thread.c

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// SPDX-License-Identifier: GPL-2.0
#include "../perf.h"
#include <errno.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <linux/kernel.h>
#include "session.h"
#include "thread.h"
#include "thread-stack.h"
#include "util.h"
#include "debug.h"
#include "namespaces.h"
#include "comm.h"
#include "unwind.h"

#include <api/fs/fs.h>

int thread__init_map_groups(struct thread *thread, struct machine *machine)
{
    pid_t pid = thread->pid_;

    if (pid == thread->tid || pid == -1) {
        thread->mg = map_groups__new(machine);
    } else {
        struct thread *leader = __machine__findnew_thread(machine, pid, pid);
        if (leader) {
            thread->mg = map_groups__get(leader->mg);
            thread__put(leader);
        }
    }

    return thread->mg ? 0 : -1;
}

struct thread *thread__new(pid_t pid, pid_t tid)
{
    char *comm_str;
    struct comm *comm;
    struct thread *thread = zalloc(sizeof(*thread));

    if (thread != NULL) {
        thread->pid_ = pid;
        thread->tid = tid;
        thread->ppid = -1;
        thread->cpu = -1;
        INIT_LIST_HEAD(&thread->namespaces_list);
        INIT_LIST_HEAD(&thread->comm_list);
        init_rwsem(&thread->namespaces_lock);
        init_rwsem(&thread->comm_lock);

        comm_str = malloc(32);
        if (!comm_str)
            goto err_thread;

        snprintf(comm_str, 32, ":%d", tid);
        comm = comm__new(comm_str, 0, false);
        free(comm_str);
        if (!comm)
            goto err_thread;

        list_add(&comm->list, &thread->comm_list);
        refcount_set(&thread->refcnt, 1);
        RB_CLEAR_NODE(&thread->rb_node);
        /* Thread holds first ref to nsdata. */
        thread->nsinfo = nsinfo__new(pid);
    }

    return thread;

err_thread:
    free(thread);
    return NULL;
}

void thread__delete(struct thread *thread)
{
    struct namespaces *namespaces, *tmp_namespaces;
    struct comm *comm, *tmp_comm;

    BUG_ON(!RB_EMPTY_NODE(&thread->rb_node));

    thread_stack__free(thread);

    if (thread->mg) {
        map_groups__put(thread->mg);
        thread->mg = NULL;
    }
    down_write(&thread->namespaces_lock);
    list_for_each_entry_safe(namespaces, tmp_namespaces,
                 &thread->namespaces_list, list) {
        list_del(&namespaces->list);
        namespaces__free(namespaces);
    }
    up_write(&thread->namespaces_lock);

    down_write(&thread->comm_lock);
    list_for_each_entry_safe(comm, tmp_comm, &thread->comm_list, list) {
        list_del(&comm->list);
        comm__free(comm);
    }
    up_write(&thread->comm_lock);

    unwind__finish_access(thread);
    nsinfo__zput(thread->nsinfo);

    exit_rwsem(&thread->namespaces_lock);
    exit_rwsem(&thread->comm_lock);
    free(thread);
}

struct thread *thread__get(struct thread *thread)
{
    if (thread)
        refcount_inc(&thread->refcnt);
    return thread;
}

void thread__put(struct thread *thread)
{
    if (thread && refcount_dec_and_test(&thread->refcnt)) {
        /*
         * Remove it from the dead_threads list, as last reference
         * is gone.
         */
        list_del_init(&thread->node);
        thread__delete(thread);
    }
}

struct namespaces *thread__namespaces(const struct thread *thread)
{
    if (list_empty(&thread->namespaces_list))
        return NULL;

    return list_first_entry(&thread->namespaces_list, struct namespaces, list);
}

static int __thread__set_namespaces(struct thread *thread, u64 timestamp,
                    struct namespaces_event *event)
{
    struct namespaces *new, *curr = thread__namespaces(thread);

    new = namespaces__new(event);
    if (!new)
        return -ENOMEM;

    list_add(&new->list, &thread->namespaces_list);

    if (timestamp && curr) {
        /*
         * setns syscall must have changed few or all the namespaces
         * of this thread. Update end time for the namespaces
         * previously used.
         */
        curr = list_next_entry(new, list);
        curr->end_time = timestamp;
    }

    return 0;
}

int thread__set_namespaces(struct thread *thread, u64 timestamp,
               struct namespaces_event *event)
{
    int ret;

    down_write(&thread->namespaces_lock);
    ret = __thread__set_namespaces(thread, timestamp, event);
    up_write(&thread->namespaces_lock);
    return ret;
}

struct comm *thread__comm(const struct thread *thread)
{
    if (list_empty(&thread->comm_list))
        return NULL;

    return list_first_entry(&thread->comm_list, struct comm, list);
}

struct comm *thread__exec_comm(const struct thread *thread)
{
    struct comm *comm, *last = NULL;

    list_for_each_entry(comm, &thread->comm_list, list) {
        if (comm->exec)
            return comm;
        last = comm;
    }

    return last;
}

static int ____thread__set_comm(struct thread *thread, const char *str,
                u64 timestamp, bool exec)
{
    struct comm *new, *curr = thread__comm(thread);

