selftests/livepatch: Don't clear dmesg when running tests

Inspired by commit f131d9edc2 ("selftests/lkdtm: Don't clear dmesg
when running tests"), keep a reference dmesg copy when beginning each
test.  This way check_result() can compare against the initial copy
rather than relying upon an empty log.

Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
Reviewed-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Reviewed-by: Yannick Cote <ycote@redhat.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20200618181040.21132-2-joe.lawrence@redhat.com

tools/testing/selftests/livepatch/test-callbacks.sh

@@ -12,8 +12,6 @@ MOD_TARGET_BUSY=test_klp_callbacks_busy
 setup_config
 
 
-# TEST: target module before livepatch
-#
 # Test a combination of loading a kernel module and a livepatch that
 # patches a function in the first module.  Load the target module
 # before the livepatch module.  Unload them in the same order.
@@ -28,8 +26,7 @@ setup_config
 #   unpatching transition starts.  klp_objects are reverted, post-patch
 #   callbacks execute and the transition completes.
 
-echo -n "TEST: target module before livepatch ... "
-dmesg -C
+start_test "target module before livepatch"
 
 load_mod $MOD_TARGET
 load_lp $MOD_LIVEPATCH
@@ -63,8 +60,6 @@ livepatch: '$MOD_LIVEPATCH': unpatching complete
 $MOD_TARGET: ${MOD_TARGET}_exit"
 
 
-# TEST: module_coming notifier
-#
 # This test is similar to the previous test, but (un)load the livepatch
 # module before the target kernel module.  This tests the livepatch
 # core's module_coming handler.
@@ -78,8 +73,7 @@ $MOD_TARGET: ${MOD_TARGET}_exit"
 # - On livepatch disable, all currently loaded klp_objects' (vmlinux and
 #   $MOD_TARGET) pre/post-unpatch callbacks are executed.
 
-echo -n "TEST: module_coming notifier ... "
-dmesg -C
+start_test "module_coming notifier"
 
 load_lp $MOD_LIVEPATCH
 load_mod $MOD_TARGET
@@ -114,8 +108,6 @@ livepatch: '$MOD_LIVEPATCH': unpatching complete
 $MOD_TARGET: ${MOD_TARGET}_exit"
 
 
-# TEST: module_going notifier
-#
 # Test loading the livepatch after a targeted kernel module, then unload
 # the kernel module before disabling the livepatch.  This tests the
 # livepatch core's module_going handler.
@@ -129,8 +121,7 @@ $MOD_TARGET: ${MOD_TARGET}_exit"
 # - When the livepatch is disabled, pre and post-unpatch callbacks are
 #   run for the remaining klp_object, vmlinux.
 
-echo -n "TEST: module_going notifier ... "
-dmesg -C
+start_test "module_going notifier"
 
 load_mod $MOD_TARGET
 load_lp $MOD_LIVEPATCH
@@ -165,8 +156,6 @@ livepatch: '$MOD_LIVEPATCH': unpatching complete
 % rmmod $MOD_LIVEPATCH"
 
 
-# TEST: module_coming and module_going notifiers
-#
 # This test is similar to the previous test, however the livepatch is
 # loaded first.  This tests the livepatch core's module_coming and
 # module_going handlers.
@@ -180,8 +169,7 @@ livepatch: '$MOD_LIVEPATCH': unpatching complete
 #   from the $MOD_TARGET klp_object.  As such, only pre and
 #   post-unpatch callbacks are executed when this occurs.
 
-echo -n "TEST: module_coming and module_going notifiers ... "
-dmesg -C
+start_test "module_coming and module_going notifiers"
 
 load_lp $MOD_LIVEPATCH
 load_mod $MOD_TARGET
@@ -217,8 +205,6 @@ livepatch: '$MOD_LIVEPATCH': unpatching complete
 % rmmod $MOD_LIVEPATCH"
 
 
-# TEST: target module not present
-#
 # A simple test of loading a livepatch without one of its patch target
 # klp_objects ever loaded ($MOD_TARGET).
 #
@@ -227,8 +213,7 @@ livepatch: '$MOD_LIVEPATCH': unpatching complete
 # - As expected, only pre/post-(un)patch handlers are executed for
 #   vmlinux.
 
-echo -n "TEST: target module not present ... "
-dmesg -C
+start_test "target module not present"
 
 load_lp $MOD_LIVEPATCH
 disable_lp $MOD_LIVEPATCH
@@ -252,8 +237,6 @@ livepatch: '$MOD_LIVEPATCH': unpatching complete
 % rmmod $MOD_LIVEPATCH"
 
 
-# TEST: pre-patch callback -ENODEV
-#
 # Test a scenario where a vmlinux pre-patch callback returns a non-zero
 # status (ie, failure).
 #
@@ -265,8 +248,7 @@ livepatch: '$MOD_LIVEPATCH': unpatching complete
 #   The result is that the insmod command refuses to load the livepatch
 #   module.
 
