blob: ab3827d31a833e1d6e81a4de0f50121190fdff76 [file] [log] [blame]
/*
* Function call tracing for gcc >= 2.95
*
* 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.
*
* 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 <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <common/compiler.h>
#include <common/time.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;
}
#if defined(__i386__) || defined(__x86_64__)
static inline unsigned long long rdtsc()
{
unsigned int a, d;
asm volatile("rdtsc" : "=a" (a), "=d" (d));
return a + ((unsigned long long)d << 32);
}
#else
static inline unsigned long long rdtsc()
{
struct timeval tv;
gettimeofday(&tv, NULL);
return tv.tv_sec * 1000000 + tv.tv_usec;
}
#endif
static void make_line(void *from, void *to, int level, char dir)
{
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);
*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, '>');
}
void __cyg_profile_func_exit(void *to, void *from)
{
if (!disabled)
return make_line(from, to, level--, '<');
}