linux-stable/lib/xz/xz_dec_bcj.c
Lasse Collin 9c1f8594df XZ: Fix incorrect XZ_BUF_ERROR
xz_dec_run() could incorrectly return XZ_BUF_ERROR if all of the
following was true:

 - The caller knows how many bytes of output to expect and only provides
   that much output space.

 - When the last output bytes are decoded, the caller-provided input
   buffer ends right before the LZMA2 end of payload marker.  So LZMA2
   won't provide more output anymore, but it won't know it yet and thus
   won't return XZ_STREAM_END yet.

 - A BCJ filter is in use and it hasn't left any unfiltered bytes in the
   temp buffer.  This can happen with any BCJ filter, but in practice
   it's more likely with filters other than the x86 BCJ.

This fixes <https://bugzilla.redhat.com/show_bug.cgi?id=735408> where
Squashfs thinks that a valid file system is corrupt.

This also fixes a similar bug in single-call mode where the uncompressed
size of a block using BCJ + LZMA2 was 0 bytes and caller provided no
output space.  Many empty .xz files don't contain any blocks and thus
don't trigger this bug.

This also tweaks a closely related detail: xz_dec_bcj_run() could call
xz_dec_lzma2_run() to decode into temp buffer when it was known to be
useless.  This was harmless although it wasted a minuscule number of CPU
cycles.

Signed-off-by: Lasse Collin <lasse.collin@tukaani.org>
Cc: stable <stable@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-09-21 13:39:59 -07:00

