Man

Command Section
PTRACE(2)                 FreeBSD System Calls Manual                PTRACE(2)

NAME
     ptrace - process tracing and debugging

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <sys/types.h>
     #include <sys/ptrace.h>

     int
     ptrace(int request, pid_t pid, caddr_t addr, int data);

DESCRIPTION
     The ptrace() system call provides tracing and debugging facilities.  It
     allows one process (the tracing process) to control another (the traced
     process).  The tracing process must first attach to the traced process,
     and then issue a series of ptrace() system calls to control the execution
     of the process, as well as access process memory and register state.  For
     the duration of the tracing session, the traced process will be
     ``re-parented'', with its parent process ID (and resulting behavior)
     changed to the tracing process.  It is permissible for a tracing process
     to attach to more than one other process at a time.  When the tracing
     process has completed its work, it must detach the traced process; if a
     tracing process exits without first detaching all processes it has
     attached, those processes will be killed.

     Most of the time, the traced process runs normally, but when it receives
     a signal (see sigaction(2)), it stops.  The tracing process is expected
     to notice this via wait(2) or the delivery of a SIGCHLD signal, examine
     the state of the stopped process, and cause it to terminate or continue
     as appropriate.  The signal may be a normal process signal, generated as
     a result of traced process behavior, or use of the kill(2) system call;
     alternatively, it may be generated by the tracing facility as a result of
     attaching, stepping by the tracing process, or an event in the traced
     process.  The tracing process may choose to intercept the signal, using
     it to observe process behavior (such as SIGTRAP), or forward the signal
     to the process if appropriate.  The ptrace() system call is the mechanism
     by which all this happens.

     A traced process may report additional signal stops corresponding to
     events in the traced process.  These additional signal stops are reported
     as SIGTRAP or SIGSTOP signals.  The tracing process can use the
     PT_LWPINFO request to determine which events are associated with a
     SIGTRAP or SIGSTOP signal.  Note that multiple events may be associated
     with a single signal.  For example, events indicated by the PL_FLAG_BORN,
     PL_FLAG_FORKED, and PL_FLAG_EXEC flags are also reported as a system call
     exit event (PL_FLAG_SCX).  The signal stop for a new child process
     enabled via PTRACE_FORK will report a SIGSTOP signal.  All other
     additional signal stops use SIGTRAP.

     Each traced process has a tracing event mask.  An event in the traced
     process only reports a signal stop if the corresponding flag is set in
     the tracing event mask.  The current set of tracing event flags include:

     PTRACE_EXEC        Report a stop for a successful invocation of
                        execve(2).  This event is indicated by the
                        PL_FLAG_EXEC flag in the pl_flags member of struct
                        ptrace_lwpinfo.

     PTRACE_SCE         Report a stop on each system call entry.  This event
                        is indicated by the PL_FLAG_SCE flag in the pl_flags
                        member of struct ptrace_lwpinfo.

     PTRACE_SCX         Report a stop on each system call exit.  This event is
                        indicated by the PL_FLAG_SCX flag in the pl_flags
                        member of struct ptrace_lwpinfo.

     PTRACE_SYSCALL     Report stops for both system call entry and exit.

     PTRACE_FORK        This event flag controls tracing for new child
                        processes of a traced process.

                        When this event flag is enabled, new child processes
                        will enable tracing and stop before executing their
                        first instruction.  The new child process will include
                        the PL_FLAG_CHILD flag in the pl_flags member of
                        struct ptrace_lwpinfo.  The traced process will report
                        a stop that includes the PL_FLAG_FORKED flag.  The
                        process ID of the new child process will also be
                        present in the pl_child_pid member of struct
                        ptrace_lwpinfo.  If the new child process was created
                        via vfork(2), the traced process's stop will also
                        include the PL_FLAG_VFORKED flag.  Note that new child
                        processes will be attached with the default tracing
                        event mask; they do not inherit the event mask of the
                        traced process.

                        When this event flag is not enabled, new child
                        processes will execute without tracing enabled.

     PTRACE_LWP         This event flag controls tracing of LWP (kernel
                        thread) creation and destruction.  When this event is
                        enabled, new LWPs will stop and report an event with
                        PL_FLAG_BORN set before executing their first
                        instruction, and exiting LWPs will stop and report an
                        event with PL_FLAG_EXITED set before completing their
                        termination.

