[PATCH v7 20/31] gpu: nova-core: Hopper/Blackwell: add FMC signature extraction

[John Hubbard <jhubbard@nvidia.com>]

Add extract_fmc_signatures() which extracts SHA-384 hash, RSA public
key, and RSA signature from FMC ELF32 firmware sections. These are
needed for FSP Chain of Trust verification.

Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 drivers/gpu/nova-core/firmware.rs |  3 +-
 drivers/gpu/nova-core/fsp.rs      | 79 +++++++++++++++++++++++++++++++
 2 files changed, 81 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/nova-core/firmware.rs b/drivers/gpu/nova-core/firmware.rs
index bc26807116e4..6d07715b3a49 100644
--- a/drivers/gpu/nova-core/firmware.rs
+++ b/drivers/gpu/nova-core/firmware.rs
@@ -26,6 +26,7 @@
     },
 };
 
+pub(crate) use elf::elf_section;
 pub(crate) mod booter;
 pub(crate) mod fsp;
 pub(crate) mod fwsec;
@@ -646,7 +647,7 @@ 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 d464ad325881..a13d883373f0 100644
--- a/drivers/gpu/nova-core/fsp.rs
+++ b/drivers/gpu/nova-core/fsp.rs
@@ -105,6 +105,18 @@ unsafe impl AsBytes for GspFmcBootParams {}
 // SAFETY: All bit patterns are valid for the primitive fields.
 unsafe impl FromBytes for GspFmcBootParams {}
 
+/// Size constraints for FSP security signatures (Hopper/Blackwell).
+const FSP_HASH_SIZE: usize = 48; // SHA-384 hash
+const FSP_PKEY_SIZE: usize = 384; // RSA-3072 public key
+const FSP_SIG_SIZE: usize = 384; // RSA-3072 signature
+
+/// Structure to hold FMC signatures.
+#[derive(Debug, Clone, Copy)]
+pub(crate) struct FmcSignatures {
+    hash384: [u8; FSP_HASH_SIZE],
+    public_key: [u8; FSP_PKEY_SIZE],
+    signature: [u8; FSP_SIG_SIZE],
+}
 /// FSP interface for Hopper/Blackwell GPUs.
 pub(crate) struct Fsp;
 
@@ -138,4 +150,71 @@ 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.
+    #[expect(dead_code)]
+    pub(crate) fn extract_fmc_signatures(
+        dev: &device::Device<device::Bound>,
+        fmc_fw_data: &[u8],
+    ) -> Result<KBox<FmcSignatures>> {
+        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"))?;
+
+        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"))?;
+
+        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"))?;
+
+        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);
+        }
+
+        if pkey_section.len() > FSP_PKEY_SIZE {
+            dev_err!(
+                dev,
+                "FMC publickey section size {} > maximum {}\n",
+                pkey_section.len(),
+                FSP_PKEY_SIZE
+            );
+            return Err(EINVAL);
+        }
+
+        if sig_section.len() > FSP_SIG_SIZE {
+            dev_err!(
+                dev,
+                "FMC signature section size {} > maximum {}\n",
+                sig_section.len(),
+                FSP_SIG_SIZE
+            );
+            return Err(EINVAL);
+        }
+
+        let mut signatures = KBox::new(
+            FmcSignatures {
+                hash384: [0u8; FSP_HASH_SIZE],
+                public_key: [0u8; FSP_PKEY_SIZE],
+                signature: [0u8; FSP_SIG_SIZE],
+            },
+            GFP_KERNEL,
+        )?;
+
+        signatures.hash384.copy_from_slice(hash_section);
+        signatures.public_key[..pkey_section.len()].copy_from_slice(pkey_section);
+        signatures.signature[..sig_section.len()].copy_from_slice(sig_section);
+
+        Ok(signatures)
+    }
 }
-- 
2.53.0