Meltdown and Spectre Samples

Example code for meltdown and spectre vulnerabilities

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This page gives a short overview of the programs. The times are mostly the result of using rdtsc of the processor.



cachetiming is a program that measures the access time of the memory when accessing cached values against uncached values. The time for the cached access should be lower than the uncached access time.

Example output:

Cached Access Time: 116
Uncached Access Time: 528

Download of cachetiming.


This program tries to read a byte via the cache access times. For this 256 bytes are read from memory and the lowest cache access time is used. The output of the program shows the byte determined by the cache access times, the number of bytes that have the lowest cache access time and the byte that was originally used to fill the cache. The expected success rate is below 50%.

Example output:

Byte read via cache access:     04
Count of bytes with min timing: 1
Expected byte from data:        53

Download of cachereadbyte.


This program is an intermediate program on the way to cachereadbyte3. This program defines a threshold that is above the minimum cache access times which leads to a higher count with values below the threshold.

Example output:

Byte read via cache access:     ff
Count of bytes with min timing: 2
Expected byte from data:        b0

Download of cachereadbyte2.


While the program cachereadbyte2 simply returns the last byte found with the cache access time below a threshold this program will retry the cache read when more than 1 result is found. This lowers the throughput but enhances the reliability.

Example output:

Byte read via cache access:     9d
Expected byte from data:        9d

Download of cachereadbyte3.


This program extends the program cachereadbyte3 and reads a complete memory area. This program is there to determine the algorithm of the byte read.

Example output (shortened):

ea 04 5b 5e a9 2a 0d e6 a5 4b 5d 28 11 cd 1c a4 - eb 04 5b 5e a9 2a 0d eb eb 4b 5d 28 11 eb 1c a4 
f2 f5 96 f8 26 7a 3c e3 5a 0f 69 e3 7b ed c7 92 - eb eb 96 eb 26 7a 3c eb 00 00 00 00 00 00 00 00 
Failed read relation: 909/4096

Download of cacheread.