                        Note that new processes do not report an event for the
                        creation of their initial thread, and exiting
                        processes do not report an event for the termination
                        of the last thread.

     PTRACE_VFORK       Report a stop event when a parent process resumes
                        after a vfork(2).

                        When a thread in the traced process creates a new
                        child process via vfork(2), the stop that reports
                        PL_FLAG_FORKED and PL_FLAG_SCX occurs just after the
                        child process is created, but before the thread waits
                        for the child process to stop sharing process memory.
                        If a debugger is not tracing the new child process, it
                        must ensure that no breakpoints are enabled in the
                        shared process memory before detaching from the new
                        child process.  This means that no breakpoints are
                        enabled in the parent process either.

                        The PTRACE_VFORK flag enables a new stop that
                        indicates when the new child process stops sharing the
                        process memory of the parent process.  A debugger can
                        reinsert breakpoints in the parent process and resume
                        it in response to this event.  This event is indicated
                        by setting the PL_FLAG_VFORK_DONE flag.

     The default tracing event mask when attaching to a process via PT_ATTACH,
     PT_TRACE_ME, or PTRACE_FORK includes only PTRACE_EXEC events.  All other
     event flags are disabled.

     The request argument specifies what operation is being performed; the
     meaning of the rest of the arguments depends on the operation, but except
     for one special case noted below, all ptrace() calls are made by the
     tracing process, and the pid argument specifies the process ID of the
     traced process or a corresponding thread ID.  The request argument can
     be:

     PT_TRACE_ME           This request is the only one 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 traced process
                           stops, it cannot be made to continue except via
                           ptrace().) When a process has used this request and
                           calls execve(2) or any of the routines built on it
                           (such as execv(3)), 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.  If the child was created
                           by vfork(2) system call or rfork(2) call with the
                           RFMEM flag specified, the debugging events are
                           reported to the parent only after the execve(2) is
                           executed.

     PT_READ_I, PT_READ_D  These requests read a single int of data from the
                           traced process's address space.  Traditionally,
                           ptrace() has allowed for machines with distinct
                           address spaces for instruction and data, which is
                           why there are two requests: conceptually, PT_READ_I
                           reads from the instruction space and PT_READ_D
                           reads from the data space.  In the current FreeBSD
                           implementation, these two requests are completely
                           identical.  The addr argument specifies the address
                           (in the traced process's 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
                           ptrace().

     PT_WRITE_I, PT_WRITE_D
                           These requests parallel PT_READ_I and PT_READ_D,
                           except that they write rather than read.  The data
                           argument supplies the value to be written.

     PT_IO                 This request allows reading and writing arbitrary
                           amounts of data in the traced process's address
                           space.  The addr argument specifies a pointer to a
                           struct ptrace_io_desc, which is defined as follows:

                           struct ptrace_io_desc {
                                   int     piod_op;        /* I/O operation */
                                   void    *piod_offs;     /* child offset */
                                   void    *piod_addr;     /* parent offset */
                                   size_t  piod_len;       /* request length */
                           };

                           /*
                            * Operations in piod_op.
                            */
                           #define PIOD_READ_D     1       /* Read from D space */
                           #define PIOD_WRITE_D    2       /* Write to D space */
                           #define PIOD_READ_I     3       /* Read from I space */
                           #define PIOD_WRITE_I    4       /* Write to I space */

                           The data argument is ignored.  The actual number of
                           bytes read or written is stored in piod_len upon
                           return.

     PT_CONTINUE           The traced process continues execution.  The addr
                           argument is an address specifying the place where
                           execution is to be resumed (a new value for the
                           program counter), or (caddr_t)1 to indicate that
                           execution is to pick up where it left off.  The
                           data argument provides a signal number to be
                           delivered to the traced process as it resumes
                           execution, or 0 if no signal is to be sent.

     PT_STEP               The traced process is single stepped one
                           instruction.  The addr argument should be passed
                           (caddr_t)1.  The data argument provides a signal
                           number to be delivered to the traced process as it
                           resumes execution, or 0 if no signal is to be sent.

     PT_KILL               The traced process terminates, as if PT_CONTINUE
                           had been used with SIGKILL given as the signal to
                           be delivered.

