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KASAN Support #1087

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cbee227
rust: Define probing macros for rustc
maurer Jun 28, 2024
6571afe
rust: Enable KASAN support
maurer Jun 28, 2024
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5 changes: 5 additions & 0 deletions scripts/Kconfig.include
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Expand Up @@ -63,3 +63,8 @@ ld-version := $(shell,set -- $(ld-info) && echo $2)
cc-option-bit = $(if-success,$(CC) -Werror $(1) -E -x c /dev/null -o /dev/null,$(1))
m32-flag := $(cc-option-bit,-m32)
m64-flag := $(cc-option-bit,-m64)

# $(rustc-option,<flag>)
# Return y if the Rust compiler supports <flag>, n otherwise
# Calls to this should be guarded so that they are not evaluated if CONFIG_HAVE_RUST is not set.
rustc-option = $(success,trap "rm -rf .tmp_$$" EXIT; mkdir .tmp_$$; $(RUSTC) $(1) --crate-type=rlib /dev/null -o .tmp_$$/tmp.rlib)
15 changes: 15 additions & 0 deletions scripts/Makefile.compiler
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Expand Up @@ -72,3 +72,18 @@ clang-min-version = $(call test-ge, $(CONFIG_CLANG_VERSION), $1)
# ld-option
# Usage: KBUILD_LDFLAGS += $(call ld-option, -X, -Y)
ld-option = $(call try-run, $(LD) $(KBUILD_LDFLAGS) $(1) -v,$(1),$(2),$(3))

# __rustc-option
# Usage: MY_RUSTFLAGS += $(call __rustc-option,$(RUSTC),$(MY_RUSTFLAGS),-Cinstrument-coverage,-Zinstrument-coverage)
__rustc-option = $(call try-run,\
$(1) $(2) $(3) --crate-type=rlib /dev/null -o "$$TMP",$(3),$(4))

# rustc-option
# Usage: rustflags-y += $(call rustc-option,-Cinstrument-coverage,-Zinstrument-coverage)
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For flags that can be determined by the version, I wonder if it would be best to tell people to use rustc-min-version instead (I sent a (broken) patch adding that one and an example use case).

On one hand, having them versioned means we can easily grep & remove them when upgrading the compiler minimum.

On the other hand, it could be that someone has patched their compiler, e.g. backporting support for a given flag in a Linux distribution. So there is value, but I am not sure if it is just a theoretical advantage (and even then, a Linux distribution could also patch their kernel instead, too).

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(Of course, we still need it for rustc-param, that is what I did too -- but perhaps we can put a comment about it if we think one or the other way is better).

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@maurer maurer Jul 9, 2024 •
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I think that in many cases rustc-min-version would be preferable, esp. because with -Z flags, the feature may be available but incomplete in some cases. However, I'd point out that users needing to look up what version of Rust added a flag they're going to use every time seems a bit more onerous than the situation in C.

I'll add a note to the docs that if you're testing for a -Z flag, you should consider rustc-min-version instead. I think rustc-option is probably better for -C options in most cases.

rustc-option = $(call __rustc-option, $(RUSTC),\
$(KBUILD_RUSTFLAGS),$(1),$(2))

# rustc-option-yn
# Usage: flag := $(call rustc-option-yn,-Cinstrument-coverage)
rustc-option-yn = $(call try-run,\
$(RUSTC) $(KBUILD_RUSTFLAGS) $(1) --crate-type=rlib /dev/null -o "$$TMP",y,n)
46 changes: 45 additions & 1 deletion scripts/Makefile.kasan
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Expand Up @@ -12,6 +12,7 @@ endif
KASAN_SHADOW_OFFSET ?= $(CONFIG_KASAN_SHADOW_OFFSET)

cc-param = $(call cc-option, -mllvm -$(1), $(call cc-option, --param $(1)))
rustc-param = $(call rustc-option, -Cllvm-args=-$(1),)

ifdef CONFIG_KASAN_STACK
stack_enable := 1
Expand All @@ -28,6 +29,7 @@ else
endif

CFLAGS_KASAN_MINIMAL := -fsanitize=kernel-address
RUSTFLAGS_KASAN_MINIMAL := -Zsanitizer=kernel-address -Zsanitizer-recover=kernel-address

