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nasm/output/outas86.c
Cyrill Gorcunov 2e6297ff1b out: Zeroify temp buffer before use 
This is a a buffer on stack big enough to hold
bigger object we might need (address, number and
etc) but it's defined as an array of bytes and
we treat it as different types depending on context,
which may lead to situation where data from stack
been treated as meaningful.

In particular in commit 5b730a197 we've fixed such
problem simply using a "big" write to zeroify stack
data before use.

Lets simply zeroify this buffer explicitly to escape
such problems in future.

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
2015-07-19 14:24:26 +03:00

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/* ----------------------------------------------------------------------- *
*
* Copyright 1996-2013 The NASM Authors - All Rights Reserved
* See the file AUTHORS included with the NASM distribution for
* the specific copyright holders.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following
* conditions are met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * 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 COPYRIGHT HOLDERS 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 COPYRIGHT OWNER 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.
*
* ----------------------------------------------------------------------- */
/*
* outas86.c output routines for the Netwide Assembler to produce
* Linux as86 (bin86-0.3) object files
*/
#include "compiler.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <inttypes.h>
#include "nasm.h"
#include "nasmlib.h"
#include "saa.h"
#include "raa.h"
#include "output/outform.h"
#include "output/outlib.h"
#ifdef OF_AS86
struct Piece {
struct Piece *next;
int type; /* 0 = absolute, 1 = seg, 2 = sym */
int32_t offset; /* relative offset */
int number; /* symbol/segment number (4=bss) */
int32_t bytes; /* size of reloc or of absolute data */
bool relative; /* relative address? */
};
struct Symbol {
int32_t strpos; /* string table position of name */
int flags; /* symbol flags */
int segment; /* 4=bss at this point */
int32_t value; /* address, or COMMON variable size */
};
/*
* Section IDs - used in Piece.number and Symbol.segment.
*/
#define SECT_TEXT 0 /* text section */
#define SECT_DATA 3 /* data section */
#define SECT_BSS 4 /* bss section */
/*
* Flags used in Symbol.flags.
*/
#define SYM_ENTRY (1<<8)
#define SYM_EXPORT (1<<7)
#define SYM_IMPORT (1<<6)
#define SYM_ABSOLUTE (1<<4)
struct Section {
struct SAA *data;
uint32_t datalen, size, len;
int32_t index;
struct Piece *head, *last, **tail;
};
static char as86_module[FILENAME_MAX];
static struct Section stext, sdata;
static uint32_t bsslen;
static int32_t bssindex;
static struct SAA *syms;
static uint32_t nsyms;
static struct RAA *bsym;
static struct SAA *strs;
static uint32_t strslen;
static int as86_reloc_size;
static void as86_write(void);
static void as86_write_section(struct Section *, int);
static int as86_add_string(char *name);
static void as86_sect_write(struct Section *, const uint8_t *,
uint32_t);
static void as86_init(void)
{
stext.data = saa_init(1L);
stext.datalen = 0L;
stext.head = stext.last = NULL;
stext.tail = &stext.head;
sdata.data = saa_init(1L);
sdata.datalen = 0L;
sdata.head = sdata.last = NULL;
sdata.tail = &sdata.head;
bsslen =
stext.len = stext.datalen = stext.size =
sdata.len = sdata.datalen = sdata.size = 0;
stext.index = seg_alloc();
sdata.index = seg_alloc();
bssindex = seg_alloc();
syms = saa_init((int32_t)sizeof(struct Symbol));
nsyms = 0;
bsym = raa_init();
strs = saa_init(1L);
strslen = 0;
as86_add_string(as86_module);
}
static void as86_cleanup(int debuginfo)
{
struct Piece *p;
(void)debuginfo;
as86_write();
saa_free(stext.data);
while (stext.head) {
p = stext.head;
stext.head = stext.head->next;
nasm_free(p);
}
saa_free(sdata.data);
while (sdata.head) {
p = sdata.head;
sdata.head = sdata.head->next;
nasm_free(p);
}
saa_free(syms);
raa_free(bsym);
saa_free(strs);
}
static int32_t as86_section_names(char *name, int pass, int *bits)
{
(void)pass;
/*
* Default is 16 bits.
