/* Copyright (c) 2011-2015 PLUMgrid, http://plumgrid.com
 * Copyright (c) 2016 Facebook
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of version 2 of the GNU General Public
 * License as published by the Free Software Foundation.
 */
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/bpf.h>
#include <linux/bpf_perf_event.h>
#include <linux/filter.h>
#include <linux/uaccess.h>
#include <linux/ctype.h>
#include "trace.h"

/**
 * trace_call_bpf - invoke BPF program
 * @prog: BPF program
 * @ctx: opaque context pointer
 *
 * kprobe handlers execute BPF programs via this helper.
 * Can be used from static tracepoints in the future.
 *
 * Return: BPF programs always return an integer which is interpreted by
 * kprobe handler as:
 * 0 - return from kprobe (event is filtered out)
 * 1 - store kprobe event into ring buffer
 * Other values are reserved and currently alias to 1
 */
unsigned int trace_call_bpf(struct bpf_prog *prog, void *ctx)
{
        unsigned int ret;

        if (in_nmi()) /* not supported yet */
                return 1;

        preempt_disable();

        if (unlikely(__this_cpu_inc_return(bpf_prog_active) != 1)) {
                /*
                 * since some bpf program is already running on this cpu,
                 * don't call into another bpf program (same or different)
                 * and don't send kprobe event into ring-buffer,
                 * so return zero here
                 */
                ret = 0;
                goto out;
        }

        rcu_read_lock();
        ret = BPF_PROG_RUN(prog, ctx);
        rcu_read_unlock();

 out:
        __this_cpu_dec(bpf_prog_active);
        preempt_enable();

        return ret;
}
EXPORT_SYMBOL_GPL(trace_call_bpf);

BPF_CALL_3(bpf_probe_read, void *, dst, u32, size, const void *, unsafe_ptr)
{
        int ret;

        ret = probe_kernel_read(dst, unsafe_ptr, size);
        if (unlikely(ret < 0))
                memset(dst, 0, size);

        return ret;
}

static const struct bpf_func_proto bpf_probe_read_proto = {
        .func           = bpf_probe_read,
        .gpl_only       = true,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_RAW_STACK,
        .arg2_type      = ARG_CONST_STACK_SIZE,
        .arg3_type      = ARG_ANYTHING,
};

BPF_CALL_3(bpf_probe_write_user, void *, unsafe_ptr, const void *, src,
           u32, size)
{
        /*
         * Ensure we're in user context which is safe for the helper to
         * run. This helper has no business in a kthread.
         *
         * access_ok() should prevent writing to non-user memory, but in
         * some situations (nommu, temporary switch, etc) access_ok() does
         * not provide enough validation, hence the check on KERNEL_DS.
         */

        if (unlikely(in_interrupt() ||
                     current->flags & (PF_KTHREAD | PF_EXITING)))
                return -EPERM;
        if (unlikely(segment_eq(get_fs(), KERNEL_DS)))
                return -EPERM;
        if (!access_ok(VERIFY_WRITE, unsafe_ptr, size))
                return -EPERM;

        return probe_kernel_write(unsafe_ptr, src, size);
}

static const struct bpf_func_proto bpf_probe_write_user_proto = {
        .func           = bpf_probe_write_user,
        .gpl_only       = true,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_ANYTHING,
        .arg2_type      = ARG_PTR_TO_STACK,
        .arg3_type      = ARG_CONST_STACK_SIZE,
};

static const struct bpf_func_proto *bpf_get_probe_write_proto(void)
{
        pr_warn_ratelimited("%s[%d] is installing a program with bpf_probe_write_user helper that may corrupt user memory!",
                            current->comm, task_pid_nr(current));

        return &bpf_probe_write_user_proto;
}

/*
 * limited trace_printk()
 * only %d %u %x %ld %lu %lx %lld %llu %llx %p %s conversion specifiers allowed
 */
BPF_CALL_5(bpf_trace_printk, char *, fmt, u32, fmt_size, u64, arg1,
           u64, arg2, u64, arg3)
{
        bool str_seen = false;
        int mod[3] = {};
        int fmt_cnt = 0;
        u64 unsafe_addr;
        char buf[64];
        int i;

