[U-Boot] [PATCH 1/2] env: Fix env_load_location

[Simon Goldschmidt]

On 08.02.2018 09:38, Maxime Ripard wrote:
> Hi,
>
> Thanks for your patch
>
> On Wed, Feb 07, 2018 at 02:17:11PM -0800, York Sun wrote:
>> Commit 7d714a24d725 ("env: Support multiple environments") added
>> static variable env_load_location. When saving environmental
>> variables, this variable is presumed to have the value set before.
>> In case the value was set before relocation and U-Boot runs from a
>> NOR flash, this variable wasn't writable. This causes failure when
>> saving the environment. To save this location, global data must be
>> used instead.

Out of curiosity: which linker sections are affected of this issue? I 
assume only initialized data ('.data') is affected as it is left in 
place. Also, I assume that uninitialized data ('.bss') is not affected 
(as your linker can place this into ram)?
If so, this issue could be fixed by changing ENVL_UNKNOWN to zero (which 
you already do in your patch) and leaving 'env_load_location' 
uninitialized, in which case it is initialized to zero (== ENVL_UNKNOWN) 
as defined by the C standard.

Another possibility to fix this would be to have your linker script put 
'data' into ram but initialize it from rom. Something like this:

.data :
{
   <your section contents here>
} >ram AT>rom

To me, both versions would be better than to add members to struct 
global_dat.

>> Signed-off-by: York Sun <york.sun at nxp.com>
>> CC: Maxime Ripard <maxime.ripard at free-electrons.com>
>> ---
>> Limited test on LS1043ARDB.
>>
>>   env/env.c                         | 8 +++-----
>>   include/asm-generic/global_data.h | 1 +
>>   include/environment.h             | 2 +-
>>   3 files changed, 5 insertions(+), 6 deletions(-)
>>
>> diff --git a/env/env.c b/env/env.c
>> index 9a89832..edfb575 100644
>> --- a/env/env.c
>> +++ b/env/env.c
>> @@ -62,8 +62,6 @@ static enum env_location env_locations[] = {
>>   #endif
>>   };
>>   
>> -static enum env_location env_load_location = ENVL_UNKNOWN;
>> -
>>   static bool env_has_inited(enum env_location location)
>>   {
>>   	return gd->env_has_init & BIT(location);
>> @@ -108,11 +106,11 @@ __weak enum env_location env_get_location(enum env_operation op, int prio)
>>   		if (prio >= ARRAY_SIZE(env_locations))
>>   			return ENVL_UNKNOWN;
>>   
>> -		env_load_location = env_locations[prio];
>> -		return env_load_location;
>> +		gd->env_load_location = env_locations[prio];
>> +		return gd->env_load_location;
>>   
>>   	case ENVOP_SAVE:
>> -		return env_load_location;
>> +		return gd->env_load_location;
>>   	}
>>   
>>   	return ENVL_UNKNOWN;
>> diff --git a/include/asm-generic/global_data.h b/include/asm-generic/global_data.h
>> index fd8cd45..10f1441 100644
>> --- a/include/asm-generic/global_data.h
>> +++ b/include/asm-generic/global_data.h
>> @@ -51,6 +51,7 @@ typedef struct global_data {
>>   	unsigned long env_addr;		/* Address  of Environment struct */
>>   	unsigned long env_valid;	/* Environment valid? enum env_valid */
>>   	unsigned long env_has_init;	/* Bitmask of boolean of struct env_location offsets */
>> +	int env_load_location;
>>   
>>   	unsigned long ram_top;		/* Top address of RAM used by U-Boot */
>>   	unsigned long relocaddr;	/* Start address of U-Boot in RAM */
>> diff --git a/include/environment.h b/include/environment.h
>> index a406050..0f339da 100644
>> --- a/include/environment.h
>> +++ b/include/environment.h
>> @@ -188,6 +188,7 @@ enum env_valid {
>>   };
>>   
>>   enum env_location {
>> +	ENVL_UNKNOWN,
>>   	ENVL_EEPROM,
>>   	ENVL_EXT4,
>>   	ENVL_FAT,
>> @@ -202,7 +203,6 @@ enum env_location {
>>   	ENVL_NOWHERE,
>>   
>>   	ENVL_COUNT,
>> -	ENVL_UNKNOWN,
> Why did you need to change this? This looks a bit odd.

The global data struct is initialized to zero. I guess this change is 
meant to ensure 'gd->env_load_location' is initialized to ENV_UNKOWN 
(see my comments above).

Simon

>
> Thanks!
> Maxime
>
>
>
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