In scripts/profile-symbolicate.py, the arguments passed to addr2line are file offsets, rather than vaddr, as required by addr2line. In most cases they are usually the same, but there are exceptions. The build process applies elfhack that compacts libxul.so and makes the file offset and vaddr of .text different. Thus most of the symbols reported in libxul.so are wrong.

More precisely, [Nr] Name Type Addr Off Size ES Flg Lk Inf Al ... [12] .text PROGBITS 00294440 069440 c5d5a8 00 AX 0 0 64 ... The address passed to addr2line should be based on 0x294440, rather than 0x69440.

Comment on attachment 707464 [details] link to patch on github So I think you're almost there. I'd like to see a few minor changes made and then re-review.

Some of your comments from the description of this bug and comment 1 are the kind of thing I'd like to see in the comments in the code.

Ting-Yuan, are you able to drive this bug to completion (whether landing or closing as INCOMPLETE)?

The solution in Bug 827846 is more compatible with other platforms, although also with more maintaining efforts. I think we should go 827846.