Date: Fri, 16 Jan 2009 10:50:51 +0200 From: Jacques Fourie <jacques.fourie@gmail.com> To: Garrett Cooper <yanefbsd@gmail.com> Cc: "amd64@freebsd.org" <amd64@freebsd.org>, Hackers freeBSD <freebsd-hackers@freebsd.org> Subject: Re: Confused by segfault with legitimate call to strerror(3) on amd64 / sysctl(3) setting `odd' errno's Message-ID: <be2f52430901160050m447b0be6yefa08de43ed6fb37@mail.gmail.com> In-Reply-To: <be2f52430901160047j18172bb9ne75066de0094e565@mail.gmail.com> References: <7d6fde3d0901160041n55466290l55f737d274a40895@mail.gmail.com> <7d6fde3d0901160044x4d7735cep16f032cd99dbc835@mail.gmail.com> <be2f52430901160047j18172bb9ne75066de0094e565@mail.gmail.com>
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On Fri, Jan 16, 2009 at 10:47 AM, Jacques Fourie
<jacques.fourie@gmail.com> wrote:
> On Fri, Jan 16, 2009 at 10:44 AM, Garrett Cooper <yanefbsd@gmail.com> wrote:
>> On Fri, Jan 16, 2009 at 12:41 AM, Garrett Cooper <yanefbsd@gmail.com> wrote:
>>> Hi amd64 and Hackers,
>>> Uh, I'm really confused why 1) this error (errno => ENOMEM) would
>>> occur when I have more than enough free memory (both on x86 and amd64)
>>> and 2) why strerror would segfault in the call to errx in the attached
>>> sourcefile on amd64 only. Not initializing len causes the second
>>> output sample (errno => 14, which is EFAULT).
>>> Any ideas?
>>> Please CC me if mailing on amd64@ as I'm not subscribed to the list.
>>> Thanks,
>>> -Garrett
>>>
>>> /* Program */
>>> #include <err.h>
>>> #include <errno.h>
>>> #include <stdio.h>
>>> #include <sys/types.h>
>>> #include <sys/sysctl.h>
>>>
>>> int
>>> main() {
>>>
>>> int mib[4];
>>>
>>> size_t len;
>>>
>>> if (sysctlnametomib("kern.ipc.shmmax", mib, &len) != 0) {
>>> printf("Errno: %d\n", errno);
>>> errx(errno, "Error: %s", strerror(errno));
>>> }
>>>
>>> printf("%lu\n", len);
>>>
>>> return 0;
>>>
>>> }
>>>
>>> # output for len preset to 0:
>>> [gcooper@optimus ~]$ ./test2
>>> Errno: 12
>>> test2: Segmentation fault: 11 (core dumped)
>>> [gcooper@optimus ~]$ uname -a
>>> FreeBSD optimus.gateway.2wire.net 8.0-CURRENT FreeBSD 8.0-CURRENT #4:
>>> Sun Jan 11 12:30:31 PST 2009
>>> root@optimus.gateway.2wire.net:/usr/obj/usr/src/sys/OPTIMUS amd64
>>>
>>> [gcooper@orangebox /usr/home/gcooper]$ ./test
>>> Errno: 12
>>> test: Error: Cannot allocate memory
>>> [gcooper@orangebox /usr/home/gcooper]$ uname -a
>>> FreeBSD orangebox.gateway.2wire.net 8.0-CURRENT FreeBSD 8.0-CURRENT
>>> #4: Sat Jan 3 22:54:52 PST 2009
>>> gcooper@orangebox.gateway.2wire.net:/usr/obj/usr/src/sys/ORANGEBOX
>>> i386
>>>
>>> # output for len not preset to 0:
>>> [gcooper@optimus ~]$ ./test2
>>> Errno: 14
>>> test2: Segmentation fault: 11 (core dumped)
>>
>> Almost forgot -- here are the actual values reported by sysctl(1),
>> just for reference:
>>
>> [gcooper@optimus ~]$ sysctl kern.ipc.shmall kern.ipc.shmmin kern.ipc.shmmax
>> kern.ipc.shmall: 8192
>> kern.ipc.shmmin: 1
>> kern.ipc.shmmax: 33554432
>>
>> [gcooper@orangebox /usr/src/sys]$ sysctl kern.ipc.shmall
>> kern.ipc.shmmin kern.ipc.shmmax
>> kern.ipc.shmall: 8192
>> kern.ipc.shmmin: 1
>> kern.ipc.shmmax: 33554432
>>
>> Thanks,
>> -Garrett
>> _______________________________________________
>> freebsd-hackers@freebsd.org mailing list
>> http://lists.freebsd.org/mailman/listinfo/freebsd-hackers
>> To unsubscribe, send any mail to "freebsd-hackers-unsubscribe@freebsd.org"
>>
>
> You need to initialize len to the number of entries in the mib array.
> Try adding 'len = 4' before calling sysctlnametomib() and see if your
> issues go away.
>
Sorry, I only scanned through the code without reading the whole
message before replying :) Please ignore...
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