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KTRACE(2) | System Calls Manual | KTRACE(2) |
NAME¶
ktrace — process tracingLIBRARY¶
Standard C Library (libc, -lc)SYNOPSIS¶
#include <sys/param.h>#include <sys/time.h>
#include <sys/uio.h>
#include <sys/ktrace.h> int
ktrace(const char *tracefile, int ops, int trpoints, int pid);
DESCRIPTION¶
The ktrace() system call enables or disables tracing of one or more processes. Users may only trace their own processes. Only the super-user can trace setuid or setgid programs. The tracefile argument gives the pathname of the file to be used for tracing. The file must exist and be a regular file writable by the calling process. All trace records are always appended to the file, so the file must be truncated to zero length to discard previous trace data. If tracing points are being disabled (see KTROP_CLEAR below), tracefile may be NULL. The ops argument specifies the requested ktrace operation. The defined operations are:KTROP_SET | Enable trace points specified in trpoints. | |
KTROP_CLEAR | Disable trace points specified in | trpoints. |
KTROP_CLEARFILE | Stop all tracing. | |
KTRFLAG_DESCEND | The tracing change should apply to the specified process and all its current children. |
KTRFAC_SYSCALL | Trace system calls. |
KTRFAC_SYSRET | Trace return values from system calls. |
KTRFAC_NAMEI | Trace name lookup operations. |
KTRFAC_GENIO | Trace all I/O (note that this option can generate much output). |
KTRFAC_PSIG | Trace posted signals. |
KTRFAC_CSW | Trace context switch points. |
KTRFAC_INHERIT | Inherit tracing to future children. |
struct ktr_header { int ktr_len; /* length of buf */ short ktr_type; /* trace record type */ pid_t ktr_pid; /* process id */ char ktr_comm[MAXCOMLEN+1]; /* command name */ struct timeval ktr_time; /* timestamp */ intptr_t ktr_tid; /* was ktr_buffer */ };
SYSCTL TUNABLES¶
The following sysctl(8) tunables influence the behaviour of ktrace():- kern.ktrace.geniosize
- bounds the amount of data a traced I/O request will log to the trace file.
- kern.ktrace.request_pool
- bounds the number of trace events being logged at a time.
RETURN VALUES¶
The ktrace() function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate the error.ERRORS¶
The ktrace() system call will fail if:- [
ENOTDIR
] - A component of the path prefix is not a directory.
- [
ENAMETOOLONG
] - A component of a pathname exceeded 255 characters, or an entire path name exceeded 1023 characters.
- [
ENOENT
] - The named tracefile does not exist.
- [
EACCES
] - Search permission is denied for a component of the path prefix.
- [
ELOOP
] - Too many symbolic links were encountered in translating the pathname.
- [
EIO
] - An I/O error occurred while reading from or writing to the file system.
- [
ENOSYS
] - The kernel was not compiled with ktrace support.
KTR_DROP
set in its ktr_type
field.
SEE ALSO¶
kdump(1), ktrace(1), utrace(2), sysctl(8), p_candebug(9)HISTORY¶
The ktrace() system call first appeared in 4.4BSD.July 13, 2008 | Debian |