trace_syscalls.c

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#include <trace/syscall.h>
#include <trace/events/syscalls.h>
#include <linux/slab.h>
#include <linux/kernel.h>
#include <linux/module.h>   /* for MODULE_NAME_LEN via KSYM_SYMBOL_LEN */
#include <linux/ftrace.h>
#include <linux/perf_event.h>
#include <asm/syscall.h>

#include "trace_output.h"
#include "trace.h"

static DEFINE_MUTEX(syscall_trace_lock);
static int sys_refcount_enter;
static int sys_refcount_exit;
static DECLARE_BITMAP(enabled_enter_syscalls, NR_syscalls);
static DECLARE_BITMAP(enabled_exit_syscalls, NR_syscalls);

static int syscall_enter_register(struct ftrace_event_call *event,
                 enum trace_reg type, void *data);
static int syscall_exit_register(struct ftrace_event_call *event,
                 enum trace_reg type, void *data);

static int syscall_enter_define_fields(struct ftrace_event_call *call);
static int syscall_exit_define_fields(struct ftrace_event_call *call);

static struct list_head *
syscall_get_enter_fields(struct ftrace_event_call *call)
{
    struct syscall_metadata *entry = call->data;

    return &entry->enter_fields;
}

struct trace_event_functions enter_syscall_print_funcs = {
    .trace      = print_syscall_enter,
};

struct trace_event_functions exit_syscall_print_funcs = {
    .trace      = print_syscall_exit,
};

struct ftrace_event_class event_class_syscall_enter = {
    .system     = "syscalls",
    .reg        = syscall_enter_register,
    .define_fields  = syscall_enter_define_fields,
    .get_fields = syscall_get_enter_fields,
    .raw_init   = init_syscall_trace,
};

struct ftrace_event_class event_class_syscall_exit = {
    .system     = "syscalls",
    .reg        = syscall_exit_register,
    .define_fields  = syscall_exit_define_fields,
    .fields     = LIST_HEAD_INIT(event_class_syscall_exit.fields),
    .raw_init   = init_syscall_trace,
};

extern struct syscall_metadata *__start_syscalls_metadata[];
extern struct syscall_metadata *__stop_syscalls_metadata[];

static struct syscall_metadata **syscalls_metadata;

#ifndef ARCH_HAS_SYSCALL_MATCH_SYM_NAME
static inline bool arch_syscall_match_sym_name(const char *sym, const char *name)
{
    /*
     * Only compare after the "sys" prefix. Archs that use
     * syscall wrappers may have syscalls symbols aliases prefixed
     * with "SyS" instead of "sys", leading to an unwanted
     * mismatch.
     */
    return !strcmp(sym + 3, name + 3);
}
#endif

static __init struct syscall_metadata *
find_syscall_meta(unsigned long syscall)
{
    struct syscall_metadata **start;
    struct syscall_metadata **stop;
    char str[KSYM_SYMBOL_LEN];


    start = __start_syscalls_metadata;
    stop = __stop_syscalls_metadata;
    kallsyms_lookup(syscall, NULL, NULL, NULL, str);

    if (arch_syscall_match_sym_name(str, "sys_ni_syscall"))
        return NULL;

    for ( ; start < stop; start++) {
        if ((*start)->name && arch_syscall_match_sym_name(str, (*start)->name))
            return *start;
    }
    return NULL;
}

static struct syscall_metadata *syscall_nr_to_meta(int nr)
{
    if (!syscalls_metadata || nr >= NR_syscalls || nr < 0)
        return NULL;

    return syscalls_metadata[nr];
}

enum print_line_t
print_syscall_enter(struct trace_iterator *iter, int flags,
            struct trace_event *event)
{
    struct trace_seq *s = &iter->seq;
    struct trace_entry *ent = iter->ent;
    struct syscall_trace_enter *trace;
    struct syscall_metadata *entry;
    int i, ret, syscall;

    trace = (typeof(trace))ent;
    syscall = trace->nr;
    entry = syscall_nr_to_meta(syscall);

    if (!entry)
        goto end;

    if (entry->enter_event->event.type != ent->type) {
        WARN_ON_ONCE(1);
        goto end;
    }

    ret = trace_seq_printf(s, "%s(", entry->name);
    if (!ret)
        return TRACE_TYPE_PARTIAL_LINE;

