Comment by mananaysiempre

Huh? Quoting a bit more from the article:

> [W]e find this in ARM.cpp:

> trapInstr = {0xd4, 0xd4, 0xd4, 0xd4};

The only thing left to explain is that the trap instruction is used as padding, but you can’t tell from here if that’s obvious or not. Opening the actual code[1], we see that the occurrences of trapInstr are all along the lines of

> void ARM::writePlt( /* ... */ ) {

> /* ... */

> memcpy(buf + 12, trapInstr.data(), 4); // Pad to 16-byte boundary

which isn’t the absolute best, but seems clear enough (if of course you know what a PLT is, which you should if you’re writing a linker).

I do think this merits an explanation that we’re using (what’s intended to be) a trap because the traditional option of using a nop makes ASLR less effective. But then the commit message you’re quoting doesn’t mention that either.

[1] https://github.com/llvm/llvm-project/blob/b20c291baec94ba370...