linux/kernel/trace/trace_events_inject.c
Masami Hiramatsu 05770dd0ad tracing: Support __rel_loc relative dynamic data location attribute
Add '__rel_loc' new dynamic data location attribute which encodes
the data location from the next to the field itself.

The '__data_loc' is used for encoding the dynamic data location on
the trace event record. But '__data_loc' is not useful if the writer
doesn't know the event header (e.g. user event), because it records
the dynamic data offset from the entry of the record, not the field
itself.

This new '__rel_loc' attribute encodes the data location relatively
from the next of the field. For example, when there is a record like
below (the number in the parentheses is the size of fields)

 |header(N)|common(M)|fields(K)|__data_loc(4)|fields(L)|data(G)|

In this case, '__data_loc' field will be

 __data_loc = (G << 16) | (N+M+K+4+L)

If '__rel_loc' is used, this will be

 |header(N)|common(M)|fields(K)|__rel_loc(4)|fields(L)|data(G)|

where

 __rel_loc = (G << 16) | (L)

This case shows L bytes after the '__rel_loc' attribute  field,
if there is no fields after the __rel_loc field, L must be 0.

This is relatively easy (and no need to consider the kernel header
change) when the event data fields are composed by user who doesn't
know header and common fields.

Link: https://lkml.kernel.org/r/163757341258.510314.4214431827833229956.stgit@devnote2

Cc: Beau Belgrave <beaub@linux.microsoft.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
2021-12-06 15:37:21 -05:00

