Re: [PATCH] firmware: socfpga: Fix a bug in fpgamgr_program_write_buf()

[Sascha Hauer <s.hauer@pengutronix.de>]

Hi Andrey,

On Mon, Apr 13, 2015 at 05:11:50AM -0700, Andrey Smirnov wrote:
> Fix a bug in fpgamgr_program_write_buf() where .rbf file whose length
> is not a multiple of 4 would cause an integer overflow which would
> result in infinite loop.
> 
> Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
> ---
>  drivers/firmware/socfpga.c | 26 ++++++++++++++++++++++----
>  1 file changed, 22 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/firmware/socfpga.c b/drivers/firmware/socfpga.c
> index a5dc607..75fb050 100644
> --- a/drivers/firmware/socfpga.c
> +++ b/drivers/firmware/socfpga.c
> @@ -321,14 +321,32 @@ static int fpgamgr_program_write_buf(struct firmware_handler *fh, const void *bu
>  		size_t size)
>  {
>  	struct fpgamgr *mgr = container_of(fh, struct fpgamgr, fh);
> -	const uint32_t *buf32 = buf;
> +	const uint8_t *buffer = buf;
> +	uint32_t word;
> +	size_t chunk_size;
> +	size_t offset = 0;
>  
>  	/* write to FPGA Manager AXI data */
>  	while (size) {

This code probably looks better when you change this loop to
while (size >= sizeof(uint32_t)){} followed by a if (size) {}

> -		writel(*buf32, mgr->regs_data);
> +		chunk_size = min(size, sizeof(uint32_t));
> +		size -= chunk_size;
> +
> +		if (likely(chunk_size == sizeof(uint32_t))) {
> +			word = *(uint32_t *)(buffer + offset);
> +			offset += sizeof(uint32_t);
> +		} else {
> +			word = buffer[offset++];
> +			word <<= 8;
> +			chunk_size--;
> +
> +			while (chunk_size--) {
> +				word |= buffer[offset++];
> +				word <<= 8;
> +			}

Isn't this the same as:

			word = 0;
			while (chunk_size--) {
				word |= buffer[offset++];
				word <<= 8;
			}


Sascha

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