/*      $NetBSD: db_elf.c,v 1.29 2017/11/06 04:08:02 christos Exp $     */

/*-
 * Copyright (c) 1997, 2009 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility,
 * NASA Ames Research Center, and by Andrew Doran.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: db_elf.c,v 1.29 2017/11/06 04:08:02 christos Exp $");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/proc.h>

#include <machine/db_machdep.h>
#include <machine/pmap.h>
#include <machine/vmparam.h>

#ifdef DB_ELF_SYMBOLS

#include <ddb/ddb.h>
#include <sys/exec_elf.h>

static char     *db_elf_find_strtab(db_symtab_t *);

#define STAB_TO_SYMSTART(stab)  ((Elf_Sym *)((stab)->start))
#define STAB_TO_SYMEND(stab)    ((Elf_Sym *)((stab)->end))
#define STAB_TO_EHDR(stab)      ((Elf_Ehdr *)((stab)->private))
#define STAB_TO_SHDR(stab, e)   ((Elf_Shdr *)((stab)->private + (e)->e_shoff))

static bool db_elf_sym_init(int, void *, void *, const char *);
static db_sym_t db_elf_lookup(db_symtab_t *, const char *);
static db_sym_t db_elf_search_symbol(db_symtab_t *, db_addr_t, db_strategy_t,
                    db_expr_t *);
static void     db_elf_symbol_values(db_symtab_t *, db_sym_t, const char **,
                    db_expr_t *);
static bool db_elf_line_at_pc(db_symtab_t *, db_sym_t, char **, int *,
                    db_expr_t);
static bool db_elf_sym_numargs(db_symtab_t *, db_sym_t, int *, char **);
static void     db_elf_forall(db_symtab_t *, db_forall_func_t db_forall_func,
                    void *);

const db_symformat_t db_symformat_elf = {
        "ELF",
        db_elf_sym_init,
        db_elf_lookup,
        db_elf_search_symbol,
        db_elf_symbol_values,
        db_elf_line_at_pc,
        db_elf_sym_numargs,
        db_elf_forall
};

static db_symtab_t db_symtabs;

/*
 * Add symbol table, with given name, to symbol tables.
 */
static int
db_add_symbol_table(char *start, char *end, const char *name, char *ref)
{

        db_symtabs.start = start;
        db_symtabs.end = end;
        db_symtabs.name = name;
        db_symtabs.private = ref;

        return(0);
}

/*
 * Find the symbol table and strings; tell ddb about them.
 */
static bool
db_elf_sym_init(
        int symsize,            /* size of symbol table */
        void *symtab,           /* pointer to start of symbol table */
        void *esymtab,          /* pointer to end of string table,
                                   for checking - rounded up to integer
                                   boundary */
        const char *name
)
{
        Elf_Ehdr *elf;
        Elf_Shdr *shp;
        Elf_Sym *symp, *symtab_start, *symtab_end;
        char *strtab_start, *strtab_end;
        int i, j;

        if (ALIGNED_POINTER(symtab, long) == 0) {
                printf("[ %s symbol table has bad start address %p ]\n",
                    name, symtab);
                return (false);
        }

        symtab_start = symtab_end = NULL;
        strtab_start = strtab_end = NULL;

        /*
         * The format of the symbols loaded by the boot program is:
         *
         *      Elf exec header
         *      first section header
         *      . . .
         *      . . .
         *      last section header
         *      first symbol or string table section
         *      . . .
         *      . . .
         *      last symbol or string table section
         */

