From d17e0940f79fd96a2bf27413c1fe682dd8ee5bac Mon Sep 17 00:00:00 2001
From: John Baldwin <jhb@FreeBSD.org>
Date: Wed, 5 May 2021 13:58:23 -0700
Subject: [PATCH] Rework compat shims in ifioctl().

Centralize logic for handling compat ioctls into two blocks of code at
the start and end of the ioctl routine.  This avoids the conversion
logic being spread out both in multiple blocks in ifioctl as well as
various helper functions.

Reviewed by:	brooks, kib
Obtained from:	CheriBSD
Sponsored by:	DARPA
Differential Revision:	https://reviews.freebsd.org/D29891
---
 sys/net/if.c | 122 +++++++++++++++++++++------------------------------
 1 file changed, 51 insertions(+), 71 deletions(-)

diff --git a/sys/net/if.c b/sys/net/if.c
index 1e410142747f..a3f5a8dc831a 100644
--- a/sys/net/if.c
+++ b/sys/net/if.c
@@ -2917,38 +2917,6 @@ struct ifconf32 {
 };
 #define	SIOCGIFCONF32	_IOWR('i', 36, struct ifconf32)
 #endif
-
-#ifdef COMPAT_FREEBSD32
-static void
-ifmr_init(struct ifmediareq *ifmr, caddr_t data)
-{
-	struct ifmediareq32 *ifmr32;
-
-	ifmr32 = (struct ifmediareq32 *)data;
-	memcpy(ifmr->ifm_name, ifmr32->ifm_name,
-	    sizeof(ifmr->ifm_name));
-	ifmr->ifm_current = ifmr32->ifm_current;
-	ifmr->ifm_mask = ifmr32->ifm_mask;
-	ifmr->ifm_status = ifmr32->ifm_status;
-	ifmr->ifm_active = ifmr32->ifm_active;
-	ifmr->ifm_count = ifmr32->ifm_count;
-	ifmr->ifm_ulist = (int *)(uintptr_t)ifmr32->ifm_ulist;
-}
-
-static void
-ifmr_update(const struct ifmediareq *ifmr, caddr_t data)
-{
-	struct ifmediareq32 *ifmr32;
-
-	ifmr32 = (struct ifmediareq32 *)data;
-	ifmr32->ifm_current = ifmr->ifm_current;
-	ifmr32->ifm_mask = ifmr->ifm_mask;
-	ifmr32->ifm_status = ifmr->ifm_status;
-	ifmr32->ifm_active = ifmr->ifm_active;
-	ifmr32->ifm_count = ifmr->ifm_count;
-}
-#endif
-
 /*
  * Interface ioctls.
  */
@@ -2956,9 +2924,14 @@ int
 ifioctl(struct socket *so, u_long cmd, caddr_t data, struct thread *td)
 {
 #ifdef COMPAT_FREEBSD32
-	caddr_t saved_data = NULL;
-	struct ifmediareq ifmr;
-	struct ifmediareq *ifmrp = NULL;
+	union {
+		struct ifconf ifc;
+		struct ifmediareq ifmr;
+	} thunk;
+	caddr_t saved_data;
+	u_long saved_cmd;
+	struct ifconf32 *ifc32;
+	struct ifmediareq32 *ifmr32;
 #endif
 	struct ifnet *ifp;
 	struct ifreq *ifr;
@@ -2978,41 +2951,40 @@ ifioctl(struct socket *so, u_long cmd, caddr_t data, struct thread *td)
 	}
 #endif
 
+#ifdef COMPAT_FREEBSD32
+	saved_cmd = cmd;
+	saved_data = data;
+	switch (cmd) {
+	case SIOCGIFCONF32:
+		ifc32 = (struct ifconf32 *)data;
+		thunk.ifc.ifc_len = ifc32->ifc_len;
+		thunk.ifc.ifc_buf = PTRIN(ifc32->ifc_buf);
+		data = (caddr_t)&thunk.ifc;
+		cmd = SIOCGIFCONF;
+		break;
+	case SIOCGIFMEDIA32:
+	case SIOCGIFXMEDIA32:
+		ifmr32 = (struct ifmediareq32 *)data;
+		memcpy(thunk.ifmr.ifm_name, ifmr32->ifm_name,
+		    sizeof(thunk.ifmr.ifm_name));
+		thunk.ifmr.ifm_current = ifmr32->ifm_current;
+		thunk.ifmr.ifm_mask = ifmr32->ifm_mask;
+		thunk.ifmr.ifm_status = ifmr32->ifm_status;
+		thunk.ifmr.ifm_active = ifmr32->ifm_active;
+		thunk.ifmr.ifm_count = ifmr32->ifm_count;
+		thunk.ifmr.ifm_ulist = PTRIN(ifmr32->ifm_ulist);
+		data = (caddr_t)&thunk.ifmr;
+		cmd = _IOC_NEWTYPE(cmd, struct ifmediareq);
+		break;
+	}
+#endif
+
 	switch (cmd) {
 	case SIOCGIFCONF:
 		error = ifconf(cmd, data);
 		goto out_noref;
-
-#ifdef COMPAT_FREEBSD32
-	case SIOCGIFCONF32:
-		{
-			struct ifconf32 *ifc32;
-			struct ifconf ifc;
-
-			ifc32 = (struct ifconf32 *)data;
-			ifc.ifc_len = ifc32->ifc_len;
-			ifc.ifc_buf = PTRIN(ifc32->ifc_buf);
-
-			error = ifconf(SIOCGIFCONF, (void *)&ifc);
-			if (error == 0)
-				ifc32->ifc_len = ifc.ifc_len;
-			goto out_noref;
-		}
-#endif
 	}
 
-#ifdef COMPAT_FREEBSD32
-	switch (cmd) {
-	case SIOCGIFMEDIA32:
-	case SIOCGIFXMEDIA32:
-		ifmrp = &ifmr;
-		ifmr_init(ifmrp, data);
-		cmd = _IOC_NEWTYPE(cmd, struct ifmediareq);
-		saved_data = data;
-		data = (caddr_t)ifmrp;
-	}
-#endif
-
 	ifr = (struct ifreq *)data;
 	switch (cmd) {
 #ifdef VIMAGE
@@ -3102,16 +3074,24 @@ ifioctl(struct socket *so, u_long cmd, caddr_t data, struct thread *td)
 out_ref:
 	if_rele(ifp);
 out_noref:
+	CURVNET_RESTORE();
 #ifdef COMPAT_FREEBSD32
-	if (ifmrp != NULL) {
-		KASSERT((cmd == SIOCGIFMEDIA || cmd == SIOCGIFXMEDIA),
-		    ("ifmrp non-NULL, but cmd is not an ifmedia req 0x%lx",
-		     cmd));
-		data = saved_data;
-		ifmr_update(ifmrp, data);
+	if (error != 0)
+		return (error);
+	switch (saved_cmd) {
+	case SIOCGIFCONF32:
+		ifc32->ifc_len = thunk.ifc.ifc_len;
+		break;
+	case SIOCGIFMEDIA32:
+	case SIOCGIFXMEDIA32:
+		ifmr32->ifm_current = thunk.ifmr.ifm_current;
+		ifmr32->ifm_mask = thunk.ifmr.ifm_mask;
+		ifmr32->ifm_status = thunk.ifmr.ifm_status;
+		ifmr32->ifm_active = thunk.ifmr.ifm_active;
+		ifmr32->ifm_count = thunk.ifmr.ifm_count;
+		break;
 	}
 #endif
-	CURVNET_RESTORE();
 	return (error);
 }