[PATCH v2 03/14] stackleak: Split KSTACK_ERASE_CFLAGS from GCC_PLUGINS_CFLAGS

Kees Cook
2025-05-23T04:39:38Z

In preparation for Clang stack depth tracking for KSTACK_ERASE,
split the stackleak-specific cflags out of GCC_PLUGINS_CFLAGS into
KSTACK_ERASE_CFLAGS.

Signed-off-by: Kees Cook <kees@kernel.org>
---
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: <x86@kernel.org>
Cc: <linux-arm-kernel@lists.infradead.org>
Cc: <sparclinux@vger.kernel.org>
Cc: <linux-kbuild@vger.kernel.org>
Cc: <linux-hardening@vger.kernel.org>
---
Makefile | 1 +
arch/arm/vdso/Makefile | 2 +-
arch/arm64/kernel/vdso/Makefile | 3 ++-
arch/sparc/vdso/Makefile | 3 ++-
arch/x86/entry/vdso/Makefile | 3 ++-
scripts/Makefile.gcc-plugins | 16 ++--------------
scripts/Makefile.kstack_erase | 15 +++++++++++++++
MAINTAINERS | 2 ++
8 files changed, 27 insertions(+), 18 deletions(-)
create mode 100644 scripts/Makefile.kstack_erase

diff --git a/Makefile b/Makefile
index 4bfac7e00d2b..4c9e4b5ec36c 100644
--- a/Makefile
+++ b/Makefile
@@ -1086,6 +1086,7 @@ include-$(CONFIG_KMSAN) += scripts/Makefile.kmsan
include-$(CONFIG_UBSAN) += scripts/Makefile.ubsan
include-$(CONFIG_KCOV) += scripts/Makefile.kcov
include-$(CONFIG_RANDSTRUCT) += scripts/Makefile.randstruct
+include-$(CONFIG_KSTACK_ERASE) += scripts/Makefile.kstack_erase
include-$(CONFIG_AUTOFDO_CLANG) += scripts/Makefile.autofdo
include-$(CONFIG_PROPELLER_CLANG) += scripts/Makefile.propeller
include-$(CONFIG_GCC_PLUGINS) += scripts/Makefile.gcc-plugins
diff --git a/arch/arm/vdso/Makefile b/arch/arm/vdso/Makefile
index cb044bfd145d..cf8cd39ab804 100644
--- a/arch/arm/vdso/Makefile
+++ b/arch/arm/vdso/Makefile
@@ -26,7 +26,7 @@ CPPFLAGS_vdso.lds += -P -C -U$(ARCH)
CFLAGS_REMOVE_vdso.o = -pg

# Force -O2 to avoid libgcc dependencies
-CFLAGS_REMOVE_vgettimeofday.o = -pg -Os $(RANDSTRUCT_CFLAGS) $(GCC_PLUGINS_CFLAGS)
+CFLAGS_REMOVE_vgettimeofday.o = -pg -Os $(RANDSTRUCT_CFLAGS) $(KSTACK_ERASE_CFLAGS) $(GCC_PLUGINS_CFLAGS)
ifeq ($(c-gettimeofday-y),)
CFLAGS_vgettimeofday.o = -O2
else
diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile
index 5e27e46aa496..7dec05dd33b7 100644
--- a/arch/arm64/kernel/vdso/Makefile
+++ b/arch/arm64/kernel/vdso/Makefile
@@ -36,7 +36,8 @@ ccflags-y += -DDISABLE_BRANCH_PROFILING -DBUILD_VDSO
# -Wmissing-prototypes and -Wmissing-declarations are removed from
# the CFLAGS to make possible to build the kernel with CONFIG_WERROR enabled.
CC_FLAGS_REMOVE_VDSO := $(CC_FLAGS_FTRACE) -Os $(CC_FLAGS_SCS) \
- $(RANDSTRUCT_CFLAGS) $(GCC_PLUGINS_CFLAGS) \
+ $(RANDSTRUCT_CFLAGS) $(KSTACK_ERASE_CFLAGS) \
+ $(GCC_PLUGINS_CFLAGS) \
$(CC_FLAGS_LTO) $(CC_FLAGS_CFI) \
-Wmissing-prototypes -Wmissing-declarations

diff --git a/arch/sparc/vdso/Makefile b/arch/sparc/vdso/Makefile
index fdc4a8f5a49c..683b2d408224 100644
--- a/arch/sparc/vdso/Makefile
+++ b/arch/sparc/vdso/Makefile
@@ -48,7 +48,7 @@ CFL := $(PROFILING) -mcmodel=medlow -fPIC -O2 -fasynchronous-unwind-tables -m64

