From 6ae8d04871f84d853673e9e9f3f713e77a2fe145 Mon Sep 17 00:00:00 2001 From: Daniel Santos Date: Thu, 21 Feb 2013 16:41:42 -0800 Subject: compiler{,-gcc4}.h, bug.h: Remove duplicate macros __linktime_error() does the same thing as __compiletime_error() and is only used in bug.h. Since the macro defines a function attribute that will cause a failure at compile-time (not link-time), it makes more sense to keep __compiletime_error(), which is also neatly mated with __compiletime_warning(). Signed-off-by: Daniel Santos Acked-by: David Rientjes Acked-by: Borislav Petkov Cc: Andi Kleen Cc: Joe Perches Cc: Josh Triplett Cc: Paul Gortmaker Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/bug.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux/bug.h') diff --git a/include/linux/bug.h b/include/linux/bug.h index b1cf40de847e..2a11774c5e64 100644 --- a/include/linux/bug.h +++ b/include/linux/bug.h @@ -74,7 +74,7 @@ extern int __build_bug_on_failed; #define BUILD_BUG() \ do { \ extern void __build_bug_failed(void) \ - __linktime_error("BUILD_BUG failed"); \ + __compiletime_error("BUILD_BUG failed");\ __build_bug_failed(); \ } while (0) -- cgit v1.2.3 From ca623c914e82c3351cd657073fdb24a1df8c27b9 Mon Sep 17 00:00:00 2001 From: Daniel Santos Date: Thu, 21 Feb 2013 16:41:44 -0800 Subject: bug.h: fix BUILD_BUG_ON macro in __CHECKER__ When __CHECKER__ is defined, we disable all of the BUILD_BUG.* macros. However, both BUILD_BUG_ON_NOT_POWER_OF_2 and BUILD_BUG_ON was evaluating to nothing in this case, and we want (0) since this is a function-like macro that will be followed by a semicolon. Signed-off-by: Daniel Santos Acked-by: Borislav Petkov Cc: Andi Kleen Cc: David Rientjes Cc: Joe Perches Cc: Josh Triplett Cc: Paul Gortmaker Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/bug.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'include/linux/bug.h') diff --git a/include/linux/bug.h b/include/linux/bug.h index 2a11774c5e64..27d404f91b3e 100644 --- a/include/linux/bug.h +++ b/include/linux/bug.h @@ -12,11 +12,11 @@ enum bug_trap_type { struct pt_regs; #ifdef __CHECKER__ -#define BUILD_BUG_ON_NOT_POWER_OF_2(n) +#define BUILD_BUG_ON_NOT_POWER_OF_2(n) (0) #define BUILD_BUG_ON_ZERO(e) (0) #define BUILD_BUG_ON_NULL(e) ((void*)0) #define BUILD_BUG_ON_INVALID(e) (0) -#define BUILD_BUG_ON(condition) +#define BUILD_BUG_ON(condition) (0) #define BUILD_BUG() (0) #else /* __CHECKER__ */ -- cgit v1.2.3 From 1d6a0d19c85587581a364850b77f30446810a560 Mon Sep 17 00:00:00 2001 From: Daniel Santos Date: Thu, 21 Feb 2013 16:41:45 -0800 Subject: bug.h: prevent double evaulation of `condition' in BUILD_BUG_ON When calling BUILD_BUG_ON in an optimized build using gcc 4.3 and later, the condition will be evaulated twice, possibily with side-effects. This patch eliminates that error. [akpm@linux-foundation.org: tweak code layout] Signed-off-by: Daniel Santos Cc: Andi Kleen Cc: Borislav Petkov Cc: David Rientjes Cc: Joe Perches Cc: Josh Triplett Cc: Paul Gortmaker Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/bug.h | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) (limited to 'include/linux/bug.h') diff --git a/include/linux/bug.h b/include/linux/bug.h index 27d404f91b3e..89fb91d0c929 100644 --- a/include/linux/bug.h +++ b/include/linux/bug.h @@ -59,9 +59,10 @@ struct pt_regs; extern int __build_bug_on_failed; #define BUILD_BUG_ON(condition) \ do { \ - ((void)sizeof(char[1 - 2*!!(condition)])); \ - if (condition) __build_bug_on_failed = 1; \ - } while(0) + bool __cond = !!(condition); \ + ((void)sizeof(char[1 - 2 * __cond])); \ + if (__cond) __build_bug_on_failed = 1; \ + } while (0) #endif /** -- cgit v1.2.3 From a3ccc497cd17147713363a4bf975f1a269fadb6d Mon Sep 17 00:00:00 2001 From: Daniel Santos Date: Thu, 21 Feb 2013 16:41:52 -0800 Subject: bug.h: make BUILD_BUG_ON generate compile-time error Negative sized arrays wont create a compile-time error in some cases starting with gcc 4.4 (e.g., inlined functions), but gcc 4.3 introduced the error function attribute that will. This patch modifies BUILD_BUG_ON to behave like BUILD_BUG already does, using the error function attribute so that you don't have to build the entire kernel to discover that you have a problem, and then enjoy trying to track it down from a link-time error. Also, we are only including asm/bug.h