        /*
         * Validate the Elf header.
         */
        elf = (Elf_Ehdr *)symtab;
        if (memcmp(elf->e_ident, ELFMAG, SELFMAG) != 0 ||
            elf->e_ident[EI_CLASS] != ELFCLASS)
                goto badheader;

        switch (elf->e_machine) {

        ELFDEFNNAME(MACHDEP_ID_CASES)

        default:
                goto badheader;
        }

        /*
         * Find the first (and, we hope, only) SHT_SYMTAB section in
         * the file, and the SHT_STRTAB section that goes with it.
         */
        if (elf->e_shoff == 0)
                goto badheader;
        shp = (Elf_Shdr *)((char *)symtab + elf->e_shoff);
        for (i = 0; i < elf->e_shnum; i++) {
                if (shp[i].sh_type == SHT_SYMTAB) {
                        if (shp[i].sh_offset == 0)
                                continue;
                        /* Got the symbol table. */
                        symtab_start = (Elf_Sym *)((char *)symtab +
                            shp[i].sh_offset);
                        symtab_end = (Elf_Sym *)((char *)symtab +
                            shp[i].sh_offset + shp[i].sh_size);
                        /* Find the string table to go with it. */
                        j = shp[i].sh_link;
                        if (shp[j].sh_offset == 0)
                                continue;
                        strtab_start = (char *)symtab + shp[j].sh_offset;
                        strtab_end = (char *)symtab + shp[j].sh_offset +
                            shp[j].sh_size;
                        /* There should only be one symbol table. */
                        break;
                }
        }

        /*
         * Now, sanity check the symbols against the string table.
         */
        if (symtab_start == NULL || strtab_start == NULL ||
            ALIGNED_POINTER(symtab_start, long) == 0 ||
            ALIGNED_POINTER(strtab_start, long) == 0)
                goto badheader;
        for (symp = symtab_start; symp < symtab_end; symp++)
                if (symp->st_name + strtab_start > strtab_end)
                        goto badheader;

        /*
         * Link the symbol table into the debugger.
         */
        if (db_add_symbol_table((char *)symtab_start,
            (char *)symtab_end, name, (char *)symtab) != -1) {
                return (true);
        }

        return (false);

 badheader:
        printf("[ %s ELF symbol table not valid ]\n", name);
        return (false);
}

/*
 * Internal helper function - return a pointer to the string table
 * for the current symbol table.
 */
static char *
db_elf_find_strtab(db_symtab_t *stab)
{
        Elf_Ehdr *elf = STAB_TO_EHDR(stab);
        Elf_Shdr *shp = STAB_TO_SHDR(stab, elf);
        int i;

        stab = &db_symtabs;

        /*
         * We don't load ELF header for ELF modules.
         * Find out if this is a loadable module. If so,
         * string table comes right after symbol table.
         */
        if ((Elf_Sym *)elf == STAB_TO_SYMSTART(stab)) {
                return ((char *)STAB_TO_SYMEND(stab));
        }
        for (i = 0; i < elf->e_shnum; i++) {
                if (shp[i].sh_type == SHT_SYMTAB)
                        return ((char*)elf + shp[shp[i].sh_link].sh_offset);
        }

        return (NULL);
}

/*
 * Lookup the symbol with the given name.
 */
static db_sym_t
db_elf_lookup(db_symtab_t *stab, const char *symstr)
{
        Elf_Sym *symp, *symtab_start, *symtab_end;
        char *strtab;

        stab = &db_symtabs;

        symtab_start = STAB_TO_SYMSTART(stab);
        symtab_end = STAB_TO_SYMEND(stab);

        strtab = db_elf_find_strtab(stab);
        if (strtab == NULL)
                return ((db_sym_t)0);

        for (symp = symtab_start; symp < symtab_end; symp++) {
                if (symp->st_name != 0 &&
                    db_eqname(strtab + symp->st_name, symstr, 0))
                        return ((db_sym_t)symp);
        }

        return ((db_sym_t)0);
}

/*
 * Search for the symbol with the given address (matching within the
 * provided threshold).
 */
static db_sym_t
db_elf_search_symbol(db_symtab_t *symtab, db_addr_t off, db_strategy_t strategy,
    db_expr_t *diffp)
{
        Elf_Sym *rsymp, *symp, *symtab_start, *symtab_end;
        db_addr_t diff = *diffp;

        symtab = &db_symtabs;

        symtab_start = STAB_TO_SYMSTART(symtab);
        symtab_end = STAB_TO_SYMEND(symtab);

        rsymp = NULL;

        for (symp = symtab_start; symp < symtab_end; symp++) {
                if (symp->st_name == 0)
                        continue;

