api/samples/bbcount.c

/* **********************************************************
 * Copyright (c) 2014 Google, Inc.  All rights reserved.
 * Copyright (c) 2008 VMware, Inc.  All rights reserved.
 * **********************************************************/

/*
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * * Redistributions of source code must retain the above copyright notice,
 *   this list of conditions and the following disclaimer.
 *
 * * Redistributions in binary form must reproduce the above copyright notice,
 *   this list of conditions and the following disclaimer in the documentation
 *   and/or other materials provided with the distribution.
 *
 * * Neither the name of VMware, Inc. nor the names of its contributors may be
 *   used to endorse or promote products derived from this software without
 *   specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL VMWARE, INC. OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGE.
 */

/* Code Manipulation API Sample:
 * bbcount.c
 *
 * Reports the dynamic execution count of all basic blocks.
 * Illustrates how to perform performant inline increments with analysis
 * on whether flags need to be preserved.
 */

#include <stddef.h> /* for offsetof */
#include "dr_api.h"

#ifdef WINDOWS
# define DISPLAY_STRING(msg) dr_messagebox(msg)
#else
# define DISPLAY_STRING(msg) dr_printf("%s\n", msg);
#endif

#define NULL_TERMINATE(buf) buf[(sizeof(buf)/sizeof(buf[0])) - 1] = '\0'

#define TESTALL(mask, var) (((mask) & (var)) == (mask))
#define TESTANY(mask, var) (((mask) & (var)) != 0)

/* we only have a global count */
static int global_count;

/* If being off a little bit is not important, or the target
 * application is single-threaded or spends most of its time in one
 * thread, performing a racy inc (i.e., not synchronized among threads)
 * is three times faster than synchronizing.
 */
#define RACY_INC 1

#ifdef SHOW_RESULTS
/* some meta-stats: static (not per-execution) */
static int bbs_eflags_saved;
static int bbs_no_eflags_saved;
#endif

static void event_exit(void);
static dr_emit_flags_t event_basic_block(void *drcontext, void *tag, instrlist_t *bb,
                                         bool for_trace, bool translating);

DR_EXPORT void
dr_init(client_id_t id)
{
    dr_set_client_name("DynamoRIO Sample Client 'bbcount'",
                       "http://dynamorio.org/issues");
    /* register events */
    dr_register_exit_event(event_exit);
    dr_register_bb_event(event_basic_block);

    /* make it easy to tell, by looking at log file, which client executed */
    dr_log(NULL, LOG_ALL, 1, "Client 'bbcount' initializing\n");
#ifdef SHOW_RESULTS
    /* also give notification to stderr */
    if (dr_is_notify_on()) {
# ifdef WINDOWS
        /* ask for best-effort printing to cmd window.  must be called in dr_init(). */
        dr_enable_console_printing();
# endif
        dr_fprintf(STDERR, "Client bbcount is running\n");
    }
#endif
}

static void
event_exit(void)
{
#ifdef SHOW_RESULTS
    char msg[512];
    int len;
    len = dr_snprintf(msg, sizeof(msg)/sizeof(msg[0]),
                      "Instrumentation results:\n"
                      "%10d basic block executions\n"
                      "%10d basic blocks needed flag saving\n"
                      "%10d basic blocks did not\n",
                      global_count, bbs_eflags_saved, bbs_no_eflags_saved);
    DR_ASSERT(len > 0);
    NULL_TERMINATE(msg);
    DISPLAY_STRING(msg);
#endif /* SHOW_RESULTS */
}

static dr_emit_flags_t
event_basic_block(void *drcontext, void *tag, instrlist_t *bb,
                  bool for_trace, bool translating)
{
    instr_t *instr, *first = instrlist_first_app(bb);
    uint flags;

#ifdef VERBOSE
    dr_printf("in dynamorio_basic_block(tag="PFX")\n", tag);
# ifdef VERBOSE_VERBOSE
    instrlist_disassemble(drcontext, tag, bb, STDOUT);
# endif
#endif

    /* Our inc can go anywhere, so find a spot where flags are dead. */
    for (instr = first; instr != NULL; instr = instr_get_next_app(instr)) {
        flags = instr_get_arith_flags(instr, DR_QUERY_DEFAULT);
        /* OP_inc doesn't write CF but not worth distinguishing */
        if (TESTALL(EFLAGS_WRITE_6, flags) && !TESTANY(EFLAGS_READ_6, flags))
            break;
    }

    if (instr == NULL) {
        dr_save_reg(drcontext, bb, first, DR_REG_XAX, SPILL_SLOT_1);
        dr_save_arith_flags_to_xax(drcontext, bb, first);
    }
    /* Increment the global counter using the lock prefix to make it atomic
     * across threads.
     */
#ifdef RACY_INC
    instrlist_meta_preinsert
        (bb, (instr == NULL) ? first : instr,
         INSTR_CREATE_inc(drcontext, OPND_CREATE_ABSMEM
                          ((byte *)&global_count, OPSZ_4)));
#else
    instrlist_meta_preinsert
        (bb, (instr == NULL) ? first : instr,
         LOCK(INSTR_CREATE_inc(drcontext, OPND_CREATE_ABSMEM
                               ((byte *)&global_count, OPSZ_4))));
#endif
    if (instr == NULL) {
        dr_restore_arith_flags_from_xax(drcontext, bb, first);
        dr_restore_reg(drcontext, bb, first, DR_REG_XAX, SPILL_SLOT_1);
    }

#ifdef SHOW_RESULTS
    if (instr == NULL)
        bbs_eflags_saved++;
    else
        bbs_no_eflags_saved++;
#endif

#if defined(VERBOSE) && defined(VERBOSE_VERBOSE)
    dr_printf("Finished instrumenting dynamorio_basic_block(tag="PFX")\n", tag);
    instrlist_disassemble(drcontext, tag, bb, STDOUT);
#endif
    return DR_EMIT_DEFAULT;
}