diff mbox

[v5,27/31] kcov: test compiler capability in Kconfig and correct dependency

Message ID 1527499328-13213-28-git-send-email-yamada.masahiro@socionext.com (mailing list archive)
State New, archived
Headers show

Commit Message

Masahiro Yamada May 28, 2018, 9:22 a.m. UTC 
As Documentation/kbuild/kconfig-language.txt notes, 'select' should be
be used with care - it forces a lower limit of another symbol, ignoring
the dependency.  Currently, KCOV can select GCC_PLUGINS even if arch
does not select HAVE_GCC_PLUGINS.  This could cause the unmet direct
dependency.

Now that Kconfig can test compiler capability, let's handle this in a
more sophisticated way.

There are two ways to enable KCOV; use the compiler that natively
supports -fsanitize-coverage=trace-pc, or build the SANCOV plugin if
the compiler has ability to build GCC plugins.  Hence, the correct
dependency for KCOV is:

  depends on CC_HAS_SANCOV_TRACE_PC || GCC_PLUGINS

You do not need to build the SANCOV plugin if the compiler already
supports -fsanitize-coverage=trace-pc.  Hence, the select should be:

  select GCC_PLUGIN_SANCOV if !CC_HAS_SANCOV_TRACE_PC

With this, GCC_PLUGIN_SANCOV is selected only when necessary, so
scripts/Makefile.gcc-plugins can be cleaner.

I also cleaned up Kconfig and scripts/Makefile.kcov as well.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
---

Changes in v5: None
Changes in v4: None
Changes in v3:
  - Replace the previous 'select -> imply' patch with
    a new approach

Changes in v2:
  - Drop depends on GCC_VERSION

 Makefile                     |  2 +-
 lib/Kconfig.debug            | 11 +++++++----
 scripts/Makefile.gcc-plugins |  6 +-----
 scripts/Makefile.kcov        | 10 ++++++----
 4 files changed, 15 insertions(+), 14 deletions(-)

