/*
 * genelf_debug.c
 * Copyright (C) 2015, Google, Inc
 *
 * Contributed by:
 *      Stephane Eranian <eranian@google.com>
 *
 * Released under the GPL v2.
 *
 * based on GPLv2 source code from Oprofile
 * @remark Copyright 2007 OProfile authors
 * @author Philippe Elie
 */
#include <linux/compiler.h>
#include <sys/types.h>
#include <stdio.h>
#include <getopt.h>
#include <stddef.h>
#include <libelf.h>
#include <string.h>
#include <stdlib.h>
#include <inttypes.h>
#include <limits.h>
#include <fcntl.h>
#include <err.h>
#include <dwarf.h>

#include "perf.h"
#include "genelf.h"
#include "../util/jitdump.h"

#define BUFFER_EXT_DFL_SIZE     (4 * 1024)

typedef uint32_t uword;
typedef uint16_t uhalf;
typedef int32_t  sword;
typedef int16_t  shalf;
typedef uint8_t  ubyte;
typedef int8_t   sbyte;

struct buffer_ext {
        size_t cur_pos;
        size_t max_sz;
        void *data;
};

static void
buffer_ext_dump(struct buffer_ext *be, const char *msg)
{
        size_t i;
        warnx("DUMP for %s", msg);
        for (i = 0 ; i < be->cur_pos; i++)
                warnx("%4zu 0x%02x", i, (((char *)be->data)[i]) & 0xff);
}

static inline int
buffer_ext_add(struct buffer_ext *be, void *addr, size_t sz)
{
        void *tmp;
        size_t be_sz = be->max_sz;

retry:
        if ((be->cur_pos + sz) < be_sz) {
                memcpy(be->data + be->cur_pos, addr, sz);
                be->cur_pos += sz;
                return 0;
        }

        if (!be_sz)
                be_sz = BUFFER_EXT_DFL_SIZE;
        else
                be_sz <<= 1;

        tmp = realloc(be->data, be_sz);
        if (!tmp)
                return -1;

        be->data   = tmp;
        be->max_sz = be_sz;

        goto retry;
}

static void
buffer_ext_init(struct buffer_ext *be)
{
        be->data = NULL;
        be->cur_pos = 0;
        be->max_sz = 0;
}

static inline size_t
buffer_ext_size(struct buffer_ext *be)
{
        return be->cur_pos;
}

static inline void *
buffer_ext_addr(struct buffer_ext *be)
{
        return be->data;
}

struct debug_line_header {
        // Not counting this field
        uword total_length;
        // version number (2 currently)
        uhalf version;
        // relative offset from next field to
        // program statement
        uword prolog_length;
        ubyte minimum_instruction_length;
        ubyte default_is_stmt;
        // line_base - see DWARF 2 specs
        sbyte line_base;
        // line_range - see DWARF 2 specs
        ubyte line_range;
        // number of opcode + 1
        ubyte opcode_base;
        /* follow the array of opcode args nr: ubytes [nr_opcode_base] */
        /* follow the search directories index, zero terminated string
         * terminated by an empty string.
         */
        /* follow an array of { filename, LEB128, LEB128, LEB128 }, first is
         * the directory index entry, 0 means current directory, then mtime
         * and filesize, last entry is followed by en empty string.
         */
        /* follow the first program statement */
} __packed;

/* DWARF 2 spec talk only about one possible compilation unit header while
 * binutils can handle two flavours of dwarf 2, 32 and 64 bits, this is not
 * related to the used arch, an ELF 32 can hold more than 4 Go of debug
 * information. For now we handle only DWARF 2 32 bits comp unit. It'll only
 * become a problem if we generate more than 4GB of debug information.
 */
struct compilation_unit_header {
        uword total_length;
        uhalf version;
        uword debug_abbrev_offset;
        ubyte pointer_size;
} __packed;

#define DW_LNS_num_opcode (DW_LNS_set_isa + 1)

/* field filled at run time are marked with -1 */
static struct debug_line_header const default_debug_line_header = {
        .total_length = -1,
        .version = 2,
        .prolog_length = -1,
        .minimum_instruction_length = 1,        /* could be better when min instruction size != 1 */
        .default_is_stmt = 1,   /* we don't take care about basic block */
        .line_base = -5,        /* sensible value for line base ... */
        .line_range = -14,     /* ... and line range are guessed statically */
        .opcode_base = DW_LNS_num_opcode
};

static ubyte standard_opcode_length[] =
{
        0, 1, 1, 1, 1, 0, 0, 0, 1, 0, 0, 1
};
#if 0
{
        [DW_LNS_advance_pc]   = 1,
        [DW_LNS_advance_line] = 1,
        [DW_LNS_set_file] =  1,
        [DW_LNS_set_column] = 1,
        [DW_LNS_fixed_advance_pc] = 1,
        [DW_LNS_set_isa] = 1,
};
#endif

