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backtrace from random $fp $pc



In a project I'm writing on we have a custom thread package. It
context-switches on select and do stack mangling when.

Now there is to way to do backtrace:ing on diffrent threads.

I have a patch (on 4.18) that enable us to do that
<http://www.stacken.kth.se/projekt/arla/gdb-4.18-backfrom.diff> by
choosning the right $fp and $sp. Se below for example (the exemple uses
wrong $pc). As you see I use a sequence to find fp/pc.

Now that question is, how should thread support really work for random
thread-packages ? We have the idea that the thread package would provide a
magic variable to a function that gdb sets and the thead package call each
time it does a thread-releated operation that gdb needs to know.

A many related question: What is tfind, since that seam to be releated to
backtrace:ing (but on remote targets ?) would that be possible to use for
the same things that my patch does ?

Love

(gdb) lwp_ps
Runnable[0]
 name: IO MANAGER
  eventlist:
  fp: 0x806aac4
  pc: 0x806aac4
 name: producer
  eventlist: 8048b00
  fp: 0x8083b40
  pc: 0x8083b40
Runnable[1]
[...]
(gdb) help backfrom
Print backtrace of FRAMEPOINTER and PROGRAMCOUNTER.

(gdb) backfrom 0x8083b40 0x8083b40
#0  0x8083b40 in ?? ()
#1  0x8049e2f in LWP_MwaitProcess (wcount=1, evlist=0x8083b70)
    at /afs/e.kth.se/home/staff/lha/src/cvs/arla-foo/lwp/lwp.c:567
#2  0x8049eaf in LWP_WaitProcess (event=0x8048b00)
    at /afs/e.kth.se/home/staff/lha/src/cvs/arla-foo/lwp/lwp.c:585
#3  0x8048b12 in Producer (foo=0x0)
    at /afs/e.kth.se/home/staff/lha/src/cvs/arla-foo/lwp/testlwp.c:76
#4  0x804a00c in Create_Process_Part2 ()
    at /afs/e.kth.se/home/staff/lha/src/cvs/arla-foo/lwp/lwp.c:629
#5  0xfffefdfc in ?? ()
#6  0x8051980 in ?? ()

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