compat_ioctl: handle PPPIOCGIDLE for 64-bit time_t

The ppp_idle structure is defined in terms of __kernel_time_t, which is
defined as 'long' on all architectures, and this usage is not affected
by the y2038 problem since it transports a time interval rather than an
absolute time.

However, the ppp user space defines the same structure as time_t, which
may be 64-bit wide on new libc versions even on 32-bit architectures.

It's easy enough to just handle both possible structure layouts on
all architectures, to deal with the possibility that a user space ppp
implementation comes with its own ppp_idle structure definition, as well
as to document the fact that the driver is y2038-safe.

Doing this also avoids the need for a special compat mode translation,
since 32-bit and 64-bit kernels now support the same interfaces.  The old
32-bit structure is also available on native 64-bit architectures now,
but this is harmless.

Cc: netdev@vger.kernel.org
Cc: linux-ppp@vger.kernel.org
Cc: Paul Mackerras <paulus@samba.org>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

2 files changed, 16 insertions, 0 deletions

diff --git a/include/uapi/linux/ppp-ioctl.h b/include/uapi/linux/ppp-ioctl.h
index 88b5f9990320..7bd2a5a75348 100644
--- a/include/uapi/linux/ppp-ioctl.h
+++ b/include/uapi/linux/ppp-ioctl.h
@@ -104,6 +104,8 @@ struct pppol2tp_ioc_stats {
 #define PPPIOCGDEBUG	_IOR('t', 65, int)	/* Read debug level */
 #define PPPIOCSDEBUG	_IOW('t', 64, int)	/* Set debug level */
 #define PPPIOCGIDLE	_IOR('t', 63, struct ppp_idle) /* get idle time */
+#define PPPIOCGIDLE32	_IOR('t', 63, struct ppp_idle32) /* 32-bit times */
+#define PPPIOCGIDLE64	_IOR('t', 63, struct ppp_idle64) /* 64-bit times */
 #define PPPIOCNEWUNIT	_IOWR('t', 62, int)	/* create new ppp unit */
 #define PPPIOCATTACH	_IOW('t', 61, int)	/* attach to ppp unit */
 #define PPPIOCDETACH	_IOW('t', 60, int)	/* obsolete, do not use */
diff --git a/include/uapi/linux/ppp_defs.h b/include/uapi/linux/ppp_defs.h
index fff51b91b409..0039fa39a358 100644
--- a/include/uapi/linux/ppp_defs.h
+++ b/include/uapi/linux/ppp_defs.h
@@ -142,10 +142,24 @@ struct ppp_comp_stats {
 /*
  * The following structure records the time in seconds since
  * the last NP packet was sent or received.
+ *
+ * Linux implements both 32-bit and 64-bit time_t versions
+ * for compatibility with user space that defines ppp_idle
+ * based on the libc time_t.
  */
 struct ppp_idle {
     __kernel_time_t xmit_idle;	/* time since last NP packet sent */
     __kernel_time_t recv_idle;	/* time since last NP packet received */
 };
 
+struct ppp_idle32 {
+    __s32 xmit_idle;		/* time since last NP packet sent */
+    __s32 recv_idle;		/* time since last NP packet received */
+};
+
+struct ppp_idle64 {
+    __s64 xmit_idle;		/* time since last NP packet sent */
+    __s64 recv_idle;		/* time since last NP packet received */
+};
+
 #endif /* _UAPI_PPP_DEFS_H_ */