[RFC PATCH v2 1/1] Fix missing __udivdi3 in SquashFS implementation.
Daniel Schwierzeck
daniel.schwierzeck at gmail.com
Wed Sep 30 23:40:07 CEST 2020
Am Mittwoch, den 30.09.2020, 17:45 +0200 schrieb Mauro Condarelli:
> Use right shift to avoid 64-bit divisions.
>
> These divisions are needed to convert from file length (potentially
> over 32-bit range) to block number, so result and remainder are
> guaranteed to fit in 32-bit integers.
>
> Signed-off-by: Mauro Condarelli <mc5686 at mclink.it>
the commit subject needs to be fixed. If you change a specific
subsystem, you need to add the according prefix. You can use the Git
log to figure out that prefix. Also you don't fix a missing __udivdi3 ,
you just want to avoid 64-bit divisions.
So maybe something like: "fs/squashfs: avoid 64-bit divisions on 32-bit
systems"
> ---
>
> Changes in v2:
> - replace division with right shift (Daniel Schwierzeck).
> - remove vocore2-specific change (Daniel Schwierzeck).
> - add warning to Kconfig about CONFIG_SYS_MALLOC_LEN (Tom Rini).
>
> fs/squashfs/Kconfig | 2 ++
> fs/squashfs/sqfs.c | 30 +++++++++++++++---------------
> fs/squashfs/sqfs_inode.c | 6 +++---
> 3 files changed, 20 insertions(+), 18 deletions(-)
>
> diff --git a/fs/squashfs/Kconfig b/fs/squashfs/Kconfig
> index 54ab1618f1..7c3f83d007 100644
> --- a/fs/squashfs/Kconfig
> +++ b/fs/squashfs/Kconfig
> @@ -9,3 +9,5 @@ config FS_SQUASHFS
> filesystem use, for archival use (i.e. in cases where a .tar.gz file
> may be used), and in constrained block device/memory systems (e.g.
> embedded systems) where low overhead is needed.
> + WARNING: if compression is enabled SquashFS needs a large amount
> + of dynamic memory; make sure CONFIG_SYS_MALLOC_LEN >= 0x4000.
> diff --git a/fs/squashfs/sqfs.c b/fs/squashfs/sqfs.c
> index 15208b4dab..90e6848e6c 100644
> --- a/fs/squashfs/sqfs.c
> +++ b/fs/squashfs/sqfs.c
> @@ -85,10 +85,10 @@ static int sqfs_calc_n_blks(__le64 start, __le64 end, u64 *offset)
> u64 start_, table_size;
>
> table_size = le64_to_cpu(end) - le64_to_cpu(start);
> - start_ = le64_to_cpu(start) / ctxt.cur_dev->blksz;
> - *offset = le64_to_cpu(start) - (start_ * ctxt.cur_dev->blksz);
> + start_ = le64_to_cpu(start) >> ctxt.cur_dev->log2blksz;
> + *offset = le64_to_cpu(start) - (start_ << ctxt.cur_dev->log2blksz);
>
> - return DIV_ROUND_UP(table_size + *offset, ctxt.cur_dev->blksz);
> + return (table_size + *offset + ctxt.cur_dev->blksz - 1) >> ctxt.cur_dev->log2blksz;
> }
>
> /*
> @@ -109,8 +109,8 @@ static int sqfs_frag_lookup(u32 inode_fragment_index,
> if (inode_fragment_index >= get_unaligned_le32(&sblk->fragments))
> return -EINVAL;
>
> - start = get_unaligned_le64(&sblk->fragment_table_start) /
> - ctxt.cur_dev->blksz;
> + start = get_unaligned_le64(&sblk->fragment_table_start) >>
> + ctxt.cur_dev->log2blksz;
> n_blks = sqfs_calc_n_blks(sblk->fragment_table_start,
> sblk->export_table_start,
> &table_offset);
> @@ -135,7 +135,7 @@ static int sqfs_frag_lookup(u32 inode_fragment_index,
> start_block = get_unaligned_le64(table + table_offset + block *
> sizeof(u64));
>
> - start = start_block / ctxt.cur_dev->blksz;
> + start = start_block >> ctxt.cur_dev->log2blksz;
> n_blks = sqfs_calc_n_blks(cpu_to_le64(start_block),
