Make ftrace tests work with remote targets

When we build a shared library for testing, it is built differently
whether it is meant for the local system or a remote one.  When it is
for the local system, the library is built with no SONAME.  So when the
executable is built, roughly in this way:

  $ gcc testfile.c /path/to/library.so

the executable will contain an absolute reference to the library.  For
example:

  $ readelf -a testsuite/gdb.python/py-shared | grep NEEDED
   0x0000000000000001 (NEEDED)             Shared library: [/home/emaisin/build/binutils-gdb/gdb/testsuite/gdb.python/py-shared-sl.sl]

When testing is done remotely, the absolute path obviously doesn't work.
Therefore, we build the library with an SONAME:

  $ readelf -a testsuite/gdb.python/py-shared-sl.sl | grep SONAME
   0x000000000000000e (SONAME)             Library soname: [py-shared-sl.sl]

which ends up in the executable's NEEDED field:

  $ readelf -a testsuite/gdb.python/py-shared | grep NEEDED
   0x0000000000000001 (NEEDED)             Shared library: [py-shared-sl.sl]

The executable and the library are then uploaded side-by-side on the
remote system.  To allow the dynamic linker to find the shared library,
we have to add the special RPATH value $ORIGIN, which tells it to search
in the executable's directory:

  $ readelf -a testsuite/gdb.python/py-shared | grep ORIGIN
   0x000000000000000f (RPATH)              Library rpath: [$ORIGIN]

The problem with the IPA library is that it doesn't have an SONAME,
making it very difficult to do testing on a remote board.  When a
test executable is linked with it, it contains an absolute reference to
the library path.  Therefore, unless the paths on the target are the
same as on the build system, it won't work.

To make it possible for tests using the IPA library to run test on
remote boards, I suggest adding an SONAME to libinproctrace.so.  I don't
think it should be a big problem for users.  All the libraries installed
on my system have an SONAME, so it should be fine if libinproctrace.so
does too.

As a consequence, native testing does not work anymore, since
executables do not contain the absolute path to the library anymore.  To
keep them working, we can have gdb_load_shlibs copy the library to the
test directory when testing natively.  That's done by modifying
gdb_load_shlibs.  We also have to add RPATH=$ORIGIN to executables, even
when testing natively.

I think it's a good change in general, as it reduces the differences
between testing a native and a remote target.  To further reduce those
differences, we can also always build test shared libraries with an
SONAME.

ftrace.exp and ftrace-lock.exp need to be modified slightly.  The code
checks that the IPA library is loaded using the absolute path on the
build machine.  That obviously doesn't work if the test is done
remotely, as the path will be different.  I changed the tests to only
search for the library basename (e.g. libinproctrace.so).

gdb/gdbserver/ChangeLog:

	* Makefile.in ($(IPA_LIB)): Set SONAME of the IPA lib.

gdb/testsuite/ChangeLog:

	* gdb.trace/ftrace-lock.exp: Check for IPA basename instead of
	absolute.
	* gdb.trace/ftrace.exp: Likewise.
	* lib/gdb.exp (gdb_compile): Set rpath $ORIGIN for non-remote
	targets as well.
	(gdb_compile_shlib): Set SONAME for non-remote targets as well.
	(gdb_load_shlibs): Copy libraries to test directory when testing
	natively.  Only set solib-search-path if testing remotely.
	* lib/mi-support.exp (mi_load_shlibs): Likewise.

