[PATCH] doc: sandbox: Add additional valgrind documentation

[Sean Anderson]

On 5/28/22 4:20 AM, Heinrich Schuchardt wrote:
> On 5/27/22 15:25, Sean Anderson wrote:
>> On 5/27/22 3:14 AM, Heinrich Schuchardt wrote:
>>> On 5/27/22 05:36, Sean Anderson wrote:
>>>> This document some additional options which can be used with
>>>> valgrind, as
>>>
>>> Thanks for enhancing this document
>>>
>>> nits
>>> %s/document/documents/
>>>
>>>> well as directions for future work. It also fixes up inline literals to
>>>> actually be inline literals (and not italics). The content of this
>>>> documentation is primarily adapted from [1].
>>>>
>>>> [1]
>>>> https://lore.kernel.org/u-boot/57cb4b49-fa30-1194-9ac3-faa53e8033bd@gmail.com/
>>>>
>>>>
>>>> Signed-off-by: Sean Anderson <seanga2 at gmail.com>
>>>> ---
>>>>
>>>>   doc/arch/sandbox.rst | 65 +++++++++++++++++++++++++++++++++++++++++---
>>>>   1 file changed, 61 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/doc/arch/sandbox.rst b/doc/arch/sandbox.rst
>>>> index e1119492b4..cd5090be71 100644
>>>> --- a/doc/arch/sandbox.rst
>>>> +++ b/doc/arch/sandbox.rst
>>>> @@ -479,19 +479,76 @@ It is possible to run U-Boot under valgrind to
>>>> check memory allocations::
>>>>
>>>>       valgrind ./u-boot
>>>>
>>>> -For more detailed results, enable `CONFIG_VALGRIND`. There are many
>>>> false
>>>> -positives due to `malloc` itself. Suppress these with::
>>>> +For more detailed results, enable ``CONFIG_VALGRIND``. There are
>>>> many false
>>>> +positives due to ``malloc`` itself. Suppress these with::
>>>
>>> What do you mean by 'malloc itself'? Is it the internal implementation
>>> of malloc? Or is it the act of calling malloc()?
>>>
>>> This paragraph should explain what CONFIG_VALGRIND does:
>>>
>>> The sandbox allocates a memory pool via mmap(). U-Boot's internal
>>> malloc() and free() work on this memory pool. Custom allocators and
>>> deallocators are by default invisible to valgrind. It is
>>> CONFIG_VARLGRIND=y that exposes U-Boot's malloc() and free() to valgrind.
>>>
>>> If I understand include/valgrind/valgrind.h correctly, it injects
>>> placeholder assembler code that valgrind can replace by library calls
>>> into valgrind itself when loading the U-Boot binary.
>>
>> I believe this is correct. I will adapt your above description for v2.
>>
>>> I miss a statement indicating that the sandbox on RISC-V has no valgrind
>>> support, yet.
>>
>> I was not aware of this. The Kconfig should probably be updated.
>>
>>> The U-Boot code does not use VALGRIND_MEMPOOL* macros to indicate which
>>> memory pools it manages. Is this the reason for the problems we are
>>> facing?
> 
> Hello Sean,
> 
> thanks for revising the patch.
> 
> Will you have a look at the usefulness of VALGRIND_MEMPOOL* for U-Boot?

I don't know if this would address anything. There's still the problem that
dlmalloc has to access the red zones.

--Sean