    for (i = 0; i < entry->nb_args; i++) {
        /* parameter types */
        if (trace_flags & TRACE_ITER_VERBOSE) {
            ret = trace_seq_printf(s, "%s ", entry->types[i]);
            if (!ret)
                return TRACE_TYPE_PARTIAL_LINE;
        }
        /* parameter values */
        ret = trace_seq_printf(s, "%s: %lx%s", entry->args[i],
                       trace->args[i],
                       i == entry->nb_args - 1 ? "" : ", ");
        if (!ret)
            return TRACE_TYPE_PARTIAL_LINE;
    }

    ret = trace_seq_putc(s, ')');
    if (!ret)
        return TRACE_TYPE_PARTIAL_LINE;

end:
    ret =  trace_seq_putc(s, '\n');
    if (!ret)
        return TRACE_TYPE_PARTIAL_LINE;

    return TRACE_TYPE_HANDLED;
}

enum print_line_t
print_syscall_exit(struct trace_iterator *iter, int flags,
           struct trace_event *event)
{
    struct trace_seq *s = &iter->seq;
    struct trace_entry *ent = iter->ent;
    struct syscall_trace_exit *trace;
    int syscall;
    struct syscall_metadata *entry;
    int ret;

    trace = (typeof(trace))ent;
    syscall = trace->nr;
    entry = syscall_nr_to_meta(syscall);

    if (!entry) {
        trace_seq_printf(s, "\n");
        return TRACE_TYPE_HANDLED;
    }

    if (entry->exit_event->event.type != ent->type) {
        WARN_ON_ONCE(1);
        return TRACE_TYPE_UNHANDLED;
    }

    ret = trace_seq_printf(s, "%s -> 0x%lx\n", entry->name,
                trace->ret);
    if (!ret)
        return TRACE_TYPE_PARTIAL_LINE;

    return TRACE_TYPE_HANDLED;
}

extern char *__bad_type_size(void);

#define SYSCALL_FIELD(type, name)                   \
    sizeof(type) != sizeof(trace.name) ?                \
        __bad_type_size() :                 \
        #type, #name, offsetof(typeof(trace), name),        \
        sizeof(trace.name), is_signed_type(type)

static
int  __set_enter_print_fmt(struct syscall_metadata *entry, char *buf, int len)
{
    int i;
    int pos = 0;

    /* When len=0, we just calculate the needed length */
#define LEN_OR_ZERO (len ? len - pos : 0)

    pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");
    for (i = 0; i < entry->nb_args; i++) {
        pos += snprintf(buf + pos, LEN_OR_ZERO, "%s: 0x%%0%zulx%s",
                entry->args[i], sizeof(unsigned long),
                i == entry->nb_args - 1 ? "" : ", ");
    }
    pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");

    for (i = 0; i < entry->nb_args; i++) {
        pos += snprintf(buf + pos, LEN_OR_ZERO,
                ", ((unsigned long)(REC->%s))", entry->args[i]);
    }

#undef LEN_OR_ZERO

    /* return the length of print_fmt */
    return pos;
}

static int set_syscall_print_fmt(struct ftrace_event_call *call)
{
    char *print_fmt;
    int len;
    struct syscall_metadata *entry = call->data;

    if (entry->enter_event != call) {
        call->print_fmt = "\"0x%lx\", REC->ret";
        return 0;
    }

    /* First: called with 0 length to calculate the needed length */
    len = __set_enter_print_fmt(entry, NULL, 0);

    print_fmt = kmalloc(len + 1, GFP_KERNEL);
    if (!print_fmt)
        return -ENOMEM;

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

    return 0;
}

static void free_syscall_print_fmt(struct ftrace_event_call *call)
{
    struct syscall_metadata *entry = call->data;

    if (entry->enter_event == call)
        kfree(call->print_fmt);
}

static int syscall_enter_define_fields(struct ftrace_event_call *call)
{
    struct syscall_trace_enter trace;
    struct syscall_metadata *meta = call->data;
    int ret;
    int i;
    int offset = offsetof(typeof(trace), args);

    ret = trace_define_field(call, SYSCALL_FIELD(int, nr), FILTER_OTHER);
    if (ret)
        return ret;

    for (i = 0; i < meta->nb_args; i++) {
        ret = trace_define_field(call, meta->types[i],
                     meta->args[i], offset,
                     sizeof(unsigned long), 0,
                     FILTER_OTHER);
        offset += sizeof(unsigned long);
    }

