/* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
 *
 * 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.
 */
#ifndef _LINUX_BPF_VERIFIER_H
#define _LINUX_BPF_VERIFIER_H 1

#include <linux/bpf.h> /* for enum bpf_reg_type */
#include <linux/filter.h> /* for MAX_BPF_STACK */
#include <linux/tnum.h>

/* Maximum variable offset umax_value permitted when resolving memory accesses.
 * In practice this is far bigger than any realistic pointer offset; this limit
 * ensures that umax_value + (int)off + (int)size cannot overflow a u64.
 */
#define BPF_MAX_VAR_OFF (1 << 29)
/* Maximum variable size permitted for ARG_CONST_SIZE[_OR_ZERO].  This ensures
 * that converting umax_value to int cannot overflow.
 */
#define BPF_MAX_VAR_SIZ (1 << 29)

/* Liveness marks, used for registers and spilled-regs (in stack slots).
 * Read marks propagate upwards until they find a write mark; they record that
 * "one of this state's descendants read this reg" (and therefore the reg is
 * relevant for states_equal() checks).
 * Write marks collect downwards and do not propagate; they record that "the
 * straight-line code that reached this state (from its parent) wrote this reg"
 * (and therefore that reads propagated from this state or its descendants
 * should not propagate to its parent).
 * A state with a write mark can receive read marks; it just won't propagate
 * them to its parent, since the write mark is a property, not of the state,
 * but of the link between it and its parent.  See mark_reg_read() and
 * mark_stack_slot_read() in kernel/bpf/verifier.c.
 */
enum bpf_reg_liveness {
        REG_LIVE_NONE = 0, /* reg hasn't been read or written this branch */
        REG_LIVE_READ, /* reg was read, so we're sensitive to initial value */
        REG_LIVE_WRITTEN, /* reg was written first, screening off later reads */
};

struct bpf_reg_state {
        enum bpf_reg_type type;
        union {
                /* valid when type == PTR_TO_PACKET */
                u16 range;

                /* valid when type == CONST_PTR_TO_MAP | PTR_TO_MAP_VALUE |
                 *   PTR_TO_MAP_VALUE_OR_NULL
                 */
                struct bpf_map *map_ptr;
        };
        /* Fixed part of pointer offset, pointer types only */
        s32 off;
        /* For PTR_TO_PACKET, used to find other pointers with the same variable
         * offset, so they can share range knowledge.
         * For PTR_TO_MAP_VALUE_OR_NULL this is used to share which map value we
         * came from, when one is tested for != NULL.
         */
        u32 id;
        /* Ordering of fields matters.  See states_equal() */
        /* For scalar types (SCALAR_VALUE), this represents our knowledge of
         * the actual value.
         * For pointer types, this represents the variable part of the offset
         * from the pointed-to object, and is shared with all bpf_reg_states
         * with the same id as us.
         */
        struct tnum var_off;
        /* Used to determine if any memory access using this register will
         * result in a bad access.
         * These refer to the same value as var_off, not necessarily the actual
         * contents of the register.
         */
        s64 smin_value; /* minimum possible (s64)value */
        s64 smax_value; /* maximum possible (s64)value */
        u64 umin_value; /* minimum possible (u64)value */
        u64 umax_value; /* maximum possible (u64)value */
        /* Inside the callee two registers can be both PTR_TO_STACK like
         * R1=fp-8 and R2=fp-8, but one of them points to this function stack
         * while another to the caller's stack. To differentiate them 'frameno'
         * is used which is an index in bpf_verifier_state->frame[] array
         * pointing to bpf_func_state.
         * This field must be second to last, for states_equal() reasons.
         */
        u32 frameno;
        /* This field must be last, for states_equal() reasons. */
        enum bpf_reg_liveness live;
};

enum bpf_stack_slot_type {
        STACK_INVALID,    /* nothing was stored in this stack slot */
        STACK_SPILL,      /* register spilled into stack */
        STACK_MISC,       /* BPF program wrote some data into this slot */
        STACK_ZERO,       /* BPF program wrote constant zero */
};

#define BPF_REG_SIZE 8  /* size of eBPF register in bytes */

struct bpf_stack_state {
        struct bpf_reg_state spilled_ptr;
        u8 slot_type[BPF_REG_SIZE];
};

