Re: [PATCH v3] mmc: dw_mmc: remove UBSAN warning in dw_mci_setup_bus()

[Jaehoon Chung]

Hi Seung-Woo,

On 06/20/2016 01:09 PM, Seung-Woo Kim wrote:
> This patch removes following UBSAN warnings in dw_mci_setup_bus().
> 
>   UBSAN: Undefined behaviour in drivers/mmc/host/dw_mmc.c:1102:14
>   shift exponent 250 is too large for 32-bit type 'unsigned int'
>   Call trace:
>   [<ffffff90080908a8>] dump_backtrace+0x0/0x380
>   [<ffffff9008090c3c>] show_stack+0x14/0x20
>   [<ffffff90087457b8>] dump_stack+0xe0/0x120
>   [<ffffff90087b1360>] ubsan_epilogue+0x18/0x68
>   [<ffffff90087b1a94>] __ubsan_handle_shift_out_of_bounds+0x18c/0x1bc
>   [<ffffff9008d89cb8>] dw_mci_setup_bus+0x3a0/0x438
>   [...]
> 
>   UBSAN: Undefined behaviour in drivers/mmc/host/dw_mmc.c:1132:27
>   shift exponent 250 is too large for 32-bit type 'unsigned int'
>   Call trace:
>   [<ffffff90080908a8>] dump_backtrace+0x0/0x380
>   [<ffffff9008090c3c>] show_stack+0x14/0x20
>   [<ffffff90087457b8>] dump_stack+0xe0/0x120
>   [<ffffff90087b1360>] ubsan_epilogue+0x18/0x68
>   [<ffffff90087b1a94>] __ubsan_handle_shift_out_of_bounds+0x18c/0x1bc
>   [<ffffff9008d89c9c>] dw_mci_setup_bus+0x384/0x438
>   [...]
> 
> The warnings are caused because of bit shift which is used to
> filter spamming message for CONFIG_MMC_CLKGATE, but the config is
> already removed. So this patch just removes the shift.
> 
> Signed-off-by: Seung-Woo Kim <sw0312.kim@xxxxxxxxxxx>

Applied this patch on my repository.
Thanks!

Best Regards,
Jaehoon Chung

> ---
>  drivers/mmc/host/dw_mmc.c |   14 +++++---------
>  drivers/mmc/host/dw_mmc.h |    4 ----
>  2 files changed, 5 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
> index 2cc6123..bada11e 100644
> --- a/drivers/mmc/host/dw_mmc.c
> +++ b/drivers/mmc/host/dw_mmc.c
> @@ -1099,12 +1099,11 @@ static void dw_mci_setup_bus(struct dw_mci_slot *slot, bool force_clkinit)
>  
>  		div = (host->bus_hz != clock) ? DIV_ROUND_UP(div, 2) : 0;
>  
> -		if ((clock << div) != slot->__clk_old || force_clkinit)
> -			dev_info(&slot->mmc->class_dev,
> -				 "Bus speed (slot %d) = %dHz (slot req %dHz, actual %dHZ div = %d)\n",
> -				 slot->id, host->bus_hz, clock,
> -				 div ? ((host->bus_hz / div) >> 1) :
> -				 host->bus_hz, div);
> +		dev_info(&slot->mmc->class_dev,
> +			 "Bus speed (slot %d) = %dHz (slot req %dHz, actual %dHZ div = %d)\n",
> +			 slot->id, host->bus_hz, clock,
> +			 div ? ((host->bus_hz / div) >> 1) :
> +			 host->bus_hz, div);
>  
>  		/* disable clock */
>  		mci_writel(host, CLKENA, 0);
> @@ -1127,9 +1126,6 @@ static void dw_mci_setup_bus(struct dw_mci_slot *slot, bool force_clkinit)
>  
>  		/* inform CIU */
>  		mci_send_cmd(slot, sdmmc_cmd_bits, 0);
> -
> -		/* keep the clock with reflecting clock dividor */
> -		slot->__clk_old = clock << div;
>  	}
>  
>  	host->current_speed = clock;
> diff --git a/drivers/mmc/host/dw_mmc.h b/drivers/mmc/host/dw_mmc.h
> index 1e8d838..5961037 100644
> --- a/drivers/mmc/host/dw_mmc.h
> +++ b/drivers/mmc/host/dw_mmc.h
> @@ -245,9 +245,6 @@ extern int dw_mci_resume(struct dw_mci *host);
>   * @queue_node: List node for placing this node in the @queue list of
>   *	&struct dw_mci.
>   * @clock: Clock rate configured by set_ios(). Protected by host->lock.
> - * @__clk_old: The last updated clock with reflecting clock divider.
> - *	Keeping track of this helps us to avoid spamming the console
> - *	with CONFIG_MMC_CLKGATE.
>   * @flags: Random state bits associated with the slot.
>   * @id: Number of this slot.
>   * @sdio_id: Number of this slot in the SDIO interrupt registers.
> @@ -262,7 +259,6 @@ struct dw_mci_slot {
>  	struct list_head	queue_node;
>  
>  	unsigned int		clock;
> -	unsigned int		__clk_old;
>  
>  	unsigned long		flags;
>  #define DW_MMC_CARD_PRESENT	0
>