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/*
LD_PRELOAD library that gives statistic on number of roundtrips in an application.
$XREPLY_BACKTRACE defines whether and how backtraces will be printed for every
roundtrip. If not set, only total number of roundtrips is printed after the process
exits. If set to a number, backtrace for every roundtrip will be printed, and the
backtraces will be as deep as the given number. If set to C<number> (e.g. C10),
the backtraces will be "compressed" - every backtrace will be printed only once
after the process exits, together with number of times it occured.
*/
#define _GNU_SOURCE
#include <dlfcn.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <execinfo.h>
#include <assert.h>
#include <X11/Xlibint.h>
/* Since these symbols are weak, the apps can provide their own, and therefore
e.g. temporarily suspend counting of roundtrips. At least theoretically,
I haven't really tried it.
*/
__attribute((weak)) long ___xreply_reply_count = 0;
__attribute((weak)) int ___xreply_reply_enabled = 1;
#define MAX_BACKTRACES 1024
extern long ___xreply_reply_count;
extern int ___xreply_reply_enabled;
typedef Status (*xreply_ptr_t)(Display*,xReply*,int,Bool);
static xreply_ptr_t xreply_ptr = NULL;
static int xreply_backtrace_set = 0;
static int xreply_backtrace_type = 0;
struct xreply_struct
{
char* key;
char* text;
int count;
};
static struct xreply_struct backtraces[ MAX_BACKTRACES ];
static int backtraces_size = 0;
static int xreply_compare( const void* left, const void* right )
{
int left_count = ((struct xreply_struct*)left)->count;
int right_count = ((struct xreply_struct*)right)->count;
return right_count - left_count;
}
static void xreply_print(void)
{
char tmp[ 1024 ];
int fd;
fd = open( "/proc/self/cmdline", O_RDONLY );
if( fd >= 0 )
{
read( fd, tmp, 1024 );
tmp[ 1023 ] = '\0';
close( fd );
}
fprintf( stderr, "XREPLY (%d : %s): %ld\n", getpid(), tmp, ___xreply_reply_count );
if( xreply_backtrace_type < 0 )
{
int i;
qsort( backtraces, backtraces_size, sizeof( struct xreply_struct ), xreply_compare );
for( i = 0;
i < backtraces_size;
++i )
fprintf( stderr, "%d:%s\n\n", backtraces[ i ].count, backtraces[ i ].text );
}
}
static void xreply_backtrace()
{
void* trace[256];
int n = backtrace(trace, 256);
char** strings = backtrace_symbols (trace, n);
if( xreply_backtrace_type > 0 )
{
fprintf( stderr, "%ld [\n", ___xreply_reply_count );
if( n > xreply_backtrace_type )
n = xreply_backtrace_type;
int i;
for( i = 0;
i < n;
++i )
fprintf( stderr, "%d: %s\n", i, strings[ i ] );
fprintf( stderr, "]\n" );
}
else
{
char stack[ 256 * 20 ];
int pos = 0;
int i;
stack[ 0 ] = '\0';
if( n > -xreply_backtrace_type )
n = -xreply_backtrace_type;
for( i = 0;
i < n;
++i )
{
const char* start = strrchr( strings[ i ], '[' );
if( start == NULL )
assert( !"No [ in address." );
long addr;
if( sscanf( start + 1, "0x%lx", &addr ) != 1 )
assert( !"Failed to parse address." );
if( sizeof( void* ) == 4 )
{
sprintf( stack + pos, "0x%8lx", addr );
pos += 10;
}
else if( sizeof( void* ) == 8 )
{
sprintf( stack + pos, "0x%16lx", addr );
pos += 18;
}
else
assert( !"Unknown sizeof( void* )." );
}
for( i = 0;
i < backtraces_size;
++i )
if( strcmp( backtraces[ i ].key, stack ) == 0 )
{
++backtraces[ i ].count;
break;
}
if( i == backtraces_size )
{
int stack_text_size = 10;
char* stack_text;
char* stack_text_pos;
for( i = 0;
i < n;
++i )
stack_text_size += strlen( strings[ i ] ) + 5;
stack_text = stack_text_pos = malloc( stack_text_size );
for( i = 0;
i < n;
++i )
{
stack_text_pos = stpcpy( stack_text_pos, "\n" );
stack_text_pos = stpcpy( stack_text_pos, strings[ i ] );
}
backtraces[ backtraces_size ].key = strdup( stack );
backtraces[ backtraces_size ].text = stack_text;
backtraces[ backtraces_size ].count = 1;
++backtraces_size;
if( backtraces_size >= MAX_BACKTRACES )
assert( !"MAX_BACKTRACES reached." );
}
}
free (strings);
}
Status
_XReply (dpy, rep, extra, discard)
register Display *dpy;
register xReply *rep;
int extra; /* number of 32-bit words expected after the reply */
Bool discard; /* should I discard data following "extra" words? */
{
if( ___xreply_reply_enabled )
++___xreply_reply_count;
if( xreply_backtrace_set == 0 )
{
if( getenv( "XREPLY_BACKTRACE" ) != NULL )
{ // C<number> - compress backtraces, saved as negative value in xreply_backtrace_type
if( getenv( "XREPLY_BACKTRACE" )[ 0 ] == 'C' )
xreply_backtrace_type = -atoi( getenv( "XREPLY_BACKTRACE" ) + 1 );
else // <number> - print the backtrace every time
xreply_backtrace_type = atoi( getenv( "XREPLY_BACKTRACE" ));
}
else
xreply_backtrace_type = 0;
}
if( xreply_backtrace_type != 0 )
xreply_backtrace();
if( xreply_ptr == NULL )
{
xreply_ptr = (xreply_ptr_t)dlsym( RTLD_NEXT, "_XReply" );
if( xreply_ptr == NULL )
assert( !"dlsym() failed." );
atexit( xreply_print );
}
return xreply_ptr( dpy, rep, extra, discard );
}
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