*/
if (!name)
*bits = 16;
if (!name)
return stext.index;
if (!strcmp(name, ".text"))
return stext.index;
else if (!strcmp(name, ".data"))
return sdata.index;
else if (!strcmp(name, ".bss"))
return bssindex;
else
return NO_SEG;
}
static int as86_add_string(char *name)
{
int pos = strslen;
int length = strlen(name);
saa_wbytes(strs, name, (int32_t)(length + 1));
strslen += 1 + length;
return pos;
}
static void as86_deflabel(char *name, int32_t segment, int64_t offset,
int is_global, char *special)
{
bool is_start = false;
struct Symbol *sym;
if (special)
nasm_error(ERR_NONFATAL, "as86 format does not support any"
" special symbol types");
if (name[0] == '.' && name[1] == '.' && name[2] != '@') {
if (strcmp(name, "..start")) {
nasm_error(ERR_NONFATAL, "unrecognised special symbol `%s'", name);
return;
} else {
is_start = true;
}
}
sym = saa_wstruct(syms);
sym->strpos = as86_add_string(name);
sym->flags = 0;
if (is_start)
sym->flags = SYM_ENTRY;
if (segment == NO_SEG)
sym->flags |= SYM_ABSOLUTE, sym->segment = 0;
else if (segment == stext.index)
sym->segment = SECT_TEXT;
else if (segment == sdata.index)
sym->segment = SECT_DATA;
else if (segment == bssindex)
sym->segment = SECT_BSS;
else {
sym->flags |= SYM_IMPORT;
sym->segment = 15;
}
if (is_global == 2)
sym->segment = 3; /* already have IMPORT */
if (is_global && !(sym->flags & SYM_IMPORT))
sym->flags |= SYM_EXPORT;
sym->value = offset;
/*
* define the references from external-symbol segment numbers
* to these symbol records.
*/
if (segment != NO_SEG && segment != stext.index &&
segment != sdata.index && segment != bssindex)
bsym = raa_write(bsym, segment, nsyms);
nsyms++;
}
static void as86_add_piece(struct Section *sect, int type, int32_t offset,
int32_t segment, int32_t bytes, int relative)
{
struct Piece *p;
sect->len += bytes;
if (type == 0 && sect->last && sect->last->type == 0) {
sect->last->bytes += bytes;
return;
}
p = sect->last = *sect->tail = nasm_malloc(sizeof(struct Piece));
sect->tail = &p->next;
p->next = NULL;
p->type = type;
p->offset = offset;
p->bytes = bytes;
p->relative = relative;
if (type == 1 && segment == stext.index)
p->number = SECT_TEXT;
else if (type == 1 && segment == sdata.index)
p->number = SECT_DATA;
else if (type == 1 && segment == bssindex)
p->number = SECT_BSS;
else if (type == 1)
p->number = raa_read(bsym, segment), p->type = 2;
}
static void as86_out(int32_t segto, const void *data,
enum out_type type, uint64_t size,
int32_t segment, int32_t wrt)
{
struct Section *s;
int32_t offset;
uint8_t mydata[4], *p;
if (wrt != NO_SEG) {
wrt = NO_SEG; /* continue to do _something_ */
nasm_error(ERR_NONFATAL, "WRT not supported by as86 output format");
}
/*
* handle absolute-assembly (structure definitions)
*/
if (segto == NO_SEG) {
if (type != OUT_RESERVE)
nasm_error(ERR_NONFATAL, "attempt to assemble code in [ABSOLUTE]"
" space");
return;
}
if (segto == stext.index)
s = &stext;
else if (segto == sdata.index)
s = &sdata;
else if (segto == bssindex)
s = NULL;
else {
nasm_error(ERR_WARNING, "attempt to assemble code in"
" segment %d: defaulting to `.text'", segto);
s = &stext;
}
if (!s && type != OUT_RESERVE) {
nasm_error(ERR_WARNING, "attempt to initialize memory in the"
" BSS section: ignored");
bsslen += realsize(type, size);
return;
}
memset(mydata, 0, sizeof(mydata));
