.\" $NetBSD: ptrace.2,v 1.3 1996/02/23 01:39:41 jtc Exp $
.\"
.\" This file is in the public domain.
-.Dd November 7, 1994
+.Dd March 25, 2015
.Dt PTRACE 2
.Os
.Sh NAME
can be:
.Bl -tag -width 12n
.It Dv PT_TRACE_ME
-This request is the only one used by the traced process; it declares
+This request is one of two used by the traced process; it declares
that the process expects to be traced by its parent. All the other
arguments are ignored. (If the parent process does not expect to trace
the child, it will probably be rather confused by the results; once the
it will stop before executing the first instruction of the new image.
Also, any setuid or setgid bits on the executable being executed will
be ignored.
-.It Dv PT_READ_I , Dv PT_READ_D
-These requests read a single
-.Li int
-of data from the traced process' address space. Traditionally,
-.Fn ptrace
-has allowed for machines with distinct address spaces for instruction
-and data, which is why there are two requests: conceptually,
-.Dv PT_READ_I
-reads from the instruction space and
-.Dv PT_READ_D
-reads from the data space. In the current OpenBSD implementation, these
-two requests are completely identical. The
-.Fa addr
-argument specifies the address (in the traced process' virtual address
-space) at which the read is to be done. This address does not have to
-meet any alignment constraints. The value read is returned as the
-return value from
-.Eo \&
-.Fn ptrace
-.Ec .
-.It Dv PT_WRITE_I , Dv PT_WRITE_D
-These requests parallel
-.Dv PT_READ_I
-and
-.Dv PT_READ_D ,
-except that they write rather than read. The
-.Fa data
-argument supplies the value to be written.
-.\" .It Dv PT_READ_U
-.\" This request reads an
-.\" .Li int
-.\" from the traced process' user structure. The
-.\" .Fa addr
-.\" argument specifies the location of the int relative to the base of the
-.\" user structure; it will usually be an integer value cast to
-.\" .Li caddr_t
-.\" either explicitly or via the presence of a prototype for
-.\" .Eo \&
-.\" .Fn ptrace
-.\" .Ec .
-.\" Unlike
-.\" .Dv PT_READ_I
-.\" and
-.\" .Dv PT_READ_D ,
-.\" .Fa addr
-.\" must be aligned on an
-.\" .Li int
-.\" boundary. The value read is returned as the return value from
-.\" .Eo \&
-.\" .Fn ptrace
-.\" .Ec .
-.\" .It Dv PT_WRITE_U
-.\" This request writes an
-.\" .Li int
-.\" into the traced process' user structure.
-.\" .Fa addr
-.\" specifies the offset, just as for
-.\" .Dv PT_READ_U ,
-.\" and
-.\" .Fa data
-.\" specifies the value to be written, just as for
-.\" .Dv PT_WRITE_I
-.\" and
-.\" .Dv PT_WRITE_D .
+.It Dv PT_DENY_ATTACH
+This request is the other operation used by the traced process; it allows
+a process that is not currently being traced to deny future traces by its
+parent. All other arguments are ignored. If the process is currently
+being traced, it will exit with the exit status of ENOTSUP; otherwise,
+it sets a flag that denies future traces. An attempt by the parent to
+trace a process which has set this flag will result in a segmentation violation
+in the parent.
.It Dv PT_CONTINUE
The traced process continues execution.
.Fa addr
.Fa data
provides a signal number to be delivered to the traced process as it
resumes execution, or 0 if no signal is to be sent.
+.It Dv PT_STEP
+The traced process continues execution for a single step. The
+parameters are identical to those passed to
+.Dv PT_CONTINUE.
.It Dv PT_KILL
The traced process terminates, as if
.Dv PT_CONTINUE
.Dv SIGKILL
given as the signal to be delivered.
.It Dv PT_ATTACH
+This call has been replaced with PT_ATTACHEXC.
