linux-kernel - Re: [PATCH] bus: mhi: core: debugfs: Use correct format specifiers for addresses

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Date:   Fri, 25 Sep 2020 12:01:54 -0600
From:   Jeffrey Hugo <jhugo@...eaurora.org>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        gregkh@...uxfoundation.org
Cc:     hemantk@...eaurora.org, bbhatt@...eaurora.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] bus: mhi: core: debugfs: Use correct format specifiers
 for addresses

On 9/25/2020 11:16 AM, Manivannan Sadhasivam wrote:
> For exposing the addresses of read/write pointers and doorbell register,
> let's use the correct format specifiers. This fixes the following issues
> generated using W=1 build in ARM32 and reported by Kbuild bot:
> 
> All warnings (new ones prefixed by >>):
> 
>>> drivers/bus/mhi/core/debugfs.c:75:7: warning: format specifies type 'unsigned long long' but the argument has type 'dma_addr_t' (aka 'unsigned int') [-Wformat]
>                                mhi_event->db_cfg.db_val);
>                                ^~~~~~~~~~~~~~~~~~~~~~~~
>     drivers/bus/mhi/core/debugfs.c:123:7: warning: format specifies type 'unsigned long long' but the argument has type 'dma_addr_t' (aka 'unsigned int') [-Wformat]
>                                mhi_chan->db_cfg.db_val);
>                                ^~~~~~~~~~~~~~~~~~~~~~~
>     2 warnings generated.
> 
> drivers/bus/mhi/core/debugfs.c: In function ‘mhi_debugfs_events_show’:
> drivers/bus/mhi/core/debugfs.c:74:51: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
>     seq_printf(m, " local rp: 0x%llx db: 0x%pad\n", (u64)ring->rp,
>                                                     ^
> drivers/bus/mhi/core/debugfs.c: In function ‘mhi_debugfs_channels_show’:
> drivers/bus/mhi/core/debugfs.c:122:7: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
>         (u64)ring->rp, (u64)ring->wp,
>         ^
> drivers/bus/mhi/core/debugfs.c:122:22: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
>         (u64)ring->rp, (u64)ring->wp,
>                        ^
> drivers/bus/mhi/core/debugfs.c:121:62: warning: format ‘%llx’ expects argument of type ‘long long unsigned int’, but argument 5 has type ‘dma_addr_t {aka unsigned int}’ [-Wformat=]
>     seq_printf(m, " local rp: 0x%llx local wp: 0x%llx db: 0x%llx\n",
>                                                             ~~~^
>                                                             %x
> drivers/bus/mhi/core/debugfs.c:123:7:
>         mhi_chan->db_cfg.db_val);
> 
> Reported-by: kernel test robot <lkp@...el.com>
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> ---
> 
> Greg: This fixes the issue seen while testing the char-misc/char-misc-testing
> branch.
> 
>   drivers/bus/mhi/core/debugfs.c | 10 +++++-----
>   1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/bus/mhi/core/debugfs.c b/drivers/bus/mhi/core/debugfs.c
> index 53d05a8e168d..2536ff92b76f 100644
> --- a/drivers/bus/mhi/core/debugfs.c
> +++ b/drivers/bus/mhi/core/debugfs.c
> @@ -71,8 +71,8 @@ static int mhi_debugfs_events_show(struct seq_file *m, void *d)
>   		seq_printf(m, " rp: 0x%llx wp: 0x%llx", er_ctxt->rp,
>   			   er_ctxt->wp);
>   
> -		seq_printf(m, " local rp: 0x%llx db: 0x%llx\n", (u64)ring->rp,
> -			   mhi_event->db_cfg.db_val);
> +		seq_printf(m, " local rp: 0x%px db: 0x%pad\n", ring->rp,
> +			   &mhi_event->db_cfg.db_val);
>   	}
>   
>   	return 0;
> @@ -118,9 +118,9 @@ static int mhi_debugfs_channels_show(struct seq_file *m, void *d)
>   		seq_printf(m, " base: 0x%llx len: 0x%llx wp: 0x%llx",
>   			   chan_ctxt->rbase, chan_ctxt->rlen, chan_ctxt->wp);
>   
> -		seq_printf(m, " local rp: 0x%llx local wp: 0x%llx db: 0x%llx\n",
> -			   (u64)ring->rp, (u64)ring->wp,
> -			   mhi_chan->db_cfg.db_val);
> +		seq_printf(m, " local rp: 0x%px local wp: 0x%px db: 0x%pad\n",
> +			   ring->rp, ring->wp,
> +			   &mhi_chan->db_cfg.db_val);
>   	}
>   
>   	return 0;
> 

Documentation/printk-formats.txt seems to point out that %px is 
"insecure" and thus perhaps not preferred.  Are we assuming that debugfs 
is only accessible by root, and thus the %px usage here is effectively 
the same as %pK?

-- 
Jeffrey Hugo
Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.