Re: [PATCH] mbcache: LLVMLinux: Remove double calculation from mbcache
On 04/29/2014 06:13 PM, H. Peter Anvin wrote: > I suspect this will generate FP instructions on x86 which will corrupt user > space state. This is thus a critical bug!! It looks like at least x86-64 gcc does the evaluation at compile time and there aren't any fp instructions left in the code. However, it should still be fixed. -hpa -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] mbcache: LLVMLinux: Remove double calculation from mbcache
I suspect this will generate FP instructions on x86 which will corrupt user space state. This is thus a critical bug!! On April 29, 2014 6:10:39 PM PDT, beh...@converseincode.com wrote: >From: Mark Charlebois > >The call to __builtin_log2 presumes there is a >double log2(double x) function defined in the kernel. > >The call to hash_log is a call to hash_64 which is >defined in include/linux/hash.h > >static __always_inline u64 hash_64(u64 val, unsigned int bits) > >That means that __builtin_log2(NR_BG_LOCKS) is converting >NR_BG_LOCKS to a double and returning a double and then that >is converted to an unsigned int. > >Using ilog2 is much more appropriate and efficient. > >Another side effect of using __builtin_log2 is that is uses >__aeabi_* functions for ARM that require linking with libgcc.a. > >Author: Mark Charlebois >Signed-off-by: Mark Charlebois >Signed-off-by: Behan Webster >--- > fs/mbcache.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > >diff --git a/fs/mbcache.c b/fs/mbcache.c >index bf166e3..2c0752b 100644 >--- a/fs/mbcache.c >+++ b/fs/mbcache.c >@@ -93,7 +93,7 @@ > > #define MB_CACHE_WRITER ((unsigned short)~0U >> 1) > >-#define MB_CACHE_ENTRY_LOCK_BITS __builtin_log2(NR_BG_LOCKS) >+#define MB_CACHE_ENTRY_LOCK_BITS ilog2(NR_BG_LOCKS) > #define MB_CACHE_ENTRY_LOCK_INDEX(ce) \ > (hash_long((unsigned long)ce, MB_CACHE_ENTRY_LOCK_BITS)) > -- Sent from my mobile phone. Please pardon brevity and lack of formatting. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH] mbcache: LLVMLinux: Remove double calculation from mbcache
From: Mark Charlebois The call to __builtin_log2 presumes there is a double log2(double x) function defined in the kernel. The call to hash_log is a call to hash_64 which is defined in include/linux/hash.h static __always_inline u64 hash_64(u64 val, unsigned int bits) That means that __builtin_log2(NR_BG_LOCKS) is converting NR_BG_LOCKS to a double and returning a double and then that is converted to an unsigned int. Using ilog2 is much more appropriate and efficient. Another side effect of using __builtin_log2 is that is uses __aeabi_* functions for ARM that require linking with libgcc.a. Author: Mark Charlebois Signed-off-by: Mark Charlebois Signed-off-by: Behan Webster --- fs/mbcache.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/mbcache.c b/fs/mbcache.c index bf166e3..2c0752b 100644 --- a/fs/mbcache.c +++ b/fs/mbcache.c @@ -93,7 +93,7 @@ #define MB_CACHE_WRITER ((unsigned short)~0U >> 1) -#define MB_CACHE_ENTRY_LOCK_BITS __builtin_log2(NR_BG_LOCKS) +#define MB_CACHE_ENTRY_LOCK_BITS ilog2(NR_BG_LOCKS) #defineMB_CACHE_ENTRY_LOCK_INDEX(ce) \ (hash_long((unsigned long)ce, MB_CACHE_ENTRY_LOCK_BITS)) -- 1.8.3.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH] mbcache: LLVMLinux: Remove double calculation from mbcache
From: Mark Charlebois charl...@gmail.com The call to __builtin_log2 presumes there is a double log2(double x) function defined in the kernel. The call to hash_log is a call to hash_64 which is defined in include/linux/hash.h static __always_inline u64 hash_64(u64 val, unsigned int bits) That means that __builtin_log2(NR_BG_LOCKS) is converting NR_BG_LOCKS to a double and returning a double and then that is converted to an unsigned int. Using ilog2 is much more appropriate and efficient. Another side effect of using __builtin_log2 is that is uses __aeabi_* functions for ARM that require linking with libgcc.a. Author: Mark Charlebois charl...@gmail.com Signed-off-by: Mark Charlebois charl...@gmail.com Signed-off-by: Behan Webster beh...@converseincode.com --- fs/mbcache.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/mbcache.c b/fs/mbcache.c index bf166e3..2c0752b 100644 --- a/fs/mbcache.c +++ b/fs/mbcache.c @@ -93,7 +93,7 @@ #define MB_CACHE_WRITER ((unsigned short)~0U 1) -#define MB_CACHE_ENTRY_LOCK_BITS __builtin_log2(NR_BG_LOCKS) +#define MB_CACHE_ENTRY_LOCK_BITS ilog2(NR_BG_LOCKS) #defineMB_CACHE_ENTRY_LOCK_INDEX(ce) \ (hash_long((unsigned long)ce, MB_CACHE_ENTRY_LOCK_BITS)) -- 1.8.3.2 -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] mbcache: LLVMLinux: Remove double calculation from mbcache
