MIPS: Fix check_bugs() modpost warning

Hi all,

This series fixes a modpost warning visible in -next from check_bugs() and helps avoid a potential, albeit unlikely, warning from check_bugs_early().

---
Changes in v2:
- Now two separate patches: one to avoid current check_bugs() warning
and one to avoid potential check_bugs_early() warning.
- Sink body of check_bugs_early() into setup_arch() directly, rather
than marking it as __init (Nick).
- Add Naresh's reported-by to patch 1, which came after v1 was sent.
- Reword commit messages to note that there is not a problem at run time
because check_bugs() and check_bugs_early(), while not marked __init,
are only called from __init functions; modpost does not know this
though, hence the warning.
- Link to v1: https://lore.kernel.org/r/20230419-mips-check_bugs-init-attribute-v1-1-91e6eed55b89@kernel.org

---
Nathan Chancellor (2):
MIPS: Mark check_bugs() as __init
MIPS: Sink body of check_bugs_early() into its only call site

 arch/mips/include/asm/bugs.h | 8 +-------
 arch/mips/kernel/setup.c     | 3 ++-
 2 files changed, 3 insertions(+), 8 deletions(-)

---
base-commit: 6a8f57ae2eb07ab39a6f0ccad60c760743051026
change-id: 20230419-mips-check_bugs-init-attribute-026103bdb255

Best regards,

Nathan Chancellor <[email protected]>

After commit ac7c3e4ff401 ("compiler: enable CONFIG_OPTIMIZE_INLINING forcibly"), a compiler may choose not to inline a function marked with just 'inline'. If check_bugs() is not inlined into start_kernel(), which occurs when building with clang after commit 9ea7e6b62c2b ("init: Mark [arch_call_]rest_init() __noreturn"), modpost complains with:

WARNING: modpost: vmlinux.o: section mismatch in reference: check_bugs (section: .text) -> check_bugs32 (section: .init.text)

check_bugs() is only called from start_kernel(), which itself is marked __init, so there would not be any issues at run time. Make it obvious to modpost that this call chain is safe by marking check_bugs() as __init, which fixes the warning.

---
 arch/mips/include/asm/bugs.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index d72dc6e1cf3c..047e14227c45 100644
@@ -30,7 +30,7 @@ static inline void check_bugs_early(void)
 		check_bugs64_early();
 }
 
-static inline void check_bugs(void)
+static inline void __init check_bugs(void)
 {
 	unsigned int cpu = smp_processor_id();
 

2.40.0

If check_bugs_early() is not inlined, which a compiler is free to do after commit ac7c3e4ff401 ("compiler: enable CONFIG_OPTIMIZE_INLINING forcibly"), modpost would warn that check_bugs_early(), a non-init function, refers to check_bugs64_early(), which is marked __init. This would not result in any run time issues, as check_bugs_early() is only called from setup_arch(), which is marked __init.

To avoid this potential warning, just sink the body of check_bugs_early() into its single call site in setup_arch().

---
 arch/mips/include/asm/bugs.h | 6 ------
 arch/mips/kernel/setup.c     | 3 ++-
 2 files changed, 2 insertions(+), 7 deletions(-)

index 047e14227c45..653f78f3a685 100644
@@ -24,12 +24,6 @@ extern void check_bugs64_early(void);
 extern void check_bugs32(void);
 extern void check_bugs64(void);
 
-static inline void check_bugs_early(void)
-{
-	if (IS_ENABLED(CONFIG_CPU_R4X00_BUGS64))
-		check_bugs64_early();
-}
-
 static inline void __init check_bugs(void)
 {
 	unsigned int cpu = smp_processor_id();

index f1c88f8a1dc5..febdc5564638 100644
@@ -786,7 +786,8 @@ void __init setup_arch(char **cmdline_p)
 	setup_early_printk();
 #endif
 	cpu_report();
-	check_bugs_early();
+	if (IS_ENABLED(CONFIG_CPU_R4X00_BUGS64))
+		check_bugs64_early();
 
 #if defined(CONFIG_VT)
 #if defined(CONFIG_VGA_CONSOLE)

2.40.0

series applied to mips-next.

Thomas.

Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]