574 lines
14 KiB
C

/*
* Branch/Call/Jump (BCJ) filter decoders
*
* Authors: Lasse Collin <lasse.collin@tukaani.org>
* Igor Pavlov <http://7-zip.org/>
*
* This file has been put into the public domain.
* You can do whatever you want with this file.
*/
#include "xz_private.h"
/*
* The rest of the file is inside this ifdef. It makes things a little more
* convenient when building without support for any BCJ filters.
*/
#ifdef XZ_DEC_BCJ
struct xz_dec_bcj {
/* Type of the BCJ filter being used */
enum {
BCJ_X86 = 4, /* x86 or x86-64 */
BCJ_POWERPC = 5, /* Big endian only */
BCJ_IA64 = 6, /* Big or little endian */
BCJ_ARM = 7, /* Little endian only */
BCJ_ARMTHUMB = 8, /* Little endian only */
BCJ_SPARC = 9 /* Big or little endian */
} type;
/*
* Return value of the next filter in the chain. We need to preserve
* this information across calls, because we must not call the next
* filter anymore once it has returned XZ_STREAM_END.
*/
enum xz_ret ret;
/* True if we are operating in single-call mode. */
bool single_call;
/*
* Absolute position relative to the beginning of the uncompressed
* data (in a single .xz Block). We care only about the lowest 32
* bits so this doesn't need to be uint64_t even with big files.
*/
uint32_t pos;
/* x86 filter state */
uint32_t x86_prev_mask;
/* Temporary space to hold the variables from struct xz_buf */
uint8_t *out;
size_t out_pos;
size_t out_size;
struct {
/* Amount of already filtered data in the beginning of buf */
size_t filtered;
/* Total amount of data currently stored in buf */
size_t size;
/*
* Buffer to hold a mix of filtered and unfiltered data. This
* needs to be big enough to hold Alignment + 2 * Look-ahead:
*
* Type Alignment Look-ahead
* x86 1 4
* PowerPC 4 0
* IA-64 16 0
* ARM 4 0
* ARM-Thumb 2 2
* SPARC 4 0
*/
uint8_t buf[16];
} temp;
};
#ifdef XZ_DEC_X86
/*
* This is used to test the most significant byte of a memory address
* in an x86 instruction.
*/
static inline int bcj_x86_test_msbyte(uint8_t b)
{
return b == 0x00 || b == 0xFF;
}
static size_t bcj_x86(struct xz_dec_bcj *s, uint8_t *buf, size_t size)
{
static const bool mask_to_allowed_status[8]
= { true, true, true, false, true, false, false, false };
static const uint8_t mask_to_bit_num[8] = { 0, 1, 2, 2, 3, 3, 3, 3 };
size_t i;
size_t prev_pos = (size_t)-1;
uint32_t prev_mask = s->x86_prev_mask;
uint32_t src;
uint32_t dest;
uint32_t j;
uint8_t b;
if (size <= 4)
return 0;
size -= 4;
for (i = 0; i < size; ++i) {
if ((buf[i] & 0xFE) != 0xE8)
continue;
prev_pos = i - prev_pos;
if (prev_pos > 3) {
prev_mask = 0;
} else {
prev_mask = (prev_mask << (prev_pos - 1)) & 7;
if (prev_mask != 0) {
b = buf[i + 4 - mask_to_bit_num[prev_mask]];
if (!mask_to_allowed_status[prev_mask]
|| bcj_x86_test_msbyte(b)) {
prev_pos = i;
prev_mask = (prev_mask << 1) | 1;
continue;
}
}
}
prev_pos = i;
if (bcj_x86_test_msbyte(buf[i + 4])) {
src = get_unaligned_le32(buf + i + 1);
while (true) {
dest = src - (s->pos + (uint32_t)i + 5);
if (prev_mask == 0)
break;
j = mask_to_bit_num[prev_mask] * 8;
b = (uint8_t)(dest >> (24 - j));
if (!bcj_x86_test_msbyte(b))
break;
src = dest ^ (((uint32_t)1 << (32 - j)) - 1);
}
dest &= 0x01FFFFFF;
dest |= (uint32_t)0 - (dest & 0x01000000);
put_unaligned_le32(dest, buf + i + 1);
i += 4;
} else {
prev_mask = (prev_mask << 1) | 1;
}
}
prev_pos = i - prev_pos;
s->x86_prev_mask = prev_pos > 3 ? 0 : prev_mask << (prev_pos - 1);
return i;
}
#endif
#ifdef XZ_DEC_POWERPC
static size_t bcj_powerpc(struct xz_dec_bcj *s, uint8_t *buf, size_t size)
{
size_t i;
uint32_t instr;
for (i = 0; i + 4 <= size; i += 4) {
instr = get_unaligned_be32(buf + i);
if ((instr & 0xFC000003) == 0x48000001) {
instr &= 0x03FFFFFC;
instr -= s->pos + (uint32_t)i;
instr &= 0x03FFFFFC;
instr |= 0x48000001;
put_unaligned_be32(instr, buf + i);
}
}
return i;
}
#endif
#ifdef XZ_DEC_IA64
static size_t bcj_ia64(struct xz_dec_bcj *s, uint8_t *buf, size_t size)
{
static const uint8_t branch_table[32] = {
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
4, 4, 6, 6, 0, 0, 7, 7,
4, 4, 0, 0, 4, 4, 0, 0
};
/*
* The local variables take a little bit stack space, but it's less
* than what LZMA2 decoder takes, so it doesn't make sense to reduce
* stack usage here without doing that for the LZMA2 decoder too.
*/
/* Loop counters */
size_t i;
