mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2026-06-21 15:43:21 +02:00
Alice Ryhl
4a44b17406
The Makefile version of rustc-option currently checks whether the option exists for the host target instead of the target actually being compiled for. It was done this way in commit46e24a545c("rust: kasan/kbuild: fix missing flags on first build") to avoid a circular dependency on target.json. However, because of this, rustc-option currently does not function when cross-compiling from x86_64 to aarch64 if CONFIG_SHADOW_CALL_STACK is enabled. This is because KBUILD_RUSTFLAGS contains -Zfixed-x18 under this configuration. Since that flag does not exist on the host target, rustc-option runs into a compilation failure every time, leading to all flags being rejected as unsupported. To fix this, update rustc-option to pass a --target parameter so that the host target is not used. For targets using target.json, use a built-in target that is as close as possible to the target created with target.json to avoid the circular dependency on target.json. One scenario where this causes a boot failure: * Cross-compiled from x86_64 to aarch64. * With CONFIG_SHADOW_CALL_STACK=y * With CONFIG_KASAN_SW_TAGS=y * With CONFIG_KASAN_INLINE=n Then the resulting kernel image will fail to boot when it first calls into Rust code with a crash along the lines of "Unable to handle kernel paging request at virtual address 0ffffffc08541796". This is because the call threshold is not specified, so rustc will inline kasan operations, but the kasan shadow offset is not specified, which leads to the inlined kasan instructions being incorrect. Note that the -Zsanitizer=kernel-hwaddress parameter itself does not lead to a rustc-option failure despite being aarch64-specific because RUSTFLAGS_KASAN has not yet been added to KBUILD_RUSTFLAGS when rustc-option is evaluated by the kasan Makefile. Cc: stable@vger.kernel.org Fixes:46e24a545c("rust: kasan/kbuild: fix missing flags on first build") Signed-off-by: Alice Ryhl <aliceryhl@google.com> Link: https://patch.msgid.link/20260507-rustc-option-cross-v2-1-2f650a49c2b5@google.com [ Edited slightly: - Reset variable to avoid using the environment. - Use a simply expanded variable flavor for simplicity. - Export variable so that behavior in sub-`make`s is consistent. This matches other variables. - Miguel ] Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
94 lines
3.5 KiB
Makefile
94 lines
3.5 KiB
Makefile
# SPDX-License-Identifier: GPL-2.0-only
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# cc-cross-prefix
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# Usage: CROSS_COMPILE := $(call cc-cross-prefix, m68k-linux-gnu- m68k-linux-)
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# Return first <prefix> where a <prefix>gcc is found in PATH.
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# If no gcc found in PATH with listed prefixes return nothing
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#
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# Note: '2>/dev/null' is here to force Make to invoke a shell. Otherwise, it
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# would try to directly execute the shell builtin 'command'. This workaround
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# should be kept for a long time since this issue was fixed only after the
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# GNU Make 4.2.1 release.
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cc-cross-prefix = $(firstword $(foreach c, $(1), \
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$(if $(shell command -v -- $(c)gcc 2>/dev/null), $(c))))
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# output directory for tests below
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TMPOUT = .tmp_$$$$
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# try-run
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# Usage: option = $(call try-run, $(CC)...-o "$$TMP",option-ok,otherwise)
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# Exit code chooses option. "$$TMP" serves as a temporary file and is
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# automatically cleaned up.
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try-run = $(shell set -e; \
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TMP=$(TMPOUT)/tmp; \
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trap "rm -rf $(TMPOUT)" EXIT; \
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mkdir -p $(TMPOUT); \
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if ($(1)) >/dev/null 2>&1; \
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then echo "$(2)"; \
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else echo "$(3)"; \
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fi)
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# as-option
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# Usage: aflags-y += $(call as-option,-Wa$(comma)-isa=foo,)
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as-option = $(call try-run,\
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$(CC) -Werror $(KBUILD_CPPFLAGS) $(KBUILD_AFLAGS) $(1) -c -x assembler-with-cpp /dev/null -o "$$TMP",$(1),$(2))
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# as-instr
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# Usage: aflags-y += $(call as-instr,instr,option1,option2)
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as-instr = $(call try-run,\
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printf "%b\n" "$(1)" | $(CC) -Werror $(CLANG_FLAGS) $(KBUILD_AFLAGS) -Wa$(comma)--fatal-warnings -c -x assembler-with-cpp -o "$$TMP" -,$(2),$(3))
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# __cc-option
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# Usage: MY_CFLAGS += $(call __cc-option,$(CC),$(MY_CFLAGS),-march=winchip-c6,-march=i586)
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__cc-option = $(call try-run,\
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$(1) -Werror $(2) $(3:-Wno-%=-W%) -c -x c /dev/null -o "$$TMP",$(3),$(4))
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# cc-option
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# Usage: cflags-y += $(call cc-option,-march=winchip-c6,-march=i586)
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cc-option = $(call __cc-option, $(CC),\
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$(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS),$(1),$(2))
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# cc-option-yn
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# Usage: flag := $(call cc-option-yn,-march=winchip-c6)
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cc-option-yn = $(if $(call cc-option,$1),y,n)
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# cc-disable-warning
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# Usage: cflags-y += $(call cc-disable-warning,unused-but-set-variable)
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cc-disable-warning = $(call cc-option,-Wno-$(strip $1))
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# gcc-min-version
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# Usage: cflags-$(call gcc-min-version, 110100) += -foo
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gcc-min-version = $(call test-ge, $(CONFIG_GCC_VERSION), $1)
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# clang-min-version
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# Usage: cflags-$(call clang-min-version, 110000) += -foo
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clang-min-version = $(call test-ge, $(CONFIG_CLANG_VERSION), $1)
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# rustc-min-version
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# Usage: rustc-$(call rustc-min-version, 108500) += -Cfoo
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rustc-min-version = $(call test-ge, $(CONFIG_RUSTC_VERSION), $1)
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# ld-option
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# Usage: KBUILD_LDFLAGS += $(call ld-option, -X, -Y)
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ld-option = $(call try-run, $(LD) $(KBUILD_LDFLAGS) $(1) -v,$(1),$(2),$(3))
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# __rustc-option
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# Usage: MY_RUSTFLAGS += $(call __rustc-option,$(RUSTC),$(MY_RUSTFLAGS),-Cinstrument-coverage,-Zinstrument-coverage)
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# TODO: remove RUSTC_BOOTSTRAP=1 when we raise the minimum GNU Make version to 4.4
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__rustc-option = $(call try-run,\
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echo '$(pound)![allow(missing_docs)]$(pound)![feature(no_core)]$(pound)![no_core]' | RUSTC_BOOTSTRAP=1\
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$(1) --sysroot=/dev/null $(KBUILD_RUSTFLAGS_OPTION_CHKS) $(filter-out --sysroot=/dev/null --target=%target.json,$(2)) $(3)\
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--crate-type=rlib --out-dir=$(TMPOUT) --emit=obj=- - >/dev/null,$(3),$(4))
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# rustc-option
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# Usage: rustflags-y += $(call rustc-option,-Cinstrument-coverage,-Zinstrument-coverage)
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rustc-option = $(call __rustc-option, $(RUSTC),\
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$(KBUILD_RUSTFLAGS),$(1),$(2))
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# rustc-option-yn
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# Usage: flag := $(call rustc-option-yn,-Cinstrument-coverage)
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rustc-option-yn = $(if $(call rustc-option,$1),y,n)
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