c42a384709
Make expand_buffer() a non-inline function, so that we can add debug messages. Expandable buffers now don't *always* round up to the next power of two. This allows e.g. loading a 137MB ISO image on a machine with only 256MB RAM...
266 lines
8.6 KiB
C
266 lines
8.6 KiB
C
/*
|
|
* Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>.
|
|
*
|
|
* This program is free software; you can redistribute it and/or
|
|
* modify it under the terms of the GNU General Public License as
|
|
* published by the Free Software Foundation; either version 2 of the
|
|
* License, or any later version.
|
|
*
|
|
* This program is distributed in the hope that it will be useful, but
|
|
* WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
* General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU General Public License
|
|
* along with this program; if not, write to the Free Software
|
|
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
|
|
*/
|
|
|
|
#include <stddef.h>
|
|
#include <string.h>
|
|
#include <errno.h>
|
|
#include <assert.h>
|
|
#include <gpxe/uaccess.h>
|
|
#include <gpxe/buffer.h>
|
|
|
|
/** @file
|
|
*
|
|
* Buffer internals.
|
|
*
|
|
* A buffer consists of a single, contiguous area of memory, some of
|
|
* which is "filled" and the remainder of which is "free". The
|
|
* "filled" and "free" spaces are not necessarily contiguous.
|
|
*
|
|
* At the start of a buffer's life, it consists of a single free
|
|
* space. As data is added to the buffer via fill_buffer(), this free
|
|
* space decreases and can become fragmented.
|
|
*
|
|
* Each free block within a buffer (except the last) starts with a @c
|
|
* struct @c buffer_free_block. This describes the size of the free
|
|
* block, and the offset to the next free block.
|
|
*
|
|
* We cannot simply start every free block (including the last) with a
|
|
* descriptor, because it is conceivable that we will, at some point,
|
|
* encounter a situation in which the final free block of a buffer is
|
|
* too small to contain a descriptor. Consider a protocol with a
|
|
* blocksize of 512 downloading a 1025-byte file into a 1025-byte
|
|
* buffer. Suppose that the first two blocks are received; we have
|
|
* now filled 1024 of the 1025 bytes in the buffer, and our only free
|
|
* block consists of the 1025th byte.
|
|
*
|
|
* Note that the rather convoluted way of manipulating the buffer
|
|
* descriptors (using copy_{to,from}_user rather than straightforward
|
|
* pointers) is needed to cope with operation as a PXE stack, when we
|
|
* may be running in real mode or 16-bit protected mode, and therefore
|
|
* cannot directly access arbitrary areas of memory using simple
|
|
* pointers.
|
|
*
|
|
*/
|
|
|
|
/**
|
|
* A free block descriptor
|
|
*
|
|
* This is the data structure that is found at the start of a free
|
|
* block within a data buffer.
|
|
*/
|
|
struct buffer_free_block {
|
|
/** Starting offset of the free block */
|
|
size_t start;
|
|
/** Ending offset of the free block */
|
|
size_t end;
|
|
/** Offset of next free block */
|
|
size_t next;
|
|
};
|
|
|
|
/**
|
|
* Get next free block within the buffer
|
|
*
|
|
* @v buffer Data buffer
|
|
* @v block Previous free block descriptor
|
|
* @ret block Next free block descriptor
|
|
* @ret rc Return status code
|
|
*
|
|
* Set @c block->next=buffer->fill before first call to
|
|
* get_next_free_block().
|
|
*/
|
|
static int get_next_free_block ( struct buffer *buffer,
|
|
struct buffer_free_block *block ) {
|
|
|
|
/* Check for end of buffer */
|
|
if ( block->next >= buffer->len )
|
|
return -ENOENT;
|
|
|
|
/* Move to next block */
|
|
block->start = block->next;
|
|
if ( block->start >= buffer->free ) {
|
|
/* Final block; no in-band descriptor */
|
|
block->next = block->end = buffer->len;
|
|
} else {
|
|
/* Retrieve block descriptor */
|
|
copy_from_user ( block, buffer->addr, block->start,
|
|
sizeof ( *block ) );
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* Write free block descriptor back to buffer
|
|
*
|
|
* @v buffer Data buffer
|
|
* @v block Free block descriptor
|
|
*/
|
|
static void store_free_block ( struct buffer *buffer,
|
|
struct buffer_free_block *block ) {
|
|
size_t free_block_size = ( block->end - block->start );
|
|
|
|
assert ( free_block_size >= sizeof ( *block ) );
|
|
copy_to_user ( buffer->addr, block->start, block, sizeof ( *block ) );
|
|
}
|
|
|
|
/**
|
|
* Write data into a buffer
|
|
*
|
|
* @v buffer Data buffer
|
|
* @v data Data to be written
|
|
* @v offset Offset within the buffer at which to write the data
|
|
* @v len Length of data to be written
|
|
* @ret rc Return status code
|
|
*
|
|
* Writes a block of data into the buffer. The block need not be
|
|
* aligned to any particular boundary, or be of any particular size,
|
|
* and it may overlap blocks already in the buffer (i.e. duplicate
|
|
* calls to fill_buffer() are explicitly permitted).
|
|
*
|
|
* @c buffer->fill will be updated to indicate the fill level of the
|
|
* buffer, i.e. the offset to the first gap within the buffer. If the
|
|
* filesize is known (e.g. as with the SLAM protocol), you can test
|
|
* for end-of-file by checking for @c buffer->fill==filesize. If the
|
|
* filesize is not known, but there is a well-defined end-of-file test
|
|
* (e.g. as with the TFTP protocol), you can read @c buffer->fill to
|
|
* determine the final filesize. If blocks are known to be delivered
|
|
* in a strictly sequential order with no packet loss or duplication,
|
|
* then you can pass in @c offset==buffer->fill.