/* field filled at run time are marked with -1 */
static struct compilation_unit_header default_comp_unit_header = {
        .total_length = -1,
        .version = 2,
        .debug_abbrev_offset = 0,     /* we reuse the same abbrev entries for all comp unit */
        .pointer_size = sizeof(void *)
};

static void emit_uword(struct buffer_ext *be, uword data)
{
        buffer_ext_add(be, &data, sizeof(uword));
}

static void emit_string(struct buffer_ext *be, const char *s)
{
        buffer_ext_add(be, (void *)s, strlen(s) + 1);
}

static void emit_unsigned_LEB128(struct buffer_ext *be,
                                 unsigned long data)
{
        do {
                ubyte cur = data & 0x7F;
                data >>= 7;
                if (data)
                        cur |= 0x80;
                buffer_ext_add(be, &cur, 1);
        } while (data);
}

static void emit_signed_LEB128(struct buffer_ext *be, long data)
{
        int more = 1;
        int negative = data < 0;
        int size = sizeof(long) * CHAR_BIT;
        while (more) {
                ubyte cur = data & 0x7F;
                data >>= 7;
                if (negative)
                        data |= - (1 << (size - 7));
                if ((data == 0 && !(cur & 0x40)) ||
                    (data == -1l && (cur & 0x40)))
                        more = 0;
                else
                        cur |= 0x80;
                buffer_ext_add(be, &cur, 1);
        }
}

static void emit_extended_opcode(struct buffer_ext *be, ubyte opcode,
                                 void *data, size_t data_len)
{
        buffer_ext_add(be, (char *)"", 1);

        emit_unsigned_LEB128(be, data_len + 1);

        buffer_ext_add(be, &opcode, 1);
        buffer_ext_add(be, data, data_len);
}

static void emit_opcode(struct buffer_ext *be, ubyte opcode)
{
        buffer_ext_add(be, &opcode, 1);
}

static void emit_opcode_signed(struct buffer_ext  *be,
                               ubyte opcode, long data)
{
        buffer_ext_add(be, &opcode, 1);
        emit_signed_LEB128(be, data);
}

static void emit_opcode_unsigned(struct buffer_ext *be, ubyte opcode,
                                 unsigned long data)
{
        buffer_ext_add(be, &opcode, 1);
        emit_unsigned_LEB128(be, data);
}

static void emit_advance_pc(struct buffer_ext *be, unsigned long delta_pc)
{
        emit_opcode_unsigned(be, DW_LNS_advance_pc, delta_pc);
}

static void emit_advance_lineno(struct buffer_ext  *be, long delta_lineno)
{
        emit_opcode_signed(be, DW_LNS_advance_line, delta_lineno);
}

static void emit_lne_end_of_sequence(struct buffer_ext *be)
{
        emit_extended_opcode(be, DW_LNE_end_sequence, NULL, 0);
}

static void emit_set_file(struct buffer_ext *be, unsigned long idx)
{
        emit_opcode_unsigned(be, DW_LNS_set_file, idx);
}

static void emit_lne_define_filename(struct buffer_ext *be,
                                     const char *filename)
{
        buffer_ext_add(be, (void *)"", 1);

        /* LNE field, strlen(filename) + zero termination, 3 bytes for: the dir entry, timestamp, filesize */
        emit_unsigned_LEB128(be, strlen(filename) + 5);
        emit_opcode(be, DW_LNE_define_file);
        emit_string(be, filename);
        /* directory index 0=do not know */
        emit_unsigned_LEB128(be, 0);
        /* last modification date on file 0=do not know */
        emit_unsigned_LEB128(be, 0);
        /* filesize 0=do not know */
        emit_unsigned_LEB128(be, 0);
}

static void emit_lne_set_address(struct buffer_ext *be,
                                 void *address)
{
        emit_extended_opcode(be, DW_LNE_set_address, &address, sizeof(unsigned long));
}

static ubyte get_special_opcode(struct debug_entry *ent,
                                unsigned int last_line,
                                unsigned long last_vma)
{
        unsigned int temp;
        unsigned long delta_addr;

        /*
         * delta from line_base
         */
        temp = (ent->lineno - last_line) - default_debug_line_header.line_base;

        if (temp >= default_debug_line_header.line_range)
                return 0;

