[fs/squashfs PATCH v3 2/2] avoid 64-bit divisions on 32-bit

[Mauro Condarelli]

Use macros in linux/kernel.h 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.

Some 32bit architectures (notably mipsel) lack an implementation of
__udivdi3() compiler helper function in reduced libgcc.

Standard strategy is to use macros and do_div() inline.

Signed-off-by: Mauro Condarelli <mc5686 at mclink.it>
---

Changes in v3:
- converted to use DIV_ROUND_(UP|DOWN)_ULL() macros (Miquel Raynal).
- split commits to handle unrelated Kconfig warning (Thomas Petazzoni).

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/sqfs.c       | 32 ++++++++++++++++----------------
 fs/squashfs/sqfs_inode.c |  7 ++++---
 2 files changed, 20 insertions(+), 19 deletions(-)

diff --git a/fs/squashfs/sqfs.c b/fs/squashfs/sqfs.c
index 15208b4dab..ef9f5e3449 100644
--- a/fs/squashfs/sqfs.c
+++ b/fs/squashfs/sqfs.c
@@ -10,14 +10,14 @@
 #include <asm/unaligned.h>
 #include <errno.h>
 #include <fs.h>
-#include <linux/types.h>
+#include <linux/kernel.h>
+#include <div64.h>
 #include <linux/byteorder/little_endian.h>
 #include <linux/byteorder/generic.h>
 #include <memalign.h>
 #include <stdlib.h>
 #include <string.h>
 #include <squashfs.h>
-#include <part.h>
 
 #include "sqfs_decompressor.h"
 #include "sqfs_filesystem.h"
@@ -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;
+	start_ = DIV_ROUND_DOWN_ULL(le64_to_cpu(start), ctxt.cur_dev->blksz);
 	*offset = le64_to_cpu(start) - (start_ * ctxt.cur_dev->blksz);
 
-	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 = DIV_ROUND_DOWN_ULL(get_unaligned_le64(&sblk->fragment_table_start),
+				   ctxt.cur_dev->blksz);
 	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 = DIV_ROUND_DOWN_ULL(start_block, ctxt.cur_dev->blksz);
 	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 = DIV_ROUND_DOWN_ULL(get_unaligned_le64(&sblk->inode_table_start),
+				   ctxt.cur_dev->blksz);
 	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 = DIV_ROUND_DOWN_ULL(get_unaligned_le64(&sblk->directory_table_start),
+				   ctxt.cur_dev->blksz);
 	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 = DIV_ROUND_DOWN_ULL(data_offset, ctxt.cur_dev->blksz);
 		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 = DIV_ROUND_UP_ULL(table_size + table_offset,
+					  ctxt.cur_dev->blksz);
 
 		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 = DIV_ROUND_DOWN_ULL(frag_entry.start, ctxt.cur_dev->blksz);
 	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 = DIV_ROUND_UP_ULL(table_size + table_offset, ctxt.cur_dev->blksz);
 
 	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 14d70cf678..43cd516468 100644
--- a/fs/squashfs/sqfs_inode.c
+++ b/fs/squashfs/sqfs_inode.c
@@ -10,7 +10,8 @@
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
-#include <string.h>
+#include <div64.h>
+#include <linux/kernel.h>
 
 #include "sqfs_decompressor.h"
 #include "sqfs_filesystem.h"
@@ -68,9 +69,9 @@ 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 = DIV_ROUND_UP_ULL(file_size, blk_size);
 		else
-			blk_list_size = file_size / blk_size;
+			blk_list_size = DIV_ROUND_DOWN_ULL(file_size, blk_size);
 
 		return sizeof(*lreg) + blk_list_size * sizeof(u32);
 	}
-- 
2.25.1