        /*
         * bpf_check()->check_func_arg()->check_stack_boundary()
         * guarantees that fmt points to bpf program stack,
         * fmt_size bytes of it were initialized and fmt_size > 0
         */
        if (fmt[--fmt_size] != 0)
                return -EINVAL;

        /* check format string for allowed specifiers */
        for (i = 0; i < fmt_size; i++) {
                if ((!isprint(fmt[i]) && !isspace(fmt[i])) || !isascii(fmt[i]))
                        return -EINVAL;

                if (fmt[i] != '%')
                        continue;

                if (fmt_cnt >= 3)
                        return -EINVAL;

                /* fmt[i] != 0 && fmt[last] == 0, so we can access fmt[i + 1] */
                i++;
                if (fmt[i] == 'l') {
                        mod[fmt_cnt]++;
                        i++;
                } else if (fmt[i] == 'p' || fmt[i] == 's') {
                        mod[fmt_cnt]++;
                        i++;
                        if (!isspace(fmt[i]) && !ispunct(fmt[i]) && fmt[i] != 0)
                                return -EINVAL;
                        fmt_cnt++;
                        if (fmt[i - 1] == 's') {
                                if (str_seen)
                                        /* allow only one '%s' per fmt string */
                                        return -EINVAL;
                                str_seen = true;

                                switch (fmt_cnt) {
                                case 1:
                                        unsafe_addr = arg1;
                                        arg1 = (long) buf;
                                        break;
                                case 2:
                                        unsafe_addr = arg2;
                                        arg2 = (long) buf;
                                        break;
                                case 3:
                                        unsafe_addr = arg3;
                                        arg3 = (long) buf;
                                        break;
                                }
                                buf[0] = 0;
                                strncpy_from_unsafe(buf,
                                                    (void *) (long) unsafe_addr,
                                                    sizeof(buf));
                        }
                        continue;
                }

                if (fmt[i] == 'l') {
                        mod[fmt_cnt]++;
                        i++;
                }

                if (fmt[i] != 'd' && fmt[i] != 'u' && fmt[i] != 'x')
                        return -EINVAL;
                fmt_cnt++;
        }

        return __trace_printk(1/* fake ip will not be printed */, fmt,
                              mod[0] == 2 ? arg1 : mod[0] == 1 ? (long) arg1 : (u32) arg1,
                              mod[1] == 2 ? arg2 : mod[1] == 1 ? (long) arg2 : (u32) arg2,
                              mod[2] == 2 ? arg3 : mod[2] == 1 ? (long) arg3 : (u32) arg3);
}

static const struct bpf_func_proto bpf_trace_printk_proto = {
        .func           = bpf_trace_printk,
        .gpl_only       = true,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_STACK,
        .arg2_type      = ARG_CONST_STACK_SIZE,
};

const struct bpf_func_proto *bpf_get_trace_printk_proto(void)
{
        /*
         * this program might be calling bpf_trace_printk,
         * so allocate per-cpu printk buffers
         */
        trace_printk_init_buffers();

        return &bpf_trace_printk_proto;
}

BPF_CALL_2(bpf_perf_event_read, struct bpf_map *, map, u64, flags)
{
        struct bpf_array *array = container_of(map, struct bpf_array, map);
        unsigned int cpu = smp_processor_id();
        u64 index = flags & BPF_F_INDEX_MASK;
        struct bpf_event_entry *ee;
        struct perf_event *event;

        if (unlikely(flags & ~(BPF_F_INDEX_MASK)))
                return -EINVAL;
        if (index == BPF_F_CURRENT_CPU)
                index = cpu;
        if (unlikely(index >= array->map.max_entries))
                return -E2BIG;

        ee = READ_ONCE(array->ptrs[index]);
        if (!ee)
                return -ENOENT;

        event = ee->event;
        if (unlikely(event->attr.type != PERF_TYPE_HARDWARE &&
                     event->attr.type != PERF_TYPE_RAW))
                return -EINVAL;

        /* make sure event is local and doesn't have pmu::count */
        if (unlikely(event->oncpu != cpu || event->pmu->count))
                return -EINVAL;

