Subject: Re: [PATCH 1/4] panic: Allow warnings to set different taint flags

From: Helge Deller <[email-masked]>
Date: Mon, 05 Apr 2010 23:38:30 +0200

On 04/03/2010 08:34 PM, Ben Hutchings wrote:
> WARN() is used in some places to report firmware or hardware bugs that
> are then worked-around.  These bugs do not affect the stability of the
> kernel and should not set the flag for TAINT_WARN.  To allow for this,
> add WARN_TAINT() and WARN_TAINT_ONCE() macros that take a taint number
> as argument.
> 
> Architectures that implement warnings using trap instructions instead
> of calls to warn_slowpath_*() now implement __WARN_TAINT(taint)
> instead of __WARN().
> 
> Signed-off-by: Ben Hutchings <[email-masked]>

Builds and works on the parisc architecture.
Acked-by: Helge Deller <[email-masked]>

> ---
> Changes since the previous version:
> - Added note to Documentation/oops-tracing.txt
> - Changed the commit message to distinguish taint numbers from taint
>   flags
> - Removed 'must' from last sentence of commit message; this patch
>   converts all mainline architectures
> 
> Ben.
> 
>  Documentation/oops-tracing.txt |    1 +
>  arch/parisc/include/asm/bug.h  |    8 ++++----
>  arch/powerpc/include/asm/bug.h |    6 +++---
>  arch/s390/include/asm/bug.h    |    8 ++++----
>  arch/sh/include/asm/bug.h      |    4 ++--
>  include/asm-generic/bug.h      |   34 ++++++++++++++++++++++++++++++++--
>  kernel/panic.c                 |   24 ++++++++++++++++++++----
>  lib/bug.c                      |    2 +-
>  8 files changed, 67 insertions(+), 20 deletions(-)
> 
> diff --git a/Documentation/oops-tracing.txt b/Documentation/oops-tracing.txt
> index c10c022..069fab3 100644
> --- a/Documentation/oops-tracing.txt
> +++ b/Documentation/oops-tracing.txt
> @@ -256,6 +256,7 @@ characters, each representing a particular tainted value.
>    9: 'A' if the ACPI table has been overridden.
>  
>   10: 'W' if a warning has previously been issued by the kernel.
> +     (Though some warnings may set more specific taint flags.)
>  
>   11: 'C' if a staging driver has been loaded.
>  
> diff --git a/arch/parisc/include/asm/bug.h b/arch/parisc/include/asm/bug.h
> index 75e46c5..72cfdb0 100644
> --- a/arch/parisc/include/asm/bug.h
> +++ b/arch/parisc/include/asm/bug.h
> @@ -44,7 +44,7 @@
>  #endif
>  
>  #ifdef CONFIG_DEBUG_BUGVERBOSE
> -#define __WARN()							\
> +#define __WARN_TAINT(taint)						\
>  	do {								\
>  		asm volatile("\n"					\
>  			     "1:\t" PARISC_BUG_BREAK_ASM "\n"		\
> @@ -54,11 +54,11 @@
>  			     "\t.org 2b+%c3\n"				\
>  			     "\t.popsection"				\
>  			     : : "i" (__FILE__), "i" (__LINE__),	\
> -			     "i" (BUGFLAG_WARNING),			\
> +			     "i" (BUGFLAG_TAINT(taint)), 		\
>  			     "i" (sizeof(struct bug_entry)) );		\
>  	} while(0)
>  #else
> -#define __WARN()							\
> +#define __WARN_TAINT(taint)						\
>  	do {								\
>  		asm volatile("\n"					\
>  			     "1:\t" PARISC_BUG_BREAK_ASM "\n"		\
> @@ -67,7 +67,7 @@
>  			     "\t.short %c0\n"				\
>  			     "\t.org 2b+%c1\n"				\
>  			     "\t.popsection"				\
> -			     : : "i" (BUGFLAG_WARNING),			\
> +			     : : "i" (BUGFLAG_TAINT(taint)),		\
>  			     "i" (sizeof(struct bug_entry)) );		\
>  	} while(0)
>  #endif
