From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933310AbcFQBa7 (ORCPT ); Thu, 16 Jun 2016 21:30:59 -0400 Received: from mailout2.samsung.com ([203.254.224.25]:47512 "EHLO mailout2.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932818AbcFQBa4 (ORCPT ); Thu, 16 Jun 2016 21:30:56 -0400 MIME-version: 1.0 Content-type: text/plain; charset=utf-8 X-AuditID: cbfee690-f79056d000001327-bb-576352cc300c Content-transfer-encoding: 8BIT Message-id: <576352CA.3080605@samsung.com> Date: Fri, 17 Jun 2016 10:30:50 +0900 From: Jaehoon Chung User-Agent: Mozilla/5.0 (X11; Linux i686; rv:31.0) Gecko/20100101 Thunderbird/31.6.0 To: sw0312.kim@samsung.com Cc: ulf.hansson@linaro.org, linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mmc: dw_mmc: remove UBSAN warning in dw_mci_setup_bus() References: <1465358840-22826-1-git-send-email-sw0312.kim@samsung.com> 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linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Seung-Woo, On 06/10/2016 10:29 AM, Seung-Woo Kim wrote: > Hi Jaehoon, > > On 2016년 06월 09일 21:38, Jaehoon Chung wrote: >> Hi Seung-Woo, >> >> On 06/08/2016 01:07 PM, Seung-Woo Kim wrote: >>> This patch removes following UBSAN warnings in dw_mci_setup_bus(). >>> The warnings are caused because of shift with more than 31 on 32 >>> bit variable, so this patch fixes to shift only for less than 32. >>> >>> 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: >>> [] dump_backtrace+0x0/0x380 >>> [] show_stack+0x14/0x20 >>> [] dump_stack+0xe0/0x120 >>> [] ubsan_epilogue+0x18/0x68 >>> [] __ubsan_handle_shift_out_of_bounds+0x18c/0x1bc >>> [] 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: >>> [] dump_backtrace+0x0/0x380 >>> [] show_stack+0x14/0x20 >>> [] dump_stack+0xe0/0x120 >>> [] ubsan_epilogue+0x18/0x68 >>> [] __ubsan_handle_shift_out_of_bounds+0x18c/0x1bc >>> [] dw_mci_setup_bus+0x384/0x438 >> >> The below message can be discarded. > > You are right, like above message, below part can be replaced as [...]. > >> >>> [] dw_mci_set_ios+0x184/0x798 >>> [] mmc_power_up+0x11c/0x260 >>> [] mmc_start_host+0x88/0x100 >>> [] mmc_add_host+0x6c/0x128 >>> [] dw_mci_probe+0x1088/0x1750 >>> [] dw_mci_pltfm_register+0x108/0x178 >>> [] dw_mci_exynos_probe+0x4c/0x88 >>> [] platform_drv_probe+0x78/0x180 >>> [] driver_probe_device+0x144/0x460 >>> [] __driver_attach+0xf4/0x140 >>> [] bus_for_each_dev+0xf0/0x160 >>> [] driver_attach+0x34/0x58 >>> [] bus_add_driver+0x2c0/0x398 >>> [] driver_register+0xbc/0x1e0 >>> [] __platform_driver_register+0x84/0xa8 >>> [] dw_mci_exynos_pltfm_driver_init+0x18/0x20 >>> [] do_one_initcall+0xa0/0x2c8 >>> [] kernel_init_freeable+0x52c/0x5dc >>> [] kernel_init+0x1c/0xf8 >>> [] ret_from_fork+0x10/0x40 >>> >>> Signed-off-by: Seung-Woo Kim >>> --- >>> drivers/mmc/host/dw_mmc.c | 5 +++-- >>> 1 files changed, 3 insertions(+), 2 deletions(-) >>> >>> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c >>> index 2cc6123..dff045e 100644 >>> --- a/drivers/mmc/host/dw_mmc.c >>> +++ b/drivers/mmc/host/dw_mmc.c >>> @@ -1099,7 +1099,8 @@ 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) >>> + if (((div < 32) ? (clock << div) : 0) != slot->__clk_old || >> >> Well, we don't expect that clock is 0. >> if clock is 0, it should be passed to " if (!clock)".. >> >> During initializing card, clock is 400KHz or less..I understood what you want to fix. >> But I taught this is not correct. > > It seems slot->__clk_old is not really clock but a kind of value to > store both clock and div in one variable. And at least, my compiler > calculates right shift with more than 32 as 0. I am not sure there is > other proper value for the case. > > By the way, in my test environment, clock is calculated as like > following steps: > mmc_host mmc0: Bus speed (slot 0) = 200000000Hz (slot req 400000Hz, > actual 400000HZ div = 250) > mmc_host mmc0: Bus speed (slot 0) = 200000000Hz (slot req 200000000Hz, > actual 200000000HZ div = 0) > mmc_host mmc0: Bus speed (slot 0) = 200000000Hz (slot req 52000000Hz, > actual 50000000HZ div = 2) > mmc_host mmc0: Bus speed (slot 0) = 400000000Hz (slot req 52000000Hz, > actual 50000000HZ div = 4) > mmc_host mmc0: Bus speed (slot 0) = 400000000Hz (slot req 200000000Hz, > actual 200000000HZ div = 1) > > and only the first case is reported as the warning. If you let me know > any proper value, then I will fix with the value. I think that "clock << div" and__old_clock are used for checking whether clock is changed. So it doesn't need to rotate with div. Could you check the below codes? if ((clock != slot->clk_old) || force_clkinit) ... slot->__clk_old = clock; Best Regards, Jaehoon Chung > > Thanks, > - Seung-Woo Kim > > >> >> >>> + 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, >>> @@ -1129,7 +1130,7 @@ static void dw_mci_setup_bus(struct dw_mci_slot *slot, bool force_clkinit) >>> mci_send_cmd(slot, sdmmc_cmd_bits, 0); >>> >>> /* keep the clock with reflecting clock dividor */ >>> - slot->__clk_old = clock << div; >>> + slot->__clk_old = (div < 32) ? (clock << div) : 0; >> >> Also, clock is not 0.. >> >> >> Best Regards, >> Jaehoon Chung >> >>> } >>> >>> host->current_speed = clock; >>> >> >> >> >