elf: Allow parsing SectionHeader from raw bytes

src/elf/section_header.rs

@@ -442,13 +442,20 @@ if_alloc! {
             self.sh_addr as usize..(self.sh_addr as usize).saturating_add(self.sh_size as usize)
         }
         /// Parse `count` section headers from `bytes` at `offset`, using the given `ctx`
+        /// Assuming this is read from the whole file, it will check offset.
         #[cfg(feature = "endian_fd")]
         pub fn parse(bytes: &[u8], mut offset: usize, mut count: usize, ctx: Ctx) -> error::Result<Vec<SectionHeader>> {
-            use scroll::Pread;
             // Zero offset means no section headers, not even the null section header.
             if offset == 0 {
                 return Ok(Vec::new());
             }
+            Self::parse_lossy(bytes, offset, count, ctx)
+        }
+        /// Parse `count` section headers from `bytes` at `offset`, using the given `ctx`
+        /// without performing any offset checking to allow parsing relatively
+        #[cfg(feature = "endian_fd")]
+        pub fn parse_lossy(bytes: &[u8], mut offset: usize, mut count: usize, ctx: Ctx) -> error::Result<Vec<SectionHeader>> {
+            use scroll::Pread;
             let empty_sh = bytes.gread_with::<SectionHeader>(&mut offset, ctx)?;
             if count == 0 as usize {
                 // Zero count means either no section headers if offset is also zero (checked