I suspect this will generate FP instructions on x86 which will corrupt user space state. This is thus a critical bug!! On April 29, 2014 6:10:39 PM PDT, beh...@converseincode.com wrote: From: Mark Charlebois charl...@gmail.com The call to __builtin_log2 presumes there is a double log2(double x) function defined in the kernel. The call to hash_log is a call to hash_64 which is defined in include/linux/hash.h static __always_inline u64 hash_64(u64 val, unsigned int bits) That means that __builtin_log2(NR_BG_LOCKS) is converting NR_BG_LOCKS to a double and returning a double and then that is converted to an unsigned int. Using ilog2 is much more appropriate and efficient. Another side effect of using __builtin_log2 is that is uses __aeabi_* functions for ARM that require linking with libgcc.a. Author: Mark Charlebois charl...@gmail.com Signed-off-by: Mark Charlebois charl...@gmail.com Signed-off-by: Behan Webster beh...@converseincode.com --- fs/mbcache.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/mbcache.c b/fs/mbcache.c index bf166e3..2c0752b 100644 --- a/fs/mbcache.c +++ b/fs/mbcache.c @@ -93,7 +93,7 @@ #define MB_CACHE_WRITER ((unsigned short)~0U 1) -#define MB_CACHE_ENTRY_LOCK_BITS __builtin_log2(NR_BG_LOCKS) +#define MB_CACHE_ENTRY_LOCK_BITS ilog2(NR_BG_LOCKS) #define MB_CACHE_ENTRY_LOCK_INDEX(ce) \ (hash_long((unsigned long)ce, MB_CACHE_ENTRY_LOCK_BITS)) -- Sent from my mobile phone. Please pardon brevity and lack of formatting. -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] mbcache: LLVMLinux: Remove double calculation from mbcache
On 04/29/2014 06:13 PM, H. Peter Anvin wrote: I suspect this will generate FP instructions on x86 which will corrupt user space state. This is thus a critical bug!! It looks like at least x86-64 gcc does the evaluation at compile time and there aren't any fp instructions left in the code. However, it should still be fixed. -hpa -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH] mbcache: LLVMLinux: Remove double calculation from mbcache
From: Mark Charlebois The call to __builtin_log2 presumes there is a double log2(double x) function defined in the kernel. The call to hash_log is a call to hash_64 which is defined in include/linux/hash.h static __always_inline u64 hash_64(u64 val, unsigned int bits) That means that __builtin_log2(NR_BG_LOCKS) is converting NR_BG_LOCKS to a double and returning a double and then that is converted to an unsigned int. Using ilog2 is much more appropriate and efficient. Another side effect of using __builtin_log2 is that is uses __aeabi_* functions for ARM that require linking with libgcc.a. Author: Mark Charlebois Signed-off-by: Mark Charlebois Signed-off-by: Behan Webster --- fs/mbcache.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/mbcache.c b/fs/mbcache.c index bf166e3..2c0752b 100644 --- a/fs/mbcache.c +++ b/fs/mbcache.c @@ -93,7 +93,7 @@ #define MB_CACHE_WRITER ((unsigned short)~0U >> 1) -#define MB_CACHE_ENTRY_LOCK_BITS __builtin_log2(NR_BG_LOCKS) +#define MB_CACHE_ENTRY_LOCK_BITS ilog2(NR_BG_LOCKS) #defineMB_CACHE_ENTRY_LOCK_INDEX(ce) \ (hash_long((unsigned long)ce, MB_CACHE_ENTRY_LOCK_BITS)) -- 1.8.3.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH] mbcache: LLVMLinux: Remove double calculation from mbcache
From: Mark Charlebois charl...@gmail.com The call to __builtin_log2 presumes there is a double log2(double x) function defined in the kernel. The call to hash_log is a call to hash_64 which is defined in include/linux/hash.h static __always_inline u64 hash_64(u64 val, unsigned int bits) That means that __builtin_log2(NR_BG_LOCKS) is converting NR_BG_LOCKS to a double and returning a double and then that is converted to an unsigned int. Using ilog2 is much more appropriate and efficient. Another side effect of using __builtin_log2 is that is uses __aeabi_* functions for ARM that require linking with libgcc.a. Author: Mark Charlebois charl...@gmail.com Signed-off-by: Mark Charlebois charl...@gmail.com Signed-off-by: Behan Webster beh...@converseincode.com --- fs/mbcache.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/mbcache.c b/fs/mbcache.c index bf166e3..2c0752b 100644 --- a/fs/mbcache.c +++ b/fs/mbcache.c @@ -93,7 +93,7 @@ #define MB_CACHE_WRITER ((unsigned short)~0U 1) -#define MB_CACHE_ENTRY_LOCK_BITS __builtin_log2(NR_BG_LOCKS) +#define MB_CACHE_ENTRY_LOCK_BITS ilog2(NR_BG_LOCKS) #defineMB_CACHE_ENTRY_LOCK_INDEX(ce) \ (hash_long((unsigned long)ce, MB_CACHE_ENTRY_LOCK_BITS)) -- 1.8.3.2 -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
