[Intel-gfx] [PATCH] drm/i915: Enable fine-grained kcov instrumentation

[Chris Wilson]

In the next merge, we can build support for kcov at the individual file,
or driver level. This is useful to filter out the noise when doing
coverage test, i.e. we do get edges through code outside of i915.ko.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/Kconfig.debug | 12 ++++++++++++
 drivers/gpu/drm/i915/Makefile      |  1 +
 2 files changed, 13 insertions(+)

diff --git a/drivers/gpu/drm/i915/Kconfig.debug b/drivers/gpu/drm/i915/Kconfig.debug
index cee87bfd10c4..eb38270d0ecd 100644
--- a/drivers/gpu/drm/i915/Kconfig.debug
+++ b/drivers/gpu/drm/i915/Kconfig.debug
@@ -42,3 +42,15 @@ config DRM_I915_DEBUG_GEM
 
           If in doubt, say "N".
 
+config DRM_I915_KCOV
+	bool "Generate fine-grained code coverage (for kcov)"
+	default n
+	select KCOV
+	help
+	  Enable instrumentation of i915.ko to generate coverage via kcov
+	  (/sys/kernel/debug/kcov). This allows coverage driven fuzzing,
+	  such as AFL, to be used and focused on the driver.
+
+	  Recommended for driver developers only.
+
+	  If in doubt, say "N".
diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
index 0afe7b3cad07..2f4bbaca5b60 100644
--- a/drivers/gpu/drm/i915/Makefile
+++ b/drivers/gpu/drm/i915/Makefile
@@ -3,6 +3,7 @@
 # Direct Rendering Infrastructure (DRI) in XFree86 4.1.0 and higher.
 
 subdir-ccflags-$(CONFIG_DRM_I915_WERROR) := -Werror
+subdir-ccflags-$(CONFIG_DRM_I915_KCOV) := $(CFLAGS_KCOV)
 subdir-ccflags-y += \
 	$(call as-instr,movntdqa (%eax)$(comma)%xmm0,-DCONFIG_AS_MOVNTDQA)
 
-- 
2.8.1