gpu: nova-core: Hopper/Blackwell: add FMC signature extraction

Extract the SHA-384 hash, RSA public key, and RSA signature from the
FMC ELF32 firmware sections. FSP Chain of Trust verification needs
these to validate the FMC image during boot.

Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Eliot Courtney <ecourtney@nvidia.com>
Link: https://patch.msgid.link/20260602032111.224790-14-jhubbard@nvidia.com
[acourbot: derive `Zeroable` on `FmcSignature` for in-place initialization]
Co-developed-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>

drivers/gpu/nova-core/firmware/fsp.rs

@@ -15,13 +15,35 @@
     gpu::Chipset, //
 };
 
+/// Size of the FSP SHA-384 hash, in bytes.
+const FSP_HASH_SIZE: usize = 48;
+/// Maximum size of the FSP public key (RSA-3072), in bytes.
+///
+/// The FMC ELF `publickey` section may be shorter, so the remaining bytes are zero-padded.
+const FSP_PKEY_SIZE: usize = 384;
+/// Maximum size of the FSP signature (RSA-3072), in bytes.
+///
+/// The FMC ELF `signature` section may be shorter, so the remaining bytes are zero-padded.
+const FSP_SIG_SIZE: usize = 384;
+
+/// Structure to hold FMC signatures.
+///
+/// C representation is used because this type is used for communication with the FSP.
+#[derive(Debug, Clone, Copy, Zeroable)]
+#[repr(C)]
+pub(crate) struct FmcSignatures {
+    pub(crate) hash384: [u8; FSP_HASH_SIZE],
+    pub(crate) public_key: [u8; FSP_PKEY_SIZE],
+    pub(crate) signature: [u8; FSP_SIG_SIZE],
+}
+
 pub(crate) struct FspFirmware {
     /// FMC firmware image data (only the "image" ELF section).
     #[expect(dead_code)]
     pub(crate) fmc_image: Coherent<[u8]>,
-    /// Full FMC ELF for signature extraction.
+    /// FMC firmware signatures.
     #[expect(dead_code)]
-    pub(crate) fmc_elf: Firmware,
+    pub(crate) fmc_sigs: KBox<FmcSignatures>,
 }
 
 impl FspFirmware {
@@ -41,7 +63,68 @@ pub(crate) fn new(
 
         Ok(Self {
             fmc_image,
-            fmc_elf: fw,
+            fmc_sigs: Self::extract_fmc_signatures(&fw, dev)?,
         })
     }
+
+    /// 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.
+    fn extract_fmc_signatures(
+        fmc_fw: &Firmware,
+        dev: &device::Device,
+    ) -> Result<KBox<FmcSignatures>> {
+        let get_section = |name: &str, max_len: usize| {
+            elf::elf_section(fmc_fw.data(), name)
+                .ok_or(EINVAL)
+                .inspect_err(|_| dev_err!(dev, "FMC firmware missing '{}' section\n", name))
+                .and_then(|section| {
+                    if section.len() > max_len {
+                        dev_err!(
+                            dev,
+                            "FMC {} section size {} > maximum {}\n",
+                            name,
+                            section.len(),
+                            max_len
+                        );
+                        Err(EINVAL)
+                    } else {
+                        Ok(section)
+                    }
+                })
+        };
+
+        let hash_section = get_section("hash", FSP_HASH_SIZE)?;
+        let pkey_section = get_section("publickey", FSP_PKEY_SIZE)?;
+        let sig_section = get_section("signature", FSP_SIG_SIZE)?;
+
+        // The hash section is a SHA-384 output: it must be exactly FSP_HASH_SIZE 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);
+        }
+
+        // Initialize the signatures in place to avoid building the large `FmcSignatures` on the
+        // stack, then fill each section from the firmware.
+        let signatures = KBox::init(
+            pin_init::init_zeroed::<FmcSignatures>().chain(|sigs| {
+                // PANIC: src and dst lengths are both FSP_HASH_SIZE (verified above).
+                sigs.hash384.copy_from_slice(hash_section);
+                // PANIC: dst is sliced to src.len(); src.len() <= FSP_PKEY_SIZE per `get_section`.
+                sigs.public_key[..pkey_section.len()].copy_from_slice(pkey_section);
+                // PANIC: dst is sliced to src.len(); src.len() <= FSP_SIG_SIZE per `get_section`.
+                sigs.signature[..sig_section.len()].copy_from_slice(sig_section);
+                Ok(())
+            }),
+            GFP_KERNEL,
+        )?;
+
+        Ok(signatures)
+    }
 }