rust: Use gendwarfksyms + extended modversions for CONFIG_MODVERSIONS

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>

diff --git a/init/Kconfig b/init/Kconfig
index a20e6efd3f0fbdd7f0df2448854cc30734a0ee4f..2cfbefe0933ed129fdc1cca4121183e6285840d3 100644 (file)
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -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

diff --git a/rust/Makefile b/rust/Makefile
index a40a3936126d603836e0ec9b42a1285916b60e45..ab300bfb46f6a3e386b86d58120d7aeddc57da37 100644 (file)
--- a/rust/Makefile
+++ b/rust/Makefile
@@ -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") > $@
 
 $(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") | \
+       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