linux-kernel - Re: [PATCH 1/2] bus: mhi: Fix pm

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Message-ID: <1624052489.10055.12.camel@codeaurora.org>
Date:   Fri, 18 Jun 2021 14:41:29 -0700
From:   Hemant Kumar <hemantk@...eaurora.org>
To:     Paul Davey <paul.davey@...iedtelesis.co.nz>,
        Manivannan Sadhasivam <mani@...nel.org>
Cc:     linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] bus: mhi: Fix pm_state conversion to string

Hi Paul,
On Fri, 2021-06-18 at 15:31 +1200, Paul Davey wrote:
> On big endian architectures the mhi debugfs files which report pm
> state
> give "Invalid State" for all states.
> 
> Fix to_mhi_pm_state_str by using a local unsigned long as an
> intemediate
> to pass the state to find_last_bit to avoid endianness issues with
> cast
> from enum mhi_pm_state * to unsigned long *.
> 
> Signed-off-by: Paul Davey <paul.davey@...iedtelesis.co.nz>
> ---
>  drivers/bus/mhi/core/init.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/bus/mhi/core/init.c
> b/drivers/bus/mhi/core/init.c
> index c81b377fca8f..87cc0c449078 100644
> --- a/drivers/bus/mhi/core/init.c
> +++ b/drivers/bus/mhi/core/init.c
> @@ -79,7 +79,8 @@ static const char * const mhi_pm_state_str[] = {
>  
>  const char *to_mhi_pm_state_str(enum mhi_pm_state state)
>  {
> -	int index = find_last_bit((unsigned long *)&state, 32);
> +	unsigned long tmp = state;
> +	int index = find_last_bit((unsigned long *)&tmp, 32);
>  
>  	if (index >= ARRAY_SIZE(mhi_pm_state_str))
>  		return "Invalid State";

Considering KASAN bugs reported in the past related to find_next_bit
https://www.spinics.net/lists/alsa-devel/msg110946.html

Since you are addressing the BE arch issue, would you please
use this solution instead :-

diff --git a/drivers/bus/mhi/core/init.c b/drivers/bus/mhi/core/init.c
index 8f4cd4d..744b617 100644
--- a/drivers/bus/mhi/core/init.c
+++ b/drivers/bus/mhi/core/init.c
@@ -77,9 +77,12 @@ static const char * const mhi_pm_state_str[] = {
 
 const char *to_mhi_pm_state_str(enum mhi_pm_state state)
 {
+	int index;
 
-	if (index >= ARRAY_SIZE(mhi_pm_state_str))
+	if (state)
+		index = __fls(state);
+
+	if (!state || index >= ARRAY_SIZE(mhi_pm_state_str))
 		return "Invalid State";
 
 	return mhi_pm_state_str[index];

Thanks,
Hemant

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