util/compatfd.c: use libc signalfd wrapper instead of raw syscall

This allows the use of native signalfd instead of the sigtimedwait
based emulation on systems other than Linux.

Signed-off-by: Kacper Słomiński <kacper.slominski72@gmail.com>
Message-Id: <20210905011621.200785-1-kacper.slominski72@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

meson.build

@@ -1420,10 +1420,9 @@ config_host_data.set('CONFIG_POSIX_MADVISE', cc.links(gnu_source_prefix + '''
   #include <stddef.h>
   int main(void) { return posix_madvise(NULL, 0, POSIX_MADV_DONTNEED); }'''))
 config_host_data.set('CONFIG_SIGNALFD', cc.links(gnu_source_prefix + '''
-  #include <unistd.h>
-  #include <sys/syscall.h>
-  #include <signal.h>
-  int main(void) { return syscall(SYS_signalfd, -1, NULL, _NSIG / 8); }'''))
+  #include <sys/signalfd.h>
+  #include <stddef.h>
+  int main(void) { return signalfd(-1, NULL, SFD_CLOEXEC); }'''))
 config_host_data.set('CONFIG_SPLICE', cc.links(gnu_source_prefix + '''
   #include <unistd.h>
   #include <fcntl.h>

util/compatfd.c

@@ -17,7 +17,7 @@
 #include "qemu/thread.h"
 
 #if defined(CONFIG_SIGNALFD)
-#include <sys/syscall.h>
+#include <sys/signalfd.h>
 #endif
 
 struct sigfd_compat_info {
@@ -96,9 +96,8 @@ int qemu_signalfd(const sigset_t *mask)
 #if defined(CONFIG_SIGNALFD)
     int ret;
 
-    ret = syscall(SYS_signalfd, -1, mask, _NSIG / 8);
+    ret = signalfd(-1, mask, SFD_CLOEXEC);
     if (ret != -1) {
-        qemu_set_cloexec(ret);
         return ret;
     }
 #endif