On Mon, Jun 15, 2009 at 02:35:10PM -0700, Steve Gonczi wrote: > > My experience with the gdb protocol has been very > > negative; it's > > very poorly designed, and prone to breakage. > > And, with a little luck, nobody from the GNU camp is reading this list :-)
I think my experience is all well-known; the lack of versioning or even verifying that the architectures both sides are using match, etc. It's just the way the protocol grew. > > While some kind of kmdb(1)-over-ethernet might be > > very cool... > > Yes.. given that trying to get a KMDB session to work through LOM is such > a pain and many new x86 hardware platforms do not have a serial port, > that would be wonderful. > > > straightforward (if > > slightly time consuming) to backtrack from the > > assembly. > > I have one significant pain point with mdb, perhaps it is just my ignorance: > > I find it difficult to reconstruct stack frames, ie. local variables > on 64 bit amd. A bit off topic, but is there an easy way to obtain at > least the rbp values for the prior stack frames? Yeah, for any given line of ::findstack -v or $C, you have: > ffffff014bdab900::findstack -v stack pointer for thread ffffff014bdab900: ffffff00041dbcc0 [ ffffff00041dbcc0 _resume_from_idle+0xf1() ] ^^^^^^^^^^^^^^^^ %rsp ^^^ PC ffffff00041dbcf0 swtch+0x147() ^ rbp ^ PC (frame 1) ffffff00041dbd50 cv_wait_sig_swap_core+0x170(ffffff014bdabade, ffffff014bdabae0, 0) ^ rbp ^ PC (frame 2) ffffff00041dbd70 cv_wait_sig_swap+0x18(ffffff014bdabade, ffffff014bdabae0) ^ rbp ^ PC (frame 3) ffffff00041dbde0 cv_waituntil_sig+0x13c(ffffff014bdabade, ffffff014bdabae0, 0 ^ rbp ^ PC (frame 4) ... etc. The main problem in AMD64 is backtracking the callee-saved variables, but at least the function arguments are saved for kernel calls. Cheers, - jonathan > E.g. the AIX kdb has an option for their stack backtrace to print > register state for each stack frame on the stack. > > To be fair, kudos to the folks at SUN for recognizing the need of > field supportability, and giving us mdb. Also, dtrace is sheer > goodness, and I do not have _much_ to complain about. Understood. Cheers, - jonathan