size_t j;
/* Instruction slot (0, 1, or 2) in the 128-bit instruction word */
uint32_t slot;
/* Bitwise offset of the instruction indicated by slot */
uint32_t bit_pos;
/* bit_pos split into byte and bit parts */
uint32_t byte_pos;
uint32_t bit_res;
/* Address part of an instruction */
uint32_t addr;
/* Mask used to detect which instructions to convert */
uint32_t mask;
/* 41-bit instruction stored somewhere in the lowest 48 bits */
uint64_t instr;
/* Instruction normalized with bit_res for easier manipulation */
uint64_t norm;
for (i = 0; i + 16 <= size; i += 16) {
mask = branch_table[buf[i] & 0x1F];
for (slot = 0, bit_pos = 5; slot < 3; ++slot, bit_pos += 41) {
if (((mask >> slot) & 1) == 0)
continue;
byte_pos = bit_pos >> 3;
bit_res = bit_pos & 7;
instr = 0;
for (j = 0; j < 6; ++j)
instr |= (uint64_t)(buf[i + j + byte_pos])
<< (8 * j);
norm = instr >> bit_res;
if (((norm >> 37) & 0x0F) == 0x05
&& ((norm >> 9) & 0x07) == 0) {
addr = (norm >> 13) & 0x0FFFFF;
addr |= ((uint32_t)(norm >> 36) & 1) << 20;
addr <<= 4;
addr -= s->pos + (uint32_t)i;
addr >>= 4;
norm &= ~((uint64_t)0x8FFFFF << 13);
norm |= (uint64_t)(addr & 0x0FFFFF) << 13;
norm |= (uint64_t)(addr & 0x100000)
<< (36 - 20);
instr &= (1 << bit_res) - 1;
instr |= norm << bit_res;
for (j = 0; j < 6; j++)
buf[i + j + byte_pos]
= (uint8_t)(instr >> (8 * j));
}
}
}
return i;
}
#endif
#ifdef XZ_DEC_ARM
static size_t bcj_arm(struct xz_dec_bcj *s, uint8_t *buf, size_t size)
{
size_t i;
uint32_t addr;
for (i = 0; i + 4 <= size; i += 4) {
if (buf[i + 3] == 0xEB) {
addr = (uint32_t)buf[i] | ((uint32_t)buf[i + 1] << 8)
| ((uint32_t)buf[i + 2] << 16);
addr <<= 2;
addr -= s->pos + (uint32_t)i + 8;
addr >>= 2;
buf[i] = (uint8_t)addr;
buf[i + 1] = (uint8_t)(addr >> 8);
buf[i + 2] = (uint8_t)(addr >> 16);
}
}
return i;
}
#endif
#ifdef XZ_DEC_ARMTHUMB
static size_t bcj_armthumb(struct xz_dec_bcj *s, uint8_t *buf, size_t size)
{
size_t i;
uint32_t addr;
for (i = 0; i + 4 <= size; i += 2) {
if ((buf[i + 1] & 0xF8) == 0xF0
&& (buf[i + 3] & 0xF8) == 0xF8) {
addr = (((uint32_t)buf[i + 1] & 0x07) << 19)
| ((uint32_t)buf[i] << 11)
| (((uint32_t)buf[i + 3] & 0x07) << 8)
| (uint32_t)buf[i + 2];
addr <<= 1;
addr -= s->pos + (uint32_t)i + 4;
addr >>= 1;
buf[i + 1] = (uint8_t)(0xF0 | ((addr >> 19) & 0x07));
buf[i] = (uint8_t)(addr >> 11);
buf[i + 3] = (uint8_t)(0xF8 | ((addr >> 8) & 0x07));
buf[i + 2] = (uint8_t)addr;
i += 2;
}
}
return i;
}
#endif
#ifdef XZ_DEC_SPARC
static size_t bcj_sparc(struct xz_dec_bcj *s, uint8_t *buf, size_t size)
{
size_t i;
uint32_t instr;
for (i = 0; i + 4 <= size; i += 4) {
instr = get_unaligned_be32(buf + i);
if ((instr >> 22) == 0x100 || (instr >> 22) == 0x1FF) {
instr <<= 2;
instr -= s->pos + (uint32_t)i;
instr >>= 2;
instr = ((uint32_t)0x40000000 - (instr & 0x400000))
| 0x40000000 | (instr & 0x3FFFFF);
put_unaligned_be32(instr, buf + i);
}
}
return i;
}
#endif
/*
* Apply the selected BCJ filter. Update *pos and s->pos to match the amount
* of data that got filtered.
*
* NOTE: This is implemented as a switch statement to avoid using function
* pointers, which could be problematic in the kernel boot code, which must
* avoid pointers to static data (at least on x86).
*/
static void bcj_apply(struct xz_dec_bcj *s,
uint8_t *buf, size_t *pos, size_t size)
{
size_t filtered;
buf += *pos;
size -= *pos;
switch (s->type) {
#ifdef XZ_DEC_X86
case BCJ_X86:
filtered = bcj_x86(s, buf, size);
break;
#endif
#ifdef XZ_DEC_POWERPC
case BCJ_POWERPC:
filtered = bcj_powerpc(s, buf, size);
break;
#endif
#ifdef XZ_DEC_IA64
case BCJ_IA64:
filtered = bcj_ia64(s, buf, size);
break;
#endif
#ifdef XZ_DEC_ARM
case BCJ_ARM:
filtered = bcj_arm(s, buf, size);
break;
#endif
#ifdef XZ_DEC_ARMTHUMB
case BCJ_ARMTHUMB:
filtered = bcj_armthumb(s, buf, size);
break;
#endif
#ifdef XZ_DEC_SPARC
case BCJ_SPARC:
filtered = bcj_sparc(s, buf, size);
break;
#endif
default:
/* Never reached but silence compiler warnings. */
filtered = 0;
break;
}
*pos += filtered;
s->pos += filtered;
}
/*
* Flush pending filtered data from temp to the output buffer.
* Move the remaining mixture of possibly filtered and unfiltered
* data to the beginning of temp.
*/
static void bcj_flush(struct xz_dec_bcj *s, struct xz_buf *b)
{
size_t copy_size;
copy_size = min_t(size_t, s->temp.filtered, b->out_size - b->out_pos);
