Add two Kconfig options for global dataflow instrumentation control: - CONFIG_KCOV_DATAFLOW_INSTRUMENT_ALL: instruments all kernel objects with dataflow tracing by default (mirrors CONFIG_KCOV_INSTRUMENT_ALL). Individual files can opt out with: KCOV_DATAFLOW_file.o := n
- CONFIG_KCOV_DATAFLOW_NO_INLINE: adds -fno-inline to instrumented files for complete argument visibility (default y). Setting to n allows global enablement without stack overflow or BUILD_BUG_ON failures. Overhead with INSTRUMENT_ALL (NO_INLINE=n, KASAN baseline): .text: +9.5%, .data: +44%, boot: +71%, syscall: +133% Comparable to KASAN (+100-200%) and acceptable for fuzzing kernels. rust/Makefile: opt out core.o from dataflow (same as KCOV_INSTRUMENT). Signed-off-by: Yunseong Kim <[email protected]> --- lib/Kconfig.debug | 23 ++++++++++++++++++++++- rust/Makefile | 1 + 2 files changed, 23 insertions(+), 1 deletion(-) diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index abd1a94589aa..3b952b6361a8 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -2261,7 +2261,6 @@ config KCOV_SELFTEST On test failure, causes the kernel to panic. Recommended to be enabled, ensuring critical functionality works as intended. - config KCOV_DATAFLOW_ARGS bool "Enable KCOV dataflow: function argument capture" depends on KCOV @@ -2283,6 +2282,28 @@ config KCOV_DATAFLOW_RET metadata, recording individual field values at runtime. Enable per-module with: KCOV_DATAFLOW_file.o := y in the Makefile. Requires clang with -fsanitize-coverage=dataflow-ret support. + +config KCOV_DATAFLOW_INSTRUMENT_ALL + bool "Instrument all code with KCOV dataflow by default" + depends on KCOV_DATAFLOW_ARGS || KCOV_DATAFLOW_RET + help + If enabled, all kernel objects are compiled with dataflow + instrumentation (like CONFIG_KCOV_INSTRUMENT_ALL for basic KCOV). + Individual files can opt out with: KCOV_DATAFLOW_file.o := n + Increases compile time and binary size significantly. + Suitable for fuzzing and security auditing kernels. + +config KCOV_DATAFLOW_NO_INLINE + bool "Disable inlining for dataflow-instrumented files" + depends on KCOV_DATAFLOW_ARGS || KCOV_DATAFLOW_RET + default y + help + Adds -fno-inline to dataflow-instrumented files for complete + argument visibility. Without this, inlined functions will not + have their arguments captured individually. + Disabling allows global enablement with lower overhead at the + cost of missing inlined function traces. + config DEBUG_AID_FOR_SYZBOT bool "Additional debug code for syzbot" default n diff --git a/rust/Makefile b/rust/Makefile index b9e9f512cec3..d122a65226dc 100644 --- a/rust/Makefile +++ b/rust/Makefile @@ -656,6 +656,7 @@ ifneq ($(or $(CONFIG_X86_64),$(CONFIG_X86_32)),) $(obj)/core.o: scripts/target.json endif KCOV_INSTRUMENT_core.o := n +KCOV_DATAFLOW_core.o := n $(obj)/compiler_builtins.o: private skip_gendwarfksyms = 1 $(obj)/compiler_builtins.o: private rustc_objcopy = -w -W '__*' -- 2.43.0
