illumos gate

Should one have a dump in which the agent LWP is present, mdb will not find it. Unfortunately, a dump with an agent is most likely because the agent itself has died, which will make the dump rather difficult to debug:

> mdb core.ksh93.17332 
Loading modules: [ libc.so.1 ld.so.1 ]
> $r
mdb: failed to get current register set: invalid thread identifier

The problem is that mdb is relying on libc_db to find the threads in a process – but the agent LWP does not exist on any libc structures. One can work around this by forcing the thread model to the LWP model (with the heretofore useless "tmodel" dcmd). The LWP model doesn't use libc_db but rather libproc to gather thread information:

> $r
mdb: failed to get current register set: invalid thread identifier
> ::tmodel lwp
> $r
%rax = 0x0000000000000009       %r8  = 0x000000000042bae0
%rbx = 0xfffffd7ffefed148       %r9  = 0x0000000000000200
%rcx = 0x000000000042b6d8       %r10 = 0x000000000042b6d8
%rdx = 0xfffffd7fffdfd2c0       %r11 = 0x000000000042bae0
%rsi = 0xfffffd7ffefed148       %r12 = 0x0000000000000048
%rdi = 0x000000000042b620       %r13 = 0x000000000042b620
                                %r14 = 0xfffffd7fff0162ea
                                %r15 = 0x000000000042b620

%cs = 0x0053    %fs = 0x0000    %gs = 0x0000
%ds = 0x004b    %es = 0x004b    %ss = 0x004b

%rip = 0xfffffd7fff39e0cb 
%rbp = 0xfffffd7fffdfd1c0
%rsp = 0xfffffd7fffdf7fa0

%rflags = 0x00010283
  id=0 vip=0 vif=0 ac=0 vm=0 rf=1 nt=0 iopl=0x0
  status=<of,df,IF,tf,SF,zf,af,pf,CF>

%gsbase = 0x0000000000000000
%fsbase = 0xfffffd7fff172a40
%trapno = 0xe
 %err = 0x6