     PT_ATTACH             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, pid specifies the
                           process ID of the to-be-traced process, and the
                           other two arguments are ignored.  This request
                           requires that the target process must have the same
                           real UID as the tracing process, and that it must
                           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.

     PT_DETACH             This request is like PT_CONTINUE, except that it
                           does not allow specifying an alternate place to
                           continue execution, and after it succeeds, the
                           traced process is no longer traced and continues
                           execution normally.

     PT_GETREGS            This request reads the traced process's machine
                           registers into the ``struct reg'' (defined in
                           <machine/reg.h>) pointed to by addr.

     PT_SETREGS            This request is the converse of PT_GETREGS; it
                           loads the traced process's machine registers from
                           the ``struct reg'' (defined in <machine/reg.h>)
                           pointed to by addr.

     PT_GETFPREGS          This request reads the traced process's floating-
                           point registers into the ``struct fpreg'' (defined
                           in <machine/reg.h>) pointed to by addr.

     PT_SETFPREGS          This request is the converse of PT_GETFPREGS; it
                           loads the traced process's floating-point registers
                           from the ``struct fpreg'' (defined in
                           <machine/reg.h>) pointed to by addr.

     PT_GETDBREGS          This request reads the traced process's debug
                           registers into the ``struct dbreg'' (defined in
                           <machine/reg.h>) pointed to by addr.

     PT_SETDBREGS          This request is the converse of PT_GETDBREGS; it
                           loads the traced process's debug registers from the
                           ``struct dbreg'' (defined in <machine/reg.h>)
                           pointed to by addr.

     PT_LWPINFO            This request can be used to obtain information
                           about the kernel thread, also known as light-weight
                           process, that caused the traced process to stop.
                           The addr argument specifies a pointer to a struct
                           ptrace_lwpinfo, which is defined as follows:

                           struct ptrace_lwpinfo {
                                   lwpid_t pl_lwpid;
                                   int     pl_event;
                                   int     pl_flags;
                                   sigset_t pl_sigmask;
                                   sigset_t pl_siglist;
                                   siginfo_t pl_siginfo;
                                   char    pl_tdname[MAXCOMLEN + 1];
                                   pid_t   pl_child_pid;
                                   u_int   pl_syscall_code;
                                   u_int   pl_syscall_narg;
                           };

                           The data argument is to be set to the size of the
                           structure known to the caller.  This allows the
                           structure to grow without affecting older programs.

