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

Jaehoon Chung
2016-06-22T01:28:01Z

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@samsung.com>

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
>