On May 7, 2017 10:59:16 AM PDT, Ingo Molnar <mingo@xxxxxxxxxx> wrote: > >* Josh Poimboeuf <jpoimboe@xxxxxxxxxx> 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. > >That's something I've been thinking about as well: if objtool generates >the >unwinder data structures then the kernel is not directly exposed to >tooling bugs >anymore. > >A fair chunk of the fragility of DWARF comes from the fact that it's >generated by >a tool chain that we cannot fix as part of the kernel project. If GCC >generates >crap debuginfo, and GDB happens to work with it but the kernel not, >we'll have to >work it around in the kernel. If GCC starts bloating debuginfo in the >future we >are screwed as well, etc. > >If objtool generates debuginfo then it's _our_ responsibility to have >sane >unwinder info and we obviously manage its structure and size as well. >Win-win. > >The unwinder itself should still do sanity checks, etc. (like all good >debugging >infrastructure code) - but the nature of the kernel's exposure to tool >chain >details changes in a very fundamental way. > >So yes, I think this is a very good idea, assuming it works in >practice! ;-) > >Thanks, > > Ingo Can objtool verify the unwinder at each address in the kernel, or is that an AI-complete problem? -- Sent from my Android device with K-9 Mail. Please excuse my brevity. -- 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