    return ret;
}

static int syscall_exit_define_fields(struct ftrace_event_call *call)
{
    struct syscall_trace_exit trace;
    int ret;

    ret = trace_define_field(call, SYSCALL_FIELD(int, nr), FILTER_OTHER);
    if (ret)
        return ret;

    ret = trace_define_field(call, SYSCALL_FIELD(long, ret),
                 FILTER_OTHER);

    return ret;
}

void ftrace_syscall_enter(void *ignore, struct pt_regs *regs, long id)
{
    struct syscall_trace_enter *entry;
    struct syscall_metadata *sys_data;
    struct ring_buffer_event *event;
    struct ring_buffer *buffer;
    int size;
    int syscall_nr;

    syscall_nr = syscall_get_nr(current, regs);
    if (syscall_nr < 0)
        return;
    if (!test_bit(syscall_nr, enabled_enter_syscalls))
        return;

    sys_data = syscall_nr_to_meta(syscall_nr);
    if (!sys_data)
        return;

    size = sizeof(*entry) + sizeof(unsigned long) * sys_data->nb_args;

    event = trace_current_buffer_lock_reserve(&buffer,
            sys_data->enter_event->event.type, size, 0, 0);
    if (!event)
        return;

    entry = ring_buffer_event_data(event);
    entry->nr = syscall_nr;
    syscall_get_arguments(current, regs, 0, sys_data->nb_args, entry->args);

    if (!filter_current_check_discard(buffer, sys_data->enter_event,
                      entry, event))
        trace_current_buffer_unlock_commit(buffer, event, 0, 0);
}

void ftrace_syscall_exit(void *ignore, struct pt_regs *regs, long ret)
{
    struct syscall_trace_exit *entry;
    struct syscall_metadata *sys_data;
    struct ring_buffer_event *event;
    struct ring_buffer *buffer;
    int syscall_nr;

    syscall_nr = syscall_get_nr(current, regs);
    if (syscall_nr < 0)
        return;
    if (!test_bit(syscall_nr, enabled_exit_syscalls))
        return;

    sys_data = syscall_nr_to_meta(syscall_nr);
    if (!sys_data)
        return;

    event = trace_current_buffer_lock_reserve(&buffer,
            sys_data->exit_event->event.type, sizeof(*entry), 0, 0);
    if (!event)
        return;

    entry = ring_buffer_event_data(event);
    entry->nr = syscall_nr;
    entry->ret = syscall_get_return_value(current, regs);

    if (!filter_current_check_discard(buffer, sys_data->exit_event,
                      entry, event))
        trace_current_buffer_unlock_commit(buffer, event, 0, 0);
}

int reg_event_syscall_enter(struct ftrace_event_call *call)
{
    int ret = 0;
    int num;

    num = ((struct syscall_metadata *)call->data)->syscall_nr;
    if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
        return -ENOSYS;
    mutex_lock(&syscall_trace_lock);
    if (!sys_refcount_enter)
        ret = register_trace_sys_enter(ftrace_syscall_enter, NULL);
    if (!ret) {
        set_bit(num, enabled_enter_syscalls);
        sys_refcount_enter++;
    }
    mutex_unlock(&syscall_trace_lock);
    return ret;
}

void unreg_event_syscall_enter(struct ftrace_event_call *call)
{
    int num;

    num = ((struct syscall_metadata *)call->data)->syscall_nr;
    if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
        return;
    mutex_lock(&syscall_trace_lock);
    sys_refcount_enter--;
    clear_bit(num, enabled_enter_syscalls);
    if (!sys_refcount_enter)
        unregister_trace_sys_enter(ftrace_syscall_enter, NULL);
    mutex_unlock(&syscall_trace_lock);
}

int reg_event_syscall_exit(struct ftrace_event_call *call)
{
    int ret = 0;
    int num;

    num = ((struct syscall_metadata *)call->data)->syscall_nr;
    if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
        return -ENOSYS;
    mutex_lock(&syscall_trace_lock);
    if (!sys_refcount_exit)
        ret = register_trace_sys_exit(ftrace_syscall_exit, NULL);
    if (!ret) {
        set_bit(num, enabled_exit_syscalls);
        sys_refcount_exit++;
    }
    mutex_unlock(&syscall_trace_lock);
    return ret;
}

void unreg_event_syscall_exit(struct ftrace_event_call *call)
{
    int num;

