From: Jinrong Liang <cloudliang@tencent.com>

The following warning appears when executing:
	make -C tools/testing/selftests/kvm

rseq_test.c: In function ‘main’:
rseq_test.c:237:33: warning: implicit declaration of function ‘gettid’; did you mean ‘getgid’? [-Wimplicit-function-declaration]
          (void *)(unsigned long)gettid());
                                 ^~~~~~
                                 getgid
/usr/bin/ld: /tmp/ccr5mMko.o: in function `main':
../kvm/tools/testing/selftests/kvm/rseq_test.c:237: undefined reference to `gettid'
collect2: error: ld returned 1 exit status
make: *** [../lib.mk:173: ../kvm/tools/testing/selftests/kvm/rseq_test] Error 1

Use the more compatible syscall(SYS_gettid) instead of gettid() to fix it.
More subsequent reuse may cause it to be wrapped in a lib file.

Signed-off-by: Jinrong Liang <cloudliang@tencent.com>
---
 tools/testing/selftests/kvm/rseq_test.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/kvm/rseq_test.c b/tools/testing/selftests/kvm/rseq_test.c
index a54d4d05a058..299d316cc759 100644
--- a/tools/testing/selftests/kvm/rseq_test.c
+++ b/tools/testing/selftests/kvm/rseq_test.c
@@ -229,7 +229,7 @@ int main(int argc, char *argv[])
 	ucall_init(vm, NULL);
 
 	pthread_create(&migration_thread, NULL, migration_worker,
-		       (void *)(unsigned long)gettid());
+		       (void *)(unsigned long)syscall(SYS_gettid));
 
 	for (i = 0; !done; i++) {
 		vcpu_run(vcpu);
-- 
2.37.1

Queued, thanks.

Paolo

On Tue, Aug 02, 2022, Jinrong Liang wrote:
> From: Jinrong Liang <cloudliang@tencent.com>
> 
> The following warning appears when executing:
> 	make -C tools/testing/selftests/kvm
> 
> rseq_test.c: In function ‘main’:
> rseq_test.c:237:33: warning: implicit declaration of function ‘gettid’; did you mean ‘getgid’? [-Wimplicit-function-declaration]
>           (void *)(unsigned long)gettid());
>                                  ^~~~~~
>                                  getgid
> /usr/bin/ld: /tmp/ccr5mMko.o: in function `main':
> ../kvm/tools/testing/selftests/kvm/rseq_test.c:237: undefined reference to `gettid'
> collect2: error: ld returned 1 exit status
> make: *** [../lib.mk:173: ../kvm/tools/testing/selftests/kvm/rseq_test] Error 1
> 
> Use the more compatible syscall(SYS_gettid) instead of gettid() to fix it.
> More subsequent reuse may cause it to be wrapped in a lib file.
> 
> Signed-off-by: Jinrong Liang <cloudliang@tencent.com>
> ---

Reviewed-by: Sean Christopherson <seanjc@google.com>


Paolo, do you want to grab this for 6.0?  It doesn't look like we're going to have
a more elegant solution anytime soon...

On 07/09/2022 17:01, Sean Christopherson wrote:
> On Tue, Aug 02, 2022, Jinrong Liang wrote:
>> From: Jinrong Liang <cloudliang@tencent.com>
>>
>> The following warning appears when executing:
>> 	make -C tools/testing/selftests/kvm
>>
>> rseq_test.c: In function ‘main’:
>> rseq_test.c:237:33: warning: implicit declaration of function ‘gettid’; did you mean ‘getgid’? [-Wimplicit-function-declaration]
>>            (void *)(unsigned long)gettid());
>>                                   ^~~~~~
>>                                   getgid
>> /usr/bin/ld: /tmp/ccr5mMko.o: in function `main':
>> ../kvm/tools/testing/selftests/kvm/rseq_test.c:237: undefined reference to `gettid'
>> collect2: error: ld returned 1 exit status
>> make: *** [../lib.mk:173: ../kvm/tools/testing/selftests/kvm/rseq_test] Error 1
>>
>> Use the more compatible syscall(SYS_gettid) instead of gettid() to fix it.
>> More subsequent reuse may cause it to be wrapped in a lib file.
>>
>> Signed-off-by: Jinrong Liang <cloudliang@tencent.com>
>> ---
> 
> Reviewed-by: Sean Christopherson <seanjc@google.com>
> 

Can a 'Cc: stable@vger.kernel.org' be added also as e923b0537d28 got 
backported to v5.15.58

Reviewed-by: Liam Merwick <liam.merwick@oracle.com>


> 
> Paolo, do you want to grab this for 6.0?  It doesn't look like we're going to have
> a more elegant solution anytime soon...

