Re: [PATCH] selftests: kvm: Fix a compile error in selftests/kvm/rseq_test.c

[Andrew Jones <andrew.jones@linux.dev>]

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
>