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

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 <[email protected]>
> > > > > > > > > > > > 
> > > > > > > > > > > > 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.

- Mani

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