usertrace/lttng_usertrace.c

   1
   2 /* LTTng user-space tracing code
   3  *
   4  * Copyright 2006 Mathieu Desnoyers
   5  *
   6  */
   7
   8
   9 #include <sys/types.h>
  10 #include <sys/wait.h>
  11 #include <unistd.h>
  12 #include <stdlib.h>
  13 #include <stdio.h>
  14 #include <signal.h>
  15 #include <syscall.h>
  16 #include <features.h>
  17 #include <pthread.h>
  18 #include <malloc.h>
  19 #include <string.h>
  20
  21 #include "lttng_usertrace.h"
  22
  23 #define MAX_TRACES 16
  24
  25
  26 /*
  27  * Notes :
  28  *
  29  * ltt_update :
  30  *
  31  * it should send the information on the traces that has their status MODIFIED.
  32  * It's a necessary assumption to have a correct lttng_free_trace_info, which
  33  * would not be reentrant otherwise.
  34  */
  35
  36
  37 /* TLS for the trace info
  38  * http://www.dis.com/gnu/gcc/C--98-Thread-Local-Edits.html
  39  *
  40  * Add after paragraph 4
  41  *
  42  *     The storage for an object of thread storage duration shall be statically
  43  *     initialized before the first statement of the thread startup function. An
  44  *     object of thread storage duration shall not require dynamic
  45  *     initialization.
  46  * GCC extention permits init of a range.
  47  */
  48
  49 static __thread struct lttng_trace_info lttng_trace_info[MAX_TRACES] =
  50 {       [ 0 ... MAX_TRACES-1 ].active = 0,
  51         [ 0 ... MAX_TRACES-1 ].filter = 0,
  52         [ 0 ... MAX_TRACES-1 ].nesting = ATOMIC_INIT(0),
  53         [ 0 ... MAX_TRACES-1 ].channel =
  54                 { NULL,
  55                         0,
  56                         ATOMIC_INIT(0),
  57                         ATOMIC_INIT(0),
  58                         ATOMIC_INIT(0),
  59                         ATOMIC_INIT(0),
  60                         ATOMIC_INIT(0)
  61                 }
  62 };
  63
  64
  65 /* Must be called we sure nobody else is using the info.
  66  * It implies that the trace should have been previously stopped
  67  * and that every writer has finished.
  68  *
  69  * Writers should always check if the trace must be destroyed when they
  70  * finish writing and the nesting level is 0.
  71  */
  72 void lttng_free_trace_info(struct lttng_trace_info *info)
  73 {
  74         int ret;
  75
  76         if(info->active) {
  77                 printf(
  78                 "LTTng ERROR : lttng_free_trace_info should be called on inactive trace\n");
  79                 exit(1);
  80         }
  81         if(!info->destroy) {
  82                 printf(
  83                 "LTTng ERROR : lttng_free_trace_info should be called on destroyed trace\n");
  84                 exit(1);
  85         }
  86         if(atomic_read(&info->nesting) > 0) {
  87                 printf(
  88                 "LTTng ERROR : lttng_free_trace_info should not be nested on tracing\n");
  89                 exit(1);
  90         }
  91
  92         /* Remove the maps */
  93         ret = munmap(info->channel.cpu.start, info->channel.cpu.length);
  94         if(ret) {
  95                 perror("LTTNG : error in munmap");
  96         }
  97         ret = munmap(info->channel.facilities.start, info->channel.facilities.length);
  98         if(ret) {
  99                 perror("LTTNG : error in munmap");
 100         }
 101
 102         /* Zero the structure */
 103         memset(info, 0, sizeof(struct lttng_trace_info));
 104 }
 105
 106
 107 static struct lttng_trace_info* find_info(unsigned long cpu_addr,
 108                 unsigned long fac_addr, unsigned int *first_empty)
 109 {
 110         struct lttng_trace_info *found = NULL;
 111         unsigned int i;
 112
 113         *first_empty = MAX_TRACES;
 114
 115         /* Try to find the trace */
 116         for(i=0;i<MAX_TRACES;i++) {
 117                 if(i<*first_empty && !lttng_trace_info[i].channel.cpu.start)
 118                         *first_empty = i;
 119                 if(cpu_addr ==
 120                                 (unsigned long)lttng_trace_info[i].channel.cpu.start &&
 121                          fac_addr ==
 122                                 (unsigned long)lttng_trace_info[i].channel.facilities.start) {
 123                         /* Found */
 124                         found = &lttng_trace_info[i];
 125                         break;
 126                 }
 127         }
 128         return found;
 129 }
 130
 131