    num = ((struct syscall_metadata *)call->data)->syscall_nr;
    if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
        return;
    mutex_lock(&syscall_trace_lock);
    sys_refcount_exit--;
    clear_bit(num, enabled_exit_syscalls);
    if (!sys_refcount_exit)
        unregister_trace_sys_exit(ftrace_syscall_exit, NULL);
    mutex_unlock(&syscall_trace_lock);
}

int init_syscall_trace(struct ftrace_event_call *call)
{
    int id;
    int num;

    num = ((struct syscall_metadata *)call->data)->syscall_nr;
    if (num < 0 || num >= NR_syscalls) {
        pr_debug("syscall %s metadata not mapped, disabling ftrace event\n",
                ((struct syscall_metadata *)call->data)->name);
        return -ENOSYS;
    }

    if (set_syscall_print_fmt(call) < 0)
        return -ENOMEM;

    id = trace_event_raw_init(call);

    if (id < 0) {
        free_syscall_print_fmt(call);
        return id;
    }

    return id;
}

unsigned long __init __weak arch_syscall_addr(int nr)
{
    return (unsigned long)sys_call_table[nr];
}

int __init init_ftrace_syscalls(void)
{
    struct syscall_metadata *meta;
    unsigned long addr;
    int i;

    syscalls_metadata = kcalloc(NR_syscalls, sizeof(*syscalls_metadata),
                    GFP_KERNEL);
    if (!syscalls_metadata) {
        WARN_ON(1);
        return -ENOMEM;
    }

    for (i = 0; i < NR_syscalls; i++) {
        addr = arch_syscall_addr(i);
        meta = find_syscall_meta(addr);
        if (!meta)
            continue;

        meta->syscall_nr = i;
        syscalls_metadata[i] = meta;
    }

    return 0;
}
early_initcall(init_ftrace_syscalls);

#ifdef CONFIG_PERF_EVENTS

static DECLARE_BITMAP(enabled_perf_enter_syscalls, NR_syscalls);
static DECLARE_BITMAP(enabled_perf_exit_syscalls, NR_syscalls);
static int sys_perf_refcount_enter;
static int sys_perf_refcount_exit;

static void perf_syscall_enter(void *ignore, struct pt_regs *regs, long id)
{
    struct syscall_metadata *sys_data;
    struct syscall_trace_enter *rec;
    struct hlist_head *head;
    int syscall_nr;
    int rctx;
    int size;

    syscall_nr = syscall_get_nr(current, regs);
    if (syscall_nr < 0)
        return;
    if (!test_bit(syscall_nr, enabled_perf_enter_syscalls))
        return;

    sys_data = syscall_nr_to_meta(syscall_nr);
    if (!sys_data)
        return;

    /* get the size after alignment with the u32 buffer size field */
    size = sizeof(unsigned long) * sys_data->nb_args + sizeof(*rec);
    size = ALIGN(size + sizeof(u32), sizeof(u64));
    size -= sizeof(u32);

    if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE,
              "perf buffer not large enough"))
        return;

    rec = (struct syscall_trace_enter *)perf_trace_buf_prepare(size,
                sys_data->enter_event->event.type, regs, &rctx);
    if (!rec)
        return;

    rec->nr = syscall_nr;
    syscall_get_arguments(current, regs, 0, sys_data->nb_args,
                   (unsigned long *)&rec->args);

    head = this_cpu_ptr(sys_data->enter_event->perf_events);
    perf_trace_buf_submit(rec, size, rctx, 0, 1, regs, head, NULL);
}

int perf_sysenter_enable(struct ftrace_event_call *call)
{
    int ret = 0;
    int num;

    num = ((struct syscall_metadata *)call->data)->syscall_nr;

    mutex_lock(&syscall_trace_lock);
    if (!sys_perf_refcount_enter)
        ret = register_trace_sys_enter(perf_syscall_enter, NULL);
    if (ret) {
        pr_info("event trace: Could not activate"
                "syscall entry trace point");
    } else {
        set_bit(num, enabled_perf_enter_syscalls);
        sys_perf_refcount_enter++;
    }
    mutex_unlock(&syscall_trace_lock);
    return ret;
}

void perf_sysenter_disable(struct ftrace_event_call *call)
{
    int num;

    num = ((struct syscall_metadata *)call->data)->syscall_nr;