        /*
         * delta of addresses
         */
        delta_addr = (ent->addr - last_vma) / default_debug_line_header.minimum_instruction_length;

        /* This is not sufficient to ensure opcode will be in [0-256] but
         * sufficient to ensure when summing with the delta lineno we will
         * not overflow the unsigned long opcode */

        if (delta_addr <= 256 / default_debug_line_header.line_range) {
                unsigned long opcode = temp +
                        (delta_addr * default_debug_line_header.line_range) +
                        default_debug_line_header.opcode_base;

                return opcode <= 255 ? opcode : 0;
        }
        return 0;
}

static void emit_lineno_info(struct buffer_ext *be,
                             struct debug_entry *ent, size_t nr_entry,
                             unsigned long code_addr)
{
        size_t i;

        /*
         * Machine state at start of a statement program
         * address = 0
         * file    = 1
         * line    = 1
         * column  = 0
         * is_stmt = default_is_stmt as given in the debug_line_header
         * basic block = 0
         * end sequence = 0
         */

        /* start state of the state machine we take care of */
        unsigned long last_vma = code_addr;
        char const  *cur_filename = NULL;
        unsigned long cur_file_idx = 0;
        int last_line = 1;

        emit_lne_set_address(be, (void *)code_addr);

        for (i = 0; i < nr_entry; i++, ent = debug_entry_next(ent)) {
                int need_copy = 0;
                ubyte special_opcode;

                /*
                 * check if filename changed, if so add it
                 */
                if (!cur_filename || strcmp(cur_filename, ent->name)) {
                        emit_lne_define_filename(be, ent->name);
                        cur_filename = ent->name;
                        emit_set_file(be, ++cur_file_idx);
                        need_copy = 1;
                }

                special_opcode = get_special_opcode(ent, last_line, last_vma);
                if (special_opcode != 0) {
                        last_line = ent->lineno;
                        last_vma  = ent->addr;
                        emit_opcode(be, special_opcode);
                } else {
                        /*
                         * lines differ, emit line delta
                         */
                        if (last_line != ent->lineno) {
                                emit_advance_lineno(be, ent->lineno - last_line);
                                last_line = ent->lineno;
                                need_copy = 1;
                        }
                        /*
                         * addresses differ, emit address delta
                         */
                        if (last_vma != ent->addr) {
                                emit_advance_pc(be, ent->addr - last_vma);
                                last_vma = ent->addr;
                                need_copy = 1;
                        }
                        /*
                         * add new row to matrix
                         */
                        if (need_copy)
                                emit_opcode(be, DW_LNS_copy);
                }
        }
}

static void add_debug_line(struct buffer_ext *be,
        struct debug_entry *ent, size_t nr_entry,
        unsigned long code_addr)
{
        struct debug_line_header * dbg_header;
        size_t old_size;

        old_size = buffer_ext_size(be);

        buffer_ext_add(be, (void *)&default_debug_line_header,
                 sizeof(default_debug_line_header));

        buffer_ext_add(be, &standard_opcode_length,  sizeof(standard_opcode_length));

        // empty directory entry
        buffer_ext_add(be, (void *)"", 1);

        // empty filename directory
        buffer_ext_add(be, (void *)"", 1);

        dbg_header = buffer_ext_addr(be) + old_size;
        dbg_header->prolog_length = (buffer_ext_size(be) - old_size) -
                offsetof(struct debug_line_header, minimum_instruction_length);

        emit_lineno_info(be, ent, nr_entry, code_addr);

        emit_lne_end_of_sequence(be);

        dbg_header = buffer_ext_addr(be) + old_size;
        dbg_header->total_length = (buffer_ext_size(be) - old_size) -
                offsetof(struct debug_line_header, version);
}

static void
add_debug_abbrev(struct buffer_ext *be)
{
        emit_unsigned_LEB128(be, 1);
        emit_unsigned_LEB128(be, DW_TAG_compile_unit);
        emit_unsigned_LEB128(be, DW_CHILDREN_yes);
        emit_unsigned_LEB128(be, DW_AT_stmt_list);
        emit_unsigned_LEB128(be, DW_FORM_data4);
        emit_unsigned_LEB128(be, 0);
        emit_unsigned_LEB128(be, 0);
        emit_unsigned_LEB128(be, 0);
}

static void
add_compilation_unit(struct buffer_ext *be,
                     size_t offset_debug_line)
{
        struct compilation_unit_header *comp_unit_header;
        size_t old_size = buffer_ext_size(be);