+.It Dv PT_ATTACHEXC
This request allows a process to gain control of an otherwise unrelated
process and begin tracing it. It does not need any cooperation from
the to-be-traced process. In this case,
not be executing a setuid or setgid executable. (If the tracing
process is running as root, these restrictions do not apply.) The
tracing process will see the newly-traced process stop and may then
-control it as if it had been traced all along.
+control it as if it had been traced all along. Note that this call differs
+from the prior call (
+.Dv PT_ATTACH )
+in that signals from the child are delivered to the parent as Mach exceptions (see EXC_SOFT_SIGNAL).
.It Dv PT_DETACH
This request is like PT_CONTINUE, except that it does not allow
specifying an alternate place to continue execution, and after it
execution normally.
.El
.Pp
-Additionally, machine-specific requests can exist. On the SPARC, these
-are:
-.Bl -tag -width 12n
-.It Dv PT_GETREGS
-This request reads the traced process' machine registers into the
-.Dq Li "struct reg"
-(defined in
-.Aq Pa machine/reg.h )
-pointed to by
-.Fa addr .
-.It Dv PT_SETREGS
-This request is the converse of
-.Dv PT_GETREGS ;
-it loads the traced process' machine registers from the
-.Dq Li "struct reg"
-(defined in
-.Aq Pa machine/reg.h )
-pointed to by
-.Fa addr .
-.It Dv PT_GETFPREGS
-This request reads the traced process' floating-point registers into
-the
-.Dq Li "struct fpreg"
-(defined in
-.Aq Pa machine/reg.h )
-pointed to by
-.Fa addr .
-.It Dv PT_SETFPREGS
-This request is the converse of
-.Dv PT_GETFPREGS ;
-it loads the traced process' floating-point registers from the
-.Dq Li "struct fpreg"
-(defined in
-.Aq Pa machine/reg.h )
-pointed to by
-.Fa addr .
-.\" .It Dv PT_SYSCALL
-.\" This request is like
-.\" .Dv PT_CONTINUE
-.\" except that the process will stop next time it executes any system
-.\" call. Information about the system call can be examined with
-.\" .Dv PT_READ_U
-.\" and potentially modified with
-.\" .Dv PT_WRITE_U
-.\" through the
-.\" .Li u_kproc.kp_proc.p_md
-.\" element of the user structure (see below). If the process is continued
-.\" with another
-.\" .Dv PT_SYSCALL
-.\" request, it will stop again on exit from the syscall, at which point
-.\" the return values can be examined and potentially changed. The
-.\" .Li u_kproc.kp_proc.p_md
-.\" element is of type
-.\" .Dq Li "struct mdproc" ,
-.\" which should be declared by including
-.\" .Aq Pa sys/param.h ,
-.\" .Aq Pa sys/user.h ,
-.\" and
-.\" .Aq Pa machine/proc.h ,
-.\" and contains the following fields (among others):
-.\" .Bl -item -compact -offset indent
-.\" .It
-.\" .Li syscall_num
-.\" .It
-.\" .Li syscall_nargs
-.\" .It
-.\" .Li syscall_args[8]
-.\" .It
-.\" .Li syscall_err
-.\" .It
-.\" .Li syscall_rv[2]
-.\" .El
-.\" When a process stops on entry to a syscall,
-.\" .Li syscall_num
-.\" holds the number of the syscall,
-.\" .Li syscall_nargs
-.\" holds the number of arguments it expects, and
-.\" .Li syscall_args
-.\" holds the arguments themselves. (Only the first
-.\" .Li syscall_nargs
-.\" elements of
-.\" .Li syscall_args
-.\" are guaranteed to be useful.) When a process stops on exit from a
-.\" syscall,
-.\" .Li syscall_num
-.\" is
-.\" .Eo \&
-.\" .Li -1
-.\" .Ec ,
-.\" .Li syscall_err
-.\" holds the error number
-.\" .Po
-.\" see
-.\" .Xr errno 2
-.\" .Pc ,
-.\" or 0 if no error occurred, and
-.\" .Li syscall_rv
-.\" holds the return values. (If the syscall returns only one value, only
-.\" .Li syscall_rv[0]
-.\" is useful.) The tracing process can modify any of these with
-.\" .Dv PT_WRITE_U ;
-.\" only some modifications are useful.
