fprobe.c
// SPDX-License-Identifier: GPL-2.0
/*
* fprobe - Simple ftrace probe wrapper for function entry.
*/
#define pr_fmt(fmt) "fprobe: " fmt
#include <linux/err.h>
#include <linux/fprobe.h>
#include <linux/kallsyms.h>
#include <linux/kprobes.h>
#include <linux/rethook.h>
#include <linux/slab.h>
#include <linux/sort.h>
#include "trace.h"
struct fprobe_rethook_node {
struct rethook_node node;
unsigned long entry_ip;
unsigned long entry_parent_ip;
char data[];
};
static inline void __fprobe_handler(unsigned long ip, unsigned long parent_ip,
struct ftrace_ops *ops, struct ftrace_regs *fregs)
{
struct fprobe_rethook_node *fpr;
struct rethook_node *rh = NULL;
struct fprobe *fp;
void *entry_data = NULL;
int ret = 0;
fp = container_of(ops, struct fprobe, ops);
if (fp->exit_handler) {
rh = rethook_try_get(fp->rethook);
if (!rh) {
fp->nmissed++;
return;
}
fpr = container_of(rh, struct fprobe_rethook_node, node);
fpr->entry_ip = ip;
fpr->entry_parent_ip = parent_ip;
if (fp->entry_data_size)
entry_data = fpr->data;
}
if (fp->entry_handler)
ret = fp->entry_handler(fp, ip, parent_ip, ftrace_get_regs(fregs), entry_data);
/* If entry_handler returns !0, nmissed is not counted. */
if (rh) {
if (ret)
rethook_recycle(rh);
else
rethook_hook(rh, ftrace_get_regs(fregs), true);
}
}
static void fprobe_handler(unsigned long ip, unsigned long parent_ip,
struct ftrace_ops *ops, struct ftrace_regs *fregs)
{
struct fprobe *fp;
int bit;
fp = container_of(ops, struct fprobe, ops);
if (fprobe_disabled(fp))
return;
/* recursion detection has to go before any traceable function and
* all functions before this point should be marked as notrace
*/
bit = ftrace_test_recursion_trylock(ip, parent_ip);
if (bit < 0) {
fp->nmissed++;
return;
}
__fprobe_handler(ip, parent_ip, ops, fregs);
ftrace_test_recursion_unlock(bit);
}
NOKPROBE_SYMBOL(fprobe_handler);
static void fprobe_kprobe_handler(unsigned long ip, unsigned long parent_ip,
struct ftrace_ops *ops, struct ftrace_regs *fregs)
{
struct fprobe *fp;
int bit;
fp = container_of(ops, struct fprobe, ops);
if (fprobe_disabled(fp))
return;
/* recursion detection has to go before any traceable function and
* all functions called before this point should be marked as notrace
*/
bit = ftrace_test_recursion_trylock(ip, parent_ip);
if (bit < 0) {
fp->nmissed++;
return;
}
/*
* This user handler is shared with other kprobes and is not expected to be
* called recursively. So if any other kprobe handler is running, this will
* exit as kprobe does. See the section 'Share the callbacks with kprobes'
* in Documentation/trace/fprobe.rst for more information.
*/
if (unlikely(kprobe_running())) {
fp->nmissed++;
goto recursion_unlock;
}
kprobe_busy_begin();
__fprobe_handler(ip, parent_ip, ops, fregs);
kprobe_busy_end();
recursion_unlock:
ftrace_test_recursion_unlock(bit);
}
static void fprobe_exit_handler(struct rethook_node *rh, void *data,
unsigned long ret_ip, struct pt_regs *regs)
{
struct fprobe *fp = (struct fprobe *)data;
struct fprobe_rethook_node *fpr;
int bit;
if (!fp || fprobe_disabled(fp))
return;
fpr = container_of(rh, struct fprobe_rethook_node, node);
/*
* we need to assure no calls to traceable functions in-between the
* end of fprobe_handler and the beginning of fprobe_exit_handler.
*/
bit = ftrace_test_recursion_trylock(fpr->entry_ip, fpr->entry_parent_ip);
if (bit < 0) {
fp->nmissed++;
return;
}
fp->exit_handler(fp, fpr->entry_ip, ret_ip, regs,
fp->entry_data_size ? (void *)fpr->data : NULL);
ftrace_test_recursion_unlock(bit);
}
NOKPROBE_SYMBOL(fprobe_exit_handler);
static int symbols_cmp(const void *a, const void *b)
{
const char **str_a = (const char **) a;
const char **str_b = (const char **) b;
return strcmp(*str_a, *str_b);
}
/* Convert ftrace location address from symbols */
static unsigned long *get_ftrace_locations(const char **syms, int num)
{
unsigned long *addrs;
/* Convert symbols to symbol address */
addrs = kcalloc(num, sizeof(*addrs), GFP_KERNEL);
if (!addrs)
return ERR_PTR(-ENOMEM);
/* ftrace_lookup_symbols expects sorted symbols */
sort(syms, num, sizeof(*syms), symbols_cmp, NULL);
if (!ftrace_lookup_symbols(syms, num, addrs))
return addrs;
kfree(addrs);
return ERR_PTR(-ENOENT);
}
static void fprobe_init(struct fprobe *fp)
{
fp->nmissed = 0;
if (fprobe_shared_with_kprobes(fp))
fp->ops.func = fprobe_kprobe_handler;
else
fp->ops.func = fprobe_handler;
fp->ops.flags |= FTRACE_OPS_FL_SAVE_REGS;
}
static int fprobe_init_rethook(struct fprobe *fp, int num)
{
int size;
if (num <= 0)
return -EINVAL;
if (!fp->exit_handler) {
fp->rethook = NULL;
return 0;
}
/* Initialize rethook if needed */
if (fp->nr_maxactive)
size = fp->nr_maxactive;
else
size = num * num_possible_cpus() * 2;
if (size <= 0)
return -EINVAL;
/* Initialize rethook */
fp->rethook = rethook_alloc((void *)fp, fprobe_exit_handler,
sizeof(struct fprobe_rethook_node), size);
if (IS_ERR(fp->rethook))
return PTR_ERR(fp->rethook);
return 0;
}
static void fprobe_fail_cleanup(struct fprobe *fp)
{
if (!IS_ERR_OR_NULL(fp->rethook)) {
/* Don't need to cleanup rethook->handler because this is not used. */
rethook_free(fp->rethook);
fp->rethook = NULL;
}
ftrace_free_filter(&fp->ops);
}
/**
* register_fprobe() - Register fprobe to ftrace by pattern.
