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Commit 774f9299 authored by Jamie Gennis's avatar Jamie Gennis Committed by Android (Google) Code Review
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libcutils: add support for app tracing 

This change adds support for tracing using the ATRACE_TAG_APP tag.  This tag is
enabled only for processes in which the /proc/<pid>/cmdline value appears in
the comma-separated list of such values in the debug.atrace.app_cmdlines system
property.  It is also only enabled if either the ro.debuggable system property
is set to 1 or the application has declared itself debuggable in its manifest,
which gets reported to libcutils by the framework.

Change-Id: Ic94ba55f4e70a9cf994056acbf151e523428b65d
parent de97f798

include/cutils/trace.h

+11 −1
Original line number Diff line number Diff line
@@ -20,6 +20,7 @@ 
#include <sys/cdefs.h>

#include <sys/types.h>

#include <stdint.h>

#include <stdbool.h>

#include <unistd.h>

#include <cutils/compiler.h>
@@ -62,7 +63,8 @@ __BEGIN_DECLS 
#define ATRACE_TAG_VIDEO            (1<<9)

#define ATRACE_TAG_CAMERA           (1<<10)

#define ATRACE_TAG_HAL              (1<<11)

#define ATRACE_TAG_LAST             ATRACE_TAG_HAL

#define ATRACE_TAG_APP              (1<<12)

#define ATRACE_TAG_LAST             ATRACE_TAG_APP



// Reserved for initialization.

#define ATRACE_TAG_NOT_READY        (1LL<<63)
@@ -96,6 +98,14 @@ void atrace_setup(); 
 */

void atrace_update_tags();



/**

 * Set whether the process is debuggable.  By default the process is not

 * considered debuggable.  If the process is not debuggable then application-

 * level tracing is not allowed unless the ro.debuggable system property is

 * set to '1'.

 */

void atrace_set_debuggable(bool debuggable);



/**

 * Flag indicating whether setup has been completed, initialized to 0.

 * Nonzero indicates setup has completed.

libcutils/trace.c

+85 −5
Original line number Diff line number Diff line
@@ -18,6 +18,7 @@ 
#include <fcntl.h>

#include <limits.h>

#include <pthread.h>

#include <stdbool.h>

#include <stdlib.h>

#include <string.h>

#include <sys/types.h>
@@ -32,9 +33,79 @@ 
int32_t                atrace_is_ready      = 0;

int                    atrace_marker_fd     = -1;

uint64_t               atrace_enabled_tags  = ATRACE_TAG_NOT_READY;

static bool            atrace_is_debuggable = false;

static pthread_once_t  atrace_once_control  = PTHREAD_ONCE_INIT;

static pthread_mutex_t atrace_tags_mutex    = PTHREAD_MUTEX_INITIALIZER;



// Set whether this process is debuggable, which determines whether

// application-level tracing is allowed when the ro.debuggable system property

// is not set to '1'.

void atrace_set_debuggable(bool debuggable)

{

    atrace_is_debuggable = debuggable;

    atrace_update_tags();

}



// Check whether the given command line matches one of the comma-separated

// values listed in the app_cmdlines property.

static bool atrace_is_cmdline_match(const char* cmdline) {

    char value[PROPERTY_VALUE_MAX];

    char* start = value;



    property_get("debug.atrace.app_cmdlines", value, "");



    while (start != NULL) {

        char* end = strchr(start, ',');



        if (end != NULL) {

            *end = '\0';

            end++;

        }



        if (strcmp(cmdline, start) == 0) {

            return true;

        }



        start = end;

    }



    return false;

}



// Determine whether application-level tracing is enabled for this process.

static bool atrace_is_app_tracing_enabled()

{

    bool sys_debuggable = false;

    bool proc_debuggable = false;

    char value[PROPERTY_VALUE_MAX];

    bool result = false;



    // Check whether the system is debuggable.

    property_get("ro.debuggable", value, "0");

    if (value[0] == '1') {

        sys_debuggable = true;

    }



    if (sys_debuggable || atrace_is_debuggable) {

        // Check whether tracing is enabled for this process.

        FILE * file = fopen("/proc/self/cmdline", "r");

        if (file) {

            char cmdline[4096];

            if (fgets(cmdline, sizeof(cmdline), file)) {

                result = atrace_is_cmdline_match(cmdline);

            } else {

                ALOGE("Error reading cmdline: %s (%d)", strerror(errno), errno);

            }

            fclose(file);

        } else {

            ALOGE("Error opening /proc/self/cmdline: %s (%d)", strerror(errno),

                    errno);

        }

    }



    return result;

}



// Read the sysprop and return the value tags should be set to

static uint64_t atrace_get_property()

{
@@ -52,6 +123,15 @@ static uint64_t atrace_get_property() 
        ALOGE("Error parsing trace property: Number too large: %s", value);

        return 0;

    }



    // Only set the "app" tag if this process was selected for app-level debug

    // tracing.

    if (atrace_is_app_tracing_enabled()) {

        tags |= ATRACE_TAG_APP;

    } else {

        tags &= ~ATRACE_TAG_APP;

    }



    return (tags | ATRACE_TAG_ALWAYS) & ATRACE_TAG_VALID_MASK;

}