2 files changed, 32 insertions, 28 deletions

diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
index 4e5c89b..1ef6a96 100644
--- a/gdb/testsuite/lib/gdb.exp
+++ b/gdb/testsuite/lib/gdb.exp
@@ -3369,12 +3369,10 @@ proc gdb_compile {source dest type options} {
         }
     }
 
-    # We typically link to shared libraries using an absolute path, and
-    # that's how they are found at runtime.  If we are going to
-    # dynamically load one by basename, we must specify rpath.  If we
-    # are using a remote host, DejaGNU will link to the shared library
-    # using a relative path, so again we must specify an rpath.
-    if { $shlib_load || ($shlib_found && [is_remote target]) } {
+    # Because we link with libraries using their basename, we may need
+    # (depending on the platform) to set a special rpath value, to allow
+    # the executable to find the libraries it depends on.
+    if { $shlib_load || $shlib_found } {
 	if { ([istarget "*-*-mingw*"]
 	      || [istarget *-*-cygwin*]
 	      || [istarget *-*-pe*]) } {
@@ -3585,14 +3583,16 @@ proc gdb_compile_shlib {sources dest options} {
 		set name ${dest}
 	    }
 	    lappend link_options "additional_flags=-Wl,--out-implib,${name}.a"
-	} elseif [is_remote target] {
-	    # By default, we do not set the soname.  This causes the linker
-	    # on ELF systems to create a DT_NEEDED entry in the executable
-	    # refering to the full path name of the library.  This is a
-	    # problem in remote testing if the library is in a different
-	    # directory there.  To fix this, we set a soname of just the
-	    # base filename for the library, and add an appropriate -rpath
-	    # to the main executable (in gdb_compile).
+	} else {
+	    # Set the soname of the library.  This causes the linker on ELF
+	    # systems to create the DT_NEEDED entry in the executable referring
+	    # to the soname of the library, and not its absolute path.  This
+	    # (using the absolute path) would be problem when testing on a
+	    # remote target.
+	    #
+	    # In conjunction with setting the soname, we add the special
+	    # rpath=$ORIGIN value when building the executable, so that it's
+	    # able to find the library in its own directory.
 	    set destbase [file tail $dest]
 	    lappend link_options "additional_flags=-Wl,-soname,$destbase"
 	}
@@ -4226,17 +4226,19 @@ proc gdb_remote_download {dest fromfile {tofile {}}} {
 # Copy the listed libraries to the target.
 
 proc gdb_load_shlibs { args } {
-    if {![is_remote target]} {
-	return
-    }
-
     foreach file $args {
 	gdb_remote_download target [shlib_target_file $file]
     }
 
-    # Even if the target supplies full paths for shared libraries,
-    # they may not be paths for this system.
-    gdb_test "set solib-search-path [file dirname [lindex $args 0]]" "" ""
+    if {[is_remote target]} {
+	# If the target is remote, we need to tell gdb where to find the
+	# libraries.
+	#
+	# We could set this even when not testing remotely, but a user
+	# generally won't set it unless necessary.  In order to make the tests
+	# more like the real-life scenarios, we don't set it for local testing.
+	gdb_test "set solib-search-path [file dirname [lindex $args 0]]" "" ""
+    }
 }
 
 #
diff --git a/gdb/testsuite/lib/mi-support.exp b/gdb/testsuite/lib/mi-support.exp
index cf3005d..87ce634 100644
--- a/gdb/testsuite/lib/mi-support.exp
+++ b/gdb/testsuite/lib/mi-support.exp
@@ -1955,17 +1955,19 @@ proc check_mi_and_console_threads {name} {
 
 # Download shared libraries to the target.
 proc mi_load_shlibs { args } {
-    if {![is_remote target]} {
-	return
-    }
-
     foreach file $args {
 	gdb_remote_download target [shlib_target_file $file]
     }
 
-    # Even if the target supplies full paths for shared libraries,
-    # they may not be paths for this system.
-    mi_gdb_test "set solib-search-path [file dirname [lindex $args 0]]" "\^done" ""
+    if {[is_remote target]} {
+	# If the target is remote, we need to tell gdb where to find the
+	# libraries.
+	#
+	# We could set this even when not testing remotely, but a user
+	# generally won't set it unless necessary.  In order to make the tests
+	# more like the real-life scenarios, we don't set it for local testing.
+	mi_gdb_test "set solib-search-path [file dirname [lindex $args 0]]" "\^done" ""
+    }
 }
 
 proc mi_check_thread_states { states test } {