On 2022/9/8 00:54, Liam Merwick wrote:
> On 07/09/2022 17:01, Sean Christopherson wrote:
>> On Tue, Aug 02, 2022, Jinrong Liang wrote:
>>> From: Jinrong Liang <cloudliang@tencent.com>
>>>
>>> The following warning appears when executing:
>>>     make -C tools/testing/selftests/kvm
>>>
>>> rseq_test.c: In function ‘main’:
>>> rseq_test.c:237:33: warning: implicit declaration of function 
>>> ‘gettid’; did you mean ‘getgid’? [-Wimplicit-function-declaration]
>>>            (void *)(unsigned long)gettid());
>>>                                   ^~~~~~
>>>                                   getgid
>>> /usr/bin/ld: /tmp/ccr5mMko.o: in function `main':
>>> ../kvm/tools/testing/selftests/kvm/rseq_test.c:237: undefined 
>>> reference to `gettid'
>>> collect2: error: ld returned 1 exit status
>>> make: *** [../lib.mk:173: 
>>> ../kvm/tools/testing/selftests/kvm/rseq_test] Error 1
>>>
>>> Use the more compatible syscall(SYS_gettid) instead of gettid() to 
>>> fix it.
>>> More subsequent reuse may cause it to be wrapped in a lib file.
>>>
>>> Signed-off-by: Jinrong Liang <cloudliang@tencent.com>
>>> ---
>>
>> Reviewed-by: Sean Christopherson <seanjc@google.com>
>>
> 
> Can a 'Cc: stable@vger.kernel.org' be added also as e923b0537d28 got 
> backported to v5.15.58
> 
> Reviewed-by: Liam Merwick <liam.merwick@oracle.com>
> 
> 
>>
>> Paolo, do you want to grab this for 6.0?  It doesn't look like we're 
>> going to have
>> a more elegant solution anytime soon...
> 
Ping?

On Fri, Sep 16, 2022 at 3:03 AM JinrongLiang <ljr.kernel@gmail.com> wrote:
>
>
>
> On 2022/9/8 00:54, Liam Merwick wrote:
> > On 07/09/2022 17:01, Sean Christopherson wrote:
> >> On Tue, Aug 02, 2022, Jinrong Liang wrote:
> >>> From: Jinrong Liang <cloudliang@tencent.com>
> >>>
> >>> The following warning appears when executing:
> >>>     make -C tools/testing/selftests/kvm
> >>>
> >>> rseq_test.c: In function ‘main’:
> >>> rseq_test.c:237:33: warning: implicit declaration of function
> >>> ‘gettid’; did you mean ‘getgid’? [-Wimplicit-function-declaration]
> >>>            (void *)(unsigned long)gettid());
> >>>                                   ^~~~~~
> >>>                                   getgid
> >>> /usr/bin/ld: /tmp/ccr5mMko.o: in function `main':
> >>> ../kvm/tools/testing/selftests/kvm/rseq_test.c:237: undefined
> >>> reference to `gettid'
> >>> collect2: error: ld returned 1 exit status
> >>> make: *** [../lib.mk:173:
> >>> ../kvm/tools/testing/selftests/kvm/rseq_test] Error 1
> >>>
> >>> Use the more compatible syscall(SYS_gettid) instead of gettid() to
> >>> fix it.
> >>> More subsequent reuse may cause it to be wrapped in a lib file.
> >>>
> >>> Signed-off-by: Jinrong Liang <cloudliang@tencent.com>
> >>> ---
> >>
> >> Reviewed-by: Sean Christopherson <seanjc@google.com>
> >>
> >
> > Can a 'Cc: stable@vger.kernel.org' be added also as e923b0537d28 got
> > backported to v5.15.58
> >
> > Reviewed-by: Liam Merwick <liam.merwick@oracle.com>
> >
> >
> >>
> >> Paolo, do you want to grab this for 6.0?  It doesn't look like we're
> >> going to have
> >> a more elegant solution anytime soon...
> >
> Ping?