|
|
*
|
|
* @b NOTE: It is the caller's responsibility to ensure that the
|
|
* boundaries between data blocks are more than @c sizeof(struct @c
|
|
* buffer_free_block) apart. If this condition is not satisfied, data
|
|
* corruption will occur.
|
|
*
|
|
* In practice this is not a problem. Callers of fill_buffer() will
|
|
* be download protocols such as TFTP, and very few protocols have a
|
|
* block size smaller than @c sizeof(struct @c buffer_free_block).
|
|
*
|
|
*/
|
|
int fill_buffer ( struct buffer *buffer, const void *data,
|
|
size_t offset, size_t len ) {
|
|
struct buffer_free_block block, before, after;
|
|
size_t data_start = offset;
|
|
size_t data_end = ( data_start + len );
|
|
int rc;
|
|
|
|
DBGC2 ( buffer, "BUFFER %p [%lx,%lx) filling portion [%lx,%lx)\n",
|
|
buffer, user_to_phys ( buffer->addr, 0 ),
|
|
user_to_phys ( buffer->addr, buffer->len ),
|
|
user_to_phys ( buffer->addr, data_start ),
|
|
user_to_phys ( buffer->addr, data_end ) );
|
|
|
|
/* Check that block fits within buffer, expand if necessary */
|
|
if ( data_end > buffer->len ) {
|
|
if ( ( rc = expand_buffer ( buffer, data_end ) ) != 0 )
|
|
return rc;
|
|
assert ( buffer->len >= data_end );
|
|
}
|
|
|
|
/* Find 'before' and 'after' blocks, if any */
|
|
before.start = before.end = 0;
|
|
after.start = after.end = buffer->len;
|
|
block.next = buffer->fill;
|
|
while ( get_next_free_block ( buffer, &block ) == 0 ) {
|
|
if ( ( block.start < data_start ) &&
|
|
( block.start >= before.start ) )
|
|
memcpy ( &before, &block, sizeof ( before ) );
|
|
if ( ( block.end > data_end ) &&
|
|
( block.end <= after.end ) )
|
|
memcpy ( &after, &block, sizeof ( after ) );
|
|
}
|
|
|
|
/* Truncate 'before' and 'after' blocks around data. */
|
|
if ( data_start < before.end )
|
|
before.end = data_start;
|
|
if ( data_end > after.start )
|
|
after.start = data_end;
|
|
|
|
/* Link 'after' block to 'before' block */
|
|
before.next = after.start;
|
|
|
|
DBGC2 ( buffer, "BUFFER %p split before [%lx,%lx) after [%lx,%lx)\n",
|
|
buffer, user_to_phys ( buffer->addr, before.start ),
|
|
user_to_phys ( buffer->addr, before.end ),
|
|
user_to_phys ( buffer->addr, after.start ),
|
|
user_to_phys ( buffer->addr, after.end ) );
|
|
|
|
/* Write back 'before' block, if any */
|
|
if ( before.end == 0 ) {
|
|
/* No 'before' block: update buffer->fill */
|
|
buffer->fill = after.start;
|
|
DBGC2 ( buffer, "BUFFER %p full up to %lx\n", buffer,
|
|
user_to_phys ( buffer->addr, buffer->fill ) );
|
|
} else {
|
|
/* Write back 'before' block */
|
|
store_free_block ( buffer, &before );
|
|
}
|
|
|
|
/* Write back 'after' block */
|
|
if ( after.end == buffer->len ) {
|
|
/* 'After' block is the final block: update buffer->free */
|
|
buffer->free = after.start;
|
|
DBGC2 ( buffer, "BUFFER %p free from %lx onwards\n", buffer,
|
|
user_to_phys ( buffer->addr, buffer->free ) );
|
|
} else {
|
|
/* Write back 'after' block */
|
|
store_free_block ( buffer, &after );
|
|
}
|
|
|
|
/* Copy data into buffer */
|
|
copy_to_user ( buffer->addr, data_start, data, len );
|
|
|
|
return 0;
|
|
}
|
|
|
|
/** Expand data buffer
|
|
*
|
|
* @v buffer Data buffer
|
|
* @v new_len New length
|
|
* @ret rc Return status code
|
|
*
|
|
* Expand the data buffer to accommodate more data. Some buffers may
|
|
* not support being expanded.
|
|
*/
|
|
int expand_buffer ( struct buffer *buffer, size_t new_len ) {
|
|
int rc;
|
|
|
|
if ( new_len <= buffer->len )
|
|
return 0;
|
|
|
|
DBGC ( buffer, "BUFFER %p attempting to expand from length %zx to "
|
|
"length %zx\n", buffer, buffer->len, new_len );
|
|
|
|
if ( ! buffer->expand ) {
|
|
DBGC ( buffer, "BUFFER %p is not expandable\n", buffer );
|
|
return -ENOBUFS;
|
|
}
|
|
|
|
if ( ( rc = buffer->expand ( buffer, new_len ) ) != 0 ) {
|
|
DBGC ( buffer, "BUFFER %p could not expand: %s\n",
|
|
buffer, strerror ( rc ) );
|
|
return rc;
|
|
}
|
|
|
|
DBGC ( buffer, "BUFFER %p expanded to [%lx,%lx)\n", buffer,
|
|
user_to_phys ( buffer->addr, 0 ),
|
|
user_to_phys ( buffer->addr, buffer->len ) );
|
|
|
|
return 0;
|
|
}
|