trace_uprobe.c

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/*
 * uprobes-based tracing events
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * Copyright (C) IBM Corporation, 2010-2012
 * Author:  Srikar Dronamraju <[email protected]>
 */

#include <linux/module.h>
#include <linux/uaccess.h>
#include <linux/uprobes.h>
#include <linux/namei.h>

#include "trace_probe.h"

#define UPROBE_EVENT_SYSTEM "uprobes"

/*
 * uprobe event core functions
 */
struct trace_uprobe;
struct uprobe_trace_consumer {
    struct uprobe_consumer      cons;
    struct trace_uprobe     *tu;
};

struct trace_uprobe {
    struct list_head        list;
    struct ftrace_event_class   class;
    struct ftrace_event_call    call;
    struct uprobe_trace_consumer    *consumer;
    struct inode            *inode;
    char                *filename;
    unsigned long           offset;
    unsigned long           nhit;
    unsigned int            flags;  /* For TP_FLAG_* */
    ssize_t             size;   /* trace entry size */
    unsigned int            nr_args;
    struct probe_arg        args[];
};

#define SIZEOF_TRACE_UPROBE(n)          \
    (offsetof(struct trace_uprobe, args) +  \
    (sizeof(struct probe_arg) * (n)))

static int register_uprobe_event(struct trace_uprobe *tu);
static void unregister_uprobe_event(struct trace_uprobe *tu);

static DEFINE_MUTEX(uprobe_lock);
static LIST_HEAD(uprobe_list);

static int uprobe_dispatcher(struct uprobe_consumer *con, struct pt_regs *regs);

/*
 * Allocate new trace_uprobe and initialize it (including uprobes).
 */
static struct trace_uprobe *
alloc_trace_uprobe(const char *group, const char *event, int nargs)
{
    struct trace_uprobe *tu;

    if (!event || !is_good_name(event))
        return ERR_PTR(-EINVAL);

    if (!group || !is_good_name(group))
        return ERR_PTR(-EINVAL);

    tu = kzalloc(SIZEOF_TRACE_UPROBE(nargs), GFP_KERNEL);
    if (!tu)
        return ERR_PTR(-ENOMEM);

    tu->call.class = &tu->class;
    tu->call.name = kstrdup(event, GFP_KERNEL);
    if (!tu->call.name)
        goto error;

    tu->class.system = kstrdup(group, GFP_KERNEL);
    if (!tu->class.system)
        goto error;

    INIT_LIST_HEAD(&tu->list);
    return tu;

error:
    kfree(tu->call.name);
    kfree(tu);

    return ERR_PTR(-ENOMEM);
}

static void free_trace_uprobe(struct trace_uprobe *tu)
{
    int i;

    for (i = 0; i < tu->nr_args; i++)
        traceprobe_free_probe_arg(&tu->args[i]);

    iput(tu->inode);
    kfree(tu->call.class->system);
    kfree(tu->call.name);
    kfree(tu->filename);
    kfree(tu);
}

static struct trace_uprobe *find_probe_event(const char *event, const char *group)
{
    struct trace_uprobe *tu;

    list_for_each_entry(tu, &uprobe_list, list)
        if (strcmp(tu->call.name, event) == 0 &&
            strcmp(tu->call.class->system, group) == 0)
            return tu;

    return NULL;
}

/* Unregister a trace_uprobe and probe_event: call with locking uprobe_lock */
static void unregister_trace_uprobe(struct trace_uprobe *tu)
{
    list_del(&tu->list);
    unregister_uprobe_event(tu);
    free_trace_uprobe(tu);
}

/* Register a trace_uprobe and probe_event */
static int register_trace_uprobe(struct trace_uprobe *tu)
{
    struct trace_uprobe *old_tp;
    int ret;

    mutex_lock(&uprobe_lock);

    /* register as an event */
    old_tp = find_probe_event(tu->call.name, tu->call.class->system);
    if (old_tp)
        /* delete old event */
        unregister_trace_uprobe(old_tp);

    ret = register_uprobe_event(tu);
    if (ret) {
        pr_warning("Failed to register probe event(%d)\n", ret);
        goto end;
    }

    list_add_tail(&tu->list, &uprobe_list);

end:
    mutex_unlock(&uprobe_lock);

    return ret;
}

/*
 * Argument syntax:
 *  - Add uprobe: p[:[GRP/]EVENT] PATH:SYMBOL[+offs] [FETCHARGS]
 *
 *  - Remove uprobe: -:[GRP/]EVENT
 */
static int create_trace_uprobe(int argc, char **argv)
{
    struct trace_uprobe *tu;
    struct inode *inode;
    char *arg, *event, *group, *filename;
    char buf[MAX_EVENT_NAME_LEN];
    struct path path;
    unsigned long offset;
    bool is_delete;
    int i, ret;

    inode = NULL;
    ret = 0;
    is_delete = false;
    event = NULL;
    group = NULL;