+1, please grab this. Every new branch I create (for new development
and to review upstream code) I have to remember to cherry-pick this
patch in because I use Clang.

On Tue, Aug 02, 2022 at 03:12:40PM +0800, Jinrong Liang wrote:
> From: Jinrong Liang <cloudliang@tencent.com>
> 
> The following warning appears when executing:
> 	make -C tools/testing/selftests/kvm
> 
> rseq_test.c: In function ‘main’:
> rseq_test.c:237:33: warning: implicit declaration of function ‘gettid’; did you mean ‘getgid’? [-Wimplicit-function-declaration]
>           (void *)(unsigned long)gettid());
>                                  ^~~~~~
>                                  getgid
> /usr/bin/ld: /tmp/ccr5mMko.o: in function `main':
> ../kvm/tools/testing/selftests/kvm/rseq_test.c:237: undefined reference to `gettid'
> collect2: error: ld returned 1 exit status
> make: *** [../lib.mk:173: ../kvm/tools/testing/selftests/kvm/rseq_test] Error 1

The man page says we need

 #define _GNU_SOURCE
 #include <unistd.h>

which rseq_test.c doesn't have. We have _GNU_SOURCE, but not unistd.h.
IOW, I think this patch can be

diff --git a/tools/testing/selftests/kvm/rseq_test.c b/tools/testing/selftests/kvm/rseq_test.c
index a54d4d05a058..8d3d5eab5e19 100644
--- a/tools/testing/selftests/kvm/rseq_test.c
+++ b/tools/testing/selftests/kvm/rseq_test.c
@@ -9,6 +9,7 @@
 #include <string.h>
 #include <signal.h>
 #include <syscall.h>
+#include <unistd.h>
 #include <sys/ioctl.h>
 #include <sys/sysinfo.h>
 #include <asm/barrier.h>

Thanks,
drew

> 
> Use the more compatible syscall(SYS_gettid) instead of gettid() to fix it.
> More subsequent reuse may cause it to be wrapped in a lib file.
> 
> Signed-off-by: Jinrong Liang <cloudliang@tencent.com>
> ---
>  tools/testing/selftests/kvm/rseq_test.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/kvm/rseq_test.c b/tools/testing/selftests/kvm/rseq_test.c
> index a54d4d05a058..299d316cc759 100644
> --- a/tools/testing/selftests/kvm/rseq_test.c
> +++ b/tools/testing/selftests/kvm/rseq_test.c
> @@ -229,7 +229,7 @@ int main(int argc, char *argv[])
>  	ucall_init(vm, NULL);
>  
>  	pthread_create(&migration_thread, NULL, migration_worker,
> -		       (void *)(unsigned long)gettid());
> +		       (void *)(unsigned long)syscall(SYS_gettid));
>  
>  	for (i = 0; !done; i++) {
>  		vcpu_run(vcpu);
> -- 
> 2.37.1
> 

My ldd version is (GNU libc) 2.28, and I get a compilation error in this case.
But I use another ldd (Ubuntu GLIBC 2.31-0ubuntu9.2) 2.31 is compiling fine.
This shows that compilation errors may occur in different GNU libc environments.
Would it be more appropriate to use syscall for better compatibility?