and then expecting that linux/compiler.h will eventually be included to define __linktime_error (used in BUILD_BUG_ON). This patch includes it directly for clarity and to avoid the possibility of changes in /*/include/asm/bug.h being changed or not including linux/compiler.h for some reason. Signed-off-by: Daniel Santos Acked-by: Borislav Petkov Cc: Andi Kleen Cc: David Rientjes Cc: Joe Perches Cc: Josh Triplett Cc: Paul Gortmaker Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/bug.h | 32 +++++++++++++++++++------------- 1 file changed, 19 insertions(+), 13 deletions(-) (limited to 'include/linux/bug.h') diff --git a/include/linux/bug.h b/include/linux/bug.h index 89fb91d0c929..73af37ca472c 100644 --- a/include/linux/bug.h +++ b/include/linux/bug.h @@ -2,6 +2,7 @@ #define _LINUX_BUG_H #include +#include enum bug_trap_type { BUG_TRAP_TYPE_NONE = 0, @@ -43,25 +44,30 @@ struct pt_regs; * @condition: the condition which the compiler should know is false. * * If you have some code which relies on certain constants being equal, or - * other compile-time-evaluated condition, you should use BUILD_BUG_ON to + * some other compile-time-evaluated condition, you should use BUILD_BUG_ON to * detect if someone changes it. * - * The implementation uses gcc's reluctance to create a negative array, but - * gcc (as of 4.4) only emits that error for obvious cases (eg. not arguments - * to inline functions). So as a fallback we use the optimizer; if it can't - * prove the condition is false, it will cause a link error on the undefined - * "__build_bug_on_failed". This error message can be harder to track down - * though, hence the two different methods. + * The implementation uses gcc's reluctance to create a negative array, but gcc + * (as of 4.4) only emits that error for obvious cases (e.g. not arguments to + * inline functions). Luckily, in 4.3 they added the "error" function + * attribute just for this type of case. Thus, we use a negative sized array + * (should always create an error on gcc versions older than 4.4) and then call + * an undefined function with the error attribute (should always create an + * error on gcc 4.3 and later). If for some reason, neither creates a + * compile-time error, we'll still have a link-time error, which is harder to + * track down. */ #ifndef __OPTIMIZE__ #define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)])) #else -extern int __build_bug_on_failed; -#define BUILD_BUG_ON(condition) \ - do { \ - bool __cond = !!(condition); \ - ((void)sizeof(char[1 - 2 * __cond])); \ - if (__cond) __build_bug_on_failed = 1; \ +#define BUILD_BUG_ON(condition) \ + do { \ + bool __cond = !!(condition); \ + extern void __build_bug_on_failed(void) \ + __compiletime_error("BUILD_BUG_ON failed"); \ + if (__cond) \ + __build_bug_on_failed(); \ + ((void)sizeof(char[1 - 2 * __cond])); \ } while (0) #endif -- cgit v1.2.3 From c361d3e54364d19bb5e803d6e766e94674da7b0e Mon Sep 17 00:00:00 2001 From: Daniel Santos Date: Thu, 21 Feb 2013 16:41:54 -0800 Subject: compiler.h, bug.h: prevent double error messages with BUILD_BUG{,_ON} Prior to the introduction of __attribute__((error("msg"))) in gcc 4.3, creating compile-time errors required a little trickery. BUILD_BUG{,_ON} uses this attribute when available to generate compile-time errors, but also uses the negative-sized array trick for older compilers, resulting in two error messages in some cases. The reason it's "some" cases is that as of gcc 4.4, the negative-sized array will not create an error in some situations, like inline functions. This patch replaces the negative-sized array code with the new __compiletime_error_fallback() macro which expands to the same thing unless the the error attribute is available, in which case it expands to do{}while(0), resulting in exactly one compile-time error on all versions of gcc. Note that we are not changing the negative-sized array code for the unoptimized version of BUILD_BUG_ON, since it has the potential to catch problems that would be disabled in later versions of gcc were __compiletime_error_fallback used. The reason is that that an unoptimized build can't always remove calls to an error-attributed function call (like we are using) that should effectively become dead code if it were optimized. However, using a negative-sized array with a similar value will not result in an false-positive (error). The only caveat being that it will also fail to catch valid conditions, which we should be expecting in an unoptimized build anyway. Signed-off-by: Daniel Santos Cc: Andi Kleen Cc: Borislav Petkov Cc: David Rientjes Cc: Joe Perches Cc: Josh Triplett Cc: Paul Gortmaker Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/bug.