crash utility has a dwarf unwinder that is derived from Linux kernel just as the one in systemtap. I'm using it in gcore extension module for crash utility, ELF core dumper on crash utility for user-mode tasks, on x86_64 to restore callee-saved register values saved at the first stack frame on kernel stack. The problem is that the dwarf unwinder doesn't work well for RHEL6's debuginfo since it supports version 1 only while RHEL6 contains CIEs with version 3. I want to make crash utility support at least version 3. BTW, I've already confirmed systemtap supports all versions, i.e. 1, 3 and 4, and appears to work fine. So, I think that the simplest way to achieve the purpose is to barrow the code. However, I don't know what was added from version 1 to 3, and from version 3 and 4. Could anyone suggest me that or tell me documentation useful to recognize the difference in addition to the original Dwarf specifications? Thanks. HATAYAMA Daisuke