🔒🌯 Provide LLVMTypeWrapper trait, add more wrappers

Instead of keeping raw pointer fields (of types like `LLVMValueRef`,
`LLVMMetadataRef`) public and defining constructors with different
names, provide the `LLVMTypeWrapper` trait with `from_ptr()` and
`as_ptr()` methods.

This will allow to convert all safe wrappers from and to raw pointers
with one method, which is going to be helpful for building macros for
them.

On top of that, add more wrappers:

* `Module`
* `BasicBlock`
* `GlobalAlias`
* `GlobalVariable`
* `Argument`

Use these wrappers in iterators, make sure they don't expose the raw
pointers to the callers.

Author: vadorovsky

src/linker.rs

@@ -14,18 +14,15 @@ use std::{
 use ar::Archive;
 use llvm_sys::{
     bit_writer::LLVMWriteBitcodeToFile,
-    core::{
-        LLVMContextCreate, LLVMContextDispose, LLVMContextSetDiagnosticHandler, LLVMDisposeModule,
-        LLVMGetTarget,
-    },
+    core::{LLVMContextCreate, LLVMContextDispose, LLVMContextSetDiagnosticHandler, LLVMGetTarget},
     error_handling::{LLVMEnablePrettyStackTrace, LLVMInstallFatalErrorHandler},
-    prelude::{LLVMContextRef, LLVMModuleRef},
+    prelude::LLVMContextRef,
     target_machine::{LLVMCodeGenFileType, LLVMDisposeTargetMachine, LLVMTargetMachineRef},
 };
 use thiserror::Error;
 use tracing::{debug, error, info, warn};
 
-use crate::llvm;
+use crate::llvm::{self, LLVMTypeError, LLVMTypeWrapper, Module};
 
 /// Linker error
 #[derive(Debug, Error)]
@@ -77,6 +74,10 @@ pub enum LinkerError {
     /// The input object file does not have embedded bitcode.
     #[error("no bitcode section found in {0}")]
     MissingBitcodeSection(PathBuf),
+
+    /// Instantiating of an LLVM type failed.
+    #[error(transparent)]
+    LLVMType(#[from] LLVMTypeError),
 }
 
 /// BPF Cpu type
@@ -224,21 +225,26 @@ pub struct LinkerOptions {
 }
 
 /// BPF Linker
-pub struct Linker {
+pub struct Linker<'ctx> {
     options: LinkerOptions,
     context: LLVMContextRef,
-    module: LLVMModuleRef,
+    module: Module<'ctx>,
     target_machine: LLVMTargetMachineRef,
     diagnostic_handler: DiagnosticHandler,
 }
 
-impl Linker {
+impl Linker<'_> {
     /// Create a new linker instance with the given options.
     pub fn new(options: LinkerOptions) -> Self {
+        let context = unsafe { LLVMContextCreate() };
+        let module = Module::new(
+            options.output.file_stem().unwrap().to_str().unwrap(),
+            context,
+        );
         Linker {
             options,
-            context: ptr::null_mut(),
-            module: ptr::null_mut(),
+            context,
+            module,
             target_machine: ptr::null_mut(),
             diagnostic_handler: DiagnosticHandler::new(),
         }
@@ -365,7 +371,7 @@ impl Linker {
             Archive => panic!("nested archives not supported duh"),
         };
 
-        if unsafe { !llvm::link_bitcode_buffer(self.context, self.module, &bitcode) } {
+        if unsafe { !llvm::link_bitcode_buffer(self.context, self.module.as_ptr(), &bitcode) } {
             return Err(LinkerError::LinkModuleError(path.to_owned()));
         }
 
@@ -407,11 +413,11 @@ impl Linker {
                 })
             }
             None => {
-                let c_triple = unsafe { LLVMGetTarget(*module) };
+                let c_triple = unsafe { LLVMGetTarget(module.as_ptr()) };
                 let triple = unsafe { CStr::from_ptr(c_triple) }.to_str().unwrap();
                 if triple.starts_with("bpf") {
                     // case 2
-                    (triple, unsafe { llvm::target_from_module(*module) })
+                    (triple, unsafe { llvm::target_from_module(module.as_ptr()) })
                 } else {
                     // case 3.
                     info!("detected non-bpf input target {} and no explicit output --target specified, selecting `bpf'", triple);
@@ -452,17 +458,18 @@ impl Linker {
 
         if self.options.btf {
             // if we want to emit BTF, we need to sanitize the debug information
-            llvm::DISanitizer::new(self.context, self.module).run(&self.options.export_symbols);
+            llvm::DISanitizer::new(self.context, &self.module)
+                .run(&mut self.module, &self.options.export_symbols)?;
         } else {
             // if we don't need BTF emission, we can strip DI
-            let ok = unsafe { llvm::strip_debug_info(self.module) };
+            let ok = unsafe { llvm::strip_debug_info(self.module.as_ptr()) };
             debug!("Stripping DI, changed={}", ok);
         }
 
         unsafe {
             llvm::optimize(
                 self.target_machine,
-                self.module,
+                &mut self.module,
                 self.options.optimize,
                 self.options.ignore_inline_never,
                 &self.options.export_symbols,
@@ -486,7 +493,7 @@ impl Linker {
     fn write_bitcode(&mut self, output: &CStr) -> Result<(), LinkerError> {
         info!("writing bitcode to {:?}", output);
 
