Rollup merge of #56979 - VardhanThigle:Vardhan/rust-sgx-unwind-support, r=alexcrichton
Adding unwinding support for x86_64_fortanix_unknown_sgx target. Unwinding support is provided by our port of LLVM's libunwind which is available from https://github.com/fortanix/libunwind/tree/release_50. libunwind requires support for rwlock and printing to stderr, which is only provided by `std` for this target. This poses two problems: 1) how to expose the `std` functionality to C and 2) dependency inversion. ### Exposing `std` For exposing the functionality we chose to expose the following symbols: * __rust_rwlock_rdlock * __rust_rwlock_wrlock * __rust_rwlock_unlock * __rust_print_err * __rust_abort Also, the following are needed from `alloc`: * __rust_alloc * __rust_dealloc #### Rust RWLock in C In `libunwind`, RWLock is initialized as a templated static variable: ```c pthread_rwlock_t DwarfFDECache<A>::_lock = PTHREAD_RWLOCK_INITIALIZER; ``` I don't know of a good way to use the Rust sys::rwlock::RWLock type and initializer there. We could have a static global variable in Rust, but that doesn't work with the templating. The variable needs to be initialized statically, since this target doesn't support the .init section. Currently, I just used a byte array and standard C array initialization. The mapping between this C type and the Rust type needs to be manually maintained. There is a compile-time check and a unit test to make sure the Rust versions of these C definitions match the actual Rust type. If any reviewer knows of a better solution, please do tell. ### Dependency inversion issue `std` depends on `panic_unwind` which depends on `libunwind`, and `libunwind` depends on `std`. This is not normally supported by Rust's linking system. Therefore we use raw C exports from `std` *and* `libunwind.a` is linked last in the target `post_link_objects` instead of being built as part of the Rust `libunwind`. Currently, all C exports are defined in `src/libstd/sys/sgx/rwlock.rs` to overcome LTO issues. Only the `__rust_rwlock_*` definitions *need* to live there for privacy reasons. Once again, if any reviewer knows of a better solution, please do tell. r? @alexcrichton
This commit is contained in:
kennytm
commit
10d949aa3e
@ -62,7 +62,7 @@
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if #[cfg(target_os = "emscripten")] {
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#[path = "emcc.rs"]
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mod imp;
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} else if #[cfg(any(target_arch = "wasm32", target_env = "sgx"))] {
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} else if #[cfg(target_arch = "wasm32")] {
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#[path = "dummy.rs"]
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mod imp;
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} else if #[cfg(all(target_env = "msvc", target_arch = "aarch64"))] {
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@ -10,28 +10,29 @@
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use std::iter;
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use super::{LinkerFlavor, Target, TargetOptions, PanicStrategy};
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use super::{LinkerFlavor, PanicStrategy, Target, TargetOptions};
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pub fn target() -> Result<Target, String> {
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const PRE_LINK_ARGS: &[&str] = &[
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"-Wl,--as-needed",
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"-Wl,-z,noexecstack",
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"-m64",
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"-fuse-ld=gold",
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"-nostdlib",
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"-shared",
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"-Wl,-e,sgx_entry",
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"-Wl,-Bstatic",
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"-Wl,--gc-sections",
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"-Wl,-z,text",
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"-Wl,-z,norelro",
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"-Wl,--rosegment",
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"-Wl,--no-undefined",
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"-Wl,--error-unresolved-symbols",
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"-Wl,--no-undefined-version",
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"-Wl,-Bsymbolic",
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"-Wl,--export-dynamic",
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"-fuse-ld=gold",
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"-nostdlib",
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"-shared",
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"-Wl,-e,sgx_entry",
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"-Wl,-Bstatic",
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"-Wl,--gc-sections",
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"-Wl,-z,text",
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"-Wl,-z,norelro",
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"-Wl,--rosegment",
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"-Wl,--no-undefined",
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"-Wl,--error-unresolved-symbols",
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"-Wl,--no-undefined-version",
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"-Wl,-Bsymbolic",
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"-Wl,--export-dynamic",
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];
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const EXPORT_SYMBOLS: &[&str] = &[
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"sgx_entry",
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"HEAP_BASE",
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@ -41,19 +42,26 @@ pub fn target() -> Result<Target, String> {
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"ENCLAVE_SIZE",
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"CFGDATA_BASE",
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"DEBUG",
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"EH_FRM_HDR_BASE",
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"EH_FRM_HDR_SIZE",
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"TEXT_BASE",
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"TEXT_SIZE",
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];
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let opts = TargetOptions {
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dynamic_linking: false,
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executables: true,
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linker_is_gnu: true,
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max_atomic_width: Some(64),
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panic_strategy: PanicStrategy::Abort,
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panic_strategy: PanicStrategy::Unwind,
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cpu: "x86-64".into(),
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features: "+rdrnd,+rdseed".into(),
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position_independent_executables: true,
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pre_link_args: iter::once(
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(LinkerFlavor::Gcc, PRE_LINK_ARGS.iter().cloned().map(String::from).collect())
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).collect(),
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pre_link_args: iter::once((
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LinkerFlavor::Gcc,
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PRE_LINK_ARGS.iter().cloned().map(String::from).collect(),
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))
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.collect(),
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post_link_objects: vec!["libunwind.a".into()],
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override_export_symbols: Some(EXPORT_SYMBOLS.iter().cloned().map(String::from).collect()),
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..Default::default()
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};
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@ -56,6 +56,14 @@ IMAGE_BASE:
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globvar CFGDATA_BASE 8
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/* Non-zero if debugging is enabled, zero otherwise */
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globvar DEBUG 1
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/* The base address (relative to enclave start) of the enclave text section */
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globvar TEXT_BASE 8
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/* The size in bytes of enclacve text section */
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globvar TEXT_SIZE 8
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/* The base address (relative to enclave start) of the enclave EH_FRM_HDR section */
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globvar EH_FRM_HDR_BASE 8
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/* The size in bytes of enclacve EH_FRM_HDR section */
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globvar EH_FRM_HDR_SIZE 8
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.Lreentry_panic_msg:
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.asciz "Re-entered panicked enclave!"
