkey_exec_prot.c either.
>>>>>>
>>>>>
>>>>> I can still see this problem on latest merge branch.
>>>>> I have following gcc version
>>>>>
>>>>> gcc version 8.3.1 20191121
>>>>
>>>> What libc version? Or just the distro & version?
>>>
>>> Sachin observed this on RHEL 8.2 with glibc-2.28.
>>> I couldn't reproduce it on Ubuntu 20.04 and Fedora 32 and both these distros
>>> are using glibc-2.31.
>>
>> OK odd. Usually it's newer glibc that hits this problem.
>>
>> I guess on RHEL 8.2 we're getting the asm-generic version? But that
>> would be quite wrong if that's what's happening.
>
> If I let GCC dump all the headers that are being used for the source file, I always
> see syscall.h being included on the RHEL 8.2 system. That is the header with the
> conflicting definition.
>
> $ cd tools/testing/selftests/powerpc/mm
> $ gcc -H -std=gnu99 -O2 -Wall -Werror -DGIT_VERSION='"v5.8-rc7-1456-gf59195f7faa4-dirty"' \
> -I../include -m64 pkey_exec_prot.c ../../kselftest_harness.h ../../kselftest.h ../harness.c ../utils.c \
> -o pkey_exec_prot 2>&1 | grep syscall
>
> On Ubuntu 20.04 and Fedora 32, grep doesn't find any matching text.
> On RHEL 8.2, it shows the following.
> ... /usr/include/sys/syscall.h
> .... /usr/include/bits/syscall.h
> In file included from /usr/include/sys/syscall.h:31,
> /usr/include/bits/syscall.h:1583: note: this is the location of the previous definition
> In file included from /usr/include/sys/syscall.h:31,
> /usr/include/bits/syscall.h:1575: note: this is the location of the previous definition
> In file included from /usr/include/sys/syscall.h:31,
> /usr/include/bits/syscall.h:1579: note: this is the location of the previous definition
> /usr/include/bits/syscall.h
> .. /usr/include/sys/syscall.h
> ... /usr/include/bits/syscall.h
> /usr/include/bits/syscall.h
> .. /usr/include/sys/syscall.h
> ... /usr/include/bits/syscall.h
> /usr/include/bits/syscall.h
>
> So utils.h is also including /usr/include/sys/syscall.h for glibc versions older than 2.30
> because of commit 743f3544fffb ("selftests/powerpc: Add wrapper for gettid") :)
Haha, of course. :facepalm_emoji:
> [...]
> . ../include/pkeys.h
> [...]
> .. ../include/utils.h
> [...]
> ... /usr/include/sys/syscall.h
> .... /usr/include/asm/unistd.h
> .... /usr/include/bits/syscall.h
> In file included from pkey_exec_prot.c:18:
> ../include/pkeys.h:34: error: "SYS_pkey_mprotect" redefined [-Werror]
> #define SYS_pkey_mprotect 386
>
> In file included from /usr/include/sys/syscall.h:31,
> from ../include/utils.h:47,
> from ../include/pkeys.h:12,
> from pkey_exec_prot.c:18:
> /usr/include/bits/syscall.h:1583: note: this is the location of the previous definition
> # define SYS_pkey_mprotect __NR_pkey_mprotect
Aha, that explains why redefining gives us an error, because we're
defining it to the literal 386 whereas the system header is defining it
to the __NR value.
Is there a reason to use the SYS_ name?
Typically we just use the __NR value directly, and that would avoid any
problems with redefinition I think, as long as we're using the same
value as the system header (which we always should be).
eg:
diff --git a/tools/testing/selftests/powerpc/include/pkeys.h b/tools/testing/selftests/powerpc/include/pkeys.h
index 6ba95039a034..3312cb1b058d 100644
--- a/tools/testing/selftests/powerpc/include/pkeys.h
+++ b/tools/testing/selftests/powerpc/include/pkeys.h
@@ -31,9 +31,9 @@
#define SI_PKEY_OFFSET 0x20
-#define SYS_pkey_mprotect 386
-#define SYS_pkey_alloc 384
-#define SYS_pkey_free 385
+#define __NR_pkey_mprotect 386
+#define __NR_pkey_alloc 384
+#define __NR_pkey_free 385
#define PKEY_BITS_PER_PKEY 2
#define NR_PKEYS 32
@@ -62,17 +62,17 @@ void pkey_set_rights(int pkey, unsigned long rights)
int sys_pkey_mprotect(void *addr, size_t len, int prot, int pkey)
{
- return syscall(SYS_pkey_mprotect, addr, len, prot, pkey);
+ return syscall(__NR_pkey_mprotect, addr, len, prot, pkey);
}
int sys_pkey_alloc(unsigned long flags, unsigned long rights)
{
- return syscall(SYS_pkey_alloc, flags, rights);
+ return syscall(__NR_pkey_alloc, flags, rights);
}
int sys_pkey_free(int pkey)
{
- return syscall(SYS_pkey_free, pkey);
+ return syscall(__NR_pkey_free, pkey);
}
int pkeys_unsupported(void)
cheers
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