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Date: Tue, 9 Sep 1997 14:57:44 +1000
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199709090457.OAA28185@godzilla.zeta.org.au>
To: emulation@FreeBSD.ORG, wirth@zerberus.hai.siemens.co.at
Subject: Re: Doscmd, debugging with gdb
Sender: owner-freebsd-emulation@FreeBSD.ORG
X-Loop: FreeBSD.org
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>The problem: Starting doscmd under gdb loads the symboltable of the
>loader, not of doscmd.kernel. This is easy to solve (symbol-file ..).
>There are other troubles (with the signals, for example,..) but there
>are solutions for this too. I can trace into doscmd.kernel, load its
>symbols, list the functions, handle the signals correctly (nostop, pass
>for SIGBUS) and continue the program. But I cannot set breakpoints!

>I think the reason for this is, that ptrace knows the text segment of
>the original loader, and it refuses to set breakpoints into what it 
>sees as the data area of a program.

There must be more to it than that, since gdb can set breakpoints
in shared libraries although it doesn't understand symbols in shared
libraries.  Perhaps it is relocating text addresses by 0x110000 when
it should use 0.

Bruce