        buffer_ext_add(be, &default_comp_unit_header,
                       sizeof(default_comp_unit_header));

        emit_unsigned_LEB128(be, 1);
        emit_uword(be, offset_debug_line);

        comp_unit_header = buffer_ext_addr(be) + old_size;
        comp_unit_header->total_length = (buffer_ext_size(be) - old_size) -
                offsetof(struct compilation_unit_header, version);
}

static int
jit_process_debug_info(uint64_t code_addr,
                       void *debug, int nr_debug_entries,
                       struct buffer_ext *dl,
                       struct buffer_ext *da,
                       struct buffer_ext *di)
{
        struct debug_entry *ent = debug;
        int i;

        for (i = 0; i < nr_debug_entries; i++) {
                ent->addr = ent->addr - code_addr;
                ent = debug_entry_next(ent);
        }
        add_compilation_unit(di, buffer_ext_size(dl));
        add_debug_line(dl, debug, nr_debug_entries, 0);
        add_debug_abbrev(da);
        if (0) buffer_ext_dump(da, "abbrev");

        return 0;
}

int
jit_add_debug_info(Elf *e, uint64_t code_addr, void *debug, int nr_debug_entries)
{
        Elf_Data *d;
        Elf_Scn *scn;
        Elf_Shdr *shdr;
        struct buffer_ext dl, di, da;
        int ret;

        buffer_ext_init(&dl);
        buffer_ext_init(&di);
        buffer_ext_init(&da);

        ret = jit_process_debug_info(code_addr, debug, nr_debug_entries, &dl, &da, &di);
        if (ret)
                return -1;
        /*
         * setup .debug_line section
         */
        scn = elf_newscn(e);
        if (!scn) {
                warnx("cannot create section");
                return -1;
        }

        d = elf_newdata(scn);
        if (!d) {
                warnx("cannot get new data");
                return -1;
        }

        d->d_align = 1;
        d->d_off = 0LL;
        d->d_buf = buffer_ext_addr(&dl);
        d->d_type = ELF_T_BYTE;
        d->d_size = buffer_ext_size(&dl);
        d->d_version = EV_CURRENT;

        shdr = elf_getshdr(scn);
        if (!shdr) {
                warnx("cannot get section header");
                return -1;
        }

        shdr->sh_name = 52; /* .debug_line */
        shdr->sh_type = SHT_PROGBITS;
        shdr->sh_addr = 0; /* must be zero or == sh_offset -> dynamic object */
        shdr->sh_flags = 0;
        shdr->sh_entsize = 0;

        /*
         * setup .debug_info section
         */
        scn = elf_newscn(e);
        if (!scn) {
                warnx("cannot create section");
                return -1;
        }

        d = elf_newdata(scn);
        if (!d) {
                warnx("cannot get new data");
                return -1;
        }

        d->d_align = 1;
        d->d_off = 0LL;
        d->d_buf = buffer_ext_addr(&di);
        d->d_type = ELF_T_BYTE;
        d->d_size = buffer_ext_size(&di);
        d->d_version = EV_CURRENT;

        shdr = elf_getshdr(scn);
        if (!shdr) {
                warnx("cannot get section header");
                return -1;
        }

        shdr->sh_name = 64; /* .debug_info */
        shdr->sh_type = SHT_PROGBITS;
        shdr->sh_addr = 0; /* must be zero or == sh_offset -> dynamic object */
        shdr->sh_flags = 0;
        shdr->sh_entsize = 0;

        /*
         * setup .debug_abbrev section
         */
        scn = elf_newscn(e);
        if (!scn) {
                warnx("cannot create section");
                return -1;
        }

        d = elf_newdata(scn);
        if (!d) {
                warnx("cannot get new data");
                return -1;
        }

        d->d_align = 1;
        d->d_off = 0LL;
        d->d_buf = buffer_ext_addr(&da);
        d->d_type = ELF_T_BYTE;
        d->d_size = buffer_ext_size(&da);
        d->d_version = EV_CURRENT;

        shdr = elf_getshdr(scn);
        if (!shdr) {
                warnx("cannot get section header");
                return -1;
        }

        shdr->sh_name = 76; /* .debug_info */
        shdr->sh_type = SHT_PROGBITS;
        shdr->sh_addr = 0; /* must be zero or == sh_offset -> dynamic object */
        shdr->sh_flags = 0;
        shdr->sh_entsize = 0;

        /*
         * now we update the ELF image with all the sections
         */
        if (elf_update(e, ELF_C_WRITE) < 0) {
                warnx("elf_update debug failed");
                return -1;
        }
        return 0;
}