linux/kernel/trace/trace_events_inject.c
Sebastian Andrzej Siewior 36590c50b2 tracing: Merge irqflags + preempt counter.
The state of the interrupts (irqflags) and the preemption counter are
both passed down to tracing_generic_entry_update(). Only one bit of
irqflags is actually required: The on/off state. The complete 32bit
of the preemption counter isn't needed. Just whether of the upper bits
(softirq, hardirq and NMI) are set and the preemption depth is needed.

The irqflags and the preemption counter could be evaluated early and the
information stored in an integer `trace_ctx'.
tracing_generic_entry_update() would use the upper bits as the
TRACE_FLAG_* and the lower 8bit as the disabled-preemption depth
(considering that one must be substracted from the counter in one
special cases).

The actual preemption value is not used except for the tracing record.
The `irqflags' variable is mostly used only for the tracing record. An
exception here is for instance wakeup_tracer_call() or
probe_wakeup_sched_switch() which explicilty disable interrupts and use
that `irqflags' to save (and restore) the IRQ state and to record the
state.

Struct trace_event_buffer has also the `pc' and flags' members which can
be replaced with `trace_ctx' since their actual value is not used
outside of trace recording.

This will reduce tracing_generic_entry_update() to simply assign values
to struct trace_entry. The evaluation of the TRACE_FLAG_* bits is moved
to _tracing_gen_ctx_flags() which replaces preempt_count() and
local_save_flags() invocations.

As an example, ftrace_syscall_enter() may invoke:
- trace_buffer_lock_reserve() -> … -> tracing_generic_entry_update()
- event_trigger_unlock_commit()
  -> ftrace_trace_stack() -> … -> tracing_generic_entry_update()
  -> ftrace_trace_userstack() -> … -> tracing_generic_entry_update()

In this case the TRACE_FLAG_* bits were evaluated three times. By using
the `trace_ctx' they are evaluated once and assigned three times.

A build with all tracers enabled on x86-64 with and without the patch:

    text     data      bss      dec      hex    filename
21970669 17084168  7639260 46694097  2c87ed1 vmlinux.old
21970293 17084168  7639260 46693721  2c87d59 vmlinux.new

text shrank by 379 bytes, data remained constant.

Link: https://lkml.kernel.org/r/20210125194511.3924915-2-bigeasy@linutronix.de

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
2021-02-02 17:02:06 -05:00

328 lines
6.3 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) {
u32 *str_item;
int str_loc = entry_size & 0xffff;
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) {
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);
*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,
};