btf: Replace / in DATASEC before load to kernel

This replaces the / character with a . which is allowed in the kernel
names. Not allowing a forward slash is perhaps a kernel bug, but lets
fix it up here as it's commonly used for Aya

Signed-off-by: Dave Tucker <dave@dtucker.co.uk>

aya/src/obj/btf/btf.rs

@@ -453,23 +453,29 @@ impl Btf {
                     // Start DataSec Fixups
                     let sec_name = self.string_at(ty.name_off)?;
                     let name = sec_name.to_string();
-                    // There are some cases when the compiler does indeed populate the
-                    // size
-                    if unsafe { ty.__bindgen_anon_1.size > 0 } {
-                        debug!("{} {}: fixup not required", kind, name);
-                        continue;
-                    }
 
                     let mut fixed_ty = *ty;
                     let mut fixed_data = data.clone();
+
+                    // Handle any "/" characters in section names
+                    // Example: "maps/hashmap"
+                    let fixed_name = name.replace('/', ".");
+                    if fixed_name != name {
+                        fixed_ty.name_off = self.add_string(fixed_name);
+                    }
+
+                    // There are some cases when the compiler does indeed populate the
+                    // size
+                    if unsafe { ty.__bindgen_anon_1.size > 0 } {
+                        debug!("{} {}: size fixup not required", kind, name);
+                    } else {
                         // We need to get the size of the section from the ELF file
                         // Fortunately, we cached these when parsing it initially
                         // and we can this up by name in section_sizes
-                    let size =
-                        section_sizes
-                            .get(&name)
-                            .ok_or_else(|| BtfError::UnknownSectionSize {
+                        let size = section_sizes.get(&name).ok_or_else(|| {
+                            BtfError::UnknownSectionSize {
                                 section_name: name.clone(),
+                            }
                         })?;
                         debug!("{} {}: fixup size to {}", kind, name, size);
                         fixed_ty.__bindgen_anon_1.size = *size as u32;
@@ -506,6 +512,7 @@ impl Btf {
                                 return Err(BtfError::InvalidDatasec);
                             }
                         }
+                    }
                     types.types[i] = BtfType::DataSec(fixed_ty, fixed_data);
                 }
                 // Fixup FUNC_PROTO
@@ -1097,7 +1104,7 @@ mod tests {
             BTF_VAR_GLOBAL_EXTERN,
         ));
 
-        let name_offset = btf.add_string(".data".to_string());
+        let name_offset = btf.add_string(".data/foo".to_string());
         let variables = vec![btf_var_secinfo {
             type_: var_type_id,
             offset: 0,
@@ -1111,14 +1118,14 @@ mod tests {
         };
 
         btf.fixup_and_sanitize(
-            &HashMap::from([(".data".to_string(), 32u64)]),
+            &HashMap::from([(".data/foo".to_string(), 32u64)]),
             &HashMap::from([("foo".to_string(), 64u64)]),
             &features,
         )
         .unwrap();
 
         if let BtfType::DataSec(fixed, sec_info) = btf.type_by_id(datasec_type_id).unwrap() {
-            assert!(fixed.name_off == name_offset);
+            assert!(fixed.name_off != name_offset);
             assert!(unsafe { fixed.__bindgen_anon_1.size } == 32);
             assert!(sec_info.len() == 1);
             assert!(sec_info[0].type_ == var_type_id);
@@ -1126,7 +1133,8 @@ mod tests {
                 sec_info[0].offset == 64,
                 "expected 64, got {}",
                 sec_info[0].offset
-            )
+            );
+            assert!(btf.string_at(fixed.name_off).unwrap() == ".data.foo")
         } else {
             panic!("not a datasec")
         }