    /* Override the default :tid entry */
    if (!thread->comm_set) {
        int err = comm__override(curr, str, timestamp, exec);
        if (err)
            return err;
    } else {
        new = comm__new(str, timestamp, exec);
        if (!new)
            return -ENOMEM;
        list_add(&new->list, &thread->comm_list);

        if (exec)
            unwind__flush_access(thread);
    }

    thread->comm_set = true;

    return 0;
}

int __thread__set_comm(struct thread *thread, const char *str, u64 timestamp,
               bool exec)
{
    int ret;

    down_write(&thread->comm_lock);
    ret = ____thread__set_comm(thread, str, timestamp, exec);
    up_write(&thread->comm_lock);
    return ret;
}

int thread__set_comm_from_proc(struct thread *thread)
{
    char path[64];
    char *comm = NULL;
    size_t sz;
    int err = -1;

    if (!(snprintf(path, sizeof(path), "%d/task/%d/comm",
               thread->pid_, thread->tid) >= (int)sizeof(path)) &&
        procfs__read_str(path, &comm, &sz) == 0) {
        comm[sz - 1] = '\0';
        err = thread__set_comm(thread, comm, 0);
    }

    return err;
}

static const char *__thread__comm_str(const struct thread *thread)
{
    const struct comm *comm = thread__comm(thread);

    if (!comm)
        return NULL;

    return comm__str(comm);
}

const char *thread__comm_str(const struct thread *thread)
{
    const char *str;

    down_read((struct rw_semaphore *)&thread->comm_lock);
    str = __thread__comm_str(thread);
    up_read((struct rw_semaphore *)&thread->comm_lock);

    return str;
}

/* CHECKME: it should probably better return the max comm len from its comm list */
int thread__comm_len(struct thread *thread)
{
    if (!thread->comm_len) {
        const char *comm = thread__comm_str(thread);
        if (!comm)
            return 0;
        thread->comm_len = strlen(comm);
    }

    return thread->comm_len;
}

size_t thread__fprintf(struct thread *thread, FILE *fp)
{
    return fprintf(fp, "Thread %d %s\n", thread->tid, thread__comm_str(thread)) +
           map_groups__fprintf(thread->mg, fp);
}

int thread__insert_map(struct thread *thread, struct map *map)
{
    int ret;

    ret = unwind__prepare_access(thread, map, NULL);
    if (ret)
        return ret;

    map_groups__fixup_overlappings(thread->mg, map, stderr);
    map_groups__insert(thread->mg, map);

    return 0;
}

static int __thread__prepare_access(struct thread *thread)
{
    bool initialized = false;
    int err = 0;
    struct maps *maps = &thread->mg->maps;
    struct map *map;

    down_read(&maps->lock);

    for (map = maps__first(maps); map; map = map__next(map)) {
        err = unwind__prepare_access(thread, map, &initialized);
        if (err || initialized)
            break;
    }

    up_read(&maps->lock);

    return err;
}

static int thread__prepare_access(struct thread *thread)
{
    int err = 0;

    if (symbol_conf.use_callchain)
        err = __thread__prepare_access(thread);

    return err;
}

static int thread__clone_map_groups(struct thread *thread,
                    struct thread *parent)
{
    /* This is new thread, we share map groups for process. */
    if (thread->pid_ == parent->pid_)
        return thread__prepare_access(thread);

    if (thread->mg == parent->mg) {
        pr_debug("broken map groups on thread %d/%d parent %d/%d\n",
             thread->pid_, thread->tid, parent->pid_, parent->tid);
        return 0;
    }

    /* But this one is new process, copy maps. */
    if (map_groups__clone(thread, parent->mg) < 0)
        return -ENOMEM;

    return 0;
}

int thread__fork(struct thread *thread, struct thread *parent, u64 timestamp)
{
    if (parent->comm_set) {
        const char *comm = thread__comm_str(parent);
        int err;
        if (!comm)
            return -ENOMEM;
        err = thread__set_comm(thread, comm, timestamp);
        if (err)
            return err;
    }

    thread->ppid = parent->tid;
    return thread__clone_map_groups(thread, parent);
}

void thread__find_cpumode_addr_location(struct thread *thread, u64 addr,
                    struct addr_location *al)
{
    size_t i;
    const u8 cpumodes[] = {
        PERF_RECORD_MISC_USER,
        PERF_RECORD_MISC_KERNEL,
        PERF_RECORD_MISC_GUEST_USER,
        PERF_RECORD_MISC_GUEST_KERNEL
    };

    for (i = 0; i < ARRAY_SIZE(cpumodes); i++) {
        thread__find_symbol(thread, cpumodes[i], addr, al);
        if (al->map)
            break;
    }
}

struct thread *thread__main_thread(struct machine *machine, struct thread *thread)
{
    if (thread->pid_ == thread->tid)
        return thread__get(thread);

    if (thread->pid_ == -1)
        return NULL;

    return machine__find_thread(machine, thread->pid_, thread->pid_);
}