SPARC_REG_CFLAGS = -ffixed-g4 -ffixed-g5 $(call cc-option,-fcall-used-g5) $(call cc-option,-fcall-used-g7)

-$(vobjs): KBUILD_CFLAGS := $(filter-out $(RANDSTRUCT_CFLAGS) $(GCC_PLUGINS_CFLAGS) $(SPARC_REG_CFLAGS),$(KBUILD_CFLAGS)) $(CFL)
+$(vobjs): KBUILD_CFLAGS := $(filter-out $(RANDSTRUCT_CFLAGS) $(KSTACK_ERASE_CFLAGS) $(GCC_PLUGINS_CFLAGS) $(SPARC_REG_CFLAGS),$(KBUILD_CFLAGS)) $(CFL)

#
# vDSO code runs in userspace and -pg doesn't help with profiling anyway.
@@ -79,6 +79,7 @@ KBUILD_CFLAGS_32 := $(filter-out -m64,$(KBUILD_CFLAGS))
KBUILD_CFLAGS_32 := $(filter-out -mcmodel=medlow,$(KBUILD_CFLAGS_32))
KBUILD_CFLAGS_32 := $(filter-out -fno-pic,$(KBUILD_CFLAGS_32))
KBUILD_CFLAGS_32 := $(filter-out $(RANDSTRUCT_CFLAGS),$(KBUILD_CFLAGS_32))
+KBUILD_CFLAGS_32 := $(filter-out $(KSTACK_ERASE_CFLAGS),$(KBUILD_CFLAGS_32))
KBUILD_CFLAGS_32 := $(filter-out $(GCC_PLUGINS_CFLAGS),$(KBUILD_CFLAGS_32))
KBUILD_CFLAGS_32 := $(filter-out $(SPARC_REG_CFLAGS),$(KBUILD_CFLAGS_32))
KBUILD_CFLAGS_32 += -m32 -msoft-float -fpic
diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
index 54d3e9774d62..f247f5f5cb44 100644
--- a/arch/x86/entry/vdso/Makefile
+++ b/arch/x86/entry/vdso/Makefile
@@ -62,7 +62,7 @@ ifneq ($(RETPOLINE_VDSO_CFLAGS),)
endif
endif

-$(vobjs): KBUILD_CFLAGS := $(filter-out $(PADDING_CFLAGS) $(CC_FLAGS_LTO) $(CC_FLAGS_CFI) $(RANDSTRUCT_CFLAGS) $(GCC_PLUGINS_CFLAGS) $(RETPOLINE_CFLAGS),$(KBUILD_CFLAGS)) $(CFL)
+$(vobjs): KBUILD_CFLAGS := $(filter-out $(PADDING_CFLAGS) $(CC_FLAGS_LTO) $(CC_FLAGS_CFI) $(RANDSTRUCT_CFLAGS) $(KSTACK_ERASE_CFLAGS) $(GCC_PLUGINS_CFLAGS) $(RETPOLINE_CFLAGS),$(KBUILD_CFLAGS)) $(CFL)
$(vobjs): KBUILD_AFLAGS += -DBUILD_VDSO

#
@@ -123,6 +123,7 @@ KBUILD_CFLAGS_32 := $(filter-out -mcmodel=kernel,$(KBUILD_CFLAGS_32))
KBUILD_CFLAGS_32 := $(filter-out -fno-pic,$(KBUILD_CFLAGS_32))
KBUILD_CFLAGS_32 := $(filter-out -mfentry,$(KBUILD_CFLAGS_32))
KBUILD_CFLAGS_32 := $(filter-out $(RANDSTRUCT_CFLAGS),$(KBUILD_CFLAGS_32))
+KBUILD_CFLAGS_32 := $(filter-out $(KSTACK_ERASE_CFLAGS),$(KBUILD_CFLAGS_32))
KBUILD_CFLAGS_32 := $(filter-out $(GCC_PLUGINS_CFLAGS),$(KBUILD_CFLAGS_32))
KBUILD_CFLAGS_32 := $(filter-out $(RETPOLINE_CFLAGS),$(KBUILD_CFLAGS_32))
KBUILD_CFLAGS_32 := $(filter-out $(CC_FLAGS_LTO),$(KBUILD_CFLAGS_32))
diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins
index 28b8867c4e84..b0e1423b09c2 100644
--- a/scripts/Makefile.gcc-plugins
+++ b/scripts/Makefile.gcc-plugins
@@ -8,20 +8,6 @@ ifdef CONFIG_GCC_PLUGIN_LATENT_ENTROPY
endif
export DISABLE_LATENT_ENTROPY_PLUGIN