        /*
         * we don't know if the function is run successfully by the
         * return value. It can be judged in other places, such as
         * eBPF programs.
         */
        return perf_event_read_local(event);
}

static const struct bpf_func_proto bpf_perf_event_read_proto = {
        .func           = bpf_perf_event_read,
        .gpl_only       = true,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_CONST_MAP_PTR,
        .arg2_type      = ARG_ANYTHING,
};

static __always_inline u64
__bpf_perf_event_output(struct pt_regs *regs, struct bpf_map *map,
                        u64 flags, struct perf_raw_record *raw)
{
        struct bpf_array *array = container_of(map, struct bpf_array, map);
        unsigned int cpu = smp_processor_id();
        u64 index = flags & BPF_F_INDEX_MASK;
        struct perf_sample_data sample_data;
        struct bpf_event_entry *ee;
        struct perf_event *event;

        if (index == BPF_F_CURRENT_CPU)
                index = cpu;
        if (unlikely(index >= array->map.max_entries))
                return -E2BIG;

        ee = READ_ONCE(array->ptrs[index]);
        if (!ee)
                return -ENOENT;

        event = ee->event;
        if (unlikely(event->attr.type != PERF_TYPE_SOFTWARE ||
                     event->attr.config != PERF_COUNT_SW_BPF_OUTPUT))
                return -EINVAL;

        if (unlikely(event->oncpu != cpu))
                return -EOPNOTSUPP;

        perf_sample_data_init(&sample_data, 0, 0);
        sample_data.raw = raw;
        perf_event_output(event, &sample_data, regs);
        return 0;
}

BPF_CALL_5(bpf_perf_event_output, struct pt_regs *, regs, struct bpf_map *, map,
           u64, flags, void *, data, u64, size)
{
        struct perf_raw_record raw = {
                .frag = {
                        .size = size,
                        .data = data,
                },
        };

        if (unlikely(flags & ~(BPF_F_INDEX_MASK)))
                return -EINVAL;

        return __bpf_perf_event_output(regs, map, flags, &raw);
}

static const struct bpf_func_proto bpf_perf_event_output_proto = {
        .func           = bpf_perf_event_output,
        .gpl_only       = true,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
        .arg2_type      = ARG_CONST_MAP_PTR,
        .arg3_type      = ARG_ANYTHING,
        .arg4_type      = ARG_PTR_TO_STACK,
        .arg5_type      = ARG_CONST_STACK_SIZE,
};

static DEFINE_PER_CPU(struct pt_regs, bpf_pt_regs);

u64 bpf_event_output(struct bpf_map *map, u64 flags, void *meta, u64 meta_size,
                     void *ctx, u64 ctx_size, bpf_ctx_copy_t ctx_copy)
{
        struct pt_regs *regs = this_cpu_ptr(&bpf_pt_regs);
        struct perf_raw_frag frag = {
                .copy           = ctx_copy,
                .size           = ctx_size,
                .data           = ctx,
        };
        struct perf_raw_record raw = {
                .frag = {
                        {
                                .next   = ctx_size ? &frag : NULL,
                        },
                        .size   = meta_size,
                        .data   = meta,
                },
        };

        perf_fetch_caller_regs(regs);

        return __bpf_perf_event_output(regs, map, flags, &raw);
}

BPF_CALL_0(bpf_get_current_task)
{
        return (long) current;
}

static const struct bpf_func_proto bpf_get_current_task_proto = {
        .func           = bpf_get_current_task,
        .gpl_only       = true,
        .ret_type       = RET_INTEGER,
};

BPF_CALL_2(bpf_current_task_under_cgroup, struct bpf_map *, map, u32, idx)
{
        struct bpf_array *array = container_of(map, struct bpf_array, map);
        struct cgroup *cgrp;

        if (unlikely(in_interrupt()))
                return -EINVAL;
        if (unlikely(idx >= array->map.max_entries))
                return -E2BIG;

        cgrp = READ_ONCE(array->ptrs[idx]);
        if (unlikely(!cgrp))
                return -EAGAIN;

        return task_under_cgroup_hierarchy(current, cgrp);
}

static const struct bpf_func_proto bpf_current_task_under_cgroup_proto = {
        .func           = bpf_current_task_under_cgroup,
        .gpl_only       = false,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_CONST_MAP_PTR,
        .arg2_type      = ARG_ANYTHING,
};

