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Rollup merge of #93269 - jacobbramley:dev/pauth-option-1, r=petrochenkov

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Use error-on-mismatch policy for PAuth module flags.

This agrees with Clang, and avoids an error when using LTO with mixed
C/Rust. LLVM considers different behaviour flags to be a mismatch,
even when the flag value itself is the same.

This also makes the flag setting explicit for all uses of
LLVMRustAddModuleFlag.

----

I believe that this fixes #92885, but have only reproduced it locally on Linux hosts so cannot confirm that it fixes the issue as reported.

I have not included a test for this because it is covered by an existing test (`src/test/run-make-fulldeps/cross-lang-lto-clang`). It is not without its problems, though:
* The test requires Clang and `--run-clang-based-tests-with=...` to run, and this is not the case on the CI.
   * Any test I add would have a similar requirement.
* With this patch applied, the test gets further, but it still fails (for other reasons). I don't think that affects #92885.
This commit is contained in:
Matthias Krüger 2022-01-25 05:51:14 +01:00 • committed by GitHub
commit 13b87d8cc7
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4 changed files with 73 additions and 13 deletions
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31
compiler/rustc_codegen_llvm/src/context.rs
View file

@ -215,16 +215,19 @@ pub unsafe fn create_module<'ll>(
// to ensure intrinsic calls don't use it.
if !sess.needs_plt() {
let avoid_plt = "RtLibUseGOT\0".as_ptr().cast();
llvm::LLVMRustAddModuleFlag(llmod, avoid_plt, 1);
llvm::LLVMRustAddModuleFlag(llmod, llvm::LLVMModFlagBehavior::Warning, avoid_plt, 1);
}
if sess.is_sanitizer_cfi_enabled() {
// FIXME(rcvalle): Add support for non canonical jump tables.
let canonical_jump_tables = "CFI Canonical Jump Tables\0".as_ptr().cast();
// FIXME(rcvalle): Add it with Override behavior flag--LLVMRustAddModuleFlag adds it with
// Warning behavior flag. Add support for specifying the behavior flag to
// LLVMRustAddModuleFlag.
llvm::LLVMRustAddModuleFlag(llmod, canonical_jump_tables, 1);
// FIXME(rcvalle): Add it with Override behavior flag.
llvm::LLVMRustAddModuleFlag(
llmod,
llvm::LLVMModFlagBehavior::Warning,
canonical_jump_tables,
1,
);
}
// Control Flow Guard is currently only supported by the MSVC linker on Windows.
@ -233,11 +236,21 @@ pub unsafe fn create_module<'ll>(
CFGuard::Disabled => {}
CFGuard::NoChecks => {
// Set `cfguard=1` module flag to emit metadata only.
llvm::LLVMRustAddModuleFlag(llmod, "cfguard\0".as_ptr() as *const _, 1)
llvm::LLVMRustAddModuleFlag(
llmod,
llvm::LLVMModFlagBehavior::Warning,
"cfguard\0".as_ptr() as *const _,
1,
)
}
CFGuard::Checks => {
// Set `cfguard=2` module flag to emit metadata and checks.
llvm::LLVMRustAddModuleFlag(llmod, "cfguard\0".as_ptr() as *const _, 2)
llvm::LLVMRustAddModuleFlag(
llmod,
llvm::LLVMModFlagBehavior::Warning,
"cfguard\0".as_ptr() as *const _,
2,
)
}
}
}
@ -247,24 +260,28 @@ pub unsafe fn create_module<'ll>(
llvm::LLVMRustAddModuleFlag(
llmod,
llvm::LLVMModFlagBehavior::Error,
"branch-target-enforcement\0".as_ptr().cast(),
bti.into(),
);
llvm::LLVMRustAddModuleFlag(
llmod,
llvm::LLVMModFlagBehavior::Error,
"sign-return-address\0".as_ptr().cast(),
pac.is_some().into(),
);
let pac_opts = pac.unwrap_or(PacRet { leaf: false, key: PAuthKey::A });
llvm::LLVMRustAddModuleFlag(
llmod,
llvm::LLVMModFlagBehavior::Error,
"sign-return-address-all\0".as_ptr().cast(),
pac_opts.leaf.into(),
);
let is_bkey = if pac_opts.key == PAuthKey::A { false } else { true };
llvm::LLVMRustAddModuleFlag(
llmod,
llvm::LLVMModFlagBehavior::Error,
"sign-return-address-with-bkey\0".as_ptr().cast(),
is_bkey.into(),
);