# -fasan-shadow-offset fails without -fsanitize
CFLAGS_KASAN_SHADOW := $(call cc-option, -fsanitize=kernel-address \
Expand All @@ -36,13 +38,36 @@ CFLAGS_KASAN_SHADOW := $(call cc-option, -fsanitize=kernel-address \
-mllvm -asan-mapping-offset=$(KASAN_SHADOW_OFFSET)))

ifeq ($(strip $(CFLAGS_KASAN_SHADOW)),)
KASAN_SHADOW_SUPPORTED := n
else
KASAN_SHADOW_SUPPORTED := y
endif

ifdef CONFIG_RUST
RUSTFLAGS_KASAN_SHADOW := $(call rustc-option $(RUSTFLAGS_KASAN_MINIMAL) \
-Cllvm-args=-asan-mapping-offset=$(KASAN_SHADOW_OFFSET))
ifeq ($(strip $(RUSTFLAGS_KASAN_SHADOW)),)
KASAN_SHADOW_SUPPORTED := n
endif
endif

ifeq ($(KASAN_SHADOW_SUPPORTED),y)
CFLAGS_KASAN := $(CFLAGS_KASAN_MINIMAL)
ifdef CONFIG_RUST
RUSTFLAGS_KASAN := $(RUSTFLAGS_KASAN_MINIMAL)
endif
else
# Now add all the compiler specific options that are valid standalone
CFLAGS_KASAN := $(CFLAGS_KASAN_SHADOW) \
$(call cc-param,asan-globals=1) \
$(call cc-param,asan-instrumentation-with-call-threshold=$(call_threshold)) \
$(call cc-param,asan-instrument-allocas=1)
ifdef CONFIG_RUST
RUSTFLAGS_KASAN := $(RUSTFLAGS_KASAN_SHADOW) \
$(call rustc-param,asan-globals=1) \
$(call rustc-param,asan-instrumentation-with-call-threshold=$(call_threshold)) \
$(call rustc-param,asan-instrument-allocas=1)
endif
endif

CFLAGS_KASAN += $(call cc-param,asan-stack=$(stack_enable))
Expand All @@ -52,6 +77,11 @@ CFLAGS_KASAN += $(call cc-param,asan-stack=$(stack_enable))
# memintrinsics won't be checked by KASAN on GENERIC_ENTRY architectures.
CFLAGS_KASAN += $(call cc-param,asan-kernel-mem-intrinsic-prefix=1)

ifdef CONFIG_RUST
RUSTFLAGS_KASAN += $(call rustc-param,asan-stack=$(stack_enable))
RUSTFLAGS_KASAN += $(call rustc-param,asan-kernel-mem-intrinsic-prefix=1)
endif

endif # CONFIG_KASAN_GENERIC

ifdef CONFIG_KASAN_SW_TAGS
Expand All @@ -73,6 +103,20 @@ ifeq ($(call clang-min-version, 150000)$(call gcc-min-version, 130000),y)
CFLAGS_KASAN += $(call cc-param,hwasan-kernel-mem-intrinsic-prefix=1)
endif

ifdef CONFIG_RUST
ifdef CONFIG_KASAN_INLINE
rust_instrumentation_flags := $(call rustc-param,hwasan-mapping-offset=$(KASAN_SHADOW_OFFSET))
else
rust_instrumentation_flags := $(call rustc-param,hwasan-instrument-with-calls=1)
endif
RUSTFLAGS_KASAN := -Zsanitizer=kernel-hwaddress -Zsanitizer-recover=kernel-hwaddress \
$(call rustc-param,hwasan-instrument-stack=$(stack_enable)) \
$(call rustc-param,hwasan-use-short-granules=0) \
$(call rustc-param,hwasan-inline-all-checks=0) \
$(call rustc-param,hwasan-kernel-mem-intrinsic-prefix=1) \
$(instrumentation_flags)
endif

endif # CONFIG_KASAN_SW_TAGS

export CFLAGS_KASAN CFLAGS_KASAN_NOSANITIZE
export CFLAGS_KASAN CFLAGS_KASAN_NOSANITIZE RUSTFLAGS_KASAN
3 changes: 3 additions & 0 deletions scripts/Makefile.lib
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Expand Up @@ -167,6 +167,9 @@ ifneq ($(CONFIG_KASAN_HW_TAGS),y)
_c_flags += $(if $(patsubst n%,, \
$(KASAN_SANITIZE_$(target-stem).o)$(KASAN_SANITIZE)$(is-kernel-object)), \
$(CFLAGS_KASAN), $(CFLAGS_KASAN_NOSANITIZE))
_rust_flags += $(if $(patsubst n%,, \
$(KASAN_SANITIZE_$(target-stem).o)$(KASAN_SANITIZE)$(is-kernel-object)), \
$(RUSTFLAGS_KASAN))
endif
endif

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