static const struct bpf_func_proto *tracing_func_proto(enum bpf_func_id func_id)
{
        switch (func_id) {
        case BPF_FUNC_map_lookup_elem:
                return &bpf_map_lookup_elem_proto;
        case BPF_FUNC_map_update_elem:
                return &bpf_map_update_elem_proto;
        case BPF_FUNC_map_delete_elem:
                return &bpf_map_delete_elem_proto;
        case BPF_FUNC_probe_read:
                return &bpf_probe_read_proto;
        case BPF_FUNC_ktime_get_ns:
                return &bpf_ktime_get_ns_proto;
        case BPF_FUNC_tail_call:
                return &bpf_tail_call_proto;
        case BPF_FUNC_get_current_pid_tgid:
                return &bpf_get_current_pid_tgid_proto;
        case BPF_FUNC_get_current_task:
                return &bpf_get_current_task_proto;
        case BPF_FUNC_get_current_uid_gid:
                return &bpf_get_current_uid_gid_proto;
        case BPF_FUNC_get_current_comm:
                return &bpf_get_current_comm_proto;
        case BPF_FUNC_trace_printk:
                return bpf_get_trace_printk_proto();
        case BPF_FUNC_get_smp_processor_id:
                return &bpf_get_smp_processor_id_proto;
        case BPF_FUNC_get_numa_node_id:
                return &bpf_get_numa_node_id_proto;
        case BPF_FUNC_perf_event_read:
                return &bpf_perf_event_read_proto;
        case BPF_FUNC_probe_write_user:
                return bpf_get_probe_write_proto();
        case BPF_FUNC_current_task_under_cgroup:
                return &bpf_current_task_under_cgroup_proto;
        case BPF_FUNC_get_prandom_u32:
                return &bpf_get_prandom_u32_proto;
        default:
                return NULL;
        }
}

static const struct bpf_func_proto *kprobe_prog_func_proto(enum bpf_func_id func_id)
{
        switch (func_id) {
        case BPF_FUNC_perf_event_output:
                return &bpf_perf_event_output_proto;
        case BPF_FUNC_get_stackid:
                return &bpf_get_stackid_proto;
        default:
                return tracing_func_proto(func_id);
        }
}

/* bpf+kprobe programs can access fields of 'struct pt_regs' */
static bool kprobe_prog_is_valid_access(int off, int size, enum bpf_access_type type,
                                        enum bpf_reg_type *reg_type)
{
        if (off < 0 || off >= sizeof(struct pt_regs))
                return false;
        if (type != BPF_READ)
                return false;
        if (off % size != 0)
                return false;
        return true;
}

static const struct bpf_verifier_ops kprobe_prog_ops = {
        .get_func_proto  = kprobe_prog_func_proto,
        .is_valid_access = kprobe_prog_is_valid_access,
};

static struct bpf_prog_type_list kprobe_tl = {
        .ops    = &kprobe_prog_ops,
        .type   = BPF_PROG_TYPE_KPROBE,
};

BPF_CALL_5(bpf_perf_event_output_tp, void *, tp_buff, struct bpf_map *, map,
           u64, flags, void *, data, u64, size)
{
        struct pt_regs *regs = *(struct pt_regs **)tp_buff;

        /*
         * r1 points to perf tracepoint buffer where first 8 bytes are hidden
         * from bpf program and contain a pointer to 'struct pt_regs'. Fetch it
         * from there and call the same bpf_perf_event_output() helper inline.
         */
        return ____bpf_perf_event_output(regs, map, flags, data, size);
}

static const struct bpf_func_proto bpf_perf_event_output_proto_tp = {
        .func           = bpf_perf_event_output_tp,
        .gpl_only       = true,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
        .arg2_type      = ARG_CONST_MAP_PTR,
        .arg3_type      = ARG_ANYTHING,
        .arg4_type      = ARG_PTR_TO_STACK,
        .arg5_type      = ARG_CONST_STACK_SIZE,
};

BPF_CALL_3(bpf_get_stackid_tp, void *, tp_buff, struct bpf_map *, map,
           u64, flags)
{
        struct pt_regs *regs = *(struct pt_regs **)tp_buff;