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux/bug.h') diff --git a/include/linux/bug.h b/include/linux/bug.h index 73af37ca472c..dc11dc762fc3 100644 --- a/include/linux/bug.h +++ b/include/linux/bug.h @@ -67,7 +67,7 @@ struct pt_regs; __compiletime_error("BUILD_BUG_ON failed"); \ if (__cond) \ __build_bug_on_failed(); \ - ((void)sizeof(char[1 - 2 * __cond])); \ + __compiletime_error_fallback(__cond); \ } while (0) #endif -- cgit v1.2.3 From 9a8ab1c39970a4938a72d94e6fd13be88a797590 Mon Sep 17 00:00:00 2001 From: Daniel Santos Date: Thu, 21 Feb 2013 16:41:55 -0800 Subject: bug.h, compiler.h: introduce compiletime_assert & BUILD_BUG_ON_MSG Introduce compiletime_assert to compiler.h, which moves the details of how to break a build and emit an error message for a specific compiler to the headers where these details should be. Following in the tradition of the POSIX assert macro, compiletime_assert creates a build-time error when the supplied condition is *false*. Next, we add BUILD_BUG_ON_MSG to bug.h which simply wraps compiletime_assert, inverting the logic, so that it fails when the condition is *true*, consistent with the language "build bug on." This macro allows you to specify the error message you want emitted when the supplied condition is true. Finally, we remove all other code from bug.h that mucks with these details (BUILD_BUG & BUILD_BUG_ON), and have them all call BUILD_BUG_ON_MSG. This not only reduces source code bloat, but also prevents the possibility of code being changed for one macro and not for the other (which was previously the case for BUILD_BUG and BUILD_BUG_ON). Since __compiletime_error_fallback is now only used in compiler.h, I'm considering it a private macro and removing the double negation that's now extraneous. [akpm@linux-foundation.org: checkpatch fixes] Signed-off-by: Daniel Santos Cc: Andi Kleen Cc: Borislav Petkov Cc: David Rientjes Cc: Joe Perches Cc: Josh Triplett Cc: Paul Gortmaker Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/bug.h | 28 +++++++++++++--------------- 1 file changed, 13 insertions(+), 15 deletions(-) (limited to 'include/linux/bug.h') diff --git a/include/linux/bug.h b/include/linux/bug.h index dc11dc762fc3..7f4818673c41 100644 --- a/include/linux/bug.h +++ b/include/linux/bug.h @@ -17,6 +17,7 @@ struct pt_regs; #define BUILD_BUG_ON_ZERO(e) (0) #define BUILD_BUG_ON_NULL(e) ((void*)0) #define BUILD_BUG_ON_INVALID(e) (0) +#define BUILD_BUG_ON_MSG(cond, msg) (0) #define BUILD_BUG_ON(condition) (0) #define BUILD_BUG() (0) #else /* __CHECKER__ */ @@ -39,6 +40,15 @@ struct pt_regs; */ #define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e)))) +/** + * BUILD_BUG_ON_MSG - break compile if a condition is true & emit supplied + * error message. + * @condition: the condition which the compiler should know is false. + * + * See BUILD_BUG_ON for description. + */ +#define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg) + /** * BUILD_BUG_ON - break compile if a condition is true. * @condition: the condition which the compiler should know is false. @@ -60,15 +70,8 @@ struct pt_regs; #ifndef __OPTIMIZE__ #define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)])) #else -#define BUILD_BUG_ON(condition) \ - do { \ - bool __cond = !!(condition); \ - extern void __build_bug_on_failed(void) \ - __compiletime_error("BUILD_BUG_ON failed"); \ - if (__cond) \ - __build_bug_on_failed(); \ - __compiletime_error_fallback(__cond); \ - } while (0) +#define BUILD_BUG_ON(condition) \ + BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition) #endif /** @@ -78,12 +81,7 @@ struct pt_regs; * build time, you should use BUILD_BUG to detect if it is * unexpectedly used. */ -#define BUILD_BUG() \ - do { \ - extern void __build_bug_failed(void) \ - __compiletime_error("BUILD_BUG failed");\ - __build_bug_failed(); \ - } while (0) +#define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed") #endif /* __CHECKER__ */ -- cgit v1.2.3