[PATCH v2 24/27] kbuild: Generate the noreturn list and validate modules against it

@@ -1750,6 +1750,13 @@ KBUILD_BUILTIN := y
 modules: vmlinux
 endif
 
+# Objtool for modules (run before module link) needs to come after objtool for
+# vmlinux.o so it can read the generated exported noreturns file.
+ifdef CONFIG_OBJTOOL_CONTROL_FLOW
+KBUILD_BUILTIN := y
+modules: vmlinux.o
+endif
+
 modules: modules_prepare
 
 # Target to prepare building external modules

@@ -1780,6 +1787,7 @@ MRPROPER_FILES += include/config include/generated          \
 		  debian snap tar-install PKGBUILD pacman \
 		  .config .config.old .version \
 		  Module.symvers \
+		  scripts/noreturns.builtin \
 		  certs/signing_key.pem \
 		  certs/x509.genkey \
 		  vmlinux-gdb.py \

@@ -5,6 +5,7 @@
 /insert-sys-cert
 /kallsyms
 /module.lds
+/noreturns.builtin
 /recordmcount
 /rustdoc_test_builder
 /rustdoc_test_gen

@@ -32,6 +32,15 @@ ifneq ($(WARN_ON_UNUSED_TRACEPOINTS),)
 cmd_check_tracepoint = $(objtree)/scripts/tracepoint-update --module $<;
 endif
 
+ifdef CONFIG_OBJTOOL_CONTROL_FLOW
+noreturns-builtin := $(wildcard $(objtree)/scripts/noreturns.builtin)
+ifeq ($(noreturns-builtin),)
+$(warning scripts/noreturns.builtin is missing)
+else
+objtool-args += --noreturns-read=$(noreturns-builtin)
+endif
+endif
+
 $(modules:%.o=%.ko): private objtool-enabled = $(CONFIG_OBJTOOL_DEFERRED)
 
 mod-objtool = $(if $(objtool-enabled),$(objtool) $(objtool-args) -o $@.o $< ;)

@@ -59,8 +68,10 @@ define rule_ld_ko_o
 	+$(if $(CONFIG_DEBUG_INFO_BTF_MODULES),$(if $(newer-prereqs),$(call cmd,btf_ko)))
 endef
 
-# Re-generate module BTFs if either module's .ko or vmlinux changed
-%.ko: %.o %.mod.o .module-common.o $(objtree)/scripts/module.lds $(and $(CONFIG_DEBUG_INFO_BTF_MODULES),$(KBUILD_BUILTIN),$(objtree)/vmlinux) FORCE
+# Re-generate module BTFs if either module's .ko or vmlinux changed.
+# Re-run module objtool if the generated noreturn list changed.
+%.ko: %.o %.mod.o .module-common.o $(objtree)/scripts/module.lds $(noreturns-builtin) \
+      $(and $(CONFIG_DEBUG_INFO_BTF_MODULES),$(KBUILD_BUILTIN),$(objtree)/vmlinux) FORCE
 	$(call if_changed_rule,ld_ko_o)
 	+$(call cmd,check_tracepoint)
 

@@ -37,6 +37,8 @@ objtool-enabled := $(CONFIG_OBJTOOL_DEFERRED)
 
 vmlinux-objtool-args-y					+= $(objtool-args-y)
 
+vmlinux-objtool-args-$(CONFIG_OBJTOOL_CONTROL_FLOW)	+= --noreturns-write=scripts/noreturns.builtin
+
 vmlinux-objtool-args-$(CONFIG_NOINSTR_VALIDATION)	+= --noinstr \
 							   $(if $(or $(CONFIG_MITIGATION_UNRET_ENTRY),$(CONFIG_MITIGATION_SRSO)), --unret)
 

@@ -334,8 +334,7 @@ the objtool maintainers.
 
    The call from foo() to bar() doesn't return, but bar() is incorrectly
    annotated.  A noreturn function must be marked __noreturn in both its
-   declaration and its definition, and must have a NORETURN() annotation
-   in tools/objtool/noreturns.h.
+   declaration and its definition.
 
 
 4. file.o: warning: objtool: func(): can't find starting instruction

@@ -393,9 +392,8 @@ the objtool maintainers.
    reasons for this:
 
    a) funcA()'s last instruction is a call to a "noreturn" function like
-      panic().  In this case the noreturn function needs to be added to
-      objtool's hard-coded global_noreturns array.  Feel free to bug the
-      objtool maintainer, or you can submit a patch.
+      panic(), and objtool doesn't know that function never returns.  See
+      warning 3 above.
 
    b) funcA() uses the unreachable() annotation in a section of code
       that is actually reachable.