-gcc-plugin-$(CONFIG_GCC_PLUGIN_STACKLEAK) += stackleak_plugin.so
-gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STACKLEAK) \
- += -DSTACKLEAK_PLUGIN
-gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STACKLEAK) \
- += -fplugin-arg-stackleak_plugin-track-min-size=$(CONFIG_KSTACK_ERASE_TRACK_MIN_SIZE)
-gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STACKLEAK) \
- += -fplugin-arg-stackleak_plugin-arch=$(SRCARCH)
-gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STACKLEAK_VERBOSE) \
- += -fplugin-arg-stackleak_plugin-verbose
-ifdef CONFIG_GCC_PLUGIN_STACKLEAK
- DISABLE_KSTACK_ERASE += -fplugin-arg-stackleak_plugin-disable
-endif
-export DISABLE_KSTACK_ERASE
-
# All the plugin CFLAGS are collected here in case a build target needs to
# filter them out of the KBUILD_CFLAGS.
GCC_PLUGINS_CFLAGS := $(strip $(addprefix -fplugin=$(objtree)/scripts/gcc-plugins/, $(gcc-plugin-y)) $(gcc-plugin-cflags-y)) -DGCC_PLUGINS
@@ -34,6 +20,8 @@ KBUILD_CFLAGS += $(GCC_PLUGINS_CFLAGS)
# be included in GCC_PLUGIN so they can get built.
gcc-plugin-external-$(CONFIG_GCC_PLUGIN_RANDSTRUCT) \
+= randomize_layout_plugin.so
+gcc-plugin-external-$(CONFIG_GCC_PLUGIN_STACKLEAK) \
+ += stackleak_plugin.so

# All enabled GCC plugins are collected here for building in
# scripts/gcc-scripts/Makefile.
diff --git a/scripts/Makefile.kstack_erase b/scripts/Makefile.kstack_erase
new file mode 100644
index 000000000000..5223d3a35817
--- /dev/null
+++ b/scripts/Makefile.kstack_erase
@@ -0,0 +1,15 @@
+# SPDX-License-Identifier: GPL-2.0
+
+ifdef CONFIG_GCC_PLUGIN_STACKLEAK
+kstack-erase-cflags-y += -fplugin=$(objtree)/scripts/gcc-plugins/stackleak_plugin.so
+kstack-erase-cflags-y += -fplugin-arg-stackleak_plugin-track-min-size=$(CONFIG_KSTACK_ERASE_TRACK_MIN_SIZE)
+kstack-erase-cflags-y += -fplugin-arg-stackleak_plugin-arch=$(SRCARCH)
+kstack-erase-cflags-$(CONFIG_GCC_PLUGIN_STACKLEAK_VERBOSE) += -fplugin-arg-stackleak_plugin-verbose
+DISABLE_KSTACK_ERASE := -fplugin-arg-stackleak_plugin-disable
+endif
+
+KSTACK_ERASE_CFLAGS := $(kstack-erase-cflags-y)
+
+export STACKLEAK_CFLAGS DISABLE_KSTACK_ERASE
+
+KBUILD_CFLAGS += $(KSTACK_ERASE_CFLAGS)
diff --git a/MAINTAINERS b/MAINTAINERS
index 9f76b329fdb3..f4dcf3c0be8d 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -13067,6 +13067,8 @@ F: kernel/kstack_erase.c
F: lib/tests/randstruct_kunit.c
F: lib/tests/usercopy_kunit.c
F: mm/usercopy.c
+F: scripts/Makefile.kstack_erase
+F: scripts/Makefile.randstruct
F: security/Kconfig.hardening
K: \b(add|choose)_random_kstack_offset\b
K: \b__check_(object_size|heap_object)\b
--
2.34.1