1LIBTRACEEVENT(3) libtraceevent Manual LIBTRACEEVENT(3)
2
6 tep_set_function_resolver, tep_reset_function_resolver,
7 tep_register_function, tep_register_print_string,
8 tep_get_function_count - function related tep APIs
9
11 #include <event-parse.h>
12 typedef char *(tep_func_resolver_t)(void *priv, unsigned long long *addrp, char **modp);
14 int tep_set_function_resolver(struct tep_handle *tep, tep_func_resolver_t *func, void *priv);
15 void tep_reset_function_resolver(struct tep_handle *tep);
16 int tep_register_function(struct tep_handle *tep, char *name, unsigned long long addr, char *mod);
17 int tep_register_print_string(struct tep_handle *tep, const char *fmt, unsigned long long addr);
18 int tep_get_function_count(struct tep_handle *tep)
19
21 Some tools may have already a way to resolve the kernel functions.
22 These APIs allow them to keep using it instead of duplicating all the
23 entries inside.
24 The tep_func_resolver_t type is the prototype of the alternative kernel
26 functions resolver. This function receives a pointer to its custom
27 context (set with the tep_set_function_resolver() call ) and the
28 address of a kernel function, which has to be resolved. In case of
29 success, it should return the name of the function and its module (if
30 any) in modp.
31 The tep_set_function_resolver() function registers func as an
33 alternative kernel functions resolver. The tep argument is trace event
34 parser context. The priv argument is a custom context of the func
35 function. The function resolver is used by the APIs
36 tep_find_function(3), tep_find_function_address(3), and
37 tep_print_func_field() to resolve a function address to a function
38 name.
39 The tep_reset_function_resolver() function resets the kernel functions
41 resolver to the default function. The tep argument is trace event
42 parser context.
43 These APIs can be used to find function name and start address, by
45 given address. The given address does not have to be exact, it will
46 select the function that would contain it.
47 The tep_register_function() function registers a function name mapped
49 to an address and (optional) module. This mapping is used in case the
50 function tracer or events have "%pS" parameter in its format string. It
51 is common to pass in the kallsyms function names with their
52 corresponding addresses with this function. The tep argument is the
53 trace event parser context. The name is the name of the function, the
54 string is copied internally. The addr is the start address of the
55 function. The mod is the kernel module the function may be in (NULL for
56 none).
57 The tep_register_print_string() function registers a string by the
59 address it was stored in the kernel. Some strings internal to the
60 kernel with static address are passed to certain events. The "%s" in
61 the event’s format field which has an address needs to know what string
62 would be at that address. The tep_register_print_string() supplies the
63 parsing with the mapping between kernel addresses and those strings.
64 The tep argument is the trace event parser context. The fmt is the
65 string to register, it is copied internally. The addr is the address
66 the string was located at.
67 tep_get_function_count() returns the number of registered functions in
69 a tep handler.
70
72 The tep_set_function_resolver() function returns 0 in case of success,
73 or -1 in case of an error.
74 The tep_register_function() function returns 0 in case of success. In
76 case of an error -1 is returned, and errno is set to the appropriate
77 error number.
78 The tep_register_print_string() function returns 0 in case of success.
80 In case of an error -1 is returned, and errno is set to the appropriate
81 error number.
82
84 #include <event-parse.h>
85 ...
86 struct tep_handle *tep = tep_alloc();
87 ...
88 char *my_resolve_kernel_addr(void *context,
89 unsigned long long *addrp, char **modp)
90 {
91 struct db *function_database = context;
92 struct symbol *sym = sql_lookup(function_database, *addrp);
93 if (!sym)
95 return NULL;
96 *modp = sym->module_name;
98 return sym->name;
99 }
100 void show_function( unsigned long long addr)
102 {
103 unsigned long long fstart;
104 const char *fname;
105 if (tep_set_function_resolver(tep, my_resolve_kernel_addr,
107 function_database) != 0) {
108 /* failed to register my_resolve_kernel_addr */
109 }
110 /* These APIs use my_resolve_kernel_addr() to resolve the addr */
112 fname = tep_find_function(tep, addr);
113 fstart = tep_find_function_address(tep, addr);
114 /*
116 addr is in function named fname, starting at fstart address,
117 at offset (addr - fstart)
118 */
119 tep_reset_function_resolver(tep);
121 }
123 ...
124 if (tep_register_function(tep, "kvm_exit",
125 (unsigned long long) 0x12345678, "kvm") != 0) {
126 /* Failed to register kvm_exit address mapping */
127 }
128 ...
129 if (tep_register_print_string(tep, "print string",
130 (unsigned long long) 0x87654321, NULL) != 0) {
131 /* Failed to register "print string" address mapping */
132 }
133 ...
134
136 event-parse.h
137 Header file to include in order to have access to the library APIs.
138 -ltraceevent
139 Linker switch to add when building a program that uses the library.
140
142 libtraceevent(3), trace-cmd(1)
143
145 Steven Rostedt <rostedt@goodmis.org[1]>, author of libtraceevent.
146 Tzvetomir Stoyanov <tz.stoyanov@gmail.com[2]>, author of this man page.
147
149 Report bugs to <linux-trace-devel@vger.kernel.org[3]>
150
152 libtraceevent is Free Software licensed under the GNU LGPL 2.1
153
155 https://git.kernel.org/pub/scm/libs/libtrace/libtraceevent.git/
156
158 1. rostedt@goodmis.org
159 mailto:rostedt@goodmis.org
160 2. tz.stoyanov@gmail.com
162 mailto:tz.stoyanov@gmail.com
163 3. linux-trace-devel@vger.kernel.org
165 mailto:linux-trace-devel@vger.kernel.org
166libtraceevent 1.7.2 04/05/2023 LIBTRACEEVENT(3)