@@ -176,49 +176,6 @@ static bool is_sibling_call(struct instruction *insn)
 	return (is_static_jump(insn) && insn_call_dest(insn));
 }
 
-/*
- * Checks if a function is a Rust "noreturn" one.
- */
-static bool is_rust_noreturn(const struct symbol *func)
-{
-	/*
-	 * If it does not start with "_R", then it is not a Rust symbol.
-	 */
-	if (strncmp(func->name, "_R", 2))
-		return false;
-
-	/*
-	 * These are just heuristics -- we do not control the precise symbol
-	 * name, due to the crate disambiguators (which depend on the compiler)
-	 * as well as changes to the source code itself between versions (since
-	 * these come from the Rust standard library).
-	 */
-	return str_ends_with(func->name, "_4core3num20from_str_radix_panic")				||
-	       str_ends_with(func->name, "_4core3num22from_ascii_radix_panic")				||
-	       str_ends_with(func->name, "_4core3num28from_ascii_bytes_radix_panic")			||
-	       str_ends_with(func->name, "_4core3str16slice_error_fail")				||
-	       str_ends_with(func->name, "_4core5sliceSp15copy_from_slice17len_mismatch_fail")		||
-	       str_ends_with(func->name, "_4core6option13expect_failed")				||
-	       str_ends_with(func->name, "_4core6option13unwrap_failed")				||
-	       str_ends_with(func->name, "_4core6result13unwrap_failed")				||
-	       str_ends_with(func->name, "_4core9panicking5panic")					||
-	       str_ends_with(func->name, "_4core9panicking9panic_fmt")					||
-	       str_ends_with(func->name, "_4core9panicking14panic_explicit")				||
-	       str_ends_with(func->name, "_4core9panicking14panic_nounwind")				||
-	       str_ends_with(func->name, "_4core9panicking18panic_bounds_check")			||
-	       str_ends_with(func->name, "_4core9panicking18panic_nounwind_fmt")			||
-	       str_ends_with(func->name, "_4core9panicking19assert_failed_inner")			||
-	       str_ends_with(func->name, "_4core9panicking30panic_null_pointer_dereference")		||
-	       str_ends_with(func->name, "_4core9panicking32panic_null_reference_constructed")		||
-	       str_ends_with(func->name, "_4core9panicking36panic_misaligned_pointer_dereference")	||
-	       str_ends_with(func->name, "_7___rustc17rust_begin_unwind")				||
-	       strstr(func->name, "_4core9panicking13assert_failed")					||
-	       strstr(func->name, "_4core9panicking11panic_const24panic_const_")			||
-	       (strstr(func->name, "_4core5slice5index") &&
-		strstr(func->name, "slice_") &&
-		str_ends_with(func->name, "_fail"));
-}
-
 static bool is_listed_noreturn(struct symbol *func)
 {
 #define NORETURN(func) __stringify(func),

@@ -230,9 +187,6 @@ static bool is_listed_noreturn(struct symbol *func)
 	if (is_local_sym(func))
 		return false;
 
-	if (is_rust_noreturn(func))
-		return true;
-
 	for (int i = 0; i < ARRAY_SIZE(global_noreturns); i++)
 		if (!strcmp(func->name, global_noreturns[i]))
 			return true;

@@ -1,22 +1,9 @@
 /* SPDX-License-Identifier: GPL-2.0 */
 
 /*
- * This is a (sorted!) list of all known __noreturn functions in the kernel.
- * It's needed for objtool to properly reverse-engineer the control flow graph.
- *
- * Yes, this is unfortunate.  A better solution is in the works.
+ * This is a list of noreturn functions which are exported *by modules*.
+ * No other noreturns need to be listed here.
  */
-NORETURN(__fortify_panic)
 NORETURN(__kunit_abort)
-NORETURN(__module_put_and_kthread_exit)
-NORETURN(__stack_chk_fail)
-NORETURN(__ubsan_handle_builtin_unreachable)
-NORETURN(abort)
-NORETURN(acpi_processor_ffh_play_dead)
-NORETURN(do_exit)
-NORETURN(kthread_complete_and_exit)
 NORETURN(kunit_try_catch_throw)
 NORETURN(mpt_halt_firmware)
-NORETURN(panic)
-NORETURN(vpanic)
-NORETURN(rust_helper_BUG)