Comments

Masahiro Yamada June 10, 2018, 2:19 p.m. UTC | #1 
2018-05-28 18:22 GMT+09:00 Masahiro Yamada <yamada.masahiro@socionext.com>:
> As Documentation/kbuild/kconfig-language.txt notes, 'select' should be
> be used with care - it forces a lower limit of another symbol, ignoring
> the dependency.  Currently, KCOV can select GCC_PLUGINS even if arch
> does not select HAVE_GCC_PLUGINS.  This could cause the unmet direct
> dependency.
>
> Now that Kconfig can test compiler capability, let's handle this in a
> more sophisticated way.
>
> There are two ways to enable KCOV; use the compiler that natively
> supports -fsanitize-coverage=trace-pc, or build the SANCOV plugin if
> the compiler has ability to build GCC plugins.  Hence, the correct
> dependency for KCOV is:
>
>   depends on CC_HAS_SANCOV_TRACE_PC || GCC_PLUGINS
>
> You do not need to build the SANCOV plugin if the compiler already
> supports -fsanitize-coverage=trace-pc.  Hence, the select should be:
>
>   select GCC_PLUGIN_SANCOV if !CC_HAS_SANCOV_TRACE_PC
>
> With this, GCC_PLUGIN_SANCOV is selected only when necessary, so
> scripts/Makefile.gcc-plugins can be cleaner.
>
> I also cleaned up Kconfig and scripts/Makefile.kcov as well.
>
> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> Reviewed-by: Kees Cook <keescook@chromium.org>
> ---
>
> Changes in v5: None
> Changes in v4: None
> Changes in v3:
>   - Replace the previous 'select -> imply' patch with
>     a new approach
>
> Changes in v2:
>   - Drop depends on GCC_VERSION
>
>  Makefile                     |  2 +-
>  lib/Kconfig.debug            | 11 +++++++----
>  scripts/Makefile.gcc-plugins |  6 +-----
>  scripts/Makefile.kcov        | 10 ++++++----
>  4 files changed, 15 insertions(+), 14 deletions(-)
>
> diff --git a/Makefile b/Makefile
> index 80e0800..4b5a17a 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -626,7 +626,7 @@ all: vmlinux
>  CFLAGS_GCOV    := -fprofile-arcs -ftest-coverage \
>         $(call cc-option,-fno-tree-loop-im) \
>         $(call cc-disable-warning,maybe-uninitialized,)
> -export CFLAGS_GCOV CFLAGS_KCOV
> +export CFLAGS_GCOV
>
>  # The arch Makefile can set ARCH_{CPP,A,C}FLAGS to override the default
>  # values of the respective KBUILD_* variables
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index c40c7b7..b76cab2 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -736,12 +736,15 @@ config ARCH_HAS_KCOV
>           only for x86_64. KCOV requires testing on other archs, and most likely
>           disabling of instrumentation for some early boot code.
>
> +config CC_HAS_SANCOV_TRACE_PC
> +       def_bool $(cc-option,-fsanitize-coverage=trace-pc)
> +
>  config KCOV
>         bool "Code coverage for fuzzing"
>         depends on ARCH_HAS_KCOV
> +       depends on CC_HAS_SANCOV_TRACE_PC || GCC_PLUGINS
>         select DEBUG_FS
> -       select GCC_PLUGINS if !COMPILE_TEST
> -       select GCC_PLUGIN_SANCOV if !COMPILE_TEST
> +       select GCC_PLUGIN_SANCOV if !CC_HAS_SANCOV_TRACE_PC
>         help
>           KCOV exposes kernel code coverage information in a form suitable
>           for coverage-guided fuzzing (randomized testing).
> @@ -755,7 +758,7 @@ config KCOV
>  config KCOV_ENABLE_COMPARISONS
>         bool "Enable comparison operands collection by KCOV"
>         depends on KCOV
> -       default n
> +       depends on $(cc-option,-fsanitize-coverage=trace-cmp)
>         help
>           KCOV also exposes operands of every comparison in the instrumented
>           code along with operand sizes and PCs of the comparison instructions.
> @@ -765,7 +768,7 @@ config KCOV_ENABLE_COMPARISONS
>  config KCOV_INSTRUMENT_ALL
>         bool "Instrument all code by default"
>         depends on KCOV
> -       default y if KCOV
> +       default y
>         help
>           If you are doing generic system call fuzzing (like e.g. syzkaller),
>           then you will want to instrument the whole kernel and you should
> diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins
> index 7f5c862..0ce3802 100644
> --- a/scripts/Makefile.gcc-plugins
> +++ b/scripts/Makefile.gcc-plugins
> @@ -14,16 +14,12 @@ ifdef CONFIG_GCC_PLUGINS
>    endif
>
>    ifdef CONFIG_GCC_PLUGIN_SANCOV
> -    ifeq ($(strip $(CFLAGS_KCOV)),)
>        # It is needed because of the gcc-plugin.sh and gcc version checks.
>        gcc-plugin-$(CONFIG_GCC_PLUGIN_SANCOV)           += sancov_plugin.so
>
> -      ifneq ($(PLUGINCC),)
> -        CFLAGS_KCOV := $(SANCOV_PLUGIN)
> -      else
> +      ifeq ($(PLUGINCC),)
>          $(warning warning: cannot use CONFIG_KCOV: -fsanitize-coverage=trace-pc is not supported by compiler)
>        endif
> -    endif
>    endif
>
>    gcc-plugin-$(CONFIG_GCC_PLUGIN_STRUCTLEAK)   += structleak_plugin.so
> diff --git a/scripts/Makefile.kcov b/scripts/Makefile.kcov
> index 5cc7203..d71ba73 100644
> --- a/scripts/Makefile.kcov
> +++ b/scripts/Makefile.kcov
> @@ -1,7 +1,9 @@
>  ifdef CONFIG_KCOV
> -CFLAGS_KCOV    := $(call cc-option,-fsanitize-coverage=trace-pc,)
> -ifeq ($(CONFIG_KCOV_ENABLE_COMPARISONS),y)
> -CFLAGS_KCOV += $(call cc-option,-fsanitize-coverage=trace-cmp,)
> -endif
> +
> +kcov-flags-$(CONFIG_CC_HAS_SANCOV_TRACE_PC)    += -fsanitize-coverage=trace-pc
> +kcov-flags-$(CONFIG_KCOV_ENABLE_COMPARISONS)   += -fsanitize-coverage=trace-cmp
> +kcov-flags-$(CONFIG_GCC_PLUGIN_SANKOV)         += -fplugin=$(objtree)/scripts/gcc-plugins/sancov_plugin.so
> +


This is my mistake.

SANKOV  ->  SANCOV


I fixed it locally.







