kcov: ignore fault-inject and stacktrace

Don't instrument 3 more files that contain debugging facilities and
produce large amounts of uninteresting coverage for every syscall.

The following snippets are sprinkled all over the place in kcov traces
in a debugging kernel.  We already try to disable instrumentation of
stack unwinding code and of most debug facilities.  I guess we did not
use fault-inject.c at the time, and stacktrace.c was somehow missed (or
something has changed in kernel/configs).  This change both speeds up
kcov (kernel doesn't need to store these PCs, user-space doesn't need to
process them) and frees trace buffer capacity for more useful coverage.

  should_fail
  lib/fault-inject.c:149
  fail_dump
  lib/fault-inject.c:45

  stack_trace_save
  kernel/stacktrace.c:124
  stack_trace_consume_entry
  kernel/stacktrace.c:86
  stack_trace_consume_entry
  kernel/stacktrace.c:89
  ... a hundred frames skipped ...
  stack_trace_consume_entry
  kernel/stacktrace.c:93
  stack_trace_consume_entry
  kernel/stacktrace.c:86

Link: http://lkml.kernel.org/r/20200116111449.217744-1-dvyukov@gmail.com
Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/Makefile b/kernel/Makefile
index f2cc0d118a0bcc4b0b10cce6a4a1ca4f4740d736..4cb4130ced32936b5060e6b05daa23e03fd6aa1e 100644 (file)
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -27,6 +27,7 @@ KCOV_INSTRUMENT_softirq.o := n
 # and produce insane amounts of uninteresting coverage.
 KCOV_INSTRUMENT_module.o := n
 KCOV_INSTRUMENT_extable.o := n
+KCOV_INSTRUMENT_stacktrace.o := n
 # Don't self-instrument.
 KCOV_INSTRUMENT_kcov.o := n
 KASAN_SANITIZE_kcov.o := n

diff --git a/lib/Makefile b/lib/Makefile
index 5fb02b93b1dcfa862e4ad0900c76fc1ff1cdf339..23ca78d43d247ec09e301781e1fd4d049e76f04a 100644 (file)
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -16,6 +16,7 @@ KCOV_INSTRUMENT_rbtree.o := n
 KCOV_INSTRUMENT_list_debug.o := n
 KCOV_INSTRUMENT_debugobjects.o := n
 KCOV_INSTRUMENT_dynamic_debug.o := n
+KCOV_INSTRUMENT_fault-inject.o := n
 
 # Early boot use of cmdline, don't instrument it
 ifdef CONFIG_AMD_MEM_ENCRYPT

diff --git a/mm/Makefile b/mm/Makefile
index 1937cc2518836dde1e2555345ba33e7a413509c4..32f08e22e82478c5530927903e324892df3f5b77 100644 (file)
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -20,6 +20,7 @@ KCOV_INSTRUMENT_kmemleak.o := n
 KCOV_INSTRUMENT_memcontrol.o := n
 KCOV_INSTRUMENT_mmzone.o := n
 KCOV_INSTRUMENT_vmstat.o := n
+KCOV_INSTRUMENT_failslab.o := n
 
 CFLAGS_init-mm.o += $(call cc-disable-warning, override-init)
 CFLAGS_init-mm.o += $(call cc-disable-warning, initializer-overrides)