    /* argc must be >= 1 */
    if (argv[0][0] == '-')
        is_delete = true;
    else if (argv[0][0] != 'p') {
        pr_info("Probe definition must be started with 'p', 'r' or" " '-'.\n");
        return -EINVAL;
    }

    if (argv[0][1] == ':') {
        event = &argv[0][2];
        arg = strchr(event, '/');

        if (arg) {
            group = event;
            event = arg + 1;
            event[-1] = '\0';

            if (strlen(group) == 0) {
                pr_info("Group name is not specified\n");
                return -EINVAL;
            }
        }
        if (strlen(event) == 0) {
            pr_info("Event name is not specified\n");
            return -EINVAL;
        }
    }
    if (!group)
        group = UPROBE_EVENT_SYSTEM;

    if (is_delete) {
        if (!event) {
            pr_info("Delete command needs an event name.\n");
            return -EINVAL;
        }
        mutex_lock(&uprobe_lock);
        tu = find_probe_event(event, group);

        if (!tu) {
            mutex_unlock(&uprobe_lock);
            pr_info("Event %s/%s doesn't exist.\n", group, event);
            return -ENOENT;
        }
        /* delete an event */
        unregister_trace_uprobe(tu);
        mutex_unlock(&uprobe_lock);
        return 0;
    }

    if (argc < 2) {
        pr_info("Probe point is not specified.\n");
        return -EINVAL;
    }
    if (isdigit(argv[1][0])) {
        pr_info("probe point must be have a filename.\n");
        return -EINVAL;
    }
    arg = strchr(argv[1], ':');
    if (!arg)
        goto fail_address_parse;

    *arg++ = '\0';
    filename = argv[1];
    ret = kern_path(filename, LOOKUP_FOLLOW, &path);
    if (ret)
        goto fail_address_parse;

    ret = strict_strtoul(arg, 0, &offset);
    if (ret)
        goto fail_address_parse;

    inode = igrab(path.dentry->d_inode);

    argc -= 2;
    argv += 2;

    /* setup a probe */
    if (!event) {
        char *tail = strrchr(filename, '/');
        char *ptr;

        ptr = kstrdup((tail ? tail + 1 : filename), GFP_KERNEL);
        if (!ptr) {
            ret = -ENOMEM;
            goto fail_address_parse;
        }

        tail = ptr;
        ptr = strpbrk(tail, ".-_");
        if (ptr)
            *ptr = '\0';

        snprintf(buf, MAX_EVENT_NAME_LEN, "%c_%s_0x%lx", 'p', tail, offset);
        event = buf;
        kfree(tail);
    }

    tu = alloc_trace_uprobe(group, event, argc);
    if (IS_ERR(tu)) {
        pr_info("Failed to allocate trace_uprobe.(%d)\n", (int)PTR_ERR(tu));
        ret = PTR_ERR(tu);
        goto fail_address_parse;
    }
    tu->offset = offset;
    tu->inode = inode;
    tu->filename = kstrdup(filename, GFP_KERNEL);

    if (!tu->filename) {
        pr_info("Failed to allocate filename.\n");
        ret = -ENOMEM;
        goto error;
    }

    /* parse arguments */
    ret = 0;
    for (i = 0; i < argc && i < MAX_TRACE_ARGS; i++) {
        /* Increment count for freeing args in error case */
        tu->nr_args++;

        /* Parse argument name */
        arg = strchr(argv[i], '=');
        if (arg) {
            *arg++ = '\0';
            tu->args[i].name = kstrdup(argv[i], GFP_KERNEL);
        } else {
            arg = argv[i];
            /* If argument name is omitted, set "argN" */
            snprintf(buf, MAX_EVENT_NAME_LEN, "arg%d", i + 1);
            tu->args[i].name = kstrdup(buf, GFP_KERNEL);
        }

        if (!tu->args[i].name) {
            pr_info("Failed to allocate argument[%d] name.\n", i);
            ret = -ENOMEM;
            goto error;
        }

        if (!is_good_name(tu->args[i].name)) {
            pr_info("Invalid argument[%d] name: %s\n", i, tu->args[i].name);
            ret = -EINVAL;
            goto error;
        }

        if (traceprobe_conflict_field_name(tu->args[i].name, tu->args, i)) {
            pr_info("Argument[%d] name '%s' conflicts with "
                "another field.\n", i, argv[i]);
            ret = -EINVAL;
            goto error;
        }

