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

[York Sun]

On 02/08/2018 02:05 AM, Simon Goldschmidt wrote:
> 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.

Leaving it as ENVL_UNKNOWN doesn't fix the problem. The
env_load_location needs to be valid after relocation. Leaving it as
unknown doesn't let you write env.

> 
> 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.

Not everything in initial RAM is copied to final RAM. After relocation,
we shouldn't be using initial RAM at all. Actually the initial RAM may
be used for other purpose.

> 
>>> 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).

Yes. That was my intention.

York