> +export CFLAGS_KCOV := $(kcov-flags-y)
>
>  endif
> --
> 2.7.4
>
> --
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diff mbox

Patch

diff --git a/Makefile b/Makefile
index 80e0800..4b5a17a 100644
--- a/Makefile
+++ b/Makefile
@@ -626,7 +626,7 @@  all: vmlinux
 CFLAGS_GCOV	:= -fprofile-arcs -ftest-coverage \
 	$(call cc-option,-fno-tree-loop-im) \
 	$(call cc-disable-warning,maybe-uninitialized,)
-export CFLAGS_GCOV CFLAGS_KCOV
+export CFLAGS_GCOV
 
 # The arch Makefile can set ARCH_{CPP,A,C}FLAGS to override the default
 # values of the respective KBUILD_* variables
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index c40c7b7..b76cab2 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -736,12 +736,15 @@  config ARCH_HAS_KCOV
 	  only for x86_64. KCOV requires testing on other archs, and most likely
 	  disabling of instrumentation for some early boot code.
 
+config CC_HAS_SANCOV_TRACE_PC
+	def_bool $(cc-option,-fsanitize-coverage=trace-pc)
+
 config KCOV
 	bool "Code coverage for fuzzing"
 	depends on ARCH_HAS_KCOV
+	depends on CC_HAS_SANCOV_TRACE_PC || GCC_PLUGINS
 	select DEBUG_FS
-	select GCC_PLUGINS if !COMPILE_TEST
-	select GCC_PLUGIN_SANCOV if !COMPILE_TEST
+	select GCC_PLUGIN_SANCOV if !CC_HAS_SANCOV_TRACE_PC
 	help
 	  KCOV exposes kernel code coverage information in a form suitable
 	  for coverage-guided fuzzing (randomized testing).
@@ -755,7 +758,7 @@  config KCOV
 config KCOV_ENABLE_COMPARISONS
 	bool "Enable comparison operands collection by KCOV"
 	depends on KCOV
-	default n
+	depends on $(cc-option,-fsanitize-coverage=trace-cmp)
 	help
 	  KCOV also exposes operands of every comparison in the instrumented
 	  code along with operand sizes and PCs of the comparison instructions.
@@ -765,7 +768,7 @@  config KCOV_ENABLE_COMPARISONS
 config KCOV_INSTRUMENT_ALL
 	bool "Instrument all code by default"
 	depends on KCOV
-	default y if KCOV
+	default y
 	help
 	  If you are doing generic system call fuzzing (like e.g. syzkaller),
 	  then you will want to instrument the whole kernel and you should
diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins
index 7f5c862..0ce3802 100644
--- a/scripts/Makefile.gcc-plugins
+++ b/scripts/Makefile.gcc-plugins
@@ -14,16 +14,12 @@  ifdef CONFIG_GCC_PLUGINS
   endif
 
   ifdef CONFIG_GCC_PLUGIN_SANCOV
-    ifeq ($(strip $(CFLAGS_KCOV)),)
       # It is needed because of the gcc-plugin.sh and gcc version checks.
       gcc-plugin-$(CONFIG_GCC_PLUGIN_SANCOV)           += sancov_plugin.so
 
-      ifneq ($(PLUGINCC),)
-        CFLAGS_KCOV := $(SANCOV_PLUGIN)
-      else
+      ifeq ($(PLUGINCC),)
         $(warning warning: cannot use CONFIG_KCOV: -fsanitize-coverage=trace-pc is not supported by compiler)
       endif
-    endif
   endif
 
   gcc-plugin-$(CONFIG_GCC_PLUGIN_STRUCTLEAK)	+= structleak_plugin.so
diff --git a/scripts/Makefile.kcov b/scripts/Makefile.kcov
index 5cc7203..d71ba73 100644
--- a/scripts/Makefile.kcov
+++ b/scripts/Makefile.kcov
@@ -1,7 +1,9 @@ 
 ifdef CONFIG_KCOV
-CFLAGS_KCOV	:= $(call cc-option,-fsanitize-coverage=trace-pc,)
-ifeq ($(CONFIG_KCOV_ENABLE_COMPARISONS),y)
-CFLAGS_KCOV += $(call cc-option,-fsanitize-coverage=trace-cmp,)
-endif
+
+kcov-flags-$(CONFIG_CC_HAS_SANCOV_TRACE_PC)	+= -fsanitize-coverage=trace-pc
+kcov-flags-$(CONFIG_KCOV_ENABLE_COMPARISONS)	+= -fsanitize-coverage=trace-cmp
+kcov-flags-$(CONFIG_GCC_PLUGIN_SANKOV)		+= -fplugin=$(objtree)/scripts/gcc-plugins/sancov_plugin.so
+
+export CFLAGS_KCOV := $(kcov-flags-y)
 
 endif