        /* Parse fetch argument */
        ret = traceprobe_parse_probe_arg(arg, &tu->size, &tu->args[i], false, false);
        if (ret) {
            pr_info("Parse error at argument[%d]. (%d)\n", i, ret);
            goto error;
        }
    }

    ret = register_trace_uprobe(tu);
    if (ret)
        goto error;
    return 0;

error:
    free_trace_uprobe(tu);
    return ret;

fail_address_parse:
    if (inode)
        iput(inode);

    pr_info("Failed to parse address.\n");

    return ret;
}

static void cleanup_all_probes(void)
{
    struct trace_uprobe *tu;

    mutex_lock(&uprobe_lock);
    while (!list_empty(&uprobe_list)) {
        tu = list_entry(uprobe_list.next, struct trace_uprobe, list);
        unregister_trace_uprobe(tu);
    }
    mutex_unlock(&uprobe_lock);
}

/* Probes listing interfaces */
static void *probes_seq_start(struct seq_file *m, loff_t *pos)
{
    mutex_lock(&uprobe_lock);
    return seq_list_start(&uprobe_list, *pos);
}

static void *probes_seq_next(struct seq_file *m, void *v, loff_t *pos)
{
    return seq_list_next(v, &uprobe_list, pos);
}

static void probes_seq_stop(struct seq_file *m, void *v)
{
    mutex_unlock(&uprobe_lock);
}

static int probes_seq_show(struct seq_file *m, void *v)
{
    struct trace_uprobe *tu = v;
    int i;

    seq_printf(m, "p:%s/%s", tu->call.class->system, tu->call.name);
    seq_printf(m, " %s:0x%p", tu->filename, (void *)tu->offset);

    for (i = 0; i < tu->nr_args; i++)
        seq_printf(m, " %s=%s", tu->args[i].name, tu->args[i].comm);

    seq_printf(m, "\n");
    return 0;
}

static const struct seq_operations probes_seq_op = {
    .start  = probes_seq_start,
    .next   = probes_seq_next,
    .stop   = probes_seq_stop,
    .show   = probes_seq_show
};

static int probes_open(struct inode *inode, struct file *file)
{
    if ((file->f_mode & FMODE_WRITE) && (file->f_flags & O_TRUNC))
        cleanup_all_probes();

    return seq_open(file, &probes_seq_op);
}

static ssize_t probes_write(struct file *file, const char __user *buffer,
                size_t count, loff_t *ppos)
{
    return traceprobe_probes_write(file, buffer, count, ppos, create_trace_uprobe);
}

static const struct file_operations uprobe_events_ops = {
    .owner      = THIS_MODULE,
    .open       = probes_open,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = seq_release,
    .write      = probes_write,
};

/* Probes profiling interfaces */
static int probes_profile_seq_show(struct seq_file *m, void *v)
{
    struct trace_uprobe *tu = v;

    seq_printf(m, "  %s %-44s %15lu\n", tu->filename, tu->call.name, tu->nhit);
    return 0;
}

static const struct seq_operations profile_seq_op = {
    .start  = probes_seq_start,
    .next   = probes_seq_next,
    .stop   = probes_seq_stop,
    .show   = probes_profile_seq_show
};

static int profile_open(struct inode *inode, struct file *file)
{
    return seq_open(file, &profile_seq_op);
}

static const struct file_operations uprobe_profile_ops = {
    .owner      = THIS_MODULE,
    .open       = profile_open,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = seq_release,
};

/* uprobe handler */
static void uprobe_trace_func(struct trace_uprobe *tu, struct pt_regs *regs)
{
    struct uprobe_trace_entry_head *entry;
    struct ring_buffer_event *event;
    struct ring_buffer *buffer;
    u8 *data;
    int size, i, pc;
    unsigned long irq_flags;
    struct ftrace_event_call *call = &tu->call;

    tu->nhit++;

    local_save_flags(irq_flags);
    pc = preempt_count();

    size = sizeof(*entry) + tu->size;

    event = trace_current_buffer_lock_reserve(&buffer, call->event.type,
                          size, irq_flags, pc);
    if (!event)
        return;

    entry = ring_buffer_event_data(event);
    entry->ip = uprobe_get_swbp_addr(task_pt_regs(current));
    data = (u8 *)&entry[1];
    for (i = 0; i < tu->nr_args; i++)
        call_fetch(&tu->args[i].fetch, regs, data + tu->args[i].offset);

    if (!filter_current_check_discard(buffer, call, entry, event))
        trace_buffer_unlock_commit(buffer, event, irq_flags, pc);
}