15
compiler/rustc_codegen_llvm/src/debuginfo/mod.rs
View file

@ -108,18 +108,29 @@ impl<'a, 'tcx> CrateDebugContext<'a, 'tcx> {
// This can be overridden using --llvm-opts -dwarf-version,N.
// Android has the same issue (#22398)
if let Some(version) = sess.target.dwarf_version {
llvm::LLVMRustAddModuleFlag(self.llmod, "Dwarf Version\0".as_ptr().cast(), version)
llvm::LLVMRustAddModuleFlag(
self.llmod,
llvm::LLVMModFlagBehavior::Warning,
"Dwarf Version\0".as_ptr().cast(),
version,
)
}
// Indicate that we want CodeView debug information on MSVC
if sess.target.is_like_msvc {
llvm::LLVMRustAddModuleFlag(self.llmod, "CodeView\0".as_ptr().cast(), 1)
llvm::LLVMRustAddModuleFlag(
self.llmod,
llvm::LLVMModFlagBehavior::Warning,
"CodeView\0".as_ptr().cast(),
1,
)
}
// Prevent bitcode readers from deleting the debug info.
let ptr = "Debug Info Version\0".as_ptr();
llvm::LLVMRustAddModuleFlag(
self.llmod,
llvm::LLVMModFlagBehavior::Warning,
ptr.cast(),
llvm::LLVMRustDebugMetadataVersion(),
);

31
compiler/rustc_codegen_llvm/src/llvm/ffi.rs
View file

@ -61,6 +61,26 @@ pub enum LLVMMachineType {
ARM = 0x01c0,
}
/// LLVM's Module::ModFlagBehavior, defined in llvm/include/llvm/IR/Module.h.
///
/// When merging modules (e.g. during LTO), their metadata flags are combined. Conflicts are
/// resolved according to the merge behaviors specified here. Flags differing only in merge
/// behavior are still considered to be in conflict.
///
/// In order for Rust-C LTO to work, we must specify behaviors compatible with Clang. Notably,
/// 'Error' and 'Warning' cannot be mixed for a given flag.
#[derive(Copy, Clone, PartialEq)]
#[repr(C)]
pub enum LLVMModFlagBehavior {
Error = 1,
Warning = 2,
Require = 3,
Override = 4,
Append = 5,
AppendUnique = 6,
Max = 7,
}
// Consts for the LLVM CallConv type, pre-cast to usize.
/// LLVM CallingConv::ID. Should we wrap this?
@ -1895,7 +1915,16 @@ extern "C" {
pub fn LLVMRustIsRustLLVM() -> bool;
pub fn LLVMRustAddModuleFlag(M: &Module, name: *const c_char, value: u32);
/// Add LLVM module flags.
///
/// In order for Rust-C LTO to work, module flags must be compatible with Clang. What
/// "compatible" means depends on the merge behaviors involved.
pub fn LLVMRustAddModuleFlag(
M: &Module,
merge_behavior: LLVMModFlagBehavior,
name: *const c_char,
value: u32,
);
pub fn LLVMRustMetadataAsValue<'a>(C: &'a Context, MD: &'a Metadata) -> &'a Value;

9
compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
View file

@ -722,9 +722,12 @@ extern "C" bool LLVMRustIsRustLLVM() {
#endif
}
extern "C" void LLVMRustAddModuleFlag(LLVMModuleRef M, const char *Name,
uint32_t Value) {
unwrap(M)->addModuleFlag(Module::Warning, Name, Value);
extern "C" void LLVMRustAddModuleFlag(
LLVMModuleRef M,
Module::ModFlagBehavior MergeBehavior,
const char *Name,
uint32_t Value) {
unwrap(M)->addModuleFlag(MergeBehavior, Name, Value);
}
extern "C" LLVMValueRef LLVMRustMetadataAsValue(LLVMContextRef C, LLVMMetadataRef MD) {