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SubjectRe: [RFC] Proposed manpage additions for ptrace(2)
Chuck,

> The following is what I propose to add the the manpages entry
> for ptrace(2). Some of it came from experimentation, some from
> linux-kernel messages and the rest came from reading the source code.

Thanks -- this looks promising. I'm not sure, but I think Daniel Jacobowitz
made a number of these additions to ptrace(). Perhaps he
has some comments on the accuracy and completeness of the text.

Any comments Daniel?

Cheers,

Michael


> PTRACE_GETSIGINFO
> Retrieve information about the signal that caused the stop.
> Copies a siginfo_t from the child to location data in the par-
> ent.
>
> PTRACE_SETSIGINFO
> Set signal information. Copies a siginfo_t from location data
> in the parent to the child.
>
> PTRACE_SETOPTIONS
> Sets ptrace options from data in the parent. data is inter-
> preted as a bitmask of options, which are specified by the fol-
> lowing (addr is ignored:)
>
> PTRACE_O_TRACESYSGOOD
> When delivering syscall traps, set bit 7 in the signal
> number (i.e. deliver (SIGTRAP | 0x80) This makes it easy
> for the tracer to tell the difference between normal
> traps and those caused by a syscall.
>
> PTRACE_O_TRACEFORK
> Stop the child at the next fork() call with SIGTRAP |
> PTRACE_EVENT_FORK << 8 and automatically start tracing
> the newly forked process, which will start with a
> SIGSTOP. The pid for the new process can be retrieved
> with PTRACE_GETEVENTMSG.
>
> PTRACE_O_TRACEVFORK
> Stop the child at the next vfork() call with SIGTRAP |
> PTRACE_EVENT_VFORK << 8 and automatically start tracing
> the the newly vforked process, which will start with a
> SIGSTOP. The pid for the new process can be retrieved
> with PTRACE_GETEVENTMSG.
>
> PTRACE_O_TRACECLONE
> Stop the child at the next clone() call with SIGTRAP |
> PTRACE_EVENT_CLONE << 8 and automatically start tracing
> the newly cloned process, which will start with a
> SIGSTOP. The pid for the new process can be retrieved
> with PTRACE_GETEVENTMSG.
>
> PTRACE_O_TRACEEXEC
> Stop the child at the next exec() call with SIGTRAP |
> PTRACE_EVENT_EXEC << 8.
>
> PTRACE_O_TRACEVFORKDONE
> Stop the child at the completion of the next vfork() call
> with SIGTRAP | PTRACE_EVENT_VFORK_DONE << 8.
>
> PTRACE_O_TRACEEXIT
> Stop the child at exit with SIGTRAP | PTRACE_EVENT_EXIT
> << 8. The child’s exit status can be retrieved with
> PTRACE_GETEVENTMSG. This stop will be done early during
> process exit whereas the normal notification is done
> after the process is done exiting.
>
> PTRACE_GETEVENTMSG
> Retrieve a message (as an unsigned long) about the ptrace event
> that just happened to the location data in the parent. For
> PTRACE_EVENT_EXIT this is the child’s exit code. For
> PTRACE_EVENT_FORK, PTRACE_EVENT_VFORK and PTRACE_EVENT_CLONE
> this is the pid of the new process.
>
> PTRACE_SYSEMU, PTRACE_SYSEMU_SINGLESTEP
> For PTRACE_SYSEMU, continue and stop on entry to the next
> syscall, which will not be executed. For PTRACE_SYSEMU_SIN-
> GLESTEP, so the same but also singlestep if not a syscall.

--
Michael Kerrisk
maintainer of Linux man pages Sections 2, 3, 4, 5, and 7

Want to help with man page maintenance?
Grab the latest tarball at
ftp://ftp.win.tue.nl/pub/linux-local/manpages/,
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