On 05/19/17 13:53, Josh Poimboeuf wrote: >> >> One instance of the structure would exist for each time the stack >> pointer changes, e.g. for every function entry, push/pop, and rsp >> add/subtract. The data could be assembled and sorted offline, possibly >> derived from DWARF, or more likely, generated by objtool. After doing >> some rough calculations, I think the section size would be comparable to >> the sizes of the DWARF .eh_frame sections it would replace. >> >> If it worked, the "undwarf" unwinder would be a lot simpler than a real >> DWARF unwinder. And validating the sanity of the data at runtime would >> be a lot more straightforward. It could ensure that each stack pointer >> is within the bounds of the current stack, like our current unwinder >> does. > > I've been hacking away at this, and so far it's working well. The code > is much simpler than a DWARF unwinder. Right now the kernel piece is > only ~350 lines of code. The vast majority of the changes are in > objtool. > > It's now successfully unwinding through entry code and most other asm > files, dumping entry regs, dealing with aligned stacks, dynamic stacks, > etc. > > Here's the struct in its current state: How are you handling control flow? -hpa -- To unsubscribe from this list: send the line "unsubscribe live-patching" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