if (type == OUT_RESERVE) {
if (s) {
nasm_error(ERR_WARNING, "uninitialized space declared in"
" %s section: zeroing",
(segto == stext.index ? "code" : "data"));
as86_sect_write(s, NULL, size);
as86_add_piece(s, 0, 0L, 0L, size, 0);
} else
bsslen += size;
} else if (type == OUT_RAWDATA) {
if (segment != NO_SEG)
nasm_error(ERR_PANIC, "OUT_RAWDATA with other than NO_SEG");
as86_sect_write(s, data, size);
as86_add_piece(s, 0, 0L, 0L, size, 0);
} else if (type == OUT_ADDRESS) {
int asize = abs(size);
if (segment != NO_SEG) {
if (segment % 2) {
nasm_error(ERR_NONFATAL, "as86 format does not support"
" segment base references");
} else {
offset = *(int64_t *)data;
as86_add_piece(s, 1, offset, segment, asize, 0);
}
} else {
p = mydata;
WRITELONG(p, *(int64_t *)data);
as86_sect_write(s, data, asize);
as86_add_piece(s, 0, 0L, 0L, asize, 0);
}
} else if (type == OUT_REL2ADR) {
if (segment == segto)
nasm_error(ERR_PANIC, "intra-segment OUT_REL2ADR");
if (segment != NO_SEG) {
if (segment % 2) {
nasm_error(ERR_NONFATAL, "as86 format does not support"
" segment base references");
} else {
offset = *(int64_t *)data;
as86_add_piece(s, 1, offset - size + 2, segment, 2L,
1);
}
}
} else if (type == OUT_REL4ADR) {
if (segment == segto)
nasm_error(ERR_PANIC, "intra-segment OUT_REL4ADR");
if (segment != NO_SEG) {
if (segment % 2) {
nasm_error(ERR_NONFATAL, "as86 format does not support"
" segment base references");
} else {
offset = *(int64_t *)data;
as86_add_piece(s, 1, offset - size + 4, segment, 4L,
1);
}
}
}
}
static void as86_write(void)
{
uint32_t i;
int32_t symlen, seglen, segsize;
/*
* First, go through the symbol records working out how big
* each will be. Also fix up BSS references at this time, and
* set the flags words up completely.
*/
symlen = 0;
saa_rewind(syms);
for (i = 0; i < nsyms; i++) {
struct Symbol *sym = saa_rstruct(syms);
if (sym->segment == SECT_BSS)
sym->segment = SECT_DATA, sym->value += sdata.len;
sym->flags |= sym->segment;
if (sym->value == 0)
sym->flags |= 0 << 14, symlen += 4;
else if (sym->value >= 0 && sym->value <= 255)
sym->flags |= 1 << 14, symlen += 5;
else if (sym->value >= 0 && sym->value <= 65535L)
sym->flags |= 2 << 14, symlen += 6;
else
sym->flags |= 3 << 14, symlen += 8;
}
/*
* Now do the same for the segments, and get the segment size
* descriptor word at the same time.
*/
seglen = segsize = 0;
if ((uint32_t)stext.len > 65535L)
segsize |= 0x03000000L, seglen += 4;
else
segsize |= 0x02000000L, seglen += 2;
if ((uint32_t)sdata.len > 65535L)
segsize |= 0xC0000000L, seglen += 4;
else
segsize |= 0x80000000L, seglen += 2;
/*
* Emit the as86 header.
*/
fwriteint32_t(0x000186A3L, ofile);
fputc(0x2A, ofile);
fwriteint32_t(27 + symlen + seglen + strslen, ofile); /* header length */
fwriteint32_t(stext.len + sdata.len + bsslen, ofile);
fwriteint16_t(strslen, ofile);
fwriteint16_t(0, ofile); /* class = revision = 0 */
fwriteint32_t(0x55555555L, ofile); /* segment max sizes: always this */
fwriteint32_t(segsize, ofile); /* segment size descriptors */
if (segsize & 0x01000000L)
fwriteint32_t(stext.len, ofile);
else
fwriteint16_t(stext.len, ofile);
if (segsize & 0x40000000L)
fwriteint32_t(sdata.len + bsslen, ofile);
else
fwriteint16_t(sdata.len + bsslen, ofile);
fwriteint16_t(nsyms, ofile);
/*
* Write the symbol table.