> diff --git a/arch/powerpc/include/asm/bug.h b/arch/powerpc/include/asm/bug.h
> index 2c15212..065c590 100644
> --- a/arch/powerpc/include/asm/bug.h
> +++ b/arch/powerpc/include/asm/bug.h
> @@ -85,12 +85,12 @@
>  	}							\
>  } while (0)
>  
> -#define __WARN() do {						\
> +#define __WARN_TAINT(taint) do {				\
>  	__asm__ __volatile__(					\
>  		"1:	twi 31,0,0\n"				\
>  		_EMIT_BUG_ENTRY					\
>  		: : "i" (__FILE__), "i" (__LINE__),		\
> -		  "i" (BUGFLAG_WARNING),			\
> +		  "i" (BUGFLAG_TAINT(taint)),			\
>  		  "i" (sizeof(struct bug_entry)));		\
>  } while (0)
>  
> @@ -104,7 +104,7 @@
>  		"1:	"PPC_TLNEI"	%4,0\n"			\
>  		_EMIT_BUG_ENTRY					\
>  		: : "i" (__FILE__), "i" (__LINE__),		\
> -		  "i" (BUGFLAG_WARNING),			\
> +		  "i" (BUGFLAG_TAINT(TAINT_WARN)),		\
>  		  "i" (sizeof(struct bug_entry)),		\
>  		  "r" (__ret_warn_on));				\
>  	}							\
> diff --git a/arch/s390/include/asm/bug.h b/arch/s390/include/asm/bug.h
> index 9beeb9d..bf90d1f 100644
> --- a/arch/s390/include/asm/bug.h
> +++ b/arch/s390/include/asm/bug.h
> @@ -46,18 +46,18 @@
>  	unreachable();					\
>  } while (0)
>  
> -#define __WARN() do {					\
> -	__EMIT_BUG(BUGFLAG_WARNING);			\
> +#define __WARN_TAINT(taint) do {			\
> +	__EMIT_BUG(BUGFLAG_TAINT(taint));		\
>  } while (0)
>  
>  #define WARN_ON(x) ({					\
>  	int __ret_warn_on = !!(x);			\
>  	if (__builtin_constant_p(__ret_warn_on)) {	\
>  		if (__ret_warn_on)			\
> -			__EMIT_BUG(BUGFLAG_WARNING);	\
> +			__WARN();			\
>  	} else {					\
>  		if (unlikely(__ret_warn_on))		\
> -			__EMIT_BUG(BUGFLAG_WARNING);	\
> +			__WARN();			\
>  	}						\
>  	unlikely(__ret_warn_on);			\
>  })
> diff --git a/arch/sh/include/asm/bug.h b/arch/sh/include/asm/bug.h
> index d02c01b..6323f86 100644
> --- a/arch/sh/include/asm/bug.h
> +++ b/arch/sh/include/asm/bug.h
> @@ -48,7 +48,7 @@ do {							\
>  		   "i" (sizeof(struct bug_entry)));	\
>  } while (0)
>  
> -#define __WARN()					\
> +#define __WARN_TAINT(taint)				\
>  do {							\
>  	__asm__ __volatile__ (				\
>  		"1:\t.short %O0\n"			\
> @@ -57,7 +57,7 @@ do {							\
>  		 : "n" (TRAPA_BUG_OPCODE),		\
>  		   "i" (__FILE__),			\
>  		   "i" (__LINE__),			\
> -		   "i" (BUGFLAG_WARNING),		\
> +		   "i" (BUGFLAG_TAINT(taint)),		\
>  		   "i" (sizeof(struct bug_entry)));	\
>  } while (0)
>  
> diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h
> index 18c435d..c2c9ba0 100644
> --- a/include/asm-generic/bug.h
> +++ b/include/asm-generic/bug.h
> @@ -25,7 +25,10 @@ struct bug_entry {
>  };
>  #endif		/* __ASSEMBLY__ */
>  
> -#define BUGFLAG_WARNING	(1<<0)
> +#define BUGFLAG_WARNING		(1 << 0)
> +#define BUGFLAG_TAINT(taint)	(BUGFLAG_WARNING | ((taint) << 8))
> +#define BUG_GET_TAINT(bug)	((bug)->flags >> 8)
> +
>  #endif	/* CONFIG_GENERIC_BUG */
>  
>  /*
> @@ -56,17 +59,25 @@ struct bug_entry {
>   * appear at runtime.  Use the versions with printk format strings
>   * to provide better diagnostics.
>   */
> -#ifndef __WARN
> +#ifndef __WARN_TAINT
>  #ifndef __ASSEMBLY__
>  extern void warn_slowpath_fmt(const char *file, const int line,
>  		const char *fmt, ...) __attribute__((format(printf, 3, 4)));
> +extern void warn_slowpath_fmt_taint(const char *file, const int line,
> +				    unsigned taint, const char *fmt, ...)
