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Message-Id: <DFUEH29UJBR9.1I03EHD1ZO88G@garyguo.net>
Date: Wed, 21 Jan 2026 16:15:57 +0000
From: "Gary Guo" <gary@...yguo.net>
To: "John Hubbard" <jhubbard@...dia.com>, "Danilo Krummrich"
<dakr@...nel.org>
Cc: "Alexandre Courbot" <acourbot@...dia.com>, "Joel Fernandes"
<joelagnelf@...dia.com>, "Timur Tabi" <ttabi@...dia.com>, "Alistair Popple"
<apopple@...dia.com>, "Edwin Peer" <epeer@...dia.com>, "Zhi Wang"
<zhiw@...dia.com>, "David Airlie" <airlied@...il.com>, "Simona Vetter"
<simona@...ll.ch>, "Bjorn Helgaas" <bhelgaas@...gle.com>, "Miguel Ojeda"
<ojeda@...nel.org>, "Alex Gaynor" <alex.gaynor@...il.com>, "Boqun Feng"
<boqun.feng@...il.com>, "Gary Guo" <gary@...yguo.net>,
Björn Roy Baron <bjorn3_gh@...tonmail.com>, "Benno Lossin"
<lossin@...nel.org>, "Andreas Hindborg" <a.hindborg@...nel.org>, "Alice
Ryhl" <aliceryhl@...gle.com>, "Trevor Gross" <tmgross@...ch.edu>,
<nouveau@...ts.freedesktop.org>, <rust-for-linux@...r.kernel.org>, "LKML"
<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 21/31] gpu: nova-core: Hopper/Blackwell: add FMC
signature extraction
On Wed Dec 3, 2025 at 5:59 AM GMT, John Hubbard wrote:
> Add extract_fmc_signatures_static() to parse cryptographic signatures
> from FMC ELF firmware sections. This extracts the SHA-384 hash, RSA
> public key, and signature needed for Chain of Trust verification.
>
> Also exposes the elf_section() helper from firmware.rs for use by FSP.
>
> Signed-off-by: John Hubbard <jhubbard@...dia.com>
> ---
> drivers/gpu/nova-core/firmware.rs | 4 +-
> drivers/gpu/nova-core/fsp.rs | 104 ++++++++++++++++++++++++++++++
> 2 files changed, 107 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/nova-core/firmware.rs b/drivers/gpu/nova-core/firmware.rs
> index 5cbb8be7434f..7f8d62f9ceba 100644
> --- a/drivers/gpu/nova-core/firmware.rs
> +++ b/drivers/gpu/nova-core/firmware.rs
> @@ -23,6 +23,8 @@
> },
> };
>
> +pub(crate) use elf::elf_section;
> +
> pub(crate) mod booter;
> pub(crate) mod fsp;
> pub(crate) mod fwsec;
> @@ -419,7 +421,7 @@ fn elf32_section<'a>(elf: &'a [u8], name: &str) -> Option<&'a [u8]> {
> }
>
> /// Automatically detects ELF32 vs ELF64 based on the ELF header.
> - pub(super) fn elf_section<'a>(elf: &'a [u8], name: &str) -> Option<&'a [u8]> {
> + pub(crate) fn elf_section<'a>(elf: &'a [u8], name: &str) -> Option<&'a [u8]> {
> // Check ELF magic.
> if elf.len() < 5 || elf.get(0..4)? != b"\x7fELF" {
> return None;
> diff --git a/drivers/gpu/nova-core/fsp.rs b/drivers/gpu/nova-core/fsp.rs
> index 389c43bfd538..311b6d4c6011 100644
> --- a/drivers/gpu/nova-core/fsp.rs
> +++ b/drivers/gpu/nova-core/fsp.rs
> @@ -256,4 +256,108 @@ pub(crate) fn wait_secure_boot(
> })
> .map(|_| ())
> }
> +
> + /// Extract FMC firmware signatures for Chain of Trust verification.
> + ///
> + /// Extracts real cryptographic signatures from FMC ELF32 firmware sections.
> + /// Returns signatures in a heap-allocated structure to prevent stack overflow.