*/
saa_rewind(syms);
for (i = 0; i < nsyms; i++) {
struct Symbol *sym = saa_rstruct(syms);
fwriteint16_t(sym->strpos, ofile);
fwriteint16_t(sym->flags, ofile);
switch (sym->flags & (3 << 14)) {
case 0 << 14:
break;
case 1 << 14:
fputc(sym->value, ofile);
break;
case 2 << 14:
fwriteint16_t(sym->value, ofile);
break;
case 3 << 14:
fwriteint32_t(sym->value, ofile);
break;
}
}
/*
* Write out the string table.
*/
saa_fpwrite(strs, ofile);
/*
* Write the program text.
*/
as86_reloc_size = -1;
as86_write_section(&stext, SECT_TEXT);
as86_write_section(&sdata, SECT_DATA);
/*
* Append the BSS section to the .data section
*/
if (bsslen > 65535L) {
fputc(0x13, ofile);
fwriteint32_t(bsslen, ofile);
} else if (bsslen > 255) {
fputc(0x12, ofile);
fwriteint16_t(bsslen, ofile);
} else if (bsslen) {
fputc(0x11, ofile);
fputc(bsslen, ofile);
}
fputc(0, ofile); /* termination */
}
static void as86_set_rsize(int size)
{
if (as86_reloc_size != size) {
switch (as86_reloc_size = size) {
case 1:
fputc(0x01, ofile);
break;
case 2:
fputc(0x02, ofile);
break;
case 4:
fputc(0x03, ofile);
break;
default:
nasm_error(ERR_PANIC, "bizarre relocation size %d", size);
break;
}
}
}
static void as86_write_section(struct Section *sect, int index)
{
struct Piece *p;
uint32_t s;
int32_t length;
fputc(0x20 + index, ofile); /* select the right section */
saa_rewind(sect->data);
for (p = sect->head; p; p = p->next)
switch (p->type) {
case 0:
/*
* Absolute data. Emit it in chunks of at most 64
* bytes.
*/
length = p->bytes;
do {
char buf[64];
int32_t tmplen = (length > 64 ? 64 : length);
fputc(0x40 | (tmplen & 0x3F), ofile);
saa_rnbytes(sect->data, buf, tmplen);
nasm_write(buf, tmplen, ofile);
length -= tmplen;
} while (length > 0);
break;
case 1:
/*
* A segment-type relocation. First fix up the BSS.
*/
if (p->number == SECT_BSS)
p->number = SECT_DATA, p->offset += sdata.len;
as86_set_rsize(p->bytes);
fputc(0x80 | (p->relative ? 0x20 : 0) | p->number, ofile);
if (as86_reloc_size == 2)
fwriteint16_t(p->offset, ofile);
else
fwriteint32_t(p->offset, ofile);
break;
case 2:
/*
* A symbol-type relocation.
*/
as86_set_rsize(p->bytes);
s = p->offset;
if (s > 65535L)
s = 3;
else if (s > 255)
s = 2;
else if (s > 0)
s = 1;
else
s = 0;
fputc(0xC0 |
(p->relative ? 0x20 : 0) |
(p->number > 255 ? 0x04 : 0) | s, ofile);
if (p->number > 255)
fwriteint16_t(p->number, ofile);
else
fputc(p->number, ofile);
switch ((int)s) {
case 0:
break;
case 1:
fputc(p->offset, ofile);
break;
case 2:
fwriteint16_t(p->offset, ofile);
break;
case 3:
fwriteint32_t(p->offset, ofile);
break;
}
break;
}
}
static void as86_sect_write(struct Section *sect,
const uint8_t *data, uint32_t len)
{
saa_wbytes(sect->data, data, len);
sect->datalen += len;
}
static int32_t as86_segbase(int32_t segment)
{
return segment;
}
static void as86_filename(char *inname, char *outname)
{
char *p;
if ((p = strrchr(inname, '.')) != NULL) {
strncpy(as86_module, inname, p - inname);
as86_module[p - inname] = '\0';
} else
strcpy(as86_module, inname);
standard_extension(inname, outname, ".o");
}
extern macros_t as86_stdmac[];
struct ofmt of_as86 = {
"Linux as86 (bin86 version 0.3) object files",
"as86",
0,
null_debug_arr,
&null_debug_form,
as86_stdmac,
as86_init,
null_setinfo,
as86_out,
as86_deflabel,
as86_section_names,
null_sectalign,
as86_segbase,
null_directive,
as86_filename,
as86_cleanup
};
#endif /* OF_AS86 */
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