                           The fields in the struct ptrace_lwpinfo have the
                           following meaning:
                           pl_lwpid
                                   LWP id of the thread
                           pl_event
                                   Event that caused the stop.  Currently
                                   defined events are:
                                   PL_EVENT_NONE       No reason given
                                   PL_EVENT_SIGNAL     Thread stopped due to
                                                       the pending signal
                           pl_flags
                                   Flags that specify additional details about
                                   observed stop.  Currently defined flags
                                   are:
                                   PL_FLAG_SCE
                                           The thread stopped due to system
                                           call entry, right after the kernel
                                           is entered.  The debugger may
                                           examine syscall arguments that are
                                           stored in memory and registers
                                           according to the ABI of the current
                                           process, and modify them, if
                                           needed.
                                   PL_FLAG_SCX
                                           The thread is stopped immediately
                                           before syscall is returning to the
                                           usermode.  The debugger may examine
                                           system call return values in the
                                           ABI-defined registers and/or
                                           memory.
                                   PL_FLAG_EXEC
                                           When PL_FLAG_SCX is set, this flag
                                           may be additionally specified to
                                           inform that the program being
                                           executed by debuggee process has
                                           been changed by successful
                                           execution of a system call from the
                                           execve(2) family.
                                   PL_FLAG_SI
                                           Indicates that pl_siginfo member of
                                           struct ptrace_lwpinfo contains
                                           valid information.
                                   PL_FLAG_FORKED
                                           Indicates that the process is
                                           returning from a call to fork(2)
                                           that created a new child process.
                                           The process identifier of the new
                                           process is available in the
                                           pl_child_pid member of struct
                                           ptrace_lwpinfo.
                                   PL_FLAG_CHILD
                                           The flag is set for first event
                                           reported from a new child which is
                                           automatically attached when
                                           PTRACE_FORK is enabled.
                                   PL_FLAG_BORN
                                           This flag is set for the first
                                           event reported from a new LWP when
                                           PTRACE_LWP is enabled.  It is
                                           reported along with PL_FLAG_SCX.
                                   PL_FLAG_EXITED
                                           This flag is set for the last event
                                           reported by an exiting LWP when
                                           PTRACE_LWP is enabled.  Note that
                                           this event is not reported when the
                                           last LWP in a process exits.  The
                                           termination of the last thread is
                                           reported via a normal process exit
                                           event.
                                   PL_FLAG_VFORKED
                                           Indicates that the thread is
                                           returning from a call to vfork(2)
                                           that created a new child process.
                                           This flag is set in addition to
                                           PL_FLAG_FORKED.
                                   PL_FLAG_VFORK_DONE
                                           Indicates that the thread has
                                           resumed after a child process
                                           created via vfork(2) has stopped
                                           sharing its address space with the
                                           traced process.
                           pl_sigmask
                                   The current signal mask of the LWP
                           pl_siglist
                                   The current pending set of signals for the
                                   LWP.  Note that signals that are delivered
                                   to the process would not appear on an LWP
                                   siglist until the thread is selected for
                                   delivery.
                           pl_siginfo
                                   The siginfo that accompanies the signal
                                   pending.  Only valid for PL_EVENT_SIGNAL
                                   stop when PL_FLAG_SI is set in pl_flags.
                           pl_tdname
                                   The name of the thread.
                           pl_child_pid
                                   The process identifier of the new child
                                   process.  Only valid for a PL_EVENT_SIGNAL
                                   stop when PL_FLAG_FORKED is set in
                                   pl_flags.
                           pl_syscall_code
                                   The ABI-specific identifier of the current
                                   system call.  Note that for indirect system
                                   calls this field reports the indirected
                                   system call.  Only valid when PL_FLAG_SCE
                                   or PL_FLAG_SCX is set in pl_flags.
                           pl_syscall_narg
                                   The number of arguments passed to the
                                   current system call not counting the system
                                   call identifier.  Note that for indirect
                                   system calls this field reports the
                                   arguments passed to the indirected system
                                   call.  Only valid when PL_FLAG_SCE or
                                   PL_FLAG_SCX is set in pl_flags.

     PT_GETNUMLWPS         This request returns the number of kernel threads
                           associated with the traced process.

     PT_GETLWPLIST         This request can be used to get the current thread
                           list.  A pointer to an array of type lwpid_t should
                           be passed in addr, with the array size specified by
                           data.  The return value from ptrace() is the count
                           of array entries filled in.

     PT_SETSTEP            This request will turn on single stepping of the
                           specified process.

     PT_CLEARSTEP          This request will turn off single stepping of the
                           specified process.

     PT_SUSPEND            This request will suspend the specified thread.

     PT_RESUME             This request will resume the specified thread.

     PT_TO_SCE             This request will set the PTRACE_SCE event flag to
                           trace all future system call entries and continue
                           the process.  The addr and data arguments are used
                           the same as for PT_CONTINUE.

     PT_TO_SCX             This request will set the PTRACE_SCX event flag to
                           trace all future system call exits and continue the
                           process.  The addr and data arguments are used the
                           same as for PT_CONTINUE.

     PT_SYSCALL            This request will set the PTRACE_SYSCALL event flag
                           to trace all future system call entries and exits
                           and continue the process.  The addr and data
                           arguments are used the same as for PT_CONTINUE.

     PT_FOLLOW_FORK        This request controls tracing for new child
                           processes of a traced process.  If data is non-
                           zero, PTRACE_FORK is set in the traced process's
                           event tracing mask.  If data is zero, PTRACE_FORK
                           is cleared from the traced process's event tracing
                           mask.

     PT_LWP_EVENTS         This request controls tracing of LWP creation and
                           destruction.  If data is non-zero, PTRACE_LWP is
                           set in the traced process's event tracing mask.  If
                           data is zero, PTRACE_LWP is cleared from the traced
                           process's event tracing mask.

     PT_GET_EVENT_MASK     This request reads the traced process's event
                           tracing mask into the integer pointed to by addr.
                           The size of the integer must be passed in data.

     PT_SET_EVENT_MASK     This request sets the traced process's event
                           tracing mask from the integer pointed to by addr.
                           The size of the integer must be passed in data.

