This past few weeks I’ve been working on an Infinity client library. This is what GDB will use to execute notes it finds. It’s early days, but it executed its first note this morning so I thought I’d put something together so people can see what I’m doing. Here’s how to try it out:

0. Install elfutils libelf development stuff if you don’t have it already, the tlsdump example program needs it:

   sudo yum install elfutils-libelf-devel  # Fedora, RHEL, etc...
   sudo apt-get install libelf-dev         # Debian, Ubuntu, etc...

1. Download and build the Infinity client library and example program:

   git clone -b libi8x-0.0.1 https://github.com/gbenson/libi8x.git libi8x-0.0.1
   cd libi8x-0.0.1
   ./autogen.sh
   ./configure --enable-logging --enable-debug
   make

2. Check the tlsdump example program built:

   bash$ ls -l examples/tlsdump
   -rwxr-xr-x. 1 gary gary 5540 Apr 20 12:52 examples/tlsdump

   Yeah, there it is! (if it’s not there go back to step 0)

3. Build a program with notes to run the example program against:

   gcc -o tests/ifact tests/ifact.S tests/main.c

4. Run the program you just built:

   bash$ tests/ifact &
   [2] 8301
   Hello world I'm 8301

5. Run the libi8x tlsdump example program with the test program’s PID as it’s argument:

   $ examples/tlsdump 8301
   0! = 1
   1! = 1
   2! = 2
   3! = 6
   4! = 24
   5! = 120
   6! = 720
   7! = 5040
   8! = 40320
   9! = 362880
   10! = 3628800
   11! = 39916800
   12! = 479001600

What just happened? The executable test/ifact you built contains a single Infinity note, test::factorial(i)i, the source for which is in tests/ifact.i8. The tlsdump example located the ifact executable, loaded test::factorial(i)i from it, and ran it a few times printing the result:

  err = i8x_ctx_get_funcref (ctx, "test", "factorial", "i", "i", &fr);
  if (err != I8X_OK)
    error_i8x (ctx, err);

  err = i8x_xctx_new (ctx, 512, &xctx);
  if (err != I8X_OK)
    error_i8x (ctx, err);

  for (int i = 0; i < 13; i++)
    {
      union i8x_value args[1], rets[1];

      args[0].i = i;
      err = i8x_xctx_call (xctx, fr, NULL, args, rets);
      if (err != I8X_OK)
	error_i8x (ctx, err);

      printf ("%d! = %d\n", i, rets[0].i);
    }

To see some debug output try this:

I8X_LOG=debug examples/tlsdump PID

Also try I8X_DEBUG=true in addition to I8X_LOG=debug to trace the bytecode as it executes.

I’m winding down for a month away from Infinity. The current status is that the language and note format changes for 0.0.2 are all done. You can get them with:

git clone https://github.com/gbenson/i8c.git

There’s also the beginnings of an Emacs major mode for i8 in there too. My glibc tree now has notes for td_ta_thr_iter as well as td_ta_map_lwp2thr. That’s two of the three hard ones done. Get them with:

git clone https://github.com/gbenson/glibc.git -b infinity2

FWIW td_thr_get_info is just legwork and td_thr_tls_get_addr is just a wrapper for td_thr_tlsbase; td_thr_tlsbase is the other hard note.

All notes have testcases with 100% bytecode coverage. I may add a flag for I8X to make not having 100% coverage a failure, and make glibc use it so nobody can commit notes with untested code.

The total note size so far is 720 bytes so I may still manage to get all five libpthread notes implemented in less than 1k:

Displaying notes found at file offset 0x00018f54 with length 0x000002d0:
  Owner                 Data size	Description
  GNU                  0x00000063	NT_GNU_INFINITY (inspection function)
    Signature: libpthread::__lookup_th_unique(i)ip
  GNU                  0x00000088	NT_GNU_INFINITY (inspection function)
    Signature: libpthread::map_lwp2thr(i)ip
  GNU                  0x000000cd	NT_GNU_INFINITY (inspection function)
    Signature: libpthread::__iterate_thread_list(Fi(po)oipii)ii
  GNU                  0x000000d2	NT_GNU_INFINITY (inspection function)
    Signature: libpthread::thr_iter(Fi(po)oiipi)i