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Today I am proud to announce that I'm releasing a tool I've used privately for well over a year now. It is a multi-threaded network testing tool which gives the user great control over how many connections, threads and processes the tool uses, and which CPU cores the threads/processes are allowed to execute on. Currently the ...

I found this neat little command to list all the GCC compiler defined symbols gcc -dM -E - < /dev/null This can help if you aren't quite sure which defines are used on your systems. For example my FreeBSD 7.1 machine outputs this: #define __DBL_MIN_EXP__ (-1021) #define __FLT_MIN__ 1.17549435e-38F #define __DEC64_DEN__ 0.000000000000001E-383DD #define __CHAR_BIT__ 8 #define __WCHAR_MAX__ 2147483647 #define __DBL_DENORM_MIN__ 4.9406564584124654e-324 #define __FLT_EVAL_METHOD__ 0 #define __DBL_MIN_10_EXP__ (-307) #define __FINITE_MATH_ONLY__ 0 #define __DEC64_MAX_EXP__ 384 #define __SHRT_MAX__ 32767 #define __LDBL_MAX__ 1.18973149535723176502e+4932L #define __UINTMAX_TYPE__ long unsigned int #define __DEC32_EPSILON__ 1E-6DF #define __unix 1 #define __SCHAR_MAX__ 127 #define __USER_LABEL_PREFIX__ #define __STDC_HOSTED__ 1 #define __DEC64_MIN_EXP__ (-383) #define __DBL_DIG__ 15 #define __FLT_EPSILON__ 1.19209290e-7F #define __LDBL_MIN__ 3.36210314311209350626e-4932L #define __DEC32_MAX__ 9.999999E96DF #define __unix__ 1 #define __DECIMAL_DIG__ 21 #define __LDBL_HAS_QUIET_NAN__ 1 #define __GNUC__ 4 #define __MMX__ 1 #define __FLT_HAS_DENORM__ 1 #define __FreeBSD_cc_version 700003 #define __DBL_MAX__ 1.7976931348623157e+308 #define __DBL_HAS_INFINITY__ 1 #define __DEC32_MIN_EXP__ (-95) #define __LDBL_HAS_DENORM__ 1 #define __DEC32_MIN__ 1E-95DF #define __DBL_MAX_EXP__ 1024 #define __DEC128_EPSILON__ 1E-33DL #define __SSE2_MATH__ 1 #define __amd64 1 #define __LONG_LONG_MAX__ 9223372036854775807LL #define __GXX_ABI_VERSION 1002 #define __FLT_MIN_EXP__ (-125) #define __x86_64 1 #define __DBL_MIN__ 2.2250738585072014e-308 #define __LP64__ 1 #define __DBL_HAS_QUIET_NAN__ 1 #define __DEC128_MIN__ 1E-6143DL #define __REGISTER_PREFIX__ #define __DBL_HAS_DENORM__ 1 #define __NO_INLINE__ 1 #define __DEC_EVAL_METHOD__ 2 #define __DEC128_MAX__ 9.999999999999999999999999999999999E6144DL #define __FLT_MANT_DIG__ 24 #define __VERSION__ "4.2.1 20070719 [FreeBSD]" #define __DEC64_EPSILON__ 1E-15DD #define __DEC128_MIN_EXP__ (-6143) #define unix 1 #define __SIZE_TYPE__ long unsigned int #define __DEC32_DEN__ 0.000001E-95DF #define __ELF__ 1 #define __FLT_RADIX__ 2 #define __LDBL_EPSILON__ 1.08420217248550443401e-19L #define __FreeBSD__ 7 #define __SSE_MATH__ 1 #define __k8 1 #define __LDBL_DIG__ 18 #define __KPRINTF_ATTRIBUTE__ 1 #define __x86_64__ 1 #define __FLT_HAS_QUIET_NAN__ 1 #define __FLT_MAX_10_EXP__ 38 #define __LONG_MAX__ 9223372036854775807L #define __FLT_HAS_INFINITY__ 1 #define __DEC64_MAX__ 9.999999999999999E384DD #define __DEC64_MANT_DIG__ 16 #define __DEC32_MAX_EXP__ 96 #define __DEC128_DEN__ 0.000000000000000000000000000000001E-6143DL #define __LDBL_MANT_DIG__ 64 #define _LONGLONG 1 #define __DEC32_MANT_DIG__ 7 #define __k8__ 1 #define __WCHAR_TYPE__ int #define __FLT_DIG__ 6 #define __INT_MAX__ 2147483647 #define __FLT_MAX_EXP__ 128 #define __DBL_MANT_DIG__ 53 #define __DEC64_MIN__ 1E-383DD #define __WINT_TYPE__ unsigned int #define __SSE__ 1 #define __LDBL_MIN_EXP__ (-16381) #define __amd64__ 1 #define __LDBL_MAX_EXP__ 16384 #define __LDBL_MAX_10_EXP__ 4932 #define __DBL_EPSILON__ 2.2204460492503131e-16 #define _LP64 1 #define __GNUC_PATCHLEVEL__ 1 #define __LDBL_HAS_INFINITY__ 1 #define __INTMAX_MAX__ 9223372036854775807L #define __FLT_DENORM_MIN__ 1.40129846e-45F #define __FLT_MAX__ 3.40282347e+38F #define __SSE2__ 1 #define __FLT_MIN_10_EXP__ (-37) #define __INTMAX_TYPE__ long int #define __DEC128_MAX_EXP__ 6144 #define __GNUC_MINOR__ 2 #define __DBL_MAX_10_EXP__ 308 #define __LDBL_DENORM_MIN__ 3.64519953188247460253e-4951L #define __STDC__ 1 #define __PTRDIFF_TYPE__ long int #define __DEC128_MANT_DIG__ 34 #define __LDBL_MIN_10_EXP__ (-4931) #define __GNUC_GNU_INLINE__ 1 and my Debian Linux machine outputs this: #define __DBL_MIN_EXP__ (-1021) #define __FLT_MIN__ 1.17549435e-38F #define __DEC64_DEN__ 0.000000000000001E-383DD #define __CHAR_BIT__ 8 #define __WCHAR_MAX__ 2147483647 #define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_1 1 #define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_2 1 #define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_4 1 #define __DBL_DENORM_MIN__ 4.9406564584124654e-324 #define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_8 1 #define __FLT_EVAL_METHOD__ 0 #define __unix__ 1 #define __x86_64 1 #define __DBL_MIN_10_EXP__ (-307) #define __FINITE_MATH_ONLY__ 0 #define __GNUC_PATCHLEVEL__ 3 #define __DEC64_MAX_EXP__ 384 #define __SHRT_MAX__ 32767 #define __LDBL_MAX__ 1.18973149535723176502e+4932L #define __UINTMAX_TYPE__ long unsigned int #define __linux 1 #define __DEC32_EPSILON__ 1E-6DF #define __unix 1 #define __LDBL_MAX_EXP__ 16384 #define __linux__ 1 #define __SCHAR_MAX__ 127 #define __DBL_DIG__ 15 #define __SIZEOF_INT__ 4 #define __SIZEOF_POINTER__ 8 #define __USER_LABEL_PREFIX__ #define __STDC_HOSTED__ 1 #define __LDBL_HAS_INFINITY__ 1 #define __FLT_EPSILON__ 1.19209290e-7F #define __LDBL_MIN__ 3.36210314311209350626e-4932L #define __DEC32_MAX__ 9.999999E96DF #define __SIZEOF_LONG__ 8 #define __DECIMAL_DIG__ 21 #define __gnu_linux__ 1 #define __LDBL_HAS_QUIET_NAN__ 1 #define __GNUC__ 4 #define __MMX__ 1 #define __FLT_HAS_DENORM__ 1 #define __SIZEOF_LONG_DOUBLE__ 16 #define __DBL_MAX__ 1.7976931348623157e+308 #define __DBL_HAS_INFINITY__ 1 #define __DEC32_MIN_EXP__ (-95) #define __LDBL_HAS_DENORM__ 1 #define __DEC128_MAX__ 9.999999999999999999999999999999999E6144DL #define __DEC32_MIN__ 1E-95DF #define __DBL_MAX_EXP__ 1024 #define __DEC128_EPSILON__ 1E-33DL #define __SSE2_MATH__ 1 #define __amd64 1 #define __LONG_LONG_MAX__ 9223372036854775807LL #define __SIZEOF_SIZE_T__ 8 #define __SIZEOF_WINT_T__ 4 #define __GXX_ABI_VERSION 1002 #define __FLT_MIN_EXP__ (-125) #define __DBL_MIN__ 2.2250738585072014e-308 #define __LP64__ 1 #define __DECIMAL_BID_FORMAT__ 1 #define __DEC128_MIN__ 1E-6143DL #define __REGISTER_PREFIX__ #define __DBL_HAS_DENORM__ 1 #define __NO_INLINE__ 1 #define __FLT_MANT_DIG__ 24 #define __VERSION__ "4.3.3" #define __DEC64_EPSILON__ 1E-15DD #define __DEC128_MIN_EXP__ (-6143) #define unix 1 #define __SIZE_TYPE__ long unsigned int #define __DEC32_DEN__ 0.000001E-95DF #define __ELF__ 1 #define __FLT_RADIX__ 2 #define __LDBL_EPSILON__ 1.08420217248550443401e-19L #define __SSE_MATH__ 1 #define __k8 1 #define __SIZEOF_PTRDIFF_T__ 8 #define __x86_64__ 1 #define __FLT_HAS_QUIET_NAN__ 1 #define __FLT_MAX_10_EXP__ 38 #define __LONG_MAX__ 9223372036854775807L #define __FLT_HAS_INFINITY__ 1 #define __DEC64_MAX__ 9.999999999999999E384DD #define __DEC64_MANT_DIG__ 16 #define __DEC32_MAX_EXP__ 96 #define linux 1 #define __DEC128_DEN__ 0.000000000000000000000000000000001E-6143DL #define __SSE2__ 1 #define __LDBL_MANT_DIG__ 64 #define __DBL_HAS_QUIET_NAN__ 1 #define __k8__ 1 #define __WCHAR_TYPE__ int #define __SIZEOF_FLOAT__ 4 #define __DEC64_MIN_EXP__ (-383) #define __FLT_DIG__ 6 #define __INT_MAX__ 2147483647 #define __amd64__ 1 #define __FLT_MAX_EXP__ 128 #define __DBL_MANT_DIG__ 53 #define __DEC64_MIN__ 1E-383DD #define __WINT_TYPE__ unsigned int #define __SIZEOF_SHORT__ 2 #define __SSE__ 1 #define __LDBL_MIN_EXP__ (-16381) #define __LDBL_MAX_10_EXP__ 4932 #define __DBL_EPSILON__ 2.2204460492503131e-16 #define _LP64 1 #define __SIZEOF_WCHAR_T__ 4 #define __DEC_EVAL_METHOD__ 2 #define __INTMAX_MAX__ 9223372036854775807L #define __FLT_DENORM_MIN__ 1.40129846e-45F #define __FLT_MAX__ 3.40282347e+38F #define __SIZEOF_DOUBLE__ 8 #define __FLT_MIN_10_EXP__ (-37) #define __INTMAX_TYPE__ long int #define __DEC128_MAX_EXP__ 6144 #define __GNUC_MINOR__ 3 #define __DEC32_MANT_DIG__ 7 #define __DBL_MAX_10_EXP__ 308 #define __LDBL_DENORM_MIN__ 3.64519953188247460253e-4951L #define __STDC__ 1 #define __PTRDIFF_TYPE__ long int #define __DEC128_MANT_DIG__ 34 #define __LDBL_MIN_10_EXP__ (-4931) #define __SIZEOF_LONG_LONG__ 8 #define __LDBL_DIG__ 18 #define __GNUC_GNU_INLINE__ 1

When debugging FreeBSD kernel modules with GDB, you have to tell GDB the correct symbols for the module, and the location the module is loaded in RAM. This is helpfully explained in the FreeBSD Developers' Handbook. First you must load the module, then run kldstat, note down the address the module is loaded at, and finally ...

VMWare 6 and above has this neat debugging functionality where you can attach gdb running on a host, to a guest running inside VMWare. This allows you to debug a running kernel, or on linux running processes. However, VMWare seems to have coded a bit of a hack to allow gdb to understand what process/threads are ...