> +	__attribute__((format(printf, 4, 5)));
>  extern void warn_slowpath_null(const char *file, const int line);
>  #define WANT_WARN_ON_SLOWPATH
>  #endif
>  #define __WARN()		warn_slowpath_null(__FILE__, __LINE__)
>  #define __WARN_printf(arg...)	warn_slowpath_fmt(__FILE__, __LINE__, arg)
> +#define __WARN_printf_taint(taint, arg...)				\
> +	warn_slowpath_fmt_taint(__FILE__, __LINE__, taint, arg)
>  #else
> +#define __WARN()		__WARN_TAINT(TAINT_WARN)
>  #define __WARN_printf(arg...)	do { printk(arg); __WARN(); } while (0)
> +#define __WARN_printf_taint(taint, arg...)				\
> +	do { printk(arg); __WARN_TAINT(taint); } while (0)
>  #endif
>  
>  #ifndef WARN_ON
> @@ -87,6 +98,13 @@ extern void warn_slowpath_null(const char *file, const int line);
>  })
>  #endif
>  
> +#define WARN_TAINT(condition, taint, format...) ({			\
> +	int __ret_warn_on = !!(condition);				\
> +	if (unlikely(__ret_warn_on))					\
> +		__WARN_printf_taint(taint, format);			\
> +	unlikely(__ret_warn_on);					\
> +})
> +
>  #else /* !CONFIG_BUG */
>  #ifndef HAVE_ARCH_BUG
>  #define BUG() do {} while(0)
> @@ -110,6 +128,8 @@ extern void warn_slowpath_null(const char *file, const int line);
>  })
>  #endif
>  
> +#define WARN_TAINT(condition, taint, format...) WARN_ON(condition)
> +
>  #endif
>  
>  #define WARN_ON_ONCE(condition)	({				\
> @@ -132,6 +152,16 @@ extern void warn_slowpath_null(const char *file, const int line);
>  	unlikely(__ret_warn_once);				\
>  })
>  
> +#define WARN_TAINT_ONCE(condition, taint, format...)	({	\
> +	static bool __warned;					\
> +	int __ret_warn_once = !!(condition);			\
> +								\
> +	if (unlikely(__ret_warn_once))				\
> +		if (WARN_TAINT(!__warned, taint, format))	\
> +			__warned = true;			\
> +	unlikely(__ret_warn_once);				\
> +})
> +
>  #define WARN_ON_RATELIMIT(condition, state)			\
>  		WARN_ON((condition) && __ratelimit(state))
>  
> diff --git a/kernel/panic.c b/kernel/panic.c
> index 13d966b..8b821bc 100644
> --- a/kernel/panic.c
> +++ b/kernel/panic.c
> @@ -365,7 +365,8 @@ struct slowpath_args {
>  	va_list args;
>  };
>  
> -static void warn_slowpath_common(const char *file, int line, void *caller, struct slowpath_args *args)
> +static void warn_slowpath_common(const char *file, int line, void *caller,
> +				 unsigned taint, struct slowpath_args *args)
>  {
>  	const char *board;
>  
> @@ -381,7 +382,7 @@ static void warn_slowpath_common(const char *file, int line, void *caller, struc
>  	print_modules();
>  	dump_stack();
>  	print_oops_end_marker();
> -	add_taint(TAINT_WARN);
> +	add_taint(taint);
>  }
>  
>  void warn_slowpath_fmt(const char *file, int line, const char *fmt, ...)
> @@ -390,14 +391,29 @@ void warn_slowpath_fmt(const char *file, int line, const char *fmt, ...)
>  
>  	args.fmt = fmt;
>  	va_start(args.args, fmt);
> -	warn_slowpath_common(file, line, __builtin_return_address(0), &args);
> +	warn_slowpath_common(file, line, __builtin_return_address(0),
> +			     TAINT_WARN, &args);
>  	va_end(args.args);
>  }
>  EXPORT_SYMBOL(warn_slowpath_fmt);
>  
> +void warn_slowpath_fmt_taint(const char *file, int line,
> +			     unsigned taint, const char *fmt, ...)
> +{
> +	struct slowpath_args args;
> +
> +	args.fmt = fmt;
> +	va_start(args.args, fmt);
> +	warn_slowpath_common(file, line, __builtin_return_address(0),
> +			     taint, &args);
> +	va_end(args.args);
> +}
> +EXPORT_SYMBOL(warn_slowpath_fmt_taint);
> +
>  void warn_slowpath_null(const char *file, int line)
>  {
> -	warn_slowpath_common(file, line, __builtin_return_address(0), NULL);
> +	warn_slowpath_common(file, line, __builtin_return_address(0),
> +			     TAINT_WARN, NULL);
>  }
>  EXPORT_SYMBOL(warn_slowpath_null);
>  #endif
> diff --git a/lib/bug.c b/lib/bug.c
> index 300e41a..f13daf4 100644
> --- a/lib/bug.c
> +++ b/lib/bug.c
> @@ -165,7 +165,7 @@ enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
>  			       (void *)bugaddr);
>  
>  		show_regs(regs);
> -		add_taint(TAINT_WARN);
> +		add_taint(BUG_GET_TAINT(bug));
>  		return BUG_TRAP_TYPE_WARN;
>  	}
>