Re: [PATCH v3] mhi: host: Add standard elf image download functionality

[Baochen Qiang <baochen.qiang@oss.qualcomm.com>]

On 12/18/2025 4:04 PM, Qiang Yu wrote:
> On Thu, Dec 18, 2025 at 10:25:08AM +0530, Manivannan Sadhasivam wrote:
>> On Tue, Dec 16, 2025 at 12:26:41AM -0800, Qiang Yu wrote:
>>> On Mon, Dec 15, 2025 at 08:41:32PM +0200, Dmitry Baryshkov wrote:
>>>> On Sun, Dec 14, 2025 at 11:09:58PM -0800, Qiang Yu wrote:
>>>>> On Sat, Dec 13, 2025 at 11:21:11AM +0900, Manivannan Sadhasivam wrote:
>>>>>> On Fri, Dec 12, 2025 at 09:24:06PM +0200, Dmitry Baryshkov wrote:
>>>>>>> On Fri, Dec 12, 2025 at 10:07:01AM +0900, Manivannan Sadhasivam wrote:
>>>>>>>> On Thu, Dec 11, 2025 at 03:57:54PM +0200, Dmitry Baryshkov wrote:
>>>>>>>>> On Thu, Dec 11, 2025 at 01:37:12AM -0800, Qiang Yu wrote:
>>>>>>>>>> On Wed, Dec 10, 2025 at 12:57:11AM +0200, Dmitry Baryshkov wrote:
>>>>>>>>>>> On Sun, Dec 07, 2025 at 10:35:26PM -0800, Qiang Yu wrote:
>>>>>>>>>>>> On Sat, Dec 06, 2025 at 01:25:34PM +0200, Dmitry Baryshkov wrote:
>>>>>>>>>>>>> On Mon, Dec 01, 2025 at 06:33:15PM -0800, Qiang Yu wrote:
>>>>>>>>>>>>>> From: Mayank Rana <mayank.rana@oss.qualcomm.com>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Currently, the FBC image is a non-standard ELF file that contains a single
>>>>>>>>>>>>>> ELF header, followed by segments for SBL, and WLAN FW. However, TME-L
>>>>>>>>>>>>>> (Trust Management Engine Lite) supported devices (eg. QCC2072) requires
>>>>>>>>>>>>>> separate ELF headers for SBL and WLAN FW segments due to TME-L image
>>>>>>>>>>>>>> authentication requirement.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Current image format contains two sections in a single binary:
>>>>>>>>>>>>>> - First 512KB: ELF header + SBL segments
>>>>>>>>>>>>>> - Remaining: WLAN FW segments
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> The TME-L supported image format contains two sections with two elf
>>>>>>>>>>>>>> headers in a single binary:
>>>>>>>>>>>>>> - First 512KB: First ELF header + SBL segments
>>>>>>>>>>>>>> - Remaining: Second ELF header + WLAN FW segments
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Download behavior:
>>>>>>>>>>>>>> - Legacy: 1. First 512KB via BHI (ELF header + SBL)
>>>>>>>>>>>>>>           2. Full image via BHIe
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> - TME-L: 1. First 512KB via BHI (First ELF header + SBL)
>>>>>>>>>>>>>>          2. Remaining via BHIe (Second ELF header + WLAN FW segments)
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Add standard_elf_image flag to mhi_controller_config to indicate TME-L
>>>>>>>>>>>>>> supported image format. When set, MHI skips the first 512KB during WLAN FW
>>>>>>>>>>>>>> download over BHIe as it is loaded in BHI phase.
>>>>>>>>>>>>>
>>>>>>>>>>>>> What is standard about it?
>>>>>>>>>>>>
>>>>>>>>>>>> The TME-L requires standard elf image format which includes single EFL
>>>>>>>>>>>> header and WLAN FW segment.
>>>>>>>>>>>>
>>>>>>>>>>>> The "standard_elf_image" seems misleading. Since the new image format is
>>>>>>>>>>>> required for TME-L image authentication, how about using 
>>>>>>>>>>>> tme_supported_image?
>>>>>>>>>>>
>>>>>>>>>>> Just elf_image?
>>>>>>>>>>
>>>>>>>>>> Is it too generic for this specific use case. Current image format also
>>>>>>>>>> contains elf header.
>>>>>>>>>
>>>>>>>>> upload_elf_image?
>>>>>>>>>
>>>>>>>>
>>>>>>>> Nope. What does 'upload' even mean here? The 'TIS and ELF' spec v1.2 clearly
>>>>>>>> defines that an ELF executable can have only one ELF header. So I'd prefer
>>>>>>>> 'standard_elf_image' to differentiate it from the non-spec-conformant ELF image
>>>>>>>> used previously.
>>>>>>>
>>>>>>> What kind of ELF image was used previously? Could you please explain
>>>>>>> what do 'First ELF header' vs 'Second ELF header' mean here?