#if 0
                /* This prevents me from seeing anythin in locore.s -- eeh */
                if (ELF_ST_TYPE(symp->st_info) != STT_OBJECT &&
                    ELF_ST_TYPE(symp->st_info) != STT_FUNC)
                        continue;
#endif

                if (off >= symp->st_value) {
                        if (off - symp->st_value < diff) {
                                diff = off - symp->st_value;
                                rsymp = symp;
                                if (diff == 0) {
                                        if (strategy == DB_STGY_PROC &&
                                            ELFDEFNNAME(ST_TYPE)(symp->st_info)
                                              == STT_FUNC &&
                                            ELFDEFNNAME(ST_BIND)(symp->st_info)
                                              != STB_LOCAL)
                                                break;
                                        if (strategy == DB_STGY_ANY &&
                                            ELFDEFNNAME(ST_BIND)(symp->st_info)
                                              != STB_LOCAL)
                                                break;
                                }
                        } else if (off - symp->st_value == diff) {
                                if (rsymp == NULL)
                                        rsymp = symp;
                                else if (ELFDEFNNAME(ST_BIND)(rsymp->st_info)
                                      == STB_LOCAL &&
                                    ELFDEFNNAME(ST_BIND)(symp->st_info)
                                      != STB_LOCAL) {
                                        /* pick the external symbol */
                                        rsymp = symp;
                                }
                        }
                }
        }

        if (rsymp == NULL)
                *diffp = off;
        else
                *diffp = diff;

        return ((db_sym_t)rsymp);
}

/*
 * Return the name and value for a symbol.
 */
static void
db_elf_symbol_values(db_symtab_t *symtab, db_sym_t sym, const char **namep,
    db_expr_t *valuep)
{
        Elf_Sym *symp = (Elf_Sym *)sym;
        char *strtab;

        symtab = &db_symtabs;

        if (namep) {
                strtab = db_elf_find_strtab(symtab);
                if (strtab == NULL)
                        *namep = NULL;
                else
                        *namep = strtab + symp->st_name;
        }

        if (valuep)
                *valuep = symp->st_value;
}

/*
 * Return the file and line number of the current program counter
 * if we can find the appropriate debugging symbol.
 */
static bool
db_elf_line_at_pc(db_symtab_t *symtab, db_sym_t cursym, char **filename, int *linenum, db_expr_t off)
{

        /*
         * XXX We don't support this (yet).
         */
        return (false);
}

/*
 * Returns the number of arguments to a function and their
 * names if we can find the appropriate debugging symbol.
 */
static bool
db_elf_sym_numargs(db_symtab_t *symtab, db_sym_t cursym, int *nargp,
    char **argnamep)
{

        /*
         * XXX We don't support this (yet).
         */
        return (false);
}

static void
db_elf_forall(db_symtab_t *stab, db_forall_func_t db_forall_func, void *arg)
{
        char *strtab;
        static char suffix[2];
        Elf_Sym *symp, *symtab_start, *symtab_end;

        stab = &db_symtabs;

        symtab_start = STAB_TO_SYMSTART(stab);
        symtab_end = STAB_TO_SYMEND(stab);

        strtab = db_elf_find_strtab(stab);
        if (strtab == NULL)
                return;

        for (symp = symtab_start; symp < symtab_end; symp++)
                if (symp->st_name != 0) {
                        suffix[1] = '\0';
                        switch (ELFDEFNNAME(ST_TYPE)(symp->st_info)) {
                        case STT_OBJECT:
                                suffix[0] = '+';
                                break;
                        case STT_FUNC:
                                suffix[0] = '*';
                                break;
                        case STT_SECTION:
                                suffix[0] = '&';
                                break;
                        case STT_FILE:
                                suffix[0] = '/';
                                break;
                        default:
                                suffix[0] = '\0';
                        }
                        (*db_forall_func)(stab, (db_sym_t)symp,
                            strtab + symp->st_name, suffix, 0, arg);
                }
        return;
}
#endif /* DB_ELF_SYMBOLS */