-        if unsafe { LLVMWriteBitcodeToFile(self.module, output.as_ptr()) } == 1 {
+        if unsafe { LLVMWriteBitcodeToFile(self.module.as_ptr(), output.as_ptr()) } == 1 {
             return Err(LinkerError::WriteBitcodeError);
         }
 
@@ -496,14 +503,21 @@ impl Linker {
     fn write_ir(&mut self, output: &CStr) -> Result<(), LinkerError> {
         info!("writing IR to {:?}", output);
 
-        unsafe { llvm::write_ir(self.module, output) }.map_err(LinkerError::WriteIRError)
+        unsafe { llvm::write_ir(self.module.as_ptr(), output) }.map_err(LinkerError::WriteIRError)
     }
 
     fn emit(&mut self, output: &CStr, output_type: LLVMCodeGenFileType) -> Result<(), LinkerError> {
         info!("emitting {:?} to {:?}", output_type, output);
 
-        unsafe { llvm::codegen(self.target_machine, self.module, output, output_type) }
-            .map_err(LinkerError::EmitCodeError)
+        unsafe {
+            llvm::codegen(
+                self.target_machine,
+                self.module.as_ptr(),
+                output,
+                output_type,
+            )
+        }
+        .map_err(LinkerError::EmitCodeError)
     }
 
     fn llvm_init(&mut self) {
@@ -542,24 +556,23 @@ impl Linker {
             );
             LLVMInstallFatalErrorHandler(Some(llvm::fatal_error));
             LLVMEnablePrettyStackTrace();
-            self.module = llvm::create_module(
+            self.module = Module::new(
                 self.options.output.file_stem().unwrap().to_str().unwrap(),
                 self.context,
-            )
-            .unwrap();
+            );
         }
     }
 }
 
-impl Drop for Linker {
+impl Drop for Linker<'_> {
     fn drop(&mut self) {
         unsafe {
             if !self.target_machine.is_null() {
                 LLVMDisposeTargetMachine(self.target_machine);
             }
-            if !self.module.is_null() {
-                LLVMDisposeModule(self.module);
-            }
+            // if !self.module.is_null() {
+            //     LLVMDisposeModule(self.module);
+            // }
             if !self.context.is_null() {
                 LLVMContextDispose(self.context);
             }

src/llvm/di.rs

@@ -3,18 +3,24 @@ use std::{
     collections::{hash_map::DefaultHasher, HashMap, HashSet},
     ffi::c_char,
     hash::Hasher,
-    ptr,
+    ptr::{self, NonNull},
 };
 
 use gimli::{DW_TAG_pointer_type, DW_TAG_structure_type, DW_TAG_variant_part};
 use llvm_sys::{core::*, debuginfo::*, prelude::*};
 use tracing::{span, trace, warn, Level};
 
-use super::types::{
-    di::DIType,
-    ir::{Function, MDNode, Metadata, Value},
+use crate::llvm::{
+    iter::*,
+    types::{
+        di::{DISubprogram, DIType},
+        ir::{
+            Argument, Function, GlobalAlias, GlobalVariable, Instruction, MDNode, Metadata, Module,
+            Value,
+        },
+        LLVMTypeError, LLVMTypeWrapper,
+    },
 };
-use crate::llvm::{iter::*, types::di::DISubprogram};
 
 // KSYM_NAME_LEN from linux kernel intentionally set
 // to lower value found accross kernel versions to ensure
@@ -23,7 +29,6 @@ const MAX_KSYM_NAME_LEN: usize = 128;
 
 pub struct DISanitizer {
     context: LLVMContextRef,
-    module: LLVMModuleRef,
     builder: LLVMDIBuilderRef,
     visited_nodes: HashSet<u64>,
     replace_operands: HashMap<u64, LLVMMetadataRef>,
@@ -59,11 +64,11 @@ fn sanitize_type_name<T: AsRef<str>>(name: T) -> String {
 }
 
 impl DISanitizer {
-    pub fn new(context: LLVMContextRef, module: LLVMModuleRef) -> DISanitizer {
+    pub fn new(context: LLVMContextRef, module: &Module<'_>) -> Self {
+        let builder = unsafe { LLVMCreateDIBuilder(module.as_ptr()) };
         DISanitizer {
             context,
-            module,
-            builder: unsafe { LLVMCreateDIBuilder(module) },
+            builder,
             visited_nodes: HashSet::new(),
             replace_operands: HashMap::new(),
             skipped_types: Vec::new(),
@@ -227,7 +232,7 @@ impl DISanitizer {
             // An operand with no value is valid and means that the operand is
             // not set
             (v, Item::Operand { .. }) if v.is_null() => return,
-            (v, _) if !v.is_null() => Value::new(v),
+            (v, _) if !v.is_null() => Value::from_ptr(NonNull::new(v).unwrap()).unwrap(),
             // All other items should have values
             (_, item) => panic!("{item:?} has no value"),
         };
@@ -283,16 +288,18 @@ impl DISanitizer {
         }
     }
 