-echo -n "TEST: pre-patch callback -ENODEV ... "
-dmesg -C
+start_test "pre-patch callback -ENODEV"
 
 load_mod $MOD_TARGET
 load_failing_mod $MOD_LIVEPATCH pre_patch_ret=-19
@@ -288,8 +270,6 @@ modprobe: ERROR: could not insert '$MOD_LIVEPATCH': No such device
 $MOD_TARGET: ${MOD_TARGET}_exit"
 
 
-# TEST: module_coming + pre-patch callback -ENODEV
-#
 # Similar to the previous test, setup a livepatch such that its vmlinux
 # pre-patch callback returns success.  However, when a targeted kernel
 # module is later loaded, have the livepatch return a failing status
@@ -307,8 +287,7 @@ $MOD_TARGET: ${MOD_TARGET}_exit"
 #
 # - Pre/post-unpatch callbacks are run for the vmlinux klp_object.
 
-echo -n "TEST: module_coming + pre-patch callback -ENODEV ... "
-dmesg -C
+start_test "module_coming + pre-patch callback -ENODEV"
 
 load_lp $MOD_LIVEPATCH
 set_pre_patch_ret $MOD_LIVEPATCH -19
@@ -341,8 +320,6 @@ livepatch: '$MOD_LIVEPATCH': unpatching complete
 % rmmod $MOD_LIVEPATCH"
 
 
-# TEST: multiple target modules
-#
 # Test loading multiple targeted kernel modules.  This test-case is
 # mainly for comparing with the next test-case.
 #
@@ -353,8 +330,7 @@ livepatch: '$MOD_LIVEPATCH': unpatching complete
 #   module.  Post-patch callbacks are executed and the transition
 #   completes quickly.
 
-echo -n "TEST: multiple target modules ... "
-dmesg -C
+start_test "multiple target modules"
 
 load_mod $MOD_TARGET_BUSY block_transition=N
 load_lp $MOD_LIVEPATCH
@@ -402,8 +378,6 @@ livepatch: '$MOD_LIVEPATCH': unpatching complete
 $MOD_TARGET_BUSY: ${MOD_TARGET_BUSY}_exit"
 
 
-# TEST: busy target module
-#
 # A similar test as the previous one, but force the "busy" kernel module
 # to block the livepatch transition.
 #
@@ -431,8 +405,7 @@ $MOD_TARGET_BUSY: ${MOD_TARGET_BUSY}_exit"
 #   klp_object's post-patch callbacks executed, the remaining
 #   klp_object's pre-unpatch callbacks are skipped.
 
-echo -n "TEST: busy target module ... "
-dmesg -C
+start_test "busy target module"
 
 load_mod $MOD_TARGET_BUSY block_transition=Y
 load_lp_nowait $MOD_LIVEPATCH
@@ -478,8 +451,6 @@ $MOD_TARGET_BUSY: busymod_work_func exit
 $MOD_TARGET_BUSY: ${MOD_TARGET_BUSY}_exit"
 
 
-# TEST: multiple livepatches
-#
 # Test loading multiple livepatches.  This test-case is mainly for comparing
 # with the next test-case.
 #
@@ -487,8 +458,7 @@ $MOD_TARGET_BUSY: ${MOD_TARGET_BUSY}_exit"
 #   execute as each patch progresses through its (un)patching
 #   transition.
 
-echo -n "TEST: multiple livepatches ... "
-dmesg -C
+start_test "multiple livepatches"
 
 load_lp $MOD_LIVEPATCH
 load_lp $MOD_LIVEPATCH2
@@ -531,8 +501,6 @@ livepatch: '$MOD_LIVEPATCH': unpatching complete
 % rmmod $MOD_LIVEPATCH"
 
 
-# TEST: atomic replace
-#
 # Load multiple livepatches, but the second as an 'atomic-replace'
 # patch.  When the latter loads, the original livepatch should be
 # disabled and *none* of its pre/post-unpatch callbacks executed.  On
@@ -547,8 +515,7 @@ livepatch: '$MOD_LIVEPATCH': unpatching complete
 # - Once the atomic replace module is loaded, only its pre and post
 #   unpatch callbacks are executed.
 
-echo -n "TEST: atomic replace ... "
-dmesg -C
+start_test "atomic replace"
 
 load_lp $MOD_LIVEPATCH
 load_lp $MOD_LIVEPATCH2 replace=1