* @fp: A fprobe data structure to be registered.
* @filter: A wildcard pattern of probed symbols.
* @notfilter: A wildcard pattern of NOT probed symbols.
*
* Register @fp to ftrace for enabling the probe on the symbols matched to @filter.
* If @notfilter is not NULL, the symbols matched the @notfilter are not probed.
*
* Return 0 if @fp is registered successfully, -errno if not.
*/
int register_fprobe(struct fprobe *fp, const char *filter, const char *notfilter)
{
struct ftrace_hash *hash;
unsigned char *str;
int ret, len;
if (!fp || !filter)
return -EINVAL;
fprobe_init(fp);
len = strlen(filter);
str = kstrdup(filter, GFP_KERNEL);
ret = ftrace_set_filter(&fp->ops, str, len, 0);
kfree(str);
if (ret)
return ret;
if (notfilter) {
len = strlen(notfilter);
str = kstrdup(notfilter, GFP_KERNEL);
ret = ftrace_set_notrace(&fp->ops, str, len, 0);
kfree(str);
if (ret)
goto out;
}
/* TODO:
* correctly calculate the total number of filtered symbols
* from both filter and notfilter.
*/
hash = rcu_access_pointer(fp->ops.local_hash.filter_hash);
if (WARN_ON_ONCE(!hash))
goto out;
ret = fprobe_init_rethook(fp, (int)hash->count);
if (!ret)
ret = register_ftrace_function(&fp->ops);
out:
if (ret)
fprobe_fail_cleanup(fp);
return ret;
}
EXPORT_SYMBOL_GPL(register_fprobe);
/**
* register_fprobe_ips() - Register fprobe to ftrace by address.
* @fp: A fprobe data structure to be registered.
* @addrs: An array of target ftrace location addresses.
* @num: The number of entries of @addrs.
*
* Register @fp to ftrace for enabling the probe on the address given by @addrs.
* The @addrs must be the addresses of ftrace location address, which may be
* the symbol address + arch-dependent offset.
* If you unsure what this mean, please use other registration functions.
*
* Return 0 if @fp is registered successfully, -errno if not.
*/
int register_fprobe_ips(struct fprobe *fp, unsigned long *addrs, int num)
{
int ret;
if (!fp || !addrs || num <= 0)
return -EINVAL;
fprobe_init(fp);
ret = ftrace_set_filter_ips(&fp->ops, addrs, num, 0, 0);
if (ret)
return ret;
ret = fprobe_init_rethook(fp, num);
if (!ret)
ret = register_ftrace_function(&fp->ops);
if (ret)
fprobe_fail_cleanup(fp);
return ret;
}
EXPORT_SYMBOL_GPL(register_fprobe_ips);
/**
* register_fprobe_syms() - Register fprobe to ftrace by symbols.
* @fp: A fprobe data structure to be registered.
* @syms: An array of target symbols.
* @num: The number of entries of @syms.
*
* Register @fp to the symbols given by @syms array. This will be useful if
* you are sure the symbols exist in the kernel.
*
* Return 0 if @fp is registered successfully, -errno if not.
*/
int register_fprobe_syms(struct fprobe *fp, const char **syms, int num)
{
unsigned long *addrs;
int ret;
if (!fp || !syms || num <= 0)
return -EINVAL;
addrs = get_ftrace_locations(syms, num);
if (IS_ERR(addrs))
return PTR_ERR(addrs);
ret = register_fprobe_ips(fp, addrs, num);
kfree(addrs);
return ret;
}
EXPORT_SYMBOL_GPL(register_fprobe_syms);
bool fprobe_is_registered(struct fprobe *fp)
{
if (!fp || (fp->ops.saved_func != fprobe_handler &&
fp->ops.saved_func != fprobe_kprobe_handler))
return false;
return true;
}
/**
* unregister_fprobe() - Unregister fprobe from ftrace
* @fp: A fprobe data structure to be unregistered.
*
* Unregister fprobe (and remove ftrace hooks from the function entries).
*
* Return 0 if @fp is unregistered successfully, -errno if not.
*/
int unregister_fprobe(struct fprobe *fp)
{
int ret;
if (!fprobe_is_registered(fp))
return -EINVAL;
if (!IS_ERR_OR_NULL(fp->rethook))
rethook_stop(fp->rethook);
ret = unregister_ftrace_function(&fp->ops);
if (ret < 0)
return ret;
if (!IS_ERR_OR_NULL(fp->rethook))
rethook_free(fp->rethook);
ftrace_free_filter(&fp->ops);
return ret;
}
EXPORT_SYMBOL_GPL(unregister_fprobe);