linux-user: Add support for KCOV_<ENABLE|DISABLE> ioctls

KCOV_ENABLE and KCOV_DISABLE play the role in kernel coverage
tracing. These ioctls do not use the third argument of ioctl()
system call and are straightforward to implement in QEMU.

Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Signed-off-by: Aleksandar Markovic <amarkovic@wavecomp.com>
Message-Id: <1579214991-19602-12-git-send-email-aleksandar.markovic@rt-rk.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

linux-user/ioctls.h

@@ -534,3 +534,8 @@
   IOCTL_IGNORE(TIOCSTART)
   IOCTL_IGNORE(TIOCSTOP)
 #endif
+
+#ifdef CONFIG_KCOV
+  IOCTL(KCOV_ENABLE, 0, TYPE_NULL)
+  IOCTL(KCOV_DISABLE, 0, TYPE_NULL)
+#endif

linux-user/syscall.c

@@ -73,6 +73,9 @@
 #ifdef CONFIG_SENDFILE
 #include <sys/sendfile.h>
 #endif
+#ifdef CONFIG_KCOV
+#include <sys/kcov.h>
+#endif
 
 #define termios host_termios
 #define winsize host_winsize

linux-user/syscall_defs.h

@@ -2434,6 +2434,10 @@ struct target_mtpos {
 #define TARGET_MTIOCGET        TARGET_IOR('m', 2, struct target_mtget)
 #define TARGET_MTIOCPOS        TARGET_IOR('m', 3, struct target_mtpos)
 
+/* kcov ioctls */
+#define TARGET_KCOV_ENABLE     TARGET_IO('c', 100)
+#define TARGET_KCOV_DISABLE    TARGET_IO('c', 101)
+
 struct target_sysinfo {
     abi_long uptime;                /* Seconds since boot */
     abi_ulong loads[3];             /* 1, 5, and 15 minute load averages */