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rust: Use gendwarfksyms + extended modversions for CONFIG_MODVERSIONS

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Previously, two things stopped Rust from using MODVERSIONS:
1. Rust symbols are occasionally too long to be represented in the
   original versions table
2. Rust types cannot be properly hashed by the existing genksyms
   approach because:
	* Looking up type definitions in Rust is more complex than C
	* Type layout is potentially dependent on the compiler in Rust,
	  not just the source type declaration.

CONFIG_EXTENDED_MODVERSIONS addresses the first point, and
CONFIG_GENDWARFKSYMS the second. If Rust wants to use MODVERSIONS, allow
it to do so by selecting both features.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Co-developed-by: Matthew Maurer <mmaurer@google.com>
Signed-off-by: Matthew Maurer <mmaurer@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
This commit is contained in:
Sami Tolvanen 2025-01-03 17:37:05 +00:00 committed by Masahiro Yamada
parent 272f8a6d62
commit be3d3e40bb
2 changed files with 34 additions and 3 deletions
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3
init/Kconfig
View File

@ -1956,7 +1956,8 @@ config RUST
bool "Rust support"
depends on HAVE_RUST
depends on RUST_IS_AVAILABLE
depends on !MODVERSIONS
select EXTENDED_MODVERSIONS if MODVERSIONS
depends on !MODVERSIONS || GENDWARFKSYMS
depends on !GCC_PLUGIN_RANDSTRUCT
depends on !RANDSTRUCT
depends on !DEBUG_INFO_BTF || PAHOLE_HAS_LANG_EXCLUDE

34
rust/Makefile
View File

@ -329,10 +329,11 @@ $(obj)/bindings/bindings_helpers_generated.rs: private bindgen_target_extra = ;
$(obj)/bindings/bindings_helpers_generated.rs: $(src)/helpers/helpers.c FORCE
$(call if_changed_dep,bindgen)
rust_exports = $(NM) -p --defined-only $(1) | awk '$$2~/(T|R|D|B)/ && $$3!~/__cfi/ { printf $(2),$(3) }'
quiet_cmd_exports = EXPORTS $@
cmd_exports = \
$(NM) -p --defined-only $< \
| awk '$$2~/(T|R|D|B)/ && $$3!~/__cfi/ {printf "EXPORT_SYMBOL_RUST_GPL(%s);\n",$$3}' > $@
$(call rust_exports,$<,"EXPORT_SYMBOL_RUST_GPL(%s);\n",$$3) > $@
$(obj)/exports_core_generated.h: $(obj)/core.o FORCE
$(call if_changed,exports)
@ -401,11 +402,36 @@ ifneq ($(or $(CONFIG_ARM64),$(and $(CONFIG_RISCV),$(CONFIG_64BIT))),)
__ashlti3 __lshrti3
endif
ifdef CONFIG_MODVERSIONS
cmd_gendwarfksyms = $(if $(skip_gendwarfksyms),, \
$(call rust_exports,$@,"%s\n",$$3) | \
scripts/gendwarfksyms/gendwarfksyms \
$(if $(KBUILD_GENDWARFKSYMS_STABLE), --stable) \
$(if $(KBUILD_SYMTYPES), --symtypes $(@:.o=.symtypes),) \
$@ >> $(dot-target).cmd)
endif
define rule_rustc_library
$(call cmd_and_fixdep,rustc_library)
$(call cmd,gen_objtooldep)
$(call cmd,gendwarfksyms)
endef
define rule_rust_cc_library
$(call if_changed_rule,cc_o_c)
$(call cmd,force_checksrc)
$(call cmd,gendwarfksyms)
endef
# helpers.o uses the same export mechanism as Rust libraries, so ensure symbol
# versions are calculated for the helpers too.
$(obj)/helpers/helpers.o: $(src)/helpers/helpers.c $(recordmcount_source) FORCE
+$(call if_changed_rule,rust_cc_library)
# Disable symbol versioning for exports.o to avoid conflicts with the actual
# symbol versions generated from Rust objects.
$(obj)/exports.o: private skip_gendwarfksyms = 1
$(obj)/core.o: private skip_clippy = 1
$(obj)/core.o: private skip_flags = -Wunreachable_pub
$(obj)/core.o: private rustc_objcopy = $(foreach sym,$(redirect-intrinsics),--redefine-sym $(sym)=__rust$(sym))
@ -417,13 +443,16 @@ ifneq ($(or $(CONFIG_X86_64),$(CONFIG_X86_32)),)
$(obj)/core.o: scripts/target.json
endif
$(obj)/compiler_builtins.o: private skip_gendwarfksyms = 1
$(obj)/compiler_builtins.o: private rustc_objcopy = -w -W '__*'
$(obj)/compiler_builtins.o: $(src)/compiler_builtins.rs $(obj)/core.o FORCE
+$(call if_changed_rule,rustc_library)
$(obj)/build_error.o: private skip_gendwarfksyms = 1
$(obj)/build_error.o: $(src)/build_error.rs $(obj)/compiler_builtins.o FORCE
+$(call if_changed_rule,rustc_library)
$(obj)/ffi.o: private skip_gendwarfksyms = 1
$(obj)/ffi.o: $(src)/ffi.rs $(obj)/compiler_builtins.o FORCE
+$(call if_changed_rule,rustc_library)
@ -435,6 +464,7 @@ $(obj)/bindings.o: $(src)/bindings/lib.rs \
+$(call if_changed_rule,rustc_library)
$(obj)/uapi.o: private rustc_target_flags = --extern ffi
$(obj)/uapi.o: private skip_gendwarfksyms = 1
$(obj)/uapi.o: $(src)/uapi/lib.rs \
$(obj)/ffi.o \
$(obj)/uapi/uapi_generated.rs FORCE