335 lines
6.6 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* trace_events_inject - trace event injection
*
* Copyright (C) 2019 Cong Wang <cwang@twitter.com>
*/
#include <linux/module.h>
#include <linux/ctype.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/rculist.h>
#include "trace.h"
static int
trace_inject_entry(struct trace_event_file *file, void *rec, int len)
{
struct trace_event_buffer fbuffer;
int written = 0;
void *entry;
rcu_read_lock_sched();
entry = trace_event_buffer_reserve(&fbuffer, file, len);
if (entry) {
memcpy(entry, rec, len);
written = len;
trace_event_buffer_commit(&fbuffer);
}
rcu_read_unlock_sched();
return written;
}
static int
parse_field(char *str, struct trace_event_call *call,
struct ftrace_event_field **pf, u64 *pv)
{
struct ftrace_event_field *field;
char *field_name;
int s, i = 0;
int len;
u64 val;
if (!str[i])
return 0;
/* First find the field to associate to */
while (isspace(str[i]))
i++;
s = i;
while (isalnum(str[i]) || str[i] == '_')
i++;
len = i - s;
if (!len)
return -EINVAL;
field_name = kmemdup_nul(str + s, len, GFP_KERNEL);
if (!field_name)
return -ENOMEM;
field = trace_find_event_field(call, field_name);
kfree(field_name);
if (!field)
return -ENOENT;
*pf = field;
while (isspace(str[i]))
i++;
if (str[i] != '=')
return -EINVAL;
i++;
while (isspace(str[i]))
i++;
s = i;
if (isdigit(str[i]) || str[i] == '-') {
char *num, c;
int ret;
/* Make sure the field is not a string */
if (is_string_field(field))
return -EINVAL;
if (str[i] == '-')
i++;
/* We allow 0xDEADBEEF */
while (isalnum(str[i]))
i++;
num = str + s;
c = str[i];
if (c != '\0' && !isspace(c))
return -EINVAL;
str[i] = '\0';
/* Make sure it is a value */
if (field->is_signed)
ret = kstrtoll(num, 0, &val);
else
ret = kstrtoull(num, 0, &val);
str[i] = c;
if (ret)
return ret;
*pv = val;
return i;
} else if (str[i] == '\'' || str[i] == '"') {
char q = str[i];
/* Make sure the field is OK for strings */
if (!is_string_field(field))
return -EINVAL;
for (i++; str[i]; i++) {
if (str[i] == '\\' && str[i + 1]) {
i++;
continue;
}
if (str[i] == q)
break;
}
if (!str[i])
return -EINVAL;
/* Skip quotes */
s++;
len = i - s;
if (len >= MAX_FILTER_STR_VAL)
return -EINVAL;
*pv = (unsigned long)(str + s);
str[i] = 0;
/* go past the last quote */
i++;
return i;
}
return -EINVAL;
}
static int trace_get_entry_size(struct trace_event_call *call)
{
struct ftrace_event_field *field;
struct list_head *head;
int size = 0;
head = trace_get_fields(call);
list_for_each_entry(field, head, link) {
if (field->size + field->offset > size)
size = field->size + field->offset;
}
return size;
}
static void *trace_alloc_entry(struct trace_event_call *call, int *size)
{
int entry_size = trace_get_entry_size(call);
struct ftrace_event_field *field;
struct list_head *head;
void *entry = NULL;
/* We need an extra '\0' at the end. */
entry = kzalloc(entry_size + 1, GFP_KERNEL);
if (!entry)
return NULL;
head = trace_get_fields(call);
list_for_each_entry(field, head, link) {
if (!is_string_field(field))
continue;
if (field->filter_type == FILTER_STATIC_STRING)
continue;
if (field->filter_type == FILTER_DYN_STRING ||
field->filter_type == FILTER_RDYN_STRING) {
u32 *str_item;
int str_loc = entry_size & 0xffff;
if (field->filter_type == FILTER_RDYN_STRING)
str_loc -= field->offset + field->size;
str_item = (u32 *)(entry + field->offset);
*str_item = str_loc; /* string length is 0. */
} else {
char **paddr;
paddr = (char **)(entry + field->offset);
*paddr = "";
}
}
*size = entry_size + 1;
return entry;
}
#define INJECT_STRING "STATIC STRING CAN NOT BE INJECTED"
/* Caller is responsible to free the *pentry. */
static int parse_entry(char *str, struct trace_event_call *call, void **pentry)
{
struct ftrace_event_field *field;
void *entry = NULL;
int entry_size;
u64 val = 0;
int len;
entry = trace_alloc_entry(call, &entry_size);
*pentry = entry;
if (!entry)
return -ENOMEM;
tracing_generic_entry_update(entry, call->event.type,
tracing_gen_ctx());
while ((len = parse_field(str, call, &field, &val)) > 0) {
if (is_function_field(field))
return -EINVAL;
if (is_string_field(field)) {
char *addr = (char *)(unsigned long) val;
if (field->filter_type == FILTER_STATIC_STRING) {
strlcpy(entry + field->offset, addr, field->size);
} else if (field->filter_type == FILTER_DYN_STRING ||
field->filter_type == FILTER_RDYN_STRING) {
int str_len = strlen(addr) + 1;
int str_loc = entry_size & 0xffff;
u32 *str_item;
entry_size += str_len;
*pentry = krealloc(entry, entry_size, GFP_KERNEL);
if (!*pentry) {
kfree(entry);
return -ENOMEM;
}
entry = *pentry;
strlcpy(entry + (entry_size - str_len), addr, str_len);
str_item = (u32 *)(entry + field->offset);
if (field->filter_type == FILTER_RDYN_STRING)
str_loc -= field->offset + field->size;
*str_item = (str_len << 16) | str_loc;
} else {
char **paddr;
paddr = (char **)(entry + field->offset);
*paddr = INJECT_STRING;
}
} else {
switch (field->size) {
case 1: {
u8 tmp = (u8) val;
memcpy(entry + field->offset, &tmp, 1);
break;
}
case 2: {
u16 tmp = (u16) val;
memcpy(entry + field->offset, &tmp, 2);
break;
}
case 4: {
u32 tmp = (u32) val;
memcpy(entry + field->offset, &tmp, 4);
break;
}
case 8:
memcpy(entry + field->offset, &val, 8);
break;
default:
return -EINVAL;
}
}
str += len;
}
if (len < 0)
return len;
return entry_size;
}
static ssize_t
event_inject_write(struct file *filp, const char __user *ubuf, size_t cnt,
loff_t *ppos)
{
struct trace_event_call *call;
struct trace_event_file *file;
int err = -ENODEV, size;
void *entry = NULL;
char *buf;
if (cnt >= PAGE_SIZE)
return -EINVAL;
buf = memdup_user_nul(ubuf, cnt);
if (IS_ERR(buf))
return PTR_ERR(buf);
strim(buf);
mutex_lock(&event_mutex);
file = event_file_data(filp);
if (file) {
call = file->event_call;
size = parse_entry(buf, call, &entry);
if (size < 0)
err = size;
else
err = trace_inject_entry(file, entry, size);
}
mutex_unlock(&event_mutex);
kfree(entry);
kfree(buf);
if (err < 0)
return err;
*ppos += err;
return cnt;
}
static ssize_t
event_inject_read(struct file *file, char __user *buf, size_t size,
loff_t *ppos)
{
return -EPERM;
}
const struct file_operations event_inject_fops = {
.open = tracing_open_generic,
.read = event_inject_read,
.write = event_inject_write,
};