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Diffstat (limited to 'src/calltrace.c')
| -rw-r--r-- | src/calltrace.c | 286 |
1 files changed, 286 insertions, 0 deletions
diff --git a/src/calltrace.c b/src/calltrace.c new file mode 100644 index 0000000..f72e121 --- /dev/null +++ b/src/calltrace.c @@ -0,0 +1,286 @@ +/* + * Function call tracing for gcc >= 2.95 + * WARNING! THIS CODE IS NOT THREAD-SAFE! + * + * Copyright 2012 Willy Tarreau <w@1wt.eu> + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version + * 2 of the License, or (at your option) any later version. + * + * gcc is able to call a specific function when entering and leaving any + * function when compiled with -finstrument-functions. This code must not + * be built with this argument. The performance impact is huge, so this + * feature should only be used when debugging. + * + * The entry and exits of all functions will be dumped into a file designated + * by the HAPROXY_TRACE environment variable, or by default "trace.out". If the + * trace file name is empty or "/dev/null", then traces are disabled. If + * opening the trace file fails, then stderr is used. If HAPROXY_TRACE_FAST is + * used, then the time is taken from the global <now> variable. Last, if + * HAPROXY_TRACE_TSC is used, then the machine's TSC is used instead of the + * real time (almost twice as fast). + * + * The output format is : + * + * <sec.usec> <level> <caller_ptr> <dir> <callee_ptr> + * or : + * <tsc> <level> <caller_ptr> <dir> <callee_ptr> + * + * where <dir> is '>' when entering a function and '<' when leaving. + * + * It is also possible to emit comments using the calltrace() function which uses + * the printf() format. Such comments are then inserted by replacing the caller + * pointer with a sharp ('#') like this : + * + * <sec.usec> <level> # <comment> + * or : + * <tsc> <level> # <comment> + * + * The article below is a nice explanation of how this works : + * http://balau82.wordpress.com/2010/10/06/trace-and-profile-function-calls-with-gcc/ + */ + +#include <sys/time.h> +#include <stdarg.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <haproxy/api.h> +#include <haproxy/clock.h> +#include <haproxy/tools.h> + +static FILE *log; +static int level; +static int disabled; +static int fast_time; +static int use_tsc; +static struct timeval trace_now; +static struct timeval *now_ptr; +static char line[128]; /* more than enough for a message (9+1+6+1+3+1+18+1+1+18+1+1) */ + +static int open_trace() +{ + const char *output = getenv("HAPROXY_TRACE"); + + if (!output) + output = "trace.out"; + + if (!*output || strcmp(output, "/dev/null") == 0) { + disabled = 1; + return 0; + } + + log = fopen(output, "w"); + if (!log) + log = stderr; + + now_ptr = &now; + if (getenv("HAPROXY_TRACE_FAST") != NULL) { + fast_time = 1; + now_ptr = &trace_now; + } + if (getenv("HAPROXY_TRACE_TSC") != NULL) { + fast_time = 1; + use_tsc = 1; + } + return 1; +} + +/* This function first divides the number by 100M then iteratively multiplies it + * by 100 (using adds and shifts). The trick is that dividing by 100M is equivalent + * to multiplying by 1/100M, which approximates to 1441151881/2^57. All local + * variables fit in registers on x86. This version outputs two digits per round. + * <min_pairs> indicates the minimum number of pairs of digits that have to be + * emitted, which might be left-padded with zeroes. + * It returns the pointer to the ending '\0'. + */ +static char *ultoad2(unsigned int x, char *out, int min_pairs) +{ + unsigned int q; + char *p = out; + int pos = 4; + unsigned long long y; + + static const unsigned short bcd[100] = { + 0x3030, 0x3130, 0x3230, 0x3330, 0x3430, 0x3530, 0x3630, 0x3730, 0x3830, 0x3930, + 0x3031, 0x3131, 0x3231, 0x3331, 0x3431, 0x3531, 0x3631, 0x3731, 0x3831, 0x3931, + 0x3032, 0x3132, 0x3232, 0x3332, 0x3432, 0x3532, 0x3632, 0x3732, 0x3832, 0x3932, + 0x3033, 0x3133, 0x3233, 0x3333, 0x3433, 0x3533, 0x3633, 0x3733, 0x3833, 0x3933, + 0x3034, 0x3134, 0x3234, 0x3334, 0x3434, 0x3534, 0x3634, 0x3734, 0x3834, 0x3934, + 0x3035, 0x3135, 0x3235, 0x3335, 0x3435, 0x3535, 