-.\" .Pp
-.\" On entry to a syscall,
-.\" .Li syscall_num
-.\" can be changed, and the syscall actually performed will correspond to
-.\" the new number (it is the responsibility of the tracing process to fill
-.\" in
-.\" .Li syscall_args
-.\" appropriately for the new call, but there is no need to modify
-.\" .Eo \&
-.\" .Li syscall_nargs
-.\" .Ec ).
-.\" If the new syscall number is 0, no syscall is actually performed;
-.\" instead,
-.\" .Li syscall_err
-.\" and
-.\" .Li syscall_rv
-.\" are passed back to the traced process directly (and therefore should be
-.\" filled in). If the syscall number is otherwise out of range, a dummy
-.\" syscall which simply produces an
-.\" .Er ENOSYS
-.\" error is effectively performed.
-.\" .Pp
-.\" On exit from a syscall, only
-.\" .Li syscall_err
-.\" and
-.\" .Li syscall_rv
-.\" can usefully be changed; they are set to the values returned by the
-.\" syscall and will be passed back to the traced process by the normal
-.\" syscall return mechanism.
-.El
.Sh ERRORS
Some requests can cause
.Fn ptrace
.Bl -bullet -compact
.It
A process attempted to use
-.Dv PT_ATTACH
+.Dv PT_ATTACHEXC
on itself.
.It
The
.Fa request
was not one of the legal requests.
-.\" .It
-.\" The
-.\" .Fa addr
-.\" to
-.\" .Dv PT_READ_U
-.\" or
-.\" .Dv PT_WRITE_U
-.\" was not
-.\" .Li int Ns \&-aligned.
.It
The signal number (in
.Fa data )
to
.Dv PT_CONTINUE
-.\" or
-.\" .Dv PT_SYSCALL
was neither 0 nor a legal signal number.
.It
.Dv PT_GETREGS ,
.It Bq Er EBUSY
.Bl -bullet -compact
.It
-.Dv PT_ATTACH
+.Dv PT_ATTACHEXC
was attempted on a process that was already being traced.
.It
A request attempted to manipulate a process that was being traced by
some process other than the one making the request.
.It
A request (other than
-.Dv PT_ATTACH )
+.Dv PT_ATTACHEXC )
specified a process that wasn't stopped.
.El
.It Bq Er EPERM
.Bl -bullet -compact
.It
A request (other than
-.Dv PT_ATTACH )
+.Dv PT_ATTACHEXC )
attempted to manipulate a process that wasn't being traced at all.
.It
An attempt was made to use
-.Dv PT_ATTACH
+.Dv PT_ATTACHEXC
on a process in violation of the requirements listed under
-.Dv PT_ATTACH
+.Dv PT_ATTACHEXC
above.
.El
-.Sh BUGS
-On the SPARC, the PC is set to the provided PC value for
-.Dv PT_CONTINUE
-and similar calls, but the NPC is set willy-nilly to 4 greater than the
-PC value. Using
-.Dv PT_GETREGS
-and
-.Dv PT_SETREGS
-to modify the PC, passing
-.Li (caddr_t)1
-to
-.Eo \&
-.Fn ptrace
-.Ec ,
-should be able to sidestep this.
-.Pp
-Single-stepping is not available.
-.\" .Pp
-.\" When using
-.\" .Dv PT_SYSCALL ,
-.\" there is no easy way to tell whether the traced process stopped because
-.\" it made a syscall or because a signal was sent at a moment that it just
-.\" happened to have valid-looking garbage in its
-.\" .Dq Li "struct mdproc" .
+.El
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