/* Event entry printers */
static enum print_line_t
print_uprobe_event(struct trace_iterator *iter, int flags, struct trace_event *event)
{
    struct uprobe_trace_entry_head *field;
    struct trace_seq *s = &iter->seq;
    struct trace_uprobe *tu;
    u8 *data;
    int i;

    field = (struct uprobe_trace_entry_head *)iter->ent;
    tu = container_of(event, struct trace_uprobe, call.event);

    if (!trace_seq_printf(s, "%s: (", tu->call.name))
        goto partial;

    if (!seq_print_ip_sym(s, field->ip, flags | TRACE_ITER_SYM_OFFSET))
        goto partial;

    if (!trace_seq_puts(s, ")"))
        goto partial;

    data = (u8 *)&field[1];
    for (i = 0; i < tu->nr_args; i++) {
        if (!tu->args[i].type->print(s, tu->args[i].name,
                         data + tu->args[i].offset, field))
            goto partial;
    }

    if (trace_seq_puts(s, "\n"))
        return TRACE_TYPE_HANDLED;

partial:
    return TRACE_TYPE_PARTIAL_LINE;
}

static int probe_event_enable(struct trace_uprobe *tu, int flag)
{
    struct uprobe_trace_consumer *utc;
    int ret = 0;

    if (!tu->inode || tu->consumer)
        return -EINTR;

    utc = kzalloc(sizeof(struct uprobe_trace_consumer), GFP_KERNEL);
    if (!utc)
        return -EINTR;

    utc->cons.handler = uprobe_dispatcher;
    utc->cons.filter = NULL;
    ret = uprobe_register(tu->inode, tu->offset, &utc->cons);
    if (ret) {
        kfree(utc);
        return ret;
    }

    tu->flags |= flag;
    utc->tu = tu;
    tu->consumer = utc;

    return 0;
}

static void probe_event_disable(struct trace_uprobe *tu, int flag)
{
    if (!tu->inode || !tu->consumer)
        return;

    uprobe_unregister(tu->inode, tu->offset, &tu->consumer->cons);
    tu->flags &= ~flag;
    kfree(tu->consumer);
    tu->consumer = NULL;
}

static int uprobe_event_define_fields(struct ftrace_event_call *event_call)
{
    int ret, i;
    struct uprobe_trace_entry_head field;
    struct trace_uprobe *tu = (struct trace_uprobe *)event_call->data;

    DEFINE_FIELD(unsigned long, ip, FIELD_STRING_IP, 0);
    /* Set argument names as fields */
    for (i = 0; i < tu->nr_args; i++) {
        ret = trace_define_field(event_call, tu->args[i].type->fmttype,
                     tu->args[i].name,
                     sizeof(field) + tu->args[i].offset,
                     tu->args[i].type->size,
                     tu->args[i].type->is_signed,
                     FILTER_OTHER);

        if (ret)
            return ret;
    }
    return 0;
}

#define LEN_OR_ZERO     (len ? len - pos : 0)
static int __set_print_fmt(struct trace_uprobe *tu, char *buf, int len)
{
    const char *fmt, *arg;
    int i;
    int pos = 0;

    fmt = "(%lx)";
    arg = "REC->" FIELD_STRING_IP;

    /* When len=0, we just calculate the needed length */

    pos += snprintf(buf + pos, LEN_OR_ZERO, "\"%s", fmt);

    for (i = 0; i < tu->nr_args; i++) {
        pos += snprintf(buf + pos, LEN_OR_ZERO, " %s=%s",
                tu->args[i].name, tu->args[i].type->fmt);
    }

    pos += snprintf(buf + pos, LEN_OR_ZERO, "\", %s", arg);

    for (i = 0; i < tu->nr_args; i++) {
        pos += snprintf(buf + pos, LEN_OR_ZERO, ", REC->%s",
                tu->args[i].name);
    }

    return pos; /* return the length of print_fmt */
}
#undef LEN_OR_ZERO

static int set_print_fmt(struct trace_uprobe *tu)
{
    char *print_fmt;
    int len;

    /* First: called with 0 length to calculate the needed length */
    len = __set_print_fmt(tu, NULL, 0);
    print_fmt = kmalloc(len + 1, GFP_KERNEL);
    if (!print_fmt)
        return -ENOMEM;