0x3635, 0x3735, 0x3835, 0x3935, + 0x3036, 0x3136, 0x3236, 0x3336, 0x3436, 0x3536, 0x3636, 0x3736, 0x3836, 0x3936, + 0x3037, 0x3137, 0x3237, 0x3337, 0x3437, 0x3537, 0x3637, 0x3737, 0x3837, 0x3937, + 0x3038, 0x3138, 0x3238, 0x3338, 0x3438, 0x3538, 0x3638, 0x3738, 0x3838, 0x3938, + 0x3039, 0x3139, 0x3239, 0x3339, 0x3439, 0x3539, 0x3639, 0x3739, 0x3839, 0x3939 }; + + y = x * 1441151881ULL; /* y>>57 will be the integer part of x/100M */ + while (1) { + q = y >> 57; + /* Q is composed of the first digit in the lower byte and the second + * digit in the higher byte. + */ + if (p != out || q > 9 || pos < min_pairs) { +#if defined(__i386__) || defined(__x86_64__) + /* unaligned accesses are fast on x86 */ + *(unsigned short *)p = bcd[q]; + p += 2; +#else + *(p++) = bcd[q]; + *(p++) = bcd[q] >> 8; +#endif + } + else if (q || !pos) { + /* only at most one digit */ + *(p++) = bcd[q] >> 8; + } + if (--pos < 0) + break; + + y &= 0x1FFFFFFFFFFFFFFULL; // remainder + + if (sizeof(long) >= sizeof(long long)) { + /* shifting is preferred on 64-bit archs, while mult is faster on 32-bit. + * We multiply by 100 by doing *5, *5 and *4, all of which are trivial. + */ + y += (y << 2); + y += (y << 2); + y <<= 2; + } + else + y *= 100; + } + + *p = '\0'; + return p; +} + +/* Send <h> as hex into <out>. Returns the pointer to the ending '\0'. */ +static char *emit_hex(unsigned long h, char *out) +{ + static unsigned char hextab[16] = "0123456789abcdef"; + int shift = sizeof(h) * 8 - 4; + unsigned int idx; + + do { + idx = (h >> shift); + if (idx || !shift) + *out++ = hextab[idx & 15]; + shift -= 4; + } while (shift >= 0); + *out = '\0'; + return out; +} + +static void make_line(void *from, void *to, int level, char dir, long ret) +{ + char *p = line; + + if (unlikely(!log) && !open_trace()) + return; + + if (unlikely(!fast_time)) + gettimeofday(now_ptr, NULL); + +#ifdef USE_SLOW_FPRINTF + if (!use_tsc) + fprintf(log, "%u.%06u %d %p %c %p\n", + (unsigned int)now_ptr->tv_sec, + (unsigned int)now_ptr->tv_usec, + level, from, dir, to); + else + fprintf(log, "%llx %d %p %c %p\n", + rdtsc(), level, from, dir, to); + return; +#endif + + if (unlikely(!use_tsc)) { + /* "%u.06u", tv_sec, tv_usec */ + p = ultoad2(now_ptr->tv_sec, p, 0); + *p++ = '.'; + p = ultoad2(now_ptr->tv_usec, p, 3); + } else { + /* "%08x%08x", high, low */ + unsigned long long t = rdtsc(); + if (sizeof(long) < sizeof(long long)) + p = emit_hex((unsigned long)(t >> 32U), p); + p = emit_hex((unsigned long)(t), p); + } + + /* " %u", level */ + *p++ = ' '; + p = ultoad2(level, p, 0); + + /* " %p", from */ + *p++ = ' '; *p++ = '0'; *p++ = 'x'; + p = emit_hex((unsigned long)from, p); + + /* " %c", dir */ + *p++ = ' '; *p++ = dir; + + /* " %p", to */ + *p++ = ' '; *p++ = '0'; *p++ = 'x'; + p = emit_hex((unsigned long)to, p); + + if (dir == '<') { + /* " %x", ret */ + *p++ = ' '; *p++ = '0'; *p++ = 'x'; + p = emit_hex(ret, p); + } + + *p++ = '\n'; + + fwrite(line, p - line, 1, log); +} + +/* These are the functions GCC calls */ +void __cyg_profile_func_enter(void *to, void *from) +{ + if (!disabled) + return make_line(from, to, ++level, '>', 0); +} + +void __cyg_profile_func_exit(void *to, void *from) +{ + long ret = 0; + +#if defined(__x86_64__) + /* on x86_64, the return value (eax) is temporarily stored in ebx + * during the call to __cyg_profile_func_exit() so we can snoop it. + */ + asm volatile("mov %%rbx, %0" : "=r"(ret)); +#endif + if (!disabled) + return make_line(from, to, level--, '<', ret); +} + +/* the one adds comments in the trace above. The output format is : + * <timestamp> <level> # <string> + */ +__attribute__((format(printf, 1, 2))) +void calltrace(char *fmt, ...) +{ + va_list ap; + + if (unlikely(!log) && !open_trace()) + return; + + if (unlikely(!fast_time)) + gettimeofday(now_ptr, NULL); + + if (!use_tsc) + fprintf(log, "%u.%06u %d # ", + (unsigned int)now_ptr->tv_sec, + (unsigned int)now_ptr->tv_usec, + level + 1); + else + fprintf(log, "%llx %d # ", + rdtsc(), level + 1); + + va_start(ap, fmt); + vfprintf(log, fmt, ap); + va_end(ap); + fputc('\n', log); + fflush(log); +} |