[PATCH] uml: reintroduce pcap support

The pcap support was not working because of some linking problems (expressing
the construct in Kbuild was a bit difficult) and because there was no user
request. Now that this has come back, here's the support.

This has been tested and works on both 32 and 64-bit hosts, even when
"cross-"building 32-bit binaries.

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <[e-mail]>
Cc: Jeff Dike <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

arch/um/Kconfig_net

···
 
 config UML_NET_PCAP
 	bool "pcap transport"
-	depends on UML_NET && BROKEN
+	depends on UML_NET && EXPERIMENTAL
 	help
 	The pcap transport makes a pcap packet stream on the host look
 	like an ethernet device inside UML.  This is useful for making 

arch/um/Makefile

···
 core-y += $(SUBARCH_CORE)
 libs-y += $(SUBARCH_LIBS)
 
+# -Dvmap=kernel_vmap affects everything, and prevents anything from
+# referencing the libpcap.o symbol so named.
+
+CFLAGS += $(CFLAGS-y) -D__arch_um__ -DSUBARCH=\"$(SUBARCH)\" \
+	$(ARCH_INCLUDE) $(MODE_INCLUDE) -Dvmap=kernel_vmap
+
+USER_CFLAGS := $(patsubst -I%,,$(CFLAGS))
+USER_CFLAGS := $(patsubst -D__KERNEL__,,$(USER_CFLAGS)) $(ARCH_INCLUDE) \
+	$(MODE_INCLUDE) $(ARCH_USER_CFLAGS)
+
 # -Derrno=kernel_errno - This turns all kernel references to errno into
 # kernel_errno to separate them from the libc errno.  This allows -fno-common
 # in CFLAGS.  Otherwise, it would cause ld to complain about the two different
 # errnos.
 
-CFLAGS += $(CFLAGS-y) -D__arch_um__ -DSUBARCH=\"$(SUBARCH)\" \
-	$(ARCH_INCLUDE) $(MODE_INCLUDE)
-
-USER_CFLAGS := $(patsubst -I%,,$(CFLAGS))
-USER_CFLAGS := $(patsubst -D__KERNEL__,,$(USER_CFLAGS)) $(ARCH_INCLUDE) \
-	$(MODE_INCLUDE) $(ARCH_USER_CFLAGS)
 CFLAGS += -Derrno=kernel_errno -Dsigprocmask=kernel_sigprocmask
 CFLAGS += $(call cc-option,-fno-unit-at-a-time,)
 

arch/um/drivers/Makefile

···
 slirp-objs := slirp_kern.o slirp_user.o
 daemon-objs := daemon_kern.o daemon_user.o
 mcast-objs := mcast_kern.o mcast_user.o
-#pcap-objs := pcap_kern.o pcap_user.o $(PCAP)
 net-objs := net_kern.o net_user.o
 mconsole-objs := mconsole_kern.o mconsole_user.o
 hostaudio-objs := hostaudio_kern.o
 ubd-objs := ubd_kern.o ubd_user.o
 port-objs := port_kern.o port_user.o
 harddog-objs := harddog_kern.o harddog_user.o
+
+LDFLAGS_pcap.o := -r $(shell $(CC) $(CFLAGS) -print-file-name=libpcap.a)
+
+$(obj)/pcap.o: $(obj)/pcap_kern.o $(obj)/pcap_user.o
+	$(LD) -r -dp -o $@ $^ $(LDFLAGS) $(LDFLAGS_pcap.o)
+#XXX: The call below does not work because the flags are added before the
+# object name, so nothing from the library gets linked.
+#$(call if_changed,ld)
+
+# When the above is fixed, don't forget to add this too!
+#targets := $(obj)/pcap.o
 
 obj-y := stdio_console.o fd.o chan_kern.o chan_user.o line.o
 obj-$(CONFIG_SSL) += ssl.o
···
 obj-$(CONFIG_UML_NET_SLIRP) += slirp.o slip_common.o
 obj-$(CONFIG_UML_NET_DAEMON) += daemon.o 
 obj-$(CONFIG_UML_NET_MCAST) += mcast.o 
-#obj-$(CONFIG_UML_NET_PCAP) += pcap.o $(PCAP)
+obj-$(CONFIG_UML_NET_PCAP) += pcap.o
 obj-$(CONFIG_UML_NET) += net.o 
 obj-$(CONFIG_MCONSOLE) += mconsole.o
 obj-$(CONFIG_MMAPPER) += mmapper_kern.o 
···
 obj-$(CONFIG_BLK_DEV_COW_COMMON) += cow_user.o
 obj-$(CONFIG_UML_RANDOM) += random.o
 
-USER_OBJS := fd.o null.o pty.o tty.o xterm.o slip_common.o
+# pcap_user.o must be added explicitly.
+USER_OBJS := fd.o null.o pty.o tty.o xterm.o slip_common.o pcap_user.o
 
 include arch/um/scripts/Makefile.rules