>>>>>>>
>>>>>>
>>>>>> I don't have the details of it, but Qiang should be able to explain. But AFAIC,
>>>>>> that was a non-standard ELF image and the new one is going to be spec
>>>>>> conformant.
>>>>>>
>>>>> Previous image format:
>>>>> ELF header + SBL segments + WLAN FW segments
>>>>>
>>>>> The TME-L supported image format:
>>>>> First ELF header + SBL segments + Second ELF header + WLAN FW segments
>>>>
>>>> What is the Second ELF header in this context? ELF files usually have
>>>> only one header. Are we repeating the same ELF header or is some kind of
>>>> an embedded ELF-in-ELF.
>>>
>>> The "Second ELF header" refers to a separate, complete ELF file embedded
>>> within the FBC image, not a duplicate header. The TME-L supported format
>>> contains:
>>>
>>> FBC Image Structure:
>>> ┌─────────────────────────────────────┐
>>> │  Complete ELF File #1 (SBL)        │
>>> │  ┌─────────────────────────────┐   │
>>> │  │ ELF Header                  │   │ ← First ELF header
>>> │  │ Program Headers             │   │
>>> │  │ SBL Segments                │   │
>>> │  └─────────────────────────────┘   │
>>> ├─────────────────────────────────────┤
>>> │  Complete ELF File #2 (WLAN FW)    │
>>> │  ┌─────────────────────────────┐   │
>>> │  │ ELF Header                  │   │ ← Second ELF header
>>> │  │ Program Headers             │   │
>>> │  │ WLAN FW Segments            │   │
>>> │  └─────────────────────────────┘   │
>>> └─────────────────────────────────────┘
>>>>
>>>>>
>>>>> As per 'TIS and ELF' spec v1.2 Mani mentioned, the previous image format
>>>>
>>>> pointer?
>>>
>>> The entire 'TIS and ELF' spec v1.2 document descibes the structure of the
>>> ELF excutable file, I can not point out a specfic sentence or phase that
>>> tell us the previous image format is standard. But at least there is an
>>> example we can refer to: Figure A-4. Executable File Example. And I can
>>> also use readelf cmd to parse the image.
>>>
>>>>
>>>>> is also standard elf image. But it doesn't meet the requirement of TME-L
>>>>> because we need separate elf header for SBL and WL FW for TME-L
>>>>> authentication.
>>>>>
>>>>> So the commit message stating "Currently, the FBC image is a non-standard
>>>>> ELF file that contains a single ELF header, followed by segments for SBL,
>>>>> and WLAN FW" is not correct and standard_elf_image is not accurate.
>>>>>
>>>>> Can we avoid saying anything about standard in commit message? Flags eg.
>>>>> separate_elf_header and tme_supported_image are more accurate.
>>>>
>>>> Please define, what is the supported image.
>>>
>>> The supported image refers to an image format that TME-L can authenticate.
>>> Both SBL and WLAN FW should be in ELF format. After powering on, SBL (ELF
>>> format, ELF header + SBL segment, first 512 KB) is loaded over BHI and
>>> authenticated by TME-L. After entering SBL, WLAN FW (ELF format, skip
>>> first 512KB of fbc image) is loaded over BHIe and also authenticated by
>>> TME-L.
>>>
>>
>> So what makes it different here is that you are now sending the two FWs
>> separately as standalone ELF image to the device for authentication by TME-L,
>> but those are combined in a single image file in the host. But what makes you to
>> combine two images in the first place? Why can't they be separate ELF files?
>>
>> I think you can avoid the hassle if you could just have separate ELF images for
>> SBL and WLAN FW and say that the TME-L just expects individual ELF image.
>>
> Yes, they are two separate images combined into a single file. I'm not
> sure of the specific reasons for this design choice, so I can't comment
> on it. The WLAN team provides a single file for both SBL and WLAN FW, and
> I don't know whether they're willing to change.
> 
> Baochen, do you have any comment on this?

Hmm, sorry, no idea :(

> 
> - Qiang Yu