Commit db25d56c authored by Markus Armbruster's avatar Markus Armbruster Committed by Stefan Hajnoczi
Browse files

trace/simple: Fix unauthorized enable 



st_set_trace_file() accidentally enables tracing.  It's called
unconditionally during startup, which is why QEMU built with the
simple trace backend always writes a trace file "trace-$PID".

This has been broken for quite a while.  I didn't track down the exact
commit.

Fix st_set_trace_file() to restore the state.

Signed-off-by: default avatarMarkus Armbruster <armbru@redhat.com>
Reviewed-by: default avatarPhilippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20200527065613.25322-1-armbru@redhat.com
Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
parent f892b494

trace/simple.c

+14 −6
Original line number Diff line number Diff line
@@ -302,10 +302,17 @@ static int st_write_event_mapping(void) 
    return 0;

}



void st_set_trace_file_enabled(bool enable)

/**

 * Enable / disable tracing, return whether it was enabled.

 *

 * @enable: enable if %true, else disable.

 */

bool st_set_trace_file_enabled(bool enable)

{

    bool was_enabled = trace_fp;



    if (enable == !!trace_fp) {

        return; /* no change */

        return was_enabled;     /* no change */

    }



    /* Halt trace writeout */
@@ -323,14 +330,14 @@ void st_set_trace_file_enabled(bool enable) 


        trace_fp = fopen(trace_file_name, "wb");

        if (!trace_fp) {

            return;

            return was_enabled;

        }



        if (fwrite(&header, sizeof header, 1, trace_fp) != 1 ||

            st_write_event_mapping() < 0) {

            fclose(trace_fp);

            trace_fp = NULL;

            return;

            return was_enabled;

        }



        /* Resume trace writeout */
@@ -340,6 +347,7 @@ void st_set_trace_file_enabled(bool enable) 
        fclose(trace_fp);

        trace_fp = NULL;

    }

    return was_enabled;

}



/**
@@ -350,7 +358,7 @@ void st_set_trace_file_enabled(bool enable) 
 */

void st_set_trace_file(const char *file)

{

    st_set_trace_file_enabled(false);

    bool saved_enable = st_set_trace_file_enabled(false);



    g_free(trace_file_name);
@@ -361,7 +369,7 @@ void st_set_trace_file(const char *file) 
        trace_file_name = g_strdup_printf("%s", file);

    }



    st_set_trace_file_enabled(true);

    st_set_trace_file_enabled(saved_enable);

}



void st_print_trace_file_status(void)

trace/simple.h

+1 −1
Original line number Diff line number Diff line
@@ -12,7 +12,7 @@ 
#define TRACE_SIMPLE_H



void st_print_trace_file_status(void);

void st_set_trace_file_enabled(bool enable);

bool st_set_trace_file_enabled(bool enable);

void st_set_trace_file(const char *file);

bool st_init(void);

void st_flush_trace_buffer(void);