[stgt] [PATCH 1/2] Compile iser driver as a loadable module

[Andy Grover]

Drivers are already modularized in the code, so it is straightforward to
change the build to target a separate loadable module. Also, modify
get_driver_index to try to load a module when lld is unknown.

This will allow packaging of base tgtd and iser module separately, so
the majority of users will not have to install dependencies they don't
need.

Signed-off-by: Andy Grover <agrover at redhat.com>
---
 usr/Makefile |   30 ++++++++++++++++++++----------
 usr/driver.c |   15 +++++++++++++++
 2 files changed, 35 insertions(+), 10 deletions(-)

diff --git a/usr/Makefile b/usr/Makefile
index e15ff6a..b8ab805 100644
--- a/usr/Makefile
+++ b/usr/Makefile
@@ -1,4 +1,5 @@
 sbindir ?= $(PREFIX)/sbin
+libdir ?= $(PREFIX)/lib/tgt
 
 ifneq ($(shell test -e /usr/include/linux/signalfd.h && echo 1),)
 CFLAGS += -DUSE_SIGNALFD
@@ -13,11 +14,6 @@ TGTD_OBJS += $(addprefix iscsi/, conn.o param.o session.o \
 		isns.o)
 TGTD_OBJS += bs_rdwr.o bs_aio.o
 
-ifneq ($(ISCSI_RDMA),)
-TGTD_OBJS += iscsi/iser.o iscsi/iser_text.o
-LIBS += -libverbs -lrdmacm
-endif
-
 INCLUDES += -I.
 
 CFLAGS += -D_GNU_SOURCE
@@ -30,9 +26,13 @@ endif
 CFLAGS += -Wall -Wstrict-prototypes -fPIC
 CFLAGS += -DTGT_VERSION=\"$(VERSION)$(EXTRAVERSION)\"
 
-LIBS += -lpthread
+LIBS += -lpthread -ldl
 
 PROGRAMS += tgtd tgtadm tgtimg
+ifneq ($(ISCSI_RDMA),)
+DRIVERS += tgt-iser.so
+endif
+
 TGTD_OBJS += tgtd.o mgmt.o target.o scsi.o log.o driver.o util.o work.o \
 		parser.o spc.o sbc.o mmc.o osd.o scc.o smc.o \
 		ssc.o bs_ssc.o libssc.o \
@@ -41,10 +41,12 @@ TGTD_OBJS += tgtd.o mgmt.o target.o scsi.o log.o driver.o util.o work.o \
 TGTD_DEP = $(TGTD_OBJS:.o=.d)
 
 .PHONY:all
-all: $(PROGRAMS)
+all: $(PROGRAMS) $(DRIVERS)
+
+LDFLAGS = -Wl,-E,-rpath=$(libdir)
 
 tgtd: $(TGTD_OBJS)
-	$(CC) $^ -o $@ $(LIBS)
+	$(CC) $^ -o $@ $(LDFLAGS) $(LIBS)
 
 -include $(TGTD_DEP)
 
@@ -58,15 +60,23 @@ tgtimg: tgtimg.o libssc.o libcrc32c.o
 
 -include tgtimg.d libssc.d
 
+tgt-iser.so: CFLAGS += -shared -libverbs -lrdmacm
+tgt-iser.so: iscsi/iser.o iscsi/iser_text.o
+	$(CC) $(CFLAGS) -o $@ $^
+
 %.o: %.c
 	$(CC) -c $(CFLAGS) $*.c -o $*.o
 	@$(CC) -MM $(CFLAGS) -MF $*.d -MT $*.o $*.c
 
 .PHONY: install
-install: $(PROGRAMS)
+install: $(PROGRAMS) $(DRIVERS)
 	install -d -m 755 $(DESTDIR)$(sbindir)
 	install -m 755 $(PROGRAMS) $(DESTDIR)$(sbindir)
+ifneq ($(DRIVERS),)
+	install -d -m 755 $(DESTDIR)$(libdir)
+	install -m 755 $(DRIVERS) $(DESTDIR)$(libdir)
+endif
 
 .PHONY: clean
 clean:
-	rm -f *.[od] $(PROGRAMS) iscsi/*.[od] ibmvio/*.[od] fc/*.[od]
+	rm -f *.[od] $(PROGRAMS) *.so iscsi/*.[od] ibmvio/*.[od] fc/*.[od]
diff --git a/usr/driver.c b/usr/driver.c
index f9e0d57..8e7e368 100644
--- a/usr/driver.c
+++ b/usr/driver.c
@@ -22,6 +22,8 @@
 #include <errno.h>
 #include <string.h>
 #include <inttypes.h>
+#include <stdio.h>
+#include <dlfcn.h>
 
 #include "list.h"
 #include "tgtd.h"
@@ -36,12 +38,25 @@ struct tgt_driver *tgt_drivers[MAX_NR_DRIVERS] = {
 int get_driver_index(char *name)
 {
 	int i;
+	char tmp_name[32];
+	void *handle;
 
 	for (i = 0; tgt_drivers[i]; i++) {
 		if (!strcmp(name, tgt_drivers[i]->name))
 			return i;
 	}
 
+	/* try loading a driver, then check again */
+	snprintf(tmp_name, sizeof(tmp_name), "tgt-%s.so", name);
+
+	handle = dlopen(tmp_name, RTLD_LAZY);
+	if (handle) {
+		for (i = 0; tgt_drivers[i]; i++) {
+			if (!strcmp(name, tgt_drivers[i]->name))
+				return i;
+		}
+	}
+
 	return -ENOENT;
 }
 
-- 
1.7.1

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