/* state of the program:
 * type of all registers and stack info
 */
struct bpf_func_state {
        struct bpf_reg_state regs[MAX_BPF_REG];
        struct bpf_verifier_state *parent;
        /* index of call instruction that called into this func */
        int callsite;
        /* stack frame number of this function state from pov of
         * enclosing bpf_verifier_state.
         * 0 = main function, 1 = first callee.
         */
        u32 frameno;
        /* subprog number == index within subprog_stack_depth
         * zero == main subprog
         */
        u32 subprogno;

        /* should be second to last. See copy_func_state() */
        int allocated_stack;
        struct bpf_stack_state *stack;
};

#define MAX_CALL_FRAMES 8
struct bpf_verifier_state {
        /* call stack tracking */
        struct bpf_func_state *frame[MAX_CALL_FRAMES];
        struct bpf_verifier_state *parent;
        u32 curframe;
};

/* linked list of verifier states used to prune search */
struct bpf_verifier_state_list {
        struct bpf_verifier_state state;
        struct bpf_verifier_state_list *next;
};

struct bpf_insn_aux_data {
        union {
                enum bpf_reg_type ptr_type;     /* pointer type for load/store insns */
                unsigned long map_state;        /* pointer/poison value for maps */
                s32 call_imm;                   /* saved imm field of call insn */
        };
        int ctx_field_size; /* the ctx field size for load insn, maybe 0 */
        int sanitize_stack_off; /* stack slot to be cleared */
        bool seen; /* this insn was processed by the verifier */
};

#define MAX_USED_MAPS 64 /* max number of maps accessed by one eBPF program */

#define BPF_VERIFIER_TMP_LOG_SIZE       1024

struct bpf_verifier_log {
        u32 level;
        char kbuf[BPF_VERIFIER_TMP_LOG_SIZE];
        char __user *ubuf;
        u32 len_used;
        u32 len_total;
};

static inline bool bpf_verifier_log_full(const struct bpf_verifier_log *log)
{
        return log->len_used >= log->len_total - 1;
}

static inline bool bpf_verifier_log_needed(const struct bpf_verifier_log *log)
{
        return log->level && log->ubuf && !bpf_verifier_log_full(log);
}

#define BPF_MAX_SUBPROGS 256

/* single container for all structs
 * one verifier_env per bpf_check() call
 */
struct bpf_verifier_env {
        struct bpf_prog *prog;          /* eBPF program being verified */
        const struct bpf_verifier_ops *ops;
        struct bpf_verifier_stack_elem *head; /* stack of verifier states to be processed */
        int stack_size;                 /* number of states to be processed */
        bool strict_alignment;          /* perform strict pointer alignment checks */
        struct bpf_verifier_state *cur_state; /* current verifier state */
        struct bpf_verifier_state_list **explored_states; /* search pruning optimization */
        struct bpf_map *used_maps[MAX_USED_MAPS]; /* array of map's used by eBPF program */
        u32 used_map_cnt;               /* number of used maps */
        u32 id_gen;                     /* used to generate unique reg IDs */
        bool allow_ptr_leaks;
        bool seen_direct_write;
        struct bpf_insn_aux_data *insn_aux_data; /* array of per-insn state */
        struct bpf_verifier_log log;
        u32 subprog_starts[BPF_MAX_SUBPROGS];
        /* computes the stack depth of each bpf function */
        u16 subprog_stack_depth[BPF_MAX_SUBPROGS + 1];
        u32 subprog_cnt;
};

void bpf_verifier_vlog(struct bpf_verifier_log *log, const char *fmt,
                       va_list args);
__printf(2, 3) void bpf_verifier_log_write(struct bpf_verifier_env *env,
                                           const char *fmt, ...);

static inline struct bpf_reg_state *cur_regs(struct bpf_verifier_env *env)
{
        struct bpf_verifier_state *cur = env->cur_state;

        return cur->frame[cur->curframe]->regs;
}

int bpf_prog_offload_verifier_prep(struct bpf_verifier_env *env);
int bpf_prog_offload_verify_insn(struct bpf_verifier_env *env,
                                 int insn_idx, int prev_insn_idx);

#endif /* _LINUX_BPF_VERIFIER_H */