illumos gate

While doing development on a system, I had screwed things up and found myself in an infinite loop in krtld. The start of the message was:

module /kernel/misc/amd64/kmdbmod: text at [0xfffffffffc1f8000, 0xfffffffffc2c73a7] data at 0xfffffffffc2c73c0
module /kernel/misc/amd64/ctf: text at [0xfffffffffbd8f2e0, 0xfffffffffbd9a7d7] data at 0xfffffffffc300900
krtld: invalid relocation type 6304771 at 0x602403: file=/kernel/misc/amd64/kmdbmod
...

After that point, we'd continue to loop with invalid relocations. While there was certainly a problem with the input data in this case, we shouldn't have been in an infinite loop. If we dig into the ammd64 do_relocate, here are the relevant facts:

• We are processing through the while (reladdr < rend) { loop here.
• At the start of the loop, the first thing that we do is increment the symnum variable; however, that has no bearing on the actual relocation address
• The relocation address is initially set before the loop and then critically adjusted after we check for the relocation type.
• When we have an invalid relocation type, note an error; however, we continue processing by restarting the loop, but this means that we never change the actual reladdr, leading us to always look at the same data

In this case, I believe we should just error out immediately like we do in the case of bad string table index. While normally we try to find all missing symbols so it's not a game of whackamole, in this case it probably is representative that we have bad data as opposed to merely a missing dependency (the usual reason do_relocate fails).

With this in place, the errant module in question ends up providing the following output:

module /kernel/misc/amd64/kmdbmod: text at [0xfffffffffc1f8000, 0xfffffffffc2c73a7] data at 0xfffffffffc2c73c0
module /kernel/misc/amd64/ctf: text at [0xfffffffffbd8f2e0, 0xfffffffffbd9a7d7] data at 0xfffffffffc300900
krtld: invalid relocation type 6304771 at 0x602403: file=/kernel/misc/amd64/kmdbmod
do_relocations: /kernel/misc/amd64/kmdbmod do_relocate failed
krtld: error during initial load/link phase