     PT_VM_TIMESTAMP       This request returns the generation number or
                           timestamp of the memory map of the traced process
                           as the return value from ptrace().  This provides a
                           low-cost way for the tracing process to determine
                           if the VM map changed since the last time this
                           request was made.

     PT_VM_ENTRY           This request is used to iterate over the entries of
                           the VM map of the traced process.  The addr
                           argument specifies a pointer to a struct
                           ptrace_vm_entry, which is defined as follows:

                           struct ptrace_vm_entry {
                                   int             pve_entry;
                                   int             pve_timestamp;
                                   u_long          pve_start;
                                   u_long          pve_end;
                                   u_long          pve_offset;
                                   u_int           pve_prot;
                                   u_int           pve_pathlen;
                                   long            pve_fileid;
                                   uint32_t        pve_fsid;
                                   char            *pve_path;
                           };

                           The first entry is returned by setting pve_entry to
                           zero.  Subsequent entries are returned by leaving
                           pve_entry unmodified from the value returned by
                           previous requests.  The pve_timestamp field can be
                           used to detect changes to the VM map while
                           iterating over the entries.  The tracing process
                           can then take appropriate action, such as
                           restarting.  By setting pve_pathlen to a non-zero
                           value on entry, the pathname of the backing object
                           is returned in the buffer pointed to by pve_path,
                           provided the entry is backed by a vnode.  The
                           pve_pathlen field is updated with the actual length
                           of the pathname (including the terminating null
                           character).  The pve_offset field is the offset
                           within the backing object at which the range
                           starts.  The range is located in the VM space at
                           pve_start and extends up to pve_end (inclusive).

                           The data argument is ignored.

x86 MACHINE-SPECIFIC REQUESTS
     PT_GETXMMREGS         Copy the XMM FPU state into the buffer pointed to
                           by the argument addr.  The buffer has the same
                           layout as the 32-bit save buffer for the machine
                           instruction FXSAVE.

                           This request is only valid for i386 programs, both
                           on native 32-bit systems and on amd64 kernels.  For
                           64-bit amd64 programs, the XMM state is reported as
                           part of the FPU state returned by the PT_GETFPREGS
                           request.

                           The data argument is ignored.

     PT_SETXMMREGS         Load the XMM FPU state for the thread from the
                           buffer pointed to by the argument addr.  The buffer
                           has the same layout as the 32-bit load buffer for
                           the machine instruction FXRSTOR.

                           As with PT_GETXMMREGS, this request is only valid
                           for i386 programs.

                           The data argument is ignored.

     PT_GETXSTATE_INFO     Report which XSAVE FPU extensions are supported by
                           the CPU and allowed in userspace programs.  The
                           addr argument must point to a variable of type
                           struct ptrace_xstate_info, which contains the
                           information on the request return.  struct
                           ptrace_xstate_info is defined as follows:

                           struct ptrace_xstate_info {
                                   uint64_t        xsave_mask;
                                   uint32_t        xsave_len;
                           };
                           The xsave_mask field is a bitmask of the currently
                           enabled extensions.  The meaning of the bits is
                           defined in the Intel and AMD processor
                           documentation.  The xsave_len field reports the
                           length of the XSAVE area for storing the hardware
                           state for currently enabled extensions in the
                           format defined by the x86 XSAVE machine
                           instruction.

                           The data argument value must be equal to the size
                           of the struct ptrace_xstate_info.

     PT_GETXSTATE          Return the content of the XSAVE area for the
                           thread.  The addr argument points to the buffer
                           where the content is copied, and the data argument
                           specifies the size of the buffer.  The kernel
                           copies out as much content as allowed by the buffer
                           size.  The buffer layout is specified by the layout
                           of the save area for the XSAVE machine instruction.

     PT_SETXSTATE          Load the XSAVE state for the thread from the buffer
                           specified by the addr pointer.  The buffer size is
                           passed in the data argument.  The buffer must be at
                           least as large as the struct savefpu (defined in
                           x86/fpu.h) to allow the complete x87 FPU and XMM
                           state load.  It must not be larger than the XSAVE
                           state length, as reported by the xsave_len field
                           from the struct ptrace_xstate_info of the
                           PT_GETXSTATE_INFO request.  Layout of the buffer is
                           identical to the layout of the load area for the
                           XRSTOR machine instruction.