-    pub fn run(mut self, exported_symbols: &HashSet<Cow<'static, str>>) {
-        let module = self.module;
+    pub fn run(
+        mut self,
+        module: &mut Module<'_>,
+        exported_symbols: &HashSet<Cow<'static, str>>,
+    ) -> Result<(), LLVMTypeError> {
+        self.replace_operands = self.fix_subprogram_linkage(module, exported_symbols)?;
 
-        self.replace_operands = self.fix_subprogram_linkage(exported_symbols);
-
-        for value in module.globals_iter() {
-            self.visit_item(Item::GlobalVariable(value));
+        for global in module.globals_iter() {
+            self.visit_item(Item::GlobalVariable(global));
         }
-        for value in module.global_aliases_iter() {
-            self.visit_item(Item::GlobalAlias(value));
+        for alias in module.global_aliases_iter() {
+            self.visit_item(Item::GlobalAlias(alias));
         }
 
         for function in module.functions_iter() {
@@ -307,6 +314,8 @@ impl DISanitizer {
         }
 
         unsafe { LLVMDisposeDIBuilder(self.builder) };
+
+        Ok(())
     }
 
     // Make it so that only exported symbols (programs marked as #[no_mangle]) get BTF
@@ -324,16 +333,13 @@ impl DISanitizer {
     // See tests/btf/assembly/exported-symbols.rs .
     fn fix_subprogram_linkage(
         &mut self,
+        module: &mut Module<'_>,
         export_symbols: &HashSet<Cow<'static, str>>,
-    ) -> HashMap<u64, LLVMMetadataRef> {
+    ) -> Result<HashMap<u64, LLVMMetadataRef>, LLVMTypeError> {
         let mut replace = HashMap::new();
 
-        for mut function in self
-            .module
-            .functions_iter()
-            .map(|value| unsafe { Function::from_value_ref(value) })
-        {
-            if export_symbols.contains(function.name()) {
+        for mut function in module.functions_iter() {
+            if export_symbols.contains(&function.name()) {
                 continue;
             }
 
@@ -370,7 +376,10 @@ impl DISanitizer {
                 // replace retained nodes manually below.
                 LLVMDIBuilderFinalizeSubprogram(self.builder, new_program);
 
-                DISubprogram::from_value_ref(LLVMMetadataAsValue(self.context, new_program))
+                let new_program = LLVMMetadataAsValue(self.context, new_program);
+                let new_program =
+                    NonNull::new(new_program).expect("new program should not be null");
+                DISubprogram::from_ptr(new_program)?
             };
 
             // Point the function to the new subprogram.
@@ -396,23 +405,23 @@ impl DISanitizer {
                 unsafe { LLVMMDNodeInContext2(self.context, core::ptr::null_mut(), 0) };
             subprogram.set_retained_nodes(empty_node);
 
-            let ret = replace.insert(subprogram.value_ref as u64, unsafe {
-                LLVMValueAsMetadata(new_program.value_ref)
+            let ret = replace.insert(subprogram.as_ptr() as u64, unsafe {
+                LLVMValueAsMetadata(new_program.as_ptr())
             });
             assert!(ret.is_none());
         }
 
-        replace
+        Ok(replace)
     }
 }
 
 #[derive(Clone, Debug, Eq, PartialEq)]
-enum Item {
-    GlobalVariable(LLVMValueRef),
-    GlobalAlias(LLVMValueRef),
-    Function(LLVMValueRef),
-    FunctionParam(LLVMValueRef),
-    Instruction(LLVMValueRef),
+enum Item<'ctx> {
+    GlobalVariable(GlobalVariable<'ctx>),
+    GlobalAlias(GlobalAlias<'ctx>),
+    Function(Function<'ctx>),
+    FunctionParam(Argument<'ctx>),
+    Instruction(Instruction<'ctx>),
     Operand(Operand),
     MetadataEntry(LLVMValueRef, u32, usize),
 }
@@ -437,16 +446,16 @@ impl Operand {
     }
 }
 
-impl Item {
+impl Item<'_> {
     fn value_ref(&self) -> LLVMValueRef {
         match self {
-            Item::GlobalVariable(value)
-            | Item::GlobalAlias(value)
-            | Item::Function(value)
-            | Item::FunctionParam(value)
-            | Item::Instruction(value)
-            | Item::Operand(Operand { value, .. })
-            | Item::MetadataEntry(value, _, _) => *value,
+            Item::GlobalVariable(global) => global.as_ptr(),
+            Item::GlobalAlias(global) => global.as_ptr(),
+            Item::Function(function) => function.as_ptr(),
+            Item::FunctionParam(function_param) => function_param.as_ptr(),
+            Item::Instruction(instruction) => instruction.as_ptr(),
+            Item::Operand(Operand { value, .. }) => *value,
+            Item::MetadataEntry(value, _, _) => *value,
         }
     }