Date: Sun, 22 Dec 2002 19:34:00 +0100 From: Aurelien Nephtali <aurelien.nephtali@wanadoo.fr> To: hackers@freebsd.org Subject: Accessing trap frame from userland? Message-ID: <20021222183400.GA77934@nebula.wanadoo.fr>
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[-- Attachment #1 --] Hi, I'm making a little debugger using ptrace(). The soft is trivial, it just fork() and runs the traced process via execve(). To break into the traced process, I use i386_set_watch()+ptrace() and choosed to break on execution. But it's here that I'm stucked: it breaks forever on the same instruction. I've read some docs and saw that I have to use the 'Resume flag' from the EFLAGS register. But, according to the Intel IA-32 documentation, this flag can only be set/unset by kernel code and the only way for a debugger to modify it is to modify the stack image of the EFLAGS register. But, there's nothing in the stack so I think (and it was confirmed by a friend) that the image is stored in a 'kernel-land stack'. So, my question is simple: how can I set the 'Resume flag' from an userland soft (without having to be root) ? Hope I was clear enough :) Thanks. -- Aurelien [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.1 (FreeBSD) iD8DBQE+BgWYDNsbHbt8ok8RAnCLAJsGz9sLIxOyrT2FXS/7lwol4ZI74gCeITOZ Kt7X0cwcZVVs84rokMnaK1E= =HQ/M -----END PGP SIGNATURE-----
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