memcpy(b->out + b->out_pos, s->temp.buf, copy_size);
b->out_pos += copy_size;
s->temp.filtered -= copy_size;
s->temp.size -= copy_size;
memmove(s->temp.buf, s->temp.buf + copy_size, s->temp.size);
}
/*
* The BCJ filter functions are primitive in sense that they process the
* data in chunks of 1-16 bytes. To hide this issue, this function does
* some buffering.
*/
XZ_EXTERN enum xz_ret xz_dec_bcj_run(struct xz_dec_bcj *s,
struct xz_dec_lzma2 *lzma2,
struct xz_buf *b)
{
size_t out_start;
/*
* Flush pending already filtered data to the output buffer. Return
* immediatelly if we couldn't flush everything, or if the next
* filter in the chain had already returned XZ_STREAM_END.
*/
if (s->temp.filtered > 0) {
bcj_flush(s, b);
if (s->temp.filtered > 0)
return XZ_OK;
if (s->ret == XZ_STREAM_END)
return XZ_STREAM_END;
}
/*
* If we have more output space than what is currently pending in
* temp, copy the unfiltered data from temp to the output buffer
* and try to fill the output buffer by decoding more data from the
* next filter in the chain. Apply the BCJ filter on the new data
* in the output buffer. If everything cannot be filtered, copy it
* to temp and rewind the output buffer position accordingly.
*
* This needs to be always run when temp.size == 0 to handle a special
* case where the output buffer is full and the next filter has no
* more output coming but hasn't returned XZ_STREAM_END yet.
*/
if (s->temp.size < b->out_size - b->out_pos || s->temp.size == 0) {
out_start = b->out_pos;
memcpy(b->out + b->out_pos, s->temp.buf, s->temp.size);
b->out_pos += s->temp.size;
s->ret = xz_dec_lzma2_run(lzma2, b);
if (s->ret != XZ_STREAM_END
&& (s->ret != XZ_OK || s->single_call))
return s->ret;
bcj_apply(s, b->out, &out_start, b->out_pos);
/*
* As an exception, if the next filter returned XZ_STREAM_END,
* we can do that too, since the last few bytes that remain
* unfiltered are meant to remain unfiltered.
*/
if (s->ret == XZ_STREAM_END)
return XZ_STREAM_END;
s->temp.size = b->out_pos - out_start;
b->out_pos -= s->temp.size;
memcpy(s->temp.buf, b->out + b->out_pos, s->temp.size);
/*
* If there wasn't enough input to the next filter to fill
* the output buffer with unfiltered data, there's no point
* to try decoding more data to temp.
*/
if (b->out_pos + s->temp.size < b->out_size)
return XZ_OK;
}
/*
* We have unfiltered data in temp. If the output buffer isn't full
* yet, try to fill the temp buffer by decoding more data from the
* next filter. Apply the BCJ filter on temp. Then we hopefully can
* fill the actual output buffer by copying filtered data from temp.
* A mix of filtered and unfiltered data may be left in temp; it will
* be taken care on the next call to this function.
*/
if (b->out_pos < b->out_size) {
/* Make b->out{,_pos,_size} temporarily point to s->temp. */
s->out = b->out;
s->out_pos = b->out_pos;
s->out_size = b->out_size;
b->out = s->temp.buf;
b->out_pos = s->temp.size;
b->out_size = sizeof(s->temp.buf);
s->ret = xz_dec_lzma2_run(lzma2, b);
s->temp.size = b->out_pos;
b->out = s->out;
b->out_pos = s->out_pos;
b->out_size = s->out_size;
if (s->ret != XZ_OK && s->ret != XZ_STREAM_END)
return s->ret;
bcj_apply(s, s->temp.buf, &s->temp.filtered, s->temp.size);
/*
* If the next filter returned XZ_STREAM_END, we mark that
* everything is filtered, since the last unfiltered bytes
* of the stream are meant to be left as is.
*/
if (s->ret == XZ_STREAM_END)
s->temp.filtered = s->temp.size;
bcj_flush(s, b);
if (s->temp.filtered > 0)
return XZ_OK;
}
return s->ret;
}
XZ_EXTERN struct xz_dec_bcj *xz_dec_bcj_create(bool single_call)
{
struct xz_dec_bcj *s = kmalloc(sizeof(*s), GFP_KERNEL);
if (s != NULL)
s->single_call = single_call;
return s;
}
XZ_EXTERN enum xz_ret xz_dec_bcj_reset(struct xz_dec_bcj *s, uint8_t id)
{
switch (id) {
#ifdef XZ_DEC_X86
case BCJ_X86:
#endif
#ifdef XZ_DEC_POWERPC
case BCJ_POWERPC:
#endif
#ifdef XZ_DEC_IA64
case BCJ_IA64:
#endif
#ifdef XZ_DEC_ARM
case BCJ_ARM:
#endif
#ifdef XZ_DEC_ARMTHUMB
case BCJ_ARMTHUMB:
#endif
#ifdef XZ_DEC_SPARC
case BCJ_SPARC:
#endif
break;
default:
/* Unsupported Filter ID */
return XZ_OPTIONS_ERROR;
}
s->type = id;
s->ret = XZ_OK;
s->pos = 0;
s->x86_prev_mask = 0;
s->temp.filtered = 0;
s->temp.size = 0;
return XZ_OK;
}
#endif