> + pub(crate) fn extract_fmc_signatures_static(
> + dev: &device::Device<device::Bound>,
> + fmc_fw_data: &[u8],
> + ) -> Result<KBox<FmcSignatures>> {
> + dev_dbg!(dev, "FMC firmware size: {} bytes\n", fmc_fw_data.len());
> +
> + // Extract hash section (SHA-384)
> + let hash_section = crate::firmware::elf_section(fmc_fw_data, "hash")
> + .ok_or(EINVAL)
> + .inspect_err(|_| dev_err!(dev, "FMC firmware missing 'hash' section\n"))?;
> +
> + // Extract public key section (RSA public key)
> + let pkey_section = crate::firmware::elf_section(fmc_fw_data, "publickey")
> + .ok_or(EINVAL)
> + .inspect_err(|_| dev_err!(dev, "FMC firmware missing 'publickey' section\n"))?;
> +
> + // Extract signature section (RSA signature)
> + let sig_section = crate::firmware::elf_section(fmc_fw_data, "signature")
> + .ok_or(EINVAL)
> + .inspect_err(|_| dev_err!(dev, "FMC firmware missing 'signature' section\n"))?;
> +
> + dev_dbg!(
> + dev,
> + "FMC ELF sections: hash={} bytes, pkey={} bytes, sig={} bytes\n",
> + hash_section.len(),
> + pkey_section.len(),
> + sig_section.len()
> + );
> +
> + // Validate section sizes - hash must be exactly 48 bytes
> + if hash_section.len() != FSP_HASH_SIZE {
> + dev_err!(
> + dev,
> + "FMC hash section size {} != expected {}\n",
> + hash_section.len(),
> + FSP_HASH_SIZE
> + );
> + return Err(EINVAL);
> + }
> +
> + // Public key and signature can be smaller than the fixed array sizes
> + if pkey_section.len() > FSP_PKEY_SIZE * 4 {
> + dev_err!(
> + dev,
> + "FMC publickey section size {} > maximum {}\n",
> + pkey_section.len(),
> + FSP_PKEY_SIZE * 4
> + );
> + return Err(EINVAL);
> + }
> +
> + if sig_section.len() > FSP_SIG_SIZE * 4 {
> + dev_err!(
> + dev,
> + "FMC signature section size {} > maximum {}\n",
> + sig_section.len(),
> + FSP_SIG_SIZE * 4
> + );
> + return Err(EINVAL);
> + }
> +
> + // Allocate signature structure on heap to avoid stack overflow
> + let mut signatures = KBox::new(FmcSignatures::default(), GFP_KERNEL)?;
> +
> + // Copy hash section directly as bytes (48 bytes exactly)
> + // SAFETY: hash384 is a [u32; 12] array (48 bytes), and we create a byte slice of
> + // exactly FSP_HASH_SIZE (48) bytes. The pointer is valid and properly aligned.
> + let hash_bytes = unsafe {
> + core::slice::from_raw_parts_mut(
> + signatures.hash384.as_mut_ptr().cast::<u8>(),
> + FSP_HASH_SIZE,
> + )
> + };
This can be `signature.hash384.as_bytes_mut()[..FSP_HASH_SIZE]` without using
`unsafe`. Same below.
Best,
Gary
> + hash_bytes.copy_from_slice(hash_section);
> +
> + // Copy public key section (up to 388 bytes, zero-padded)
> + // SAFETY: public_key is a [u32; 96] array (384 bytes), and we create a byte slice of
> + // FSP_PKEY_SIZE * 4 bytes. The pointer is valid and properly aligned.
> + let pkey_bytes = unsafe {
> + core::slice::from_raw_parts_mut(
> + signatures.public_key.as_mut_ptr().cast::<u8>(),
> + FSP_PKEY_SIZE * 4,
> + )
> + };
> + pkey_bytes[..pkey_section.len()].copy_from_slice(pkey_section);
> +
> + // Copy signature section (up to 384 bytes, zero-padded)
> + // SAFETY: signature is a [u32; 96] array (384 bytes), and we create a byte slice of
> + // FSP_SIG_SIZE * 4 bytes. The pointer is valid and properly aligned.
> + let sig_bytes = unsafe {
> + core::slice::from_raw_parts_mut(
> + signatures.signature.as_mut_ptr().cast::<u8>(),
> + FSP_SIG_SIZE * 4,
> + )
> + };
> + sig_bytes[..sig_section.len()].copy_from_slice(sig_section);
> +
> + Ok(signatures)
> + }
> }
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