    /* Second: actually write the @print_fmt */
    __set_print_fmt(tu, print_fmt, len + 1);
    tu->call.print_fmt = print_fmt;

    return 0;
}

#ifdef CONFIG_PERF_EVENTS
/* uprobe profile handler */
static void uprobe_perf_func(struct trace_uprobe *tu, struct pt_regs *regs)
{
    struct ftrace_event_call *call = &tu->call;
    struct uprobe_trace_entry_head *entry;
    struct hlist_head *head;
    u8 *data;
    int size, __size, i;
    int rctx;

    __size = sizeof(*entry) + tu->size;
    size = ALIGN(__size + sizeof(u32), sizeof(u64));
    size -= sizeof(u32);
    if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE, "profile buffer not large enough"))
        return;

    preempt_disable();

    entry = perf_trace_buf_prepare(size, call->event.type, regs, &rctx);
    if (!entry)
        goto out;

    entry->ip = uprobe_get_swbp_addr(task_pt_regs(current));
    data = (u8 *)&entry[1];
    for (i = 0; i < tu->nr_args; i++)
        call_fetch(&tu->args[i].fetch, regs, data + tu->args[i].offset);

    head = this_cpu_ptr(call->perf_events);
    perf_trace_buf_submit(entry, size, rctx, entry->ip, 1, regs, head, NULL);

 out:
    preempt_enable();
}
#endif  /* CONFIG_PERF_EVENTS */

static
int trace_uprobe_register(struct ftrace_event_call *event, enum trace_reg type, void *data)
{
    struct trace_uprobe *tu = (struct trace_uprobe *)event->data;

    switch (type) {
    case TRACE_REG_REGISTER:
        return probe_event_enable(tu, TP_FLAG_TRACE);

    case TRACE_REG_UNREGISTER:
        probe_event_disable(tu, TP_FLAG_TRACE);
        return 0;

#ifdef CONFIG_PERF_EVENTS
    case TRACE_REG_PERF_REGISTER:
        return probe_event_enable(tu, TP_FLAG_PROFILE);

    case TRACE_REG_PERF_UNREGISTER:
        probe_event_disable(tu, TP_FLAG_PROFILE);
        return 0;
#endif
    default:
        return 0;
    }
    return 0;
}

static int uprobe_dispatcher(struct uprobe_consumer *con, struct pt_regs *regs)
{
    struct uprobe_trace_consumer *utc;
    struct trace_uprobe *tu;

    utc = container_of(con, struct uprobe_trace_consumer, cons);
    tu = utc->tu;
    if (!tu || tu->consumer != utc)
        return 0;

    if (tu->flags & TP_FLAG_TRACE)
        uprobe_trace_func(tu, regs);

#ifdef CONFIG_PERF_EVENTS
    if (tu->flags & TP_FLAG_PROFILE)
        uprobe_perf_func(tu, regs);
#endif
    return 0;
}

static struct trace_event_functions uprobe_funcs = {
    .trace      = print_uprobe_event
};

static int register_uprobe_event(struct trace_uprobe *tu)
{
    struct ftrace_event_call *call = &tu->call;
    int ret;

    /* Initialize ftrace_event_call */
    INIT_LIST_HEAD(&call->class->fields);
    call->event.funcs = &uprobe_funcs;
    call->class->define_fields = uprobe_event_define_fields;

    if (set_print_fmt(tu) < 0)
        return -ENOMEM;

    ret = register_ftrace_event(&call->event);
    if (!ret) {
        kfree(call->print_fmt);
        return -ENODEV;
    }
    call->flags = 0;
    call->class->reg = trace_uprobe_register;
    call->data = tu;
    ret = trace_add_event_call(call);

    if (ret) {
        pr_info("Failed to register uprobe event: %s\n", call->name);
        kfree(call->print_fmt);
        unregister_ftrace_event(&call->event);
    }

    return ret;
}

static void unregister_uprobe_event(struct trace_uprobe *tu)
{
    /* tu->event is unregistered in trace_remove_event_call() */
    trace_remove_event_call(&tu->call);
    kfree(tu->call.print_fmt);
    tu->call.print_fmt = NULL;
}

/* Make a trace interface for controling probe points */
static __init int init_uprobe_trace(void)
{
    struct dentry *d_tracer;

    d_tracer = tracing_init_dentry();
    if (!d_tracer)
        return 0;

    trace_create_file("uprobe_events", 0644, d_tracer,
                    NULL, &uprobe_events_ops);
    /* Profile interface */
    trace_create_file("uprobe_profile", 0444, d_tracer,
                    NULL, &uprobe_profile_ops);
    return 0;
}

fs_initcall(init_uprobe_trace);