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Diffstat (limited to 'Documentation/libtraceevent-func_apis.txt')
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diff --git a/Documentation/libtraceevent-func_apis.txt b/Documentation/libtraceevent-func_apis.txt new file mode 100644 index 0000000..1b836a1 --- /dev/null +++ b/Documentation/libtraceevent-func_apis.txt @@ -0,0 +1,168 @@ +libtraceevent(3) +================ + +NAME +---- +tep_set_function_resolver, tep_reset_function_resolver, tep_register_function, tep_register_print_string, +tep_get_function_count - function related tep APIs + +SYNOPSIS +-------- +[verse] +-- +*#include <event-parse.h>* + +typedef char pass:[*](*tep_func_resolver_t*)(void pass:[*]_priv_, unsigned long long pass:[*]_addrp_, char pass:[**]_modp_); +int *tep_set_function_resolver*(struct tep_handle pass:[*]_tep_, tep_func_resolver_t pass:[*]_func_, void pass:[*]_priv_); +void *tep_reset_function_resolver*(struct tep_handle pass:[*]_tep_); +int *tep_register_function*(struct tep_handle pass:[*]_tep_, char pass:[*]_name_, unsigned long long _addr_, char pass:[*]_mod_); +int *tep_register_print_string*(struct tep_handle pass:[*]_tep_, const char pass:[*]_fmt_, unsigned long long _addr_); +int *tep_get_function_count*(struct tep_handle *_tep_) +-- + +DESCRIPTION +----------- +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. + +RETURN VALUE +------------ +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. + +EXAMPLE +------- +[source,c] +-- +#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 */ + } +... +-- + +FILES +----- +[verse] +-- +*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. +-- + +SEE ALSO +-------- +*libtraceevent*(3), *trace-cmd*(1) + +AUTHOR +------ +[verse] +-- +*Steven Rostedt* <rostedt@goodmis.org>, author of *libtraceevent*. +*Tzvetomir Stoyanov* <tz.stoyanov@gmail.com>, author of this man page. +-- +REPORTING BUGS +-------------- +Report bugs to <linux-trace-devel@vger.kernel.org> + +LICENSE +------- +libtraceevent is Free Software licensed under the GNU LGPL 2.1 + +RESOURCES +--------- +https://git.kernel.org/pub/scm/libs/libtrace/libtraceevent.git/ |