Author:

• Name: Anonymous 2001
  Location: GB - United Kingdom of Great Britain and Northern Ireland (United Kingdom)

To build:

    make

The programs that this program is supposed to act on, anonymous.ten.c and anonymous.bed.c, compiled with make, MUST be compiled as 32-bit ELF binaries. In the case that this fails these programs will be compiled as 64-bit binaries as alternate code, anonymous.ten.alt and anonymous.bed.alt, ELF or otherwise. However trying to use the entry on these files will fail. See Alternate code below for information on how to compile these programs as 64-bit binaries (or whatever your system will compile them as).

Bugs and (Mis)features:

The current status of this entry is:

STATUS: INABIAF - please DO NOT fix

For more detailed information see 2001/anonymous in bugs.html.

To use:

    ./anonymous x86_program

Try:

    ./try.sh

    ./anonymous anonymous.bed # if able to compile as a 32-bit (-m32) ELF binary

NOTE: if the 32-bit version cannot be compiled the script will at least compile anonymous.ten as a 64-bit program (or whatever your system is set to) and run it directly.

What happens if the x86 program has already been modified by this program? The judges’ remarks below might give you a hint!

What happens if you try it on another file like anonymous.c? Can you recompile it okay? What if you run it on anonymous itself? Can you run the program successfully after it without recompiling?

Alternate code:

In the case you you wish to manually compile the extra programs as 64-bit code you may do so. Using the entry on these binaries will very likely crash the program or do something terribly wrong like slaughtering all the elves of Imladris! :-) so please don’t do that :-(

Alternate build:

    make alt

Alternate use:

    ./anonymous.ten.alt

    ./anonymous.bed.alt

A 2023 note about the warning from the author:

The author suggested that this might somewhat destroy the binaries this touches but after the fix of 2023 this was not observed (yet?). It does indeed modify the files (though not all files are modified: can you figure out why that is?) but using them after did not result in any problems. It could be that it’s no longer known exactly what is supposed to happen and possibly that the modification might not be entirely correct for that reason though it does appear to be correct.

It appears that the corruption happens only if the modification fails in the middle of doing so so that might be why it hasn’t been observed.

Judges’ remarks:

Is emulation the sincerest form of flattery? This small program does quite a lot of bit twiddling.

Author’s remarks:

This program is an optimizing dynamic binary translator, allowing you to run x86 programs on any machine (x86 or otherwise).

I have included a simple 10 Green Bottles program (try make anonymous.ten), meant to be compiled as a 32-bit ELF binary.

The program anonymous.ten, and its source (dull) are included as data files.

Warning

Note that the translator screws around with the binary you run on it and might corrupt the binary to some extent and in so doing might leave any program you run on it unusable.

The build script should give an example command to compile the program.

Features

Basic Block Cache: Rather than translating each instruction individually the dynamic binary translator generates a translation for an entire basic block of subject code. Having translated a block once, the target code generated will be stored for the duration that the program is running, so as a program runs its performance will improve, as it hits cached blocks. This can be clearly observed in the example program, anonymous.ten which must be compiled as a 32-bit ELF binary.

Target Library Linking:

The program runs dynamically linked ELF binaries, and when the subject program attempts to make a call to a standard library, the translator attempts to make an appropriate call to the native system libraries on the target machine. This involves mangling between different calling conventions, etc.

Automatic Endian Detection/Reversal:

There are various problems raised when attempting to run little endian x86 code on a big endian chip, such as a PPC. These problems are dealt with in a manner that is entirely transparent to the user.

Configuration:

Warnings:

By default the build script should compile the program with a set of switches such that while compiling the program it generates one error (which I feel is useful advice). The program should generate no further compiler errors while it is running (yes, the program can generate compiler errors while it is running). If you do not wish to see this error, or if the program generates any further error when compiled using your C compiler please remove the -Dwarning='-Dprocessor' line and the $$warning from the compiler invocation.

Optimization

The build script contains a -O1 switch for the compiler. Increasing the optimization level will make the program run slower, while compiling the program without any optimization will allow it to run faster.

Obfuscation

The most obvious part of the obfuscation is probably the mess of #defines at the top. This may seem a somewhat tired old obfuscation - however since many of these macros are (sometimes only) used by the program once it has dynamically recompiled itself, they are only referenced within the source code from within strings - and therefore the macros cannot be expanded. Furthermore, some of these strings of code are not given as strings, but instead are wrapped up in macros that use the # preprocessor operator to turn them into strings. In the hope of throwing off a few C beautifiers the macro to generate the strings is not contained within the source code but instead is passed in on the command line.

Buried under all this, and the fact that the entire program is just a call to exit(3), there are some nice subtle little obfuscations. For example, you may notice that there are a couple of macros that use the ## preprocessor operator to build pairs of functions. One of these macros is used to build pairs of functions of which only one has local variables which shadow global variables: so one modifies the global state, and the other doesn’t.

There is also quite a nice trick where I wave a magic wand, and a chunk of code which should only be run when the program is run for the first time (setting the PC/IP to point at main() etc.) gets turned into a frogstring. The C compiler sees a string by itself in the code, thinks “yup, that’s a valid C expression”, and quietly moves on to the next line of code.

Limitations

Due to space limitations only a handful of instructions are supported; these instructions which are supported are supported in somewhat non-conventional ways: chunks of the architecture (e.g. flags) are just ignored, the ELF loader does not really load the ELF binary, the target library linking can only pass up to 3 parameters to the target library function, etc.

In short, please consider this a full disclaimer for any bug that may turn up - yes the program is unsafe, but it’s pretty cool anyway.

Despite all this, the translator is not exclusively limited to running the anonymous.ten program. Other trivial x86 programs may run on the translator - and I have successfully run a wide range of “Hello World” programs, including one of last year’s IOCCC entries, 2000/tomx.

Complete Program

The fact that the program makes calls to system(3) and execv(3) may imply that it is not a complete program in its own right, as it relies on other programs. The call to system(3) is a call to ask gcc to recompile the translator with a new set of switches, and the call to execv(3) asks for the newly compiled program to be executed. I would point out that almost every other entry to this competition also require a C compiler (well, the published winning entries at any rate, and I recognize that a few don’t). There is little real difference between this program and one like last year’s entry dhyang; both are just C programs that generate C code as their output.

Enjoy and thanks!

Primary files

• anonymous.c - entry source code
• Makefile - entry Makefile
• anonymous.orig.c - original source code
• anonymous.bed.c - Ten In the Bed song C source
• anonymous.ten.c - Ten Green Bottles song C source
• try.sh - script to try entry

Secondary files

• 2001_anonymous.tar.bz2 - download entry tarball
• README.md - markdown source for this web page
• .entry.json - entry summary and manifest in JSON
• .gitignore - list of files that should not be committed under git
• .path - directory path from top level directory
• index.html - this web page

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