    mutex_lock(&syscall_trace_lock);
    sys_perf_refcount_enter--;
    clear_bit(num, enabled_perf_enter_syscalls);
    if (!sys_perf_refcount_enter)
        unregister_trace_sys_enter(perf_syscall_enter, NULL);
    mutex_unlock(&syscall_trace_lock);
}

static void perf_syscall_exit(void *ignore, struct pt_regs *regs, long ret)
{
    struct syscall_metadata *sys_data;
    struct syscall_trace_exit *rec;
    struct hlist_head *head;
    int syscall_nr;
    int rctx;
    int size;

    syscall_nr = syscall_get_nr(current, regs);
    if (syscall_nr < 0)
        return;
    if (!test_bit(syscall_nr, enabled_perf_exit_syscalls))
        return;

    sys_data = syscall_nr_to_meta(syscall_nr);
    if (!sys_data)
        return;

    /* We can probably do that at build time */
    size = ALIGN(sizeof(*rec) + sizeof(u32), sizeof(u64));
    size -= sizeof(u32);

    /*
     * Impossible, but be paranoid with the future
     * How to put this check outside runtime?
     */
    if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE,
        "exit event has grown above perf buffer size"))
        return;

    rec = (struct syscall_trace_exit *)perf_trace_buf_prepare(size,
                sys_data->exit_event->event.type, regs, &rctx);
    if (!rec)
        return;

    rec->nr = syscall_nr;
    rec->ret = syscall_get_return_value(current, regs);

    head = this_cpu_ptr(sys_data->exit_event->perf_events);
    perf_trace_buf_submit(rec, size, rctx, 0, 1, regs, head, NULL);
}

int perf_sysexit_enable(struct ftrace_event_call *call)
{
    int ret = 0;
    int num;

    num = ((struct syscall_metadata *)call->data)->syscall_nr;

    mutex_lock(&syscall_trace_lock);
    if (!sys_perf_refcount_exit)
        ret = register_trace_sys_exit(perf_syscall_exit, NULL);
    if (ret) {
        pr_info("event trace: Could not activate"
                "syscall exit trace point");
    } else {
        set_bit(num, enabled_perf_exit_syscalls);
        sys_perf_refcount_exit++;
    }
    mutex_unlock(&syscall_trace_lock);
    return ret;
}

void perf_sysexit_disable(struct ftrace_event_call *call)
{
    int num;

    num = ((struct syscall_metadata *)call->data)->syscall_nr;

    mutex_lock(&syscall_trace_lock);
    sys_perf_refcount_exit--;
    clear_bit(num, enabled_perf_exit_syscalls);
    if (!sys_perf_refcount_exit)
        unregister_trace_sys_exit(perf_syscall_exit, NULL);
    mutex_unlock(&syscall_trace_lock);
}

#endif /* CONFIG_PERF_EVENTS */

static int syscall_enter_register(struct ftrace_event_call *event,
                 enum trace_reg type, void *data)
{
    switch (type) {
    case TRACE_REG_REGISTER:
        return reg_event_syscall_enter(event);
    case TRACE_REG_UNREGISTER:
        unreg_event_syscall_enter(event);
        return 0;

#ifdef CONFIG_PERF_EVENTS
    case TRACE_REG_PERF_REGISTER:
        return perf_sysenter_enable(event);
    case TRACE_REG_PERF_UNREGISTER:
        perf_sysenter_disable(event);
        return 0;
    case TRACE_REG_PERF_OPEN:
    case TRACE_REG_PERF_CLOSE:
    case TRACE_REG_PERF_ADD:
    case TRACE_REG_PERF_DEL:
        return 0;
#endif
    }
    return 0;
}

static int syscall_exit_register(struct ftrace_event_call *event,
                 enum trace_reg type, void *data)
{
    switch (type) {
    case TRACE_REG_REGISTER:
        return reg_event_syscall_exit(event);
    case TRACE_REG_UNREGISTER:
        unreg_event_syscall_exit(event);
        return 0;

#ifdef CONFIG_PERF_EVENTS
    case TRACE_REG_PERF_REGISTER:
        return perf_sysexit_enable(event);
    case TRACE_REG_PERF_UNREGISTER:
        perf_sysexit_disable(event);
        return 0;
    case TRACE_REG_PERF_OPEN:
    case TRACE_REG_PERF_CLOSE:
    case TRACE_REG_PERF_ADD:
    case TRACE_REG_PERF_DEL:
        return 0;
#endif
    }
    return 0;
}