[PATCH v4 22/33] gpu: nova-core: Hopper/Blackwell: add FMC signature extraction

[John Hubbard <jhubbard@nvidia.com>]

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.

Cc: Joel Fernandes <joelagnelf@nvidia.com>
Cc: Gary Guo <gary@garyguo.net>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 drivers/gpu/nova-core/firmware.rs |  4 +-
 drivers/gpu/nova-core/fsp.rs      | 76 +++++++++++++++++++++++++++++--
 2 files changed, 76 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/nova-core/firmware.rs b/drivers/gpu/nova-core/firmware.rs
index 9a9b969aaf79..e9101a08511f 100644
--- a/drivers/gpu/nova-core/firmware.rs
+++ b/drivers/gpu/nova-core/firmware.rs
@@ -27,6 +27,8 @@
     },
 };
 
+pub(crate) use elf::elf_section;
+
 pub(crate) mod booter;
 pub(crate) mod fsp;
 pub(crate) mod fwsec;
@@ -607,7 +609,7 @@ 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 7775f1b673c0..fca03e25134d 100644
--- a/drivers/gpu/nova-core/fsp.rs
+++ b/drivers/gpu/nova-core/fsp.rs
@@ -124,10 +124,10 @@ 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.
+/// Size constraints for FSP security signatures (in bytes).
 const FSP_HASH_SIZE: usize = 48; // SHA-384 hash
-const FSP_PKEY_SIZE: usize = 97; // Public key size for GB202 (not 384!)
-const FSP_SIG_SIZE: usize = 96; // Signature size for GB202 (not 384!)
+const FSP_PKEY_SIZE: usize = 384; // RSA public key
+const FSP_SIG_SIZE: usize = 384; // RSA signature
 
 /// Structure to hold FMC signatures.
 #[derive(Debug, Clone, Copy)]
@@ -241,4 +241,74 @@ 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>> {
+        // 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"))?;
+
+        // 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 {
+            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);
+        }
+
+        // Allocate signature structure on heap to avoid stack overflow
+        let mut signatures = KBox::new(FmcSignatures::default(), GFP_KERNEL)?;
+
+        // Copy hash section directly (48 bytes exactly)
+        signatures.hash384.copy_from_slice(hash_section);
+
+        // Copy public key section (up to 384 bytes, zero-padded)
+        signatures.public_key[..pkey_section.len()].copy_from_slice(pkey_section);
+
+        // Copy signature section (up to 384 bytes, zero-padded)
+        signatures.signature[..sig_section.len()].copy_from_slice(sig_section);
+
+        Ok(signatures)
+    }
 }
-- 
2.53.0