Learn to collect dynamic instruction tracking

[hi JK]

Hi, 
I'm approaching DBI for the first time and I'm facing difficulties with dynamoRIO apis. I tried to use instrace_ simple.C dynamically tracks the jump instructions of the executable file and finds that the number of instructions collected is much higher than the number of instructions after decompiling the executable file. Why？

Thanks

[Derek Bruening]

You're asking why a dynamic instruction trace which has a separate entry for each instance of each instruction and thus has many entries for repeatedly executed instructions in loops might have more total instruction entries than the static count of instructions in the executable?

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[hi JK]

Yes, but in fact, in executable files without loops, the number of instructions tracked is still more than the static count of executable files. I don't understand why

What is the difference between tracked instructions and static instructions？

[Derek Bruening]

On Linux, DynamoRIO runs every user-mode instruction, starting with the dynamic loader.  Thousands of instructions will be executed before the application executable is even reached.  If you want a truly tiny app you have to write it in assembly and link it as pure-static.

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[hi JK]

Thank you！ I'll try it later