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Thu, 12 May 2022 12:24:01 +0200 (CEST) Date: Thu, 12 May 2022 12:24:01 +0200 From: Pali =?utf-8?B?Um9ow6Fy?= To: Miquel Raynal Cc: Tom Rini , Sean Nyekjaer , Joao Marcos Costa , Thomas Petazzoni , u-boot@lists.denx.de, Sean Nyekjaer Subject: Re: [PATCH] fs/squashfs: use do_div function for math Message-ID: <20220512102401.3zcyvcek6nytxc7d@pali> References: <20220505092637.1856223-1-sean@geanix.com> <20220505131500.GF3580959@bill-the-cat> <20220509150815.43d7543c@xps13> <20220512101901.egbghfpf76f23tfs@pali> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20220512101901.egbghfpf76f23tfs@pali> User-Agent: NeoMutt/20180716 X-BeenThere: u-boot@lists.denx.de X-Mailman-Version: 2.1.39 Precedence: list List-Id: U-Boot discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: u-boot-bounces@lists.denx.de Sender: "U-Boot" X-Virus-Scanned: clamav-milter 0.103.5 at phobos.denx.de X-Virus-Status: Clean On Thursday 12 May 2022 12:19:01 Pali Rohár wrote: > On Monday 09 May 2022 15:08:15 Miquel Raynal wrote: > > Hello, > > > > trini@konsulko.com wrote on Thu, 5 May 2022 09:15:00 -0400: > > > > > On Thu, May 05, 2022 at 11:26:37AM +0200, Sean Nyekjaer wrote: > > > > > > > From: Sean Nyekjaer > > > > > > > > When compling for x86: > > > > ld.bfd: fs/squashfs/sqfs.o: in function `sqfs_read': > > > > u-boot/fs/squashfs/sqfs.c:1443: undefined reference to `__udivmoddi4' > > > > ld.bfd: u-boot/fs/squashfs/sqfs.c:1521: undefined reference to `__udivmoddi4' > > > > > > > > Signed-off-by: Sean Nyekjaer > > > > --- > > > > fs/squashfs/sqfs.c | 5 +++-- > > > > 1 file changed, 3 insertions(+), 2 deletions(-) > > > > > > > > diff --git a/fs/squashfs/sqfs.c b/fs/squashfs/sqfs.c > > > > index 5d9c52af80..6405db4ff3 100644 > > > > --- a/fs/squashfs/sqfs.c > > > > +++ b/fs/squashfs/sqfs.c > > > > @@ -8,6 +8,7 @@ > > > > */ > > > > > > > > #include > > > > +#include > > > > #include > > > > #include > > > > #include > > > > @@ -1440,7 +1441,7 @@ 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 = do_div(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, > > > > @@ -1516,7 +1517,7 @@ int sqfs_read(const char *filename, void *buf, loff_t offset, loff_t len, > > > > goto out; > > > > } > > > > > > > > - start = frag_entry.start / ctxt.cur_dev->blksz; > > > > + start = do_div(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); > > > > > > Adding maintainers... > > > > I guess that's a correct fix, so > > > > Reviewed-by: Miquel Raynal > > > > Thanks, > > Miquèl > > Hello! do_div() macro modifies its first argument. It is correct? > Because previous code did not modify anything. * The semantics of do_div() are: * * u32 do_div(u64 *n, u32 base) * { * u32 remainder = *n % base; * *n = *n / base; * return remainder; * } And this patch replaced: start = data_offset / ctxt.cur_dev->blksz; by: start = do_div(data_offset, ctxt.cur_dev->blksz); which expands to: start = data_offset % ctxt.cur_dev->blksz; data_offset = data_offset / ctxt.cur_dev->blksz; Which is wrong as it calculates something totally different. So this patch is incorrect.