91 lines
2.3 KiB
C++
91 lines
2.3 KiB
C++
// Turbo Pascal v3.02a generates apps that try to determine the speed of the CPU at startup.
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// On emulators this can cause many instructions to be executed and throws off benchmark numbers.
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// This code replaces the call to do the speed check with NOP instructions.
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#include <stdio.h>
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#include <string.h>
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#include <process.h>
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#include <stdint.h>
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void usage()
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{
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printf( "usage: p app.com\n" );
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exit( 1 );
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} //usage
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long portable_filelen( FILE * fp )
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{
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long current = ftell( fp );
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fseek( fp, 0, SEEK_END );
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long len = ftell( fp );
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fseek( fp, current, SEEK_SET );
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return len;
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} //portable_filelen
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int main( int argc, char * argv[] )
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{
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if ( 2 != argc )
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usage();
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FILE * fp = fopen( argv[1], "r+b" );
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if ( !fp )
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{
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printf( "can't open file %s\n", argv[1] );
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usage();
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}
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long len = portable_filelen( fp );
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if ( len < 0x8a9 )
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{
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printf( "file length: %ld\n", len );
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printf( "file seems too small\n" );
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exit( 1 );
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}
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char acBuf[ 32 ];
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fseek( fp, 7, SEEK_SET );
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fread( acBuf, 30, 1, fp );
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acBuf[ 30 ] = 0;
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if ( strcmp( acBuf, "Copyright (C) 1985 BORLAND Inc" ) )
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{
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printf( "file doesn't appear to be a Turbo Pascal v3.02a generated app\n" );
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exit( 1 );
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}
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uint8_t abytes[ 3 ] = { 0 };
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fseek( fp, 0x8a7, SEEK_SET );
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fread( abytes, 3, 1, fp );
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if ( 0x90 == abytes[ 0 ] && 0x90 == abytes[ 1 ] && 0x90 == abytes[ 2 ] )
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{
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printf( "file is apparently already patched\n" );
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exit( 0 );
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}
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if ( 0xe8 != abytes[ 0 ] || 0xe8 != abytes[ 1 ] || 0xf7 != abytes[ 2 ] )
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{
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printf( "file doesn't have call 0f7e8h at offset 08a7h\n" );
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printf( "values there: %02x, %02x, %02x\n", abytes[ 0 ], abytes[ 1 ], abytes[ 2 ] );
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exit( 1 );
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}
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abytes[ 0 ] = 0x90;
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abytes[ 1 ] = 0x90;
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abytes[ 2 ] = 0x90;
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fseek( fp, 0x8a7, SEEK_SET );
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int result = fwrite( abytes, 3, 1, fp );
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if ( 1 != result )
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{
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printf( "couldn't write the NOP instructions, error %d\n", errno );
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exit( 1 );
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}
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fclose( fp );
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printf( "file %s successfully patched to remove startup cpu timing code\n", argv[ 1 ] );
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return 0;
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} //main
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