[PATCH v12 09/22] gpu: nova-core: add auto-detection of 32-bit, 64-bit firmware images

[John Hubbard <jhubbard@nvidia.com>]

A firmware image may be either a 32-bit or a 64-bit ELF, and callers
should not have to know which. Detect the ELF class from the image
header at parse time and dispatch to the matching parser, so a single
entry point handles both layouts.

Reviewed-by: Eliot Courtney <ecourtney@nvidia.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 drivers/gpu/nova-core/firmware.rs     | 27 +++++++++++++++++++++++----
 drivers/gpu/nova-core/firmware/gsp.rs |  4 ++--
 2 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/nova-core/firmware.rs b/drivers/gpu/nova-core/firmware.rs
index e4dcc9a87b7e..87588cb24f11 100644
--- a/drivers/gpu/nova-core/firmware.rs
+++ b/drivers/gpu/nova-core/firmware.rs
@@ -629,14 +629,33 @@ fn elf_section_generic<'a, F>(elf: &'a [u8], name: &str) -> Option<&'a [u8]>
         })
     }
 
-    /// Tries to extract section with name `name` from the ELF64 image `elf`, and returns it.
-    pub(super) fn elf64_section<'a>(elf: &'a [u8], name: &str) -> Option<&'a [u8]> {
+    /// Extract the section with name `name` from the ELF64 image `elf`.
+    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]> {
+    fn elf32_section<'a>(elf: &'a [u8], name: &str) -> Option<&'a [u8]> {
         elf_section_generic::<Elf32Format>(elf, name)
     }
+
+    /// Automatically detects ELF32 vs ELF64 based on the ELF header.
+    pub(super) fn elf_section<'a>(elf: &'a [u8], name: &str) -> Option<&'a [u8]> {
+        // ELF identification: a 4-byte magic followed by a class byte (32- vs 64-bit).
+        const ELFMAG: &[u8] = b"\x7fELF";
+        const SELFMAG: usize = ELFMAG.len();
+        const EI_CLASS: usize = 4;
+        const ELFCLASS32: u8 = 1;
+        const ELFCLASS64: u8 = 2;
+
+        if elf.get(0..SELFMAG) != Some(ELFMAG) {
+            return None;
+        }
+
+        match *elf.get(EI_CLASS)? {
+            ELFCLASS32 => elf32_section(elf, name),
+            ELFCLASS64 => elf64_section(elf, name),
+            _ => None,
+        }
+    }
 }
diff --git a/drivers/gpu/nova-core/firmware/gsp.rs b/drivers/gpu/nova-core/firmware/gsp.rs
index e576bc8a9b1c..99a302bae567 100644
--- a/drivers/gpu/nova-core/firmware/gsp.rs
+++ b/drivers/gpu/nova-core/firmware/gsp.rs
@@ -88,7 +88,7 @@ pub(crate) fn new<'a>(
         pin_init::pin_init_scope(move || {
             let firmware = super::request_firmware(dev, chipset, "gsp", ver)?;
 
-            let fw_section = elf::elf64_section(firmware.data(), ".fwimage").ok_or(EINVAL)?;
+            let fw_section = elf::elf_section(firmware.data(), ".fwimage").ok_or(EINVAL)?;
 
             let size = fw_section.len();
 
@@ -148,7 +148,7 @@ pub(crate) fn new<'a>(
                 signatures: {
                     let sigs_section = Self::find_gsp_sigs_section(chipset);
 
-                    elf::elf64_section(firmware.data(), sigs_section)
+                    elf::elf_section(firmware.data(), sigs_section)
                         .ok_or(EINVAL)
                         .and_then(|data| Coherent::from_slice(dev, data, GFP_KERNEL))?
                 },
-- 
2.54.0