gpu: nova-core: add support for 32-bit firmware images

Some GPU firmware images are packaged as 32-bit ELF rather than 64-bit.
Add a 32-bit implementation of the shared ELF section-parsing
abstraction so those images can be parsed alongside the existing 64-bit
path.

Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Eliot Courtney <ecourtney@nvidia.com>
Link: https://patch.msgid.link/20260602032111.224790-9-jhubbard@nvidia.com
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>

Author: johnhubbard

drivers/gpu/nova-core/firmware.rs

@@ -534,6 +534,53 @@ mod elf {
         type SectionHeader = Elf64SHdr;
     }
 
+    /// Newtype to provide [`FromBytes`] and [`ElfHeader`] implementations for ELF32.
+    #[repr(transparent)]
+    struct Elf32Hdr(bindings::elf32_hdr);
+    // SAFETY: all bit patterns are valid for this type, and it doesn't use interior mutability.
+    unsafe impl FromBytes for Elf32Hdr {}
+
+    impl ElfHeader for Elf32Hdr {
+        fn shnum(&self) -> u16 {
+            self.0.e_shnum
+        }
+
+        fn shoff(&self) -> u64 {
+            u64::from(self.0.e_shoff)
+        }
+
+        fn shstrndx(&self) -> u16 {
+            self.0.e_shstrndx
+        }
+    }
+
+    /// Newtype to provide [`FromBytes`] and [`ElfSectionHeader`] implementations for ELF32.
+    #[repr(transparent)]
+    struct Elf32SHdr(bindings::elf32_shdr);
+    // SAFETY: all bit patterns are valid for this type, and it doesn't use interior mutability.
+    unsafe impl FromBytes for Elf32SHdr {}
+
+    impl ElfSectionHeader for Elf32SHdr {
+        fn name(&self) -> u32 {
+            self.0.sh_name
+        }
+
+        fn offset(&self) -> u64 {
+            u64::from(self.0.sh_offset)
+        }
+
+        fn size(&self) -> u64 {
+            u64::from(self.0.sh_size)
+        }
+    }
+
+    struct Elf32Format;
+
+    impl ElfFormat for Elf32Format {
+        type Header = Elf32Hdr;
+        type SectionHeader = Elf32SHdr;
+    }
+
     /// Returns a NULL-terminated string from the ELF image at `offset`.
     fn elf_str(elf: &[u8], offset: u64) -> Option<&str> {
         let idx = usize::try_from(offset).ok()?;
@@ -586,4 +633,10 @@ mod elf {
     pub(super) fn elf64_section<'a>(elf: &'a [u8], name: &str) -> Option<&'a [u8]> {
         elf_section_generic::<Elf64Format>(elf, name)
     }
+
+    /// Extract the section with name `name` from the ELF32 image `elf`.
+    #[expect(dead_code)]
+    pub(super) fn elf32_section<'a>(elf: &'a [u8], name: &str) -> Option<&'a [u8]> {
+        elf_section_generic::<Elf32Format>(elf, name)
+    }
 }