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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | EXAMPLE | FILES | SEE ALSO | AUTHOR | REPORTING BUGS | LICENSE | RESOURCES | NOTES | COLOPHON |
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LIBTRACEEVENT(3) libtraceevent Manual LIBTRACEEVENT(3)
tep_set_function_resolver, tep_reset_function_resolver,
tep_register_function, tep_register_print_string,
tep_get_function_count - function related tep APIs
#include <event-parse.h>
typedef char *(tep_func_resolver_t)(void *priv, unsigned long long *addrp, char **modp);
int tep_set_function_resolver(struct tep_handle *tep, tep_func_resolver_t *func, void *priv);
void tep_reset_function_resolver(struct tep_handle *tep);
int tep_register_function(struct tep_handle *tep, char *name, unsigned long long addr, char *mod);
int tep_register_print_string(struct tep_handle *tep, const char *fmt, unsigned long long addr);
int tep_get_function_count(struct tep_handle *tep)
Some tools may have already a way to resolve the kernel
functions. These APIs allow them to keep using it instead of
duplicating all the entries inside.
The tep_func_resolver_t type is the prototype of the alternative
kernel functions resolver. This function receives a pointer to
its custom context (set with the tep_set_function_resolver() call
) and the address of a kernel function, which has to be resolved.
In case of success, it should return the name of the function and
its module (if any) in modp.
The tep_set_function_resolver() function registers func as an
alternative kernel functions resolver. The tep argument is trace
event parser context. The priv argument is a custom context of
the func function. The function resolver is used by the APIs
tep_find_function(3), tep_find_function_address(3), and
tep_print_func_field() to resolve a function address to a
function name.
The tep_reset_function_resolver() function resets the kernel
functions resolver to the default function. The tep argument is
trace event parser context.
These APIs can be used to find function name and start address,
by given address. The given address does not have to be exact, it
will select the function that would contain it.
The tep_register_function() function registers a function name
mapped to an address and (optional) module. This mapping is used
in case the function tracer or events have "%pS" parameter in its
format string. It is common to pass in the kallsyms function
names with their corresponding addresses with this function. The
tep argument is the trace event parser context. The name is the
name of the function, the string is copied internally. The addr
is the start address of the function. The mod is the kernel
module the function may be in (NULL for none).
The tep_register_print_string() function registers a string by
the address it was stored in the kernel. Some strings internal to
the kernel with static address are passed to certain events. The
"%s" in the event’s format field which has an address needs to
know what string would be at that address. The
tep_register_print_string() supplies the parsing with the mapping
between kernel addresses and those strings. The tep argument is
the trace event parser context. The fmt is the string to
register, it is copied internally. The addr is the address the
string was located at.
tep_get_function_count() returns the number of registered
functions in a tep handler.
The tep_set_function_resolver() function returns 0 in case of
success, or -1 in case of an error.
The tep_register_function() function returns 0 in case of
success. In case of an error -1 is returned, and errno is set to
the appropriate error number.
The tep_register_print_string() function returns 0 in case of
success. In case of an error -1 is returned, and errno is set to
the appropriate error number.
#include <event-parse.h>
...
struct tep_handle *tep = tep_alloc();
...
char *my_resolve_kernel_addr(void *context,
unsigned long long *addrp, char **modp)
{
struct db *function_database = context;
struct symbol *sym = sql_lookup(function_database, *addrp);
if (!sym)
return NULL;
*modp = sym->module_name;
return sym->name;
}
void show_function( unsigned long long addr)
{
unsigned long long fstart;
const char *fname;
if (tep_set_function_resolver(tep, my_resolve_kernel_addr,
function_database) != 0) {
/* failed to register my_resolve_kernel_addr */
}
/* These APIs use my_resolve_kernel_addr() to resolve the addr */
fname = tep_find_function(tep, addr);
fstart = tep_find_function_address(tep, addr);
/*
addr is in function named fname, starting at fstart address,
at offset (addr - fstart)
*/
tep_reset_function_resolver(tep);
}
...
if (tep_register_function(tep, "kvm_exit",
(unsigned long long) 0x12345678, "kvm") != 0) {
/* Failed to register kvm_exit address mapping */
}
...
if (tep_register_print_string(tep, "print string",
(unsigned long long) 0x87654321, NULL) != 0) {
/* Failed to register "print string" address mapping */
}
...
event-parse.h
Header file to include in order to have access to the library APIs.
-ltraceevent
Linker switch to add when building a program that uses the library.
libtraceevent(3), trace-cmd(1)
Steven Rostedt <rostedt@goodmis.org[1]>, author of libtraceevent.
Tzvetomir Stoyanov <tz.stoyanov@gmail.com[2]>, author of this man page.
Report bugs to <linux-trace-devel@vger.kernel.org[3]>
libtraceevent is Free Software licensed under the GNU LGPL 2.1
https://git.kernel.org/pub/scm/libs/libtrace/libtraceevent.git/
1. rostedt@goodmis.org
mailto:rostedt@goodmis.org
2. tz.stoyanov@gmail.com
mailto:tz.stoyanov@gmail.com
3. linux-trace-devel@vger.kernel.org
mailto:linux-trace-devel@vger.kernel.org
This page is part of the libtraceevent (Linux kernel trace event
library) project. Information about the project can be found at
⟨https://www.trace-cmd.org/⟩. If you have a bug report for this
manual page, see ⟨https://www.trace-cmd.org/⟩. This page was
obtained from the project's upstream Git repository
⟨https://git.kernel.org/pub/scm/libs/libtrace/libtraceevent.git⟩
on 2023-12-22. (At that time, the date of the most recent commit
that was found in the repository was 2023-06-07.) If you
discover any rendering problems in this HTML version of the page,
or you believe there is a better or more up-to-date source for
the page, or you have corrections or improvements to the
information in this COLOPHON (which is not part of the original
manual page), send a mail to man-pages@man7.org
libtraceevent 1.7.3 09/24/2023 LIBTRACEEVENT(3)
Pages that refer to this page: tep_parse_saved_cmdlines(3)
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HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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