Thanks,
Jinrong Liang

Andrew Jones <andrew.jones@linux.dev> 于2022年8月2日周二 23:08写道：

>
> On Tue, Aug 02, 2022 at 03:12:40PM +0800, Jinrong Liang wrote:
> > From: Jinrong Liang <cloudliang@tencent.com>
> >
> > The following warning appears when executing:
> >       make -C tools/testing/selftests/kvm
> >
> > rseq_test.c: In function ‘main’:
> > rseq_test.c:237:33: warning: implicit declaration of function ‘gettid’; did you mean ‘getgid’? [-Wimplicit-function-declaration]
> >           (void *)(unsigned long)gettid());
> >                                  ^~~~~~
> >                                  getgid
> > /usr/bin/ld: /tmp/ccr5mMko.o: in function `main':
> > ../kvm/tools/testing/selftests/kvm/rseq_test.c:237: undefined reference to `gettid'
> > collect2: error: ld returned 1 exit status
> > make: *** [../lib.mk:173: ../kvm/tools/testing/selftests/kvm/rseq_test] Error 1
>
> The man page says we need
>
>  #define _GNU_SOURCE
>  #include <unistd.h>
>
> which rseq_test.c doesn't have. We have _GNU_SOURCE, but not unistd.h.
> IOW, I think this patch can be
>
> diff --git a/tools/testing/selftests/kvm/rseq_test.c b/tools/testing/selftests/kvm/rseq_test.c
> index a54d4d05a058..8d3d5eab5e19 100644
> --- a/tools/testing/selftests/kvm/rseq_test.c
> +++ b/tools/testing/selftests/kvm/rseq_test.c
> @@ -9,6 +9,7 @@
>  #include <string.h>
>  #include <signal.h>
>  #include <syscall.h>
> +#include <unistd.h>
>  #include <sys/ioctl.h>
>  #include <sys/sysinfo.h>
>  #include <asm/barrier.h>
>
> Thanks,
> drew
>
> >
> > Use the more compatible syscall(SYS_gettid) instead of gettid() to fix it.
> > More subsequent reuse may cause it to be wrapped in a lib file.
> >
> > Signed-off-by: Jinrong Liang <cloudliang@tencent.com>
> > ---
> >  tools/testing/selftests/kvm/rseq_test.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/tools/testing/selftests/kvm/rseq_test.c b/tools/testing/selftests/kvm/rseq_test.c
> > index a54d4d05a058..299d316cc759 100644
> > --- a/tools/testing/selftests/kvm/rseq_test.c
> > +++ b/tools/testing/selftests/kvm/rseq_test.c
> > @@ -229,7 +229,7 @@ int main(int argc, char *argv[])
> >       ucall_init(vm, NULL);
> >
> >       pthread_create(&migration_thread, NULL, migration_worker,
> > -                    (void *)(unsigned long)gettid());
> > +                    (void *)(unsigned long)syscall(SYS_gettid));
> >
> >       for (i = 0; !done; i++) {
> >               vcpu_run(vcpu);
> > --
> > 2.37.1
> >

On Wed, Aug 03, 2022 at 09:58:51PM +0800, Jinrong Liang wrote:
> My ldd version is (GNU libc) 2.28, and I get a compilation error in this case.
> But I use another ldd (Ubuntu GLIBC 2.31-0ubuntu9.2) 2.31 is compiling fine.
> This shows that compilation errors may occur in different GNU libc environments.
> Would it be more appropriate to use syscall for better compatibility?

OK, it's a pity, but no big deal to use syscall().

Reviewed-by: Andrew Jones <andrew.jones@linux.dev>

Thanks,
drew

On Wed, Aug 03, 2022, Andrew Jones wrote:
> On Wed, Aug 03, 2022 at 09:58:51PM +0800, Jinrong Liang wrote:
> > My ldd version is (GNU libc) 2.28, and I get a compilation error in this case.
> > But I use another ldd (Ubuntu GLIBC 2.31-0ubuntu9.2) 2.31 is compiling fine.
> > This shows that compilation errors may occur in different GNU libc environments.
> > Would it be more appropriate to use syscall for better compatibility?
> 
> OK, it's a pity, but no big deal to use syscall().

Ya, https://man7.org/linux/man-pages/man2/gettid.2.html says:

  The gettid() system call first appeared on Linux in kernel 2.4.11.  Library
  support was added in glibc 2.30.

But there are already two other instances of syscall(SYS_gettid) in KVM selftests,
tools/testing/selftests/kvm/lib/assert.c even adds a _gettid() wrapper.

So rather than having to remember (or discover) to use syscall(SYS_gettid), I wonder
if it's possible to conditionally define gettid()?  E.g. check for GLIBC version?
Or do

  #define gettid() syscall(SYS_gettid)

so that it's always available and simply overrides the library's gettid() if it's
provided?