> sblk->fragment_table_start, &table_offset);
>
> @@ -641,8 +641,8 @@ static int sqfs_read_inode_table(unsigned char **inode_table)
>
> table_size = get_unaligned_le64(&sblk->directory_table_start) -
> get_unaligned_le64(&sblk->inode_table_start);
> - start = get_unaligned_le64(&sblk->inode_table_start) /
> - ctxt.cur_dev->blksz;
> + start = get_unaligned_le64(&sblk->inode_table_start) >>
> + ctxt.cur_dev->log2blksz;
> n_blks = sqfs_calc_n_blks(sblk->inode_table_start,
> sblk->directory_table_start, &table_offset);
>
> @@ -725,8 +725,8 @@ static int sqfs_read_directory_table(unsigned char **dir_table, u32 **pos_list)
> /* DIRECTORY TABLE */
> table_size = get_unaligned_le64(&sblk->fragment_table_start) -
> get_unaligned_le64(&sblk->directory_table_start);
> - start = get_unaligned_le64(&sblk->directory_table_start) /
> - ctxt.cur_dev->blksz;
> + start = get_unaligned_le64(&sblk->directory_table_start) >>
> + ctxt.cur_dev->log2blksz;
> n_blks = sqfs_calc_n_blks(sblk->directory_table_start,
> sblk->fragment_table_start, &table_offset);
>
> @@ -1334,11 +1334,11 @@ int sqfs_read(const char *filename, void *buf, loff_t offset, loff_t len,
> }
>
> for (j = 0; j < datablk_count; j++) {
> - start = data_offset / ctxt.cur_dev->blksz;
> + start = data_offset >> ctxt.cur_dev->log2blksz;
> table_size = SQFS_BLOCK_SIZE(finfo.blk_sizes[j]);
> table_offset = data_offset - (start * ctxt.cur_dev->blksz);
> - n_blks = DIV_ROUND_UP(table_size + table_offset,
> - ctxt.cur_dev->blksz);
> + n_blks = (table_size + table_offset + ctxt.cur_dev->blksz - 1) >>
> + ctxt.cur_dev->log2blksz;
>
> data_buffer = malloc_cache_aligned(n_blks * ctxt.cur_dev->blksz);
>
> @@ -1388,10 +1388,10 @@ int sqfs_read(const char *filename, void *buf, loff_t offset, loff_t len,
> goto free_buffer;
> }
>
> - start = frag_entry.start / ctxt.cur_dev->blksz;
> + start = frag_entry.start >> ctxt.cur_dev->log2blksz;
> table_size = SQFS_BLOCK_SIZE(frag_entry.size);
> table_offset = frag_entry.start - (start * ctxt.cur_dev->blksz);
> - n_blks = DIV_ROUND_UP(table_size + table_offset, ctxt.cur_dev->blksz);
> + n_blks = (table_size + table_offset + ctxt.cur_dev->blksz - 1) >> ctxt.cur_dev->log2blksz;
>
> fragment = malloc_cache_aligned(n_blks * ctxt.cur_dev->blksz);
>
> diff --git a/fs/squashfs/sqfs_inode.c b/fs/squashfs/sqfs_inode.c
> index 1368f3063c..5dbf945c80 100644
> --- a/fs/squashfs/sqfs_inode.c
> +++ b/fs/squashfs/sqfs_inode.c
> @@ -10,7 +10,7 @@
> #include <stdint.h>
> #include <stdio.h>
> #include <stdlib.h>
> -#include <string.h>
> +#include <part.h>
>
> #include "sqfs_decompressor.h"
> #include "sqfs_filesystem.h"
> @@ -68,9 +68,9 @@ int sqfs_inode_size(struct squashfs_base_inode *inode, u32 blk_size)
> unsigned int blk_list_size;
>
> if (fragment == 0xFFFFFFFF)
> - blk_list_size = DIV_ROUND_UP(file_size, blk_size);
> + blk_list_size = (file_size + blk_size - 1) >> LOG2(blk_size);
> else
> - blk_list_size = file_size / blk_size;
> + blk_list_size = file_size > LOG2(blk_size);
one > is missing:
blk_list_size = file_size >> LOG2(blk_size);
>
> return sizeof(*lreg) + blk_list_size * sizeof(u32);
> }
--
- Daniel
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