        /*
         * Same comment as in bpf_perf_event_output_tp(), only that this time
         * the other helper's function body cannot be inlined due to being
         * external, thus we need to call raw helper function.
         */
        return bpf_get_stackid((unsigned long) regs, (unsigned long) map,
                               flags, 0, 0);
}

static const struct bpf_func_proto bpf_get_stackid_proto_tp = {
        .func           = bpf_get_stackid_tp,
        .gpl_only       = true,
        .ret_type       = RET_INTEGER,
        .arg1_type      = ARG_PTR_TO_CTX,
        .arg2_type      = ARG_CONST_MAP_PTR,
        .arg3_type      = ARG_ANYTHING,
};

static const struct bpf_func_proto *tp_prog_func_proto(enum bpf_func_id func_id)
{
        switch (func_id) {
        case BPF_FUNC_perf_event_output:
                return &bpf_perf_event_output_proto_tp;
        case BPF_FUNC_get_stackid:
                return &bpf_get_stackid_proto_tp;
        default:
                return tracing_func_proto(func_id);
        }
}

static bool tp_prog_is_valid_access(int off, int size, enum bpf_access_type type,
                                    enum bpf_reg_type *reg_type)
{
        if (off < sizeof(void *) || off >= PERF_MAX_TRACE_SIZE)
                return false;
        if (type != BPF_READ)
                return false;
        if (off % size != 0)
                return false;
        return true;
}

static const struct bpf_verifier_ops tracepoint_prog_ops = {
        .get_func_proto  = tp_prog_func_proto,
        .is_valid_access = tp_prog_is_valid_access,
};

static struct bpf_prog_type_list tracepoint_tl = {
        .ops    = &tracepoint_prog_ops,
        .type   = BPF_PROG_TYPE_TRACEPOINT,
};

static bool pe_prog_is_valid_access(int off, int size, enum bpf_access_type type,
                                    enum bpf_reg_type *reg_type)
{
        if (off < 0 || off >= sizeof(struct bpf_perf_event_data))
                return false;
        if (type != BPF_READ)
                return false;
        if (off % size != 0)
                return false;
        if (off == offsetof(struct bpf_perf_event_data, sample_period)) {
                if (size != sizeof(u64))
                        return false;
        } else {
                if (size != sizeof(long))
                        return false;
        }
        return true;
}

static u32 pe_prog_convert_ctx_access(enum bpf_access_type type, int dst_reg,
                                      int src_reg, int ctx_off,
                                      struct bpf_insn *insn_buf,
                                      struct bpf_prog *prog)
{
        struct bpf_insn *insn = insn_buf;

        switch (ctx_off) {
        case offsetof(struct bpf_perf_event_data, sample_period):
                BUILD_BUG_ON(FIELD_SIZEOF(struct perf_sample_data, period) != sizeof(u64));

                *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct bpf_perf_event_data_kern,
                                                       data), dst_reg, src_reg,
                                      offsetof(struct bpf_perf_event_data_kern, data));
                *insn++ = BPF_LDX_MEM(BPF_DW, dst_reg, dst_reg,
                                      offsetof(struct perf_sample_data, period));
                break;
        default:
                *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct bpf_perf_event_data_kern,
                                                       regs), dst_reg, src_reg,
                                      offsetof(struct bpf_perf_event_data_kern, regs));
                *insn++ = BPF_LDX_MEM(BPF_SIZEOF(long), dst_reg, dst_reg, ctx_off);
                break;
        }

        return insn - insn_buf;
}

static const struct bpf_verifier_ops perf_event_prog_ops = {
        .get_func_proto         = tp_prog_func_proto,
        .is_valid_access        = pe_prog_is_valid_access,
        .convert_ctx_access     = pe_prog_convert_ctx_access,
};

static struct bpf_prog_type_list perf_event_tl = {
        .ops    = &perf_event_prog_ops,
        .type   = BPF_PROG_TYPE_PERF_EVENT,
};

static int __init register_kprobe_prog_ops(void)
{
        bpf_register_prog_type(&kprobe_tl);
        bpf_register_prog_type(&tracepoint_tl);
        bpf_register_prog_type(&perf_event_tl);
        return 0;
}
late_initcall(register_kprobe_prog_ops);