freebsd/sys/ddb/db_elf.c

/* $FreeBSD$ */
/*	$NetBSD: db_elf.c,v 1.4 1998/05/03 18:49:54 thorpej Exp $	*/

/*-
 * Copyright (c) 1997 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.
 *
 * 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.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the NetBSD
 *	Foundation, Inc. and its contributors.
 * 4. Neither the name of The NetBSD Foundation nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * 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 "opt_ddb.h"

#ifdef DDB_NOKLDSYM

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

#ifdef __i386__
#include <machine/bootinfo.h>
#endif

#include <ddb/ddb.h>
#include <ddb/db_sym.h>

#include <machine/elf.h>

#ifndef _ALIGNED_POINTER
#define	_ALIGNED_POINTER(ptr, type)	1
#endif

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))

void X_db_sym_init(void *symtab, void *esymtab, char *name);

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

	if (_ALIGNED_POINTER(symtab, long) == 0) {
		printf("DDB: bad symbol table start address %p\n", symtab);
		return;
	}

	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 (elf->e_ident[EI_MAG0] != ELFMAG0
	    || elf->e_ident[EI_MAG1] != ELFMAG1
	    || elf->e_ident[EI_MAG2] != ELFMAG2
	    || elf->e_ident[EI_MAG3] != ELFMAG3)
		goto badheader;

	if (!ELF_MACHINE_OK(elf->e_machine))
		goto badheader;

	/*
	 * We need to avoid the section header string table (small string
	 * table which names the sections).  We do this by assuming that
	 * the following two conditions will be true:
	 *
	 *	(1) .shstrtab will be smaller than one page.
	 *	(2) .strtab will be larger than one page.
	 *
	 * When we encounter what we think is the .shstrtab, we change
	 * its section type Elf_sht_null so that it will be ignored
	 * later.
	 */
	shp = (Elf_Shdr *)((char*)symtab + elf->e_shoff);
	for (i = 0; i < elf->e_shnum; i++) {
		if (shp[i].sh_addr || i == elf->e_shstrndx)
			continue;
		switch (shp[i].sh_type) {
		case SHT_STRTAB:
			if (shp[i].sh_size < PAGE_SIZE) {
				shp[i].sh_type = SHT_NULL;
				continue;
			}
			if (strtab_start != NULL)
				goto multiple_strtab;
			strtab_start = (char *)symtab + shp[i].sh_offset;
			strtab_end = (char *)symtab + shp[i].sh_offset +
			    shp[i].sh_size;
			break;

		case SHT_SYMTAB:
			if (symtab_start != NULL)
				goto multiple_symtab;
			symtab_start = (Elf_Sym *)((char*)symtab + shp[i].sh_offset);
			symtab_end = (Elf_Sym *)((char*)symtab + shp[i].sh_offset +
			    shp[i].sh_size);
			break;

		default:
			/* Ignore all other sections. */
			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.
	 */
	db_add_symbol_table((char *)symtab_start,
			    (char *)symtab_end, name, (char *)symtab);
	printf("[ preserving %lu bytes of %s symbol table ]\n",
	       (u_long)roundup(((char*)esymtab - (char*)symtab), sizeof(u_long)), name);
	return;

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

 multiple_strtab:
	printf("[ %s has multiple string tables ]\n", name);
	return;

 multiple_symtab:
	printf("[ %s has multiple symbol tables ]\n", name);
	return;
}

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

	for (i = 0; i < elf->e_shnum; i++) {
		if (shp[i].sh_type == SHT_STRTAB
		    && !shp[i].sh_addr && i != elf->e_shstrndx)
			return (stab->private + shp[i].sh_offset);
	}

	return (NULL);
}

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

	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).
 */
c_db_sym_t
X_db_search_symbol(symtab, off, strategy, diffp)
	db_symtab_t *symtab;
	db_addr_t off;
	db_strategy_t strategy;
	db_expr_t *diffp;		/* in/out */
{
	Elf_Sym *rsymp, *symp, *symtab_start, *symtab_end;
	db_expr_t diff = *diffp;

	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 (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 &&
					    ELF_ST_TYPE(symp->st_info) ==
					      STT_FUNC &&
					    ELF_ST_BIND(symp->st_info) !=
					      STB_LOCAL)
						break;
					if (strategy == DB_STGY_ANY &&
					    ELF_ST_BIND(symp->st_info) !=
					      STB_LOCAL)
						break;
				}
			} else if ((off - symp->st_value) == diff) {
				if (rsymp == NULL)
					rsymp = symp;
				else if (ELF_ST_BIND(rsymp->st_info) ==
				      STB_LOCAL &&
				    ELF_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.
 */
void
X_db_symbol_values(symtab, sym, namep, valuep)
	db_symtab_t *symtab;
	c_db_sym_t sym;
	const char **namep;
	db_expr_t *valuep;
{
	const Elf_Sym *symp = (const Elf_Sym *)sym;
	char *strtab;

	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.
 */
boolean_t
X_db_line_at_pc(symtab, cursym, filename, linenum, off)
	db_symtab_t *symtab;
	c_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.
 */
boolean_t
X_db_sym_numargs(symtab, cursym, nargp, argnamep)
	db_symtab_t *symtab;
	c_db_sym_t cursym;
	int *nargp;
	char **argnamep;
{

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

/*
 * Initialization routine for Elf files.
 */

#ifdef __i386__
void *ksym_start, *ksym_end;
#else
extern void *ksym_start, *ksym_end;
#endif

void
kdb_init(void)
{
	static Elf_Ehdr elf;
	static Elf_Shdr sh[2];

#ifdef __i386__
	ksym_start = (void *)bootinfo.bi_symtab;
	ksym_end = (void *)bootinfo.bi_esymtab;
#endif
	if (ksym_end <= ksym_start)
		return;

	/*
	 * The FreeBSD boot program doesn't actually load any headers, so
	 * fake just enough for the routines in this file to work.
	 */
	elf.e_ident[EI_MAG0] = ELFMAG0;
	elf.e_ident[EI_MAG1] = ELFMAG1;
	elf.e_ident[EI_MAG2] = ELFMAG2;
	elf.e_ident[EI_MAG3] = ELFMAG3;
	elf.e_machine = EM_486;
	elf.e_shoff = (uintptr_t)(void *)&sh[0] - (uintptr_t)(void *)&elf;
	sh[0].sh_type = SHT_SYMTAB;
	sh[0].sh_offset = (uintptr_t)ksym_start + sizeof(long) -
	    (uintptr_t)(void *)&elf;
	sh[0].sh_size = *(int *)ksym_start;
	sh[1].sh_type = SHT_STRTAB;
	sh[1].sh_offset = sh[0].sh_offset + sh[0].sh_size + sizeof(long);
	sh[1].sh_size = (uintptr_t)ksym_end - (uintptr_t)ksym_start -
	    sizeof(long) - sh[0].sh_size - sizeof(long);
	elf.e_shstrndx = -1;
	elf.e_shnum = 2;

	X_db_sym_init(&elf, ksym_end, "kernel");
}

#endif /* DDB_NOKLDSYM */