linux-kernel - Re: [COMBO PATCH 6/5] bugs/arch: Wire in the 'cond_str' string to the WARN/BUG output machinery of PowerPC, LoongArch, S390, RISC-V, PA-RISC and SH

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Message-ID: <Z-UOnlDWeII5IbI6@gmail.com>
Date: Thu, 27 Mar 2025 09:38:54 +0100
From: Ingo Molnar <mingo@...nel.org>
To: Peter Zijlstra <peterz@...radead.org>
Cc: linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [COMBO PATCH 6/5] bugs/arch: Wire in the 'cond_str' string to
 the WARN/BUG output machinery of PowerPC, LoongArch, S390, RISC-V, PA-RISC
 and SH


* Ingo Molnar <mingo@...nel.org> wrote:

> ... some time later:
> 
>  b2becbe8b469 bugs/s390: Pass in 'cond_str' to __EMIT_BUG() and use it

> --- a/arch/s390/include/asm/bug.h
> +++ b/arch/s390/include/asm/bug.h
> @@ -8,7 +8,7 @@
>  
>  #ifdef CONFIG_DEBUG_BUGVERBOSE
>  
> -#define __EMIT_BUG(x) do {					\
> +#define __EMIT_BUG(cond_str, x) do {				\
>  	asm_inline volatile(					\
>  		"0:	mc	0,0\n"				\
>  		".section .rodata.str,\"aMS\",@progbits,1\n"	\
> @@ -20,14 +20,14 @@
>  		"	.short	%0,%1\n"			\
>  		"	.org	2b+%2\n"			\
>  		".previous\n"					\
> -		: : "i" (__LINE__),				\
> +		: : "i" (cond_str __LINE__),			\
>  		    "i" (x),					\
>  		    "i" (sizeof(struct bug_entry)));		\
>  } while (0)
>  
>  #else /* CONFIG_DEBUG_BUGVERBOSE */
>  
> -#define __EMIT_BUG(x) do {					\
> +#define __EMIT_BUG(cond_str, x) do {				\
>  	asm_inline volatile(					\
>  		"0:	mc	0,0\n"				\
>  		".section __bug_table,\"aw\"\n"			\
> @@ -42,12 +42,12 @@
>  #endif /* CONFIG_DEBUG_BUGVERBOSE */
>  
>  #define BUG() do {					\
> -	__EMIT_BUG(0);					\
> +	__EMIT_BUG("", 0);				\
>  	unreachable();					\
>  } while (0)
>  
>  #define __WARN_FLAGS(cond_str, flags) do {		\
> -	__EMIT_BUG(BUGFLAG_WARNING|(flags));		\
> +	__EMIT_BUG(cond_str, BUGFLAG_WARNING|(flags));	\
>  } while (0)
>  
>  #define WARN_ON(x) ({					\

So the fix below makes it build on S390, but it won't link:

 kernel/exit.o:(__bug_table+0x8): relocation truncated to fit: R_390_16 against `.rodata.str1.2'
 kernel/exit.o:(__bug_table+0x14): relocation truncated to fit: R_390_16 against `.rodata.str1.2'
 kernel/exit.o:(__bug_table+0x20): relocation truncated to fit: R_390_16 against `.rodata.str1.2'
 kernel/exit.o:(__bug_table+0x2c): relocation truncated to fit: R_390_16 against `.rodata.str1.2'
 kernel/exit.o:(__bug_table+0x38): relocation truncated to fit: R_390_16 against `.rodata.str1.2'
 kernel/exit.o:(__bug_table+0x44): relocation truncated to fit: R_390_16 against `.rodata.str1.2'
 kernel/exit.o:(__bug_table+0x50): relocation truncated to fit: R_390_16 against `.rodata.str1.2'
 init/main.o:(__bug_table+0x8): relocation truncated to fit: R_390_16 against `.rodata.str1.2'
 init/main.o:(__bug_table+0x14): relocation truncated to fit: R_390_16 against `.rodata.str1.2'
 init/main.o:(__bug_table+0x20): relocation truncated to fit: R_390_16 against `.rodata.str1.2'
 init/main.o:(__bug_table+0x2c): additional relocation overflows omitted from the output

>From the _16 name my rough guess is that the larger string table has 
overflown 16 bits (64k)?

At which point I'd much rather go back to plan-A: pass in cond_str to 
__WARN_FLAGS(), and wash my hands and leave architectures to make use 
of them as they wish to. :-)

Thanks,

	Ingo

=====================>

 arch/s390/include/asm/bug.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/s390/include/asm/bug.h b/arch/s390/include/asm/bug.h
index e3d839517c17..7eb9b44f78cb 100644
--- a/arch/s390/include/asm/bug.h
+++ b/arch/s390/include/asm/bug.h
@@ -20,7 +20,7 @@
 		"	.short	%0,%1\n"			\
 		"	.org	2b+%2\n"			\
 		".previous\n"					\
-		: : "i" (cond_str __LINE__),			\
+		: : "i" (__stringify(cond_str __LINE__)),	\
 		    "i" (x),					\
 		    "i" (sizeof(struct bug_entry)));		\
 } while (0)