184 lines
6.3 KiB
Plaintext
184 lines
6.3 KiB
Plaintext
libtraceevent(3)
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================
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NAME
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----
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tep_find_function, tep_find_function_address, tep_set_function_resolver,
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tep_reset_function_resolver, tep_register_function, tep_register_print_string -
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function related tep APIs
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SYNOPSIS
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--------
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[verse]
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--
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*#include <event-parse.h>*
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typedef char pass:[*](*tep_func_resolver_t*)(void pass:[*]_priv_, unsigned long long pass:[*]_addrp_, char pass:[**]_modp_);
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int *tep_set_function_resolver*(struct tep_handle pass:[*]_tep_, tep_func_resolver_t pass:[*]_func_, void pass:[*]_priv_);
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void *tep_reset_function_resolver*(struct tep_handle pass:[*]_tep_);
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const char pass:[*]*tep_find_function*(struct tep_handle pass:[*]_tep_, unsigned long long _addr_);
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unsigned long long *tep_find_function_address*(struct tep_handle pass:[*]_tep_, unsigned long long _addr_);
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int *tep_register_function*(struct tep_handle pass:[*]_tep_, char pass:[*]_name_, unsigned long long _addr_, char pass:[*]_mod_);
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int *tep_register_print_string*(struct tep_handle pass:[*]_tep_, const char pass:[*]_fmt_, unsigned long long _addr_);
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--
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DESCRIPTION
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-----------
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Some tools may have already a way to resolve the kernel functions. These APIs
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allow them to keep using it instead of duplicating all the entries inside.
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The _tep_func_resolver_t_ type is the prototype of the alternative kernel
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functions resolver. This function receives a pointer to its custom context
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(set with the _tep_set_function_resolver()_ call ) and the address of a kernel
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function, which has to be resolved. In case of success, it should return
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the name of the function and its module (if any) in _modp_.
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The _tep_set_function_resolver()_ function registers _func_ as an alternative
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kernel functions resolver. The _tep_ argument is trace event parser context.
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The _priv_ argument is a custom context of the _func_ function. The function
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resolver is used by the APIs _tep_find_function()_,
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_tep_find_function_address()_, and _tep_print_func_field()_ to resolve
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a function address to a function name.
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The _tep_reset_function_resolver()_ function resets the kernel functions
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resolver to the default function. The _tep_ argument is trace event parser
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context.
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These APIs can be used to find function name and start address, by given
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address. The given address does not have to be exact, it will select
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the function that would contain it.
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The _tep_find_function()_ function returns the function name, which contains the
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given address _addr_. The _tep_ argument is the trace event parser context.
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The _tep_find_function_address()_ function returns the function start address,
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by given address _addr_. The _addr_ does not have to be exact, it will select
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the function that would contain it. The _tep_ argument is the trace event
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parser context.
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The _tep_register_function()_ function registers a function name mapped to an
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address and (optional) module. This mapping is used in case the function tracer
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or events have "%pS" parameter in its format string. It is common to pass in
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the kallsyms function names with their corresponding addresses with this
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function. The _tep_ argument is the trace event parser context. The _name_ is
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the name of the function, the string is copied internally. The _addr_ is the
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start address of the function. The _mod_ is the kernel module the function may
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be in (NULL for none).
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The _tep_register_print_string()_ function registers a string by the address
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it was stored in the kernel. Some strings internal to the kernel with static
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address are passed to certain events. The "%s" in the event's format field
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which has an address needs to know what string would be at that address. The
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tep_register_print_string() supplies the parsing with the mapping between kernel
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addresses and those strings. The _tep_ argument is the trace event parser
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context. The _fmt_ is the string to register, it is copied internally.
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The _addr_ is the address the string was located at.
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RETURN VALUE
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------------
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The _tep_set_function_resolver()_ function returns 0 in case of success, or -1
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in case of an error.
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The _tep_find_function()_ function returns the function name, or NULL in case
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it cannot be found.
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The _tep_find_function_address()_ function returns the function start address,
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or 0 in case it cannot be found.
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The _tep_register_function()_ function returns 0 in case of success. In case of
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an error -1 is returned, and errno is set to the appropriate error number.
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The _tep_register_print_string()_ function returns 0 in case of success. In case
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of an error -1 is returned, and errno is set to the appropriate error number.
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EXAMPLE
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-------
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[source,c]
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--
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#include <event-parse.h>
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...
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struct tep_handle *tep = tep_alloc();
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...
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char *my_resolve_kernel_addr(void *context,
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unsigned long long *addrp, char **modp)
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{
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struct db *function_database = context;
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struct symbol *sym = sql_lookup(function_database, *addrp);
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if (!sym)
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return NULL;
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*modp = sym->module_name;
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return sym->name;
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}
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void show_function( unsigned long long addr)
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{
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unsigned long long fstart;
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const char *fname;
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if (tep_set_function_resolver(tep, my_resolve_kernel_addr,
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function_database) != 0) {
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/* failed to register my_resolve_kernel_addr */
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}
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/* These APIs use my_resolve_kernel_addr() to resolve the addr */
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fname = tep_find_function(tep, addr);
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fstart = tep_find_function_address(tep, addr);
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/*
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addr is in function named fname, starting at fstart address,
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at offset (addr - fstart)
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*/
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tep_reset_function_resolver(tep);
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}
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...
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if (tep_register_function(tep, "kvm_exit",
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(unsigned long long) 0x12345678, "kvm") != 0) {
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/* Failed to register kvm_exit address mapping */
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}
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...
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if (tep_register_print_string(tep, "print string",
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(unsigned long long) 0x87654321, NULL) != 0) {
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/* Failed to register "print string" address mapping */
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}
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...
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--
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FILES
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-----
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[verse]
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--
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*event-parse.h*
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Header file to include in order to have access to the library APIs.
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*-ltraceevent*
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Linker switch to add when building a program that uses the library.
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--
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SEE ALSO
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--------
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_libtraceevent(3)_, _trace-cmd(1)_
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AUTHOR
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------
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[verse]
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--
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*Steven Rostedt* <rostedt@goodmis.org>, author of *libtraceevent*.
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*Tzvetomir Stoyanov* <tz.stoyanov@gmail.com>, author of this man page.
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--
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REPORTING BUGS
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--------------
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Report bugs to <linux-trace-devel@vger.kernel.org>
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LICENSE
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-------
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libtraceevent is Free Software licensed under the GNU LGPL 2.1
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RESOURCES
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---------
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https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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