[RFC PATCH v1 21/23] objtool: Add arch-specific "noreturn" function handling

[Youling Tang <tangyouling@xxxxxxxxxxx>]

Fix the following warnings:
arch/loongarch/mm/fault.o: warning: objtool: no_context.part.0() falls through to
next function do_sigsegv()

It should mark 'dead_end' when the function is "noreturn/__noreturn".

Signed-off-by: Youling Tang <tangyouling@xxxxxxxxxxx>
---
 tools/objtool/arch/loongarch/special.c  | 5 +++++
 tools/objtool/arch/powerpc/special.c    | 3 +++
 tools/objtool/arch/x86/special.c        | 4 ++++
 tools/objtool/check.c                   | 7 ++++++-
 tools/objtool/include/objtool/special.h | 3 +++
 5 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/tools/objtool/arch/loongarch/special.c b/tools/objtool/arch/loongarch/special.c
index 8669dbe44459..be4d5d83e331 100644
--- a/tools/objtool/arch/loongarch/special.c
+++ b/tools/objtool/arch/loongarch/special.c
@@ -5,6 +5,11 @@
 #include <objtool/special.h>
 #include <objtool/builtin.h>
 
+/* Architecture specific "noreturn" function */
+const char * const arch_noreturns[] = {
+	"die",
+};
+int arch_noreturns_size = ARRAY_SIZE(arch_noreturns);
 
 bool arch_support_alt_relocation(struct special_alt *special_alt,
 				 struct instruction *insn,
diff --git a/tools/objtool/arch/powerpc/special.c b/tools/objtool/arch/powerpc/special.c
index d33868147196..35107e6ae2f1 100644
--- a/tools/objtool/arch/powerpc/special.c
+++ b/tools/objtool/arch/powerpc/special.c
@@ -4,6 +4,9 @@
 #include <objtool/special.h>
 #include <objtool/builtin.h>
 
+/* Architecture specific "noreturn" function */
+const char * const arch_noreturns[] = {};
+int arch_noreturns_size = ARRAY_SIZE(arch_noreturns);
 
 bool arch_support_alt_relocation(struct special_alt *special_alt,
 				 struct instruction *insn,
diff --git a/tools/objtool/arch/x86/special.c b/tools/objtool/arch/x86/special.c
index 7c97b7391279..48fa72f564f9 100644
--- a/tools/objtool/arch/x86/special.c
+++ b/tools/objtool/arch/x86/special.c
@@ -7,6 +7,10 @@
 #define X86_FEATURE_POPCNT (4 * 32 + 23)
 #define X86_FEATURE_SMAP   (9 * 32 + 20)
 
+/* Architecture specific "noreturn" function */
+const char * const arch_noreturns[] = {};
+int arch_noreturns_size = ARRAY_SIZE(arch_noreturns);
+
 void arch_handle_alternative(unsigned short feature, struct special_alt *alt)
 {
 	switch (feature) {
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index f91723010d6b..c637e54088f6 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -110,11 +110,16 @@ static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
 	if (func->bind == STB_WEAK)
 		return false;
 
-	if (func->bind == STB_GLOBAL)
+	if (func->bind == STB_GLOBAL) {
 		for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
 			if (!strcmp(func->name, global_noreturns[i]))
 				return true;
 
+		for (i = 0; i < arch_noreturns_size; i++)
+			if (!strcmp(func->name, arch_noreturns[i]))
+				return true;
+	}
+
 	if (!func->len)
 		return false;
 
diff --git a/tools/objtool/include/objtool/special.h b/tools/objtool/include/objtool/special.h
index 86d4af9c5aa9..f800817f0ed8 100644
--- a/tools/objtool/include/objtool/special.h
+++ b/tools/objtool/include/objtool/special.h
@@ -30,6 +30,9 @@ struct special_alt {
 	unsigned int orig_len, new_len; /* group only */
 };
 
+extern const char * const arch_noreturns[];
+extern int arch_noreturns_size;
+
 int special_get_alts(struct elf *elf, struct list_head *alts);
 
 void arch_handle_alternative(unsigned short feature, struct special_alt *alt);
-- 
2.39.2