     PT_GETFSBASE          Return the value of the base used when doing
                           segmented memory addressing using the %fs segment
                           register.  The addr argument points to an unsigned
                           long variable where the base value is stored.

                           The data argument is ignored.

     PT_GETGSBASE          Like the PT_GETFSBASE request, but returns the base
                           for the %gs segment register.

     PT_SETFSBASE          Set the base for the %fs segment register to the
                           value pointed to by the addr argument.  addr must
                           point to the unsigned long variable containing the
                           new base.

                           The data argument is ignored.

     PT_SETGSBASE          Like the PT_SETFSBASE request, but sets the base
                           for the %gs segment register.

PowerPC MACHINE-SPECIFIC REQUESTS
     PT_GETVRREGS     Return the thread's ALTIVEC machine state in the buffer
                      pointed to by addr.

                      The data argument is ignored.

     PT_SETVRREGS     Set the thread's ALTIVEC machine state from the buffer
                      pointed to by addr.

                      The data argument is ignored.

     Additionally, other machine-specific requests can exist.

RETURN VALUES
     Most requests return 0 on success and -1 on error.  Some requests can
     cause ptrace() to return -1 as a non-error value, among them are
     PT_READ_I and PT_READ_D, which return the value read from the process
     memory on success.  To disambiguate, errno can be set to 0 before the
     call and checked afterwards.

     The current ptrace() implementation always sets errno to 0 before calling
     into the kernel, both for historic reasons and for consistency with other
     operating systems.  It is recommended to assign zero to errno explicitly
     for forward compatibility.

ERRORS
     The ptrace() system call may fail if:

     [ESRCH]
                           No process having the specified process ID exists.

     [EINVAL]
                           A process attempted to use PT_ATTACH on itself.
                           The request argument was not one of the legal
                            requests.
                           The signal number (in data) to PT_CONTINUE was
                            neither 0 nor a legal signal number.
                           PT_GETREGS, PT_SETREGS, PT_GETFPREGS,
                            PT_SETFPREGS, PT_GETDBREGS, or PT_SETDBREGS was
                            attempted on a process with no valid register set.
                            (This is normally true only of system processes.)
                           PT_VM_ENTRY was given an invalid value for
                            pve_entry.  This can also be caused by changes to
                            the VM map of the process.
                           The size (in data) provided to PT_LWPINFO was less
                            than or equal to zero, or larger than the
                            ptrace_lwpinfo structure known to the kernel.
                           The size (in data) provided to the x86-specific
                            PT_GETXSTATE_INFO request was not equal to the
                            size of the struct ptrace_xstate_info.
                           The size (in data) provided to the x86-specific
                            PT_SETXSTATE request was less than the size of the
                            x87 plus the XMM save area.
                           The size (in data) provided to the x86-specific
                            PT_SETXSTATE request was larger than returned in
                            the xsave_len member of the struct
                            ptrace_xstate_info from the PT_GETXSTATE_INFO
                            request.
                           The base value, provided to the amd64-specific
                            requests PT_SETFSBASE or PT_SETGSBASE, pointed
                            outside of the valid user address space.  This
                            error will not occur in 32-bit programs.

     [EBUSY]
                           PT_ATTACH was attempted on a process that was
                            already being traced.
                           A request attempted to manipulate a process that
                            was being traced by some process other than the
                            one making the request.
                           A request (other than PT_ATTACH) specified a
                            process that was not stopped.

     [EPERM]
                           A request (other than PT_ATTACH) attempted to
                            manipulate a process that was not being traced at
                            all.
                           An attempt was made to use PT_ATTACH on a process
                            in violation of the requirements listed under
                            PT_ATTACH above.

     [ENOENT]
                           PT_VM_ENTRY previously returned the last entry of
                            the memory map.  No more entries exist.

     [ENAMETOOLONG]
                           PT_VM_ENTRY cannot return the pathname of the
                            backing object because the buffer is not big
                            enough.  pve_pathlen holds the minimum buffer size
                            required on return.

SEE ALSO
     execve(2), sigaction(2), wait(2), execv(3), i386_clr_watch(3),
     i386_set_watch(3)

HISTORY
     The ptrace() function appeared in Version 7 AT&T UNIX.

FreeBSD 11.1-RELEASE-p4         August 29, 2016        FreeBSD 11.1-RELEASE-p4
Command Section