On Wed, Aug 03, 2022 at 04:10:53PM +0000, Sean Christopherson wrote:
> On Wed, Aug 03, 2022, Andrew Jones wrote:
> > On Wed, Aug 03, 2022 at 09:58:51PM +0800, Jinrong Liang wrote:
> > > My ldd version is (GNU libc) 2.28, and I get a compilation error in this case.
> > > But I use another ldd (Ubuntu GLIBC 2.31-0ubuntu9.2) 2.31 is compiling fine.
> > > This shows that compilation errors may occur in different GNU libc environments.
> > > Would it be more appropriate to use syscall for better compatibility?
> > 
> > OK, it's a pity, but no big deal to use syscall().
> 
> Ya, https://man7.org/linux/man-pages/man2/gettid.2.html says:
> 
>   The gettid() system call first appeared on Linux in kernel 2.4.11.  Library
>   support was added in glibc 2.30.
> 
> But there are already two other instances of syscall(SYS_gettid) in KVM selftests,
> tools/testing/selftests/kvm/lib/assert.c even adds a _gettid() wrapper.

Ha! And I found four more in selftests...

testing/selftests/powerpc/include/utils.h
testing/selftests/proc/proc.h
testing/selftests/rseq/param_test.c
testing/selftests/sched/cs_prctl_test.c

and even more in tools...

> 
> So rather than having to remember (or discover) to use syscall(SYS_gettid), I wonder
> if it's possible to conditionally define gettid()?  E.g. check for GLIBC version?
> Or do
> 
>   #define gettid() syscall(SYS_gettid)
> 
> so that it's always available and simply overrides the library's gettid() if it's
> provided?

Sounds good to me. Now the question is where to put it? kvm_util.h,
test_util.h, or maybe we should create a new header just for stuff
like this?

It doesn't really "fit" in kvm_util.h, but if we put it there, then we
greatly reduce the chance that we'll have to revisit this issue again.
We could also create a new header just for stuff like this and then
include that from kvm_util.h...

Thanks,
drew

On Wed, Aug 03, 2022, Andrew Jones wrote:
> On Wed, Aug 03, 2022 at 04:10:53PM +0000, Sean Christopherson wrote:
> > On Wed, Aug 03, 2022, Andrew Jones wrote:
> > > On Wed, Aug 03, 2022 at 09:58:51PM +0800, Jinrong Liang wrote:
> > > > My ldd version is (GNU libc) 2.28, and I get a compilation error in this case.
> > > > But I use another ldd (Ubuntu GLIBC 2.31-0ubuntu9.2) 2.31 is compiling fine.
> > > > This shows that compilation errors may occur in different GNU libc environments.
> > > > Would it be more appropriate to use syscall for better compatibility?
> > > 
> > > OK, it's a pity, but no big deal to use syscall().
> > 
> > Ya, https://man7.org/linux/man-pages/man2/gettid.2.html says:
> > 
> >   The gettid() system call first appeared on Linux in kernel 2.4.11.  Library
> >   support was added in glibc 2.30.
> > 
> > But there are already two other instances of syscall(SYS_gettid) in KVM selftests,
> > tools/testing/selftests/kvm/lib/assert.c even adds a _gettid() wrapper.
> 
> Ha! And I found four more in selftests...
> 
> testing/selftests/powerpc/include/utils.h
> testing/selftests/proc/proc.h
> testing/selftests/rseq/param_test.c
> testing/selftests/sched/cs_prctl_test.c
> 
> and even more in tools...

Ha, and tools/testing/selftests/sched/cs_prctl_test.c even has the GLIBC crud.

#if __GLIBC_PREREQ(2, 30) == 0
#include <sys/syscall.h>
static pid_t gettid(void)
{
	return syscall(SYS_gettid);
}
#endif

> > So rather than having to remember (or discover) to use syscall(SYS_gettid), I wonder
> > if it's possible to conditionally define gettid()?  E.g. check for GLIBC version?
> > Or do
> > 
> >   #define gettid() syscall(SYS_gettid)
> > 
> > so that it's always available and simply overrides the library's gettid() if it's
> > provided?
> 
> Sounds good to me. Now the question is where to put it? kvm_util.h,
> test_util.h, or maybe we should create a new header just for stuff
> like this?

tools/include/uapi/linux/syscall.h?

Kind of dirty, but not thaaaat dirty.