 132 static void lttng_get_new_info(void)
 133 {
 134         unsigned long cpu_addr, fac_addr;
 135         unsigned int i, first_empty;
 136         int active, filter, destroy;
 137         int ret;
 138         struct lttng_trace_info *info;
 139         sigset_t set, oldset;
 140
 141         /* Disable signals */
 142         ret = sigfillset(&set);
 143         if(ret) {
 144                 printf("Error in sigfillset\n");
 145                 exit(1);
 146         }
 147
 148         ret = pthread_sigmask(SIG_BLOCK, &set, &oldset);
 149         if(ret) {
 150                 printf("Error in sigprocmask\n");
 151                 exit(1);
 152         }
 153
 154         /* Get all the new traces */
 155         while(1) {
 156                 cpu_addr = fac_addr = 0;
 157                 active = filter = destroy = 0;
 158                 ret = ltt_update(&cpu_addr, &fac_addr, &active, &filter, &destroy);
 159                 if(ret) {
 160                         printf("LTTng : error in ltt_update\n");
 161                         exit(1);
 162                 }
 163
 164                 if(!cpu_addr || !fac_addr) break;
 165
 166                 info = find_info(cpu_addr, fac_addr, &first_empty);
 167                 if(info) {
 168                         info->filter = filter;
 169                         info->active = active;
 170                         info->destroy = destroy;
 171                         if(destroy && !atomic_read(&info->nesting))
 172                                 lttng_free_trace_info(info);
 173                 } else {
 174                         /* Not found. Must take an empty slot */
 175                         if(first_empty == MAX_TRACES) {
 176                                 printf(
 177                                 "LTTng WARNING : too many traces requested for pid %d by the kernel.\n"
 178                                 "                Compilation defined maximum is %u\n",
 179                                         getpid(), MAX_TRACES);
 180
 181                         } else {
 182                                 info = &lttng_trace_info[first_empty];
 183                                 info->channel.cpu.start = (void*)cpu_addr;
 184                                 info->channel.cpu.length = PAGE_SIZE;
 185                                 info->channel.facilities.start = (void*)fac_addr;
 186                                 info->channel.facilities.length = PAGE_SIZE;
 187                                 info->filter = filter;
 188                                 info->active = active;
 189                                 info->destroy = destroy;
 190                                 if(destroy && !atomic_read(&info->nesting))
 191                                         lttng_free_trace_info(info);
 192                         }
 193                 }
 194         }
 195
 196         /* Enable signals */
 197         ret = pthread_sigmask(SIG_SETMASK, &oldset, NULL);
 198         if(ret) {
 199                 printf("Error in sigprocmask\n");
 200                 exit(1);
 201         }
 202 }
 203
 204
 205 /* signal handler */
 206 void __lttng_sig_trace_handler(int signo)
 207 {
 208   printf("LTTng signal handler : thread id : %lu, pid %lu\n", pthread_self(), getpid());
 209         lttng_get_new_info();
 210 }
 211
 212
 213 static void thread_init(void)
 214 {
 215         int err;
 216         lttng_get_new_info();
 217
 218         /* Make some ltt_switch syscalls */
 219         err = ltt_switch((unsigned long)NULL);
 220         if(err) {
 221                 printf("Error in ltt_switch system call\n");
 222                 exit(1);
 223         }
 224 }
 225
 226 void __attribute__((constructor)) __lttng_user_init(void)
 227 {
 228         static struct sigaction act;
 229         int err;
 230
 231   printf("LTTng user init\n");
 232
 233         /* Activate the signal */
 234         act.sa_handler = __lttng_sig_trace_handler;
 235         err = sigemptyset(&(act.sa_mask));
 236         if(err) perror("Error with sigemptyset");
 237         err = sigaddset(&(act.sa_mask), SIGRTMIN+3);
 238         if(err) perror("Error with sigaddset");
 239         err = sigaction(SIGRTMIN+3, &act, NULL);
 240         if(err) perror("Error with sigaction");
 241
 242         thread_init();
 243 }
 244
 245
 246 void lttng_thread_init(void)
 247 {
 248         thread_init();
 249 }
 250
 251