KTRACE(2) | System Calls Manual | KTRACE(2) |
ktrace
— process
tracing
#include
<sys/types.h>
#include <sys/param.h>
#include <sys/uio.h>
#include <sys/ktrace.h>
int
ktrace
(const
char *tracefile, int
ops, int trpoints,
pid_t pid);
The ktrace
() function enables or disables
tracing of one or more processes. Users may only trace their own processes.
Only the superuser can trace setuid or setgid programs. This function is
only available on kernels compiled with the KTRACE
option.
tracefile gives the pathname of the file to
be used for tracing. The file must exist, be writable by the calling
process, and not be a symbolic link. If tracing points are being disabled
(see KTROP_CLEAR
below),
tracefile must be NULL
.
Trace records are always appended to the file, ignoring the file offset, so the caller will usually want to truncate the file before calling these functions.
The ops parameter specifies the requested ktrace operation. The defined operations are:
KTROP_SET
KTROP_CLEAR
KTROP_CLEARFILE
KTRFLAG_DESCEND
The trpoints parameter specifies the trace points of interest. The defined trace points are:
KTRFAC_SYSCALL
KTRFAC_SYSRET
KTRFAC_NAMEI
KTRFAC_GENIO
KTRFAC_PSIG
KTRFAC_STRUCT
KTRFAC_USER
KTRFAC_EXECARGS
KTRFAC_EXECENV
KTRFAC_PLEDGE
KTRFAC_INHERIT
The pid parameter refers to a process ID. If it is negative, it refers to a process group ID.
Each tracing event outputs a record composed of a generic header followed by a trace point specific structure. The generic header is:
struct ktr_header { uint ktr_type; /* trace record type */ pid_t ktr_pid; /* process id */ pid_t ktr_tid; /* thread id */ struct timespec ktr_time; /* timestamp */ char ktr_comm[MAXCOMLEN+1]; /* command name */ size_t ktr_len; /* length of buf */ };
The ktr_len field specifies the length of the ktr_type data that follows this header. The ktr_pid, ktr_tid, and ktr_comm fields specify the process, thread, and command generating the record. The ktr_time field gives the time (with nanosecond resolution) that the record was generated.
The generic header is followed by ktr_len
bytes of a ktr_type record. The type specific records
are defined in the
<sys/ktrace.h>
include
file.
Upon successful completion, the value 0 is returned; otherwise the value -1 is returned and the global variable errno is set to indicate the error.
ktrace
() will fail if:
EINVAL
]EPERM
]KTROP_CLEARFILE
, this error is returned if it
could not stop tracing any of the processes tracing to the file.ESRCH
]EACCES
]EIO
]Additionally, ktrace
() will fail if:
ENOTDIR
]ENAMETOOLONG
]NAME_MAX
characters, or an entire pathname (including the terminating NUL) exceeded
PATH_MAX
bytes.ENOENT
]EACCES
]ELOOP
]EFAULT
]A ktrace
() function call first appeared in
4.4BSD.
January 6, 2019 | OpenBSD-current |