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@ -9,14 +9,25 @@
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// except according to those terms.
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use num::NonZeroUsize;
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use slice;
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use str;
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use super::waitqueue::{WaitVariable, WaitQueue, SpinMutex, NotifiedTcs, try_lock_or_false};
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use super::waitqueue::{
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try_lock_or_false, NotifiedTcs, SpinMutex, SpinMutexGuard, WaitQueue, WaitVariable,
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};
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use mem;
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pub struct RWLock {
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readers: SpinMutex<WaitVariable<Option<NonZeroUsize>>>,
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writer: SpinMutex<WaitVariable<bool>>,
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}
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// Below is to check at compile time, that RWLock has size of 128 bytes.
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#[allow(dead_code)]
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unsafe fn rw_lock_size_assert(r: RWLock) {
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mem::transmute::<RWLock, [u8; 128]>(r);
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}
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//unsafe impl Send for RWLock {}
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//unsafe impl Sync for RWLock {} // FIXME
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@ -24,7 +35,7 @@ impl RWLock {
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pub const fn new() -> RWLock {
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RWLock {
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readers: SpinMutex::new(WaitVariable::new(None)),
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writer: SpinMutex::new(WaitVariable::new(false))
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writer: SpinMutex::new(WaitVariable::new(false)),
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}
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}
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@ -89,9 +100,11 @@ pub unsafe fn try_write(&self) -> bool {
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}
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#[inline]
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pub unsafe fn read_unlock(&self) {
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let mut rguard = self.readers.lock();
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let wguard = self.writer.lock();
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unsafe fn __read_unlock(
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&self,
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mut rguard: SpinMutexGuard<WaitVariable<Option<NonZeroUsize>>>,
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wguard: SpinMutexGuard<WaitVariable<bool>>,
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) {
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*rguard.lock_var_mut() = NonZeroUsize::new(rguard.lock_var().unwrap().get() - 1);
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if rguard.lock_var().is_some() {
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// There are other active readers
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@ -107,9 +120,18 @@ pub unsafe fn read_unlock(&self) {
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}
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#[inline]
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pub unsafe fn write_unlock(&self) {
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pub unsafe fn read_unlock(&self) {
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let rguard = self.readers.lock();
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let wguard = self.writer.lock();
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self.__read_unlock(rguard, wguard);
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}
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#[inline]
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unsafe fn __write_unlock(
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&self,
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rguard: SpinMutexGuard<WaitVariable<Option<NonZeroUsize>>>,
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wguard: SpinMutexGuard<WaitVariable<bool>>,
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) {
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if let Err(mut wguard) = WaitQueue::notify_one(wguard) {
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// No writers waiting, release the write lock
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*wguard.lock_var_mut() = false;
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@ -128,6 +150,109 @@ pub unsafe fn write_unlock(&self) {
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}
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}
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#[inline]
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pub unsafe fn write_unlock(&self) {
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let rguard = self.readers.lock();
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let wguard = self.writer.lock();
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self.__write_unlock(rguard, wguard);
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}
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#[inline]
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unsafe fn unlock(&self) {
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let rguard = self.readers.lock();
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let wguard = self.writer.lock();
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if *wguard.lock_var() == true {
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self.__write_unlock(rguard, wguard);
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} else {
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self.__read_unlock(rguard, wguard);
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}
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}
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#[inline]
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pub unsafe fn destroy(&self) {}
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}
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const EINVAL: i32 = 22;
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#[no_mangle]
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pub unsafe extern "C" fn __rust_rwlock_rdlock(p: *mut RWLock) -> i32 {
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if p.is_null() {
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return EINVAL;
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}
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(*p).read();
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return 0;
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}
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#[no_mangle]
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pub unsafe extern "C" fn __rust_rwlock_wrlock(p: *mut RWLock) -> i32 {
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if p.is_null() {
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return EINVAL;
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}
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(*p).write();
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return 0;
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}
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#[no_mangle]
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pub unsafe extern "C" fn __rust_rwlock_unlock(p: *mut RWLock) -> i32 {
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if p.is_null() {
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return EINVAL;
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}
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(*p).unlock();
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return 0;
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}
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#[no_mangle]
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pub unsafe extern "C" fn __rust_print_err(m: *mut u8, s: i32) {
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if s < 0 {
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return;
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}
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let buf = slice::from_raw_parts(m as *const u8, s as _);
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if let Ok(s) = str::from_utf8(&buf[..buf.iter().position(|&b| b == 0).unwrap_or(buf.len())]) {
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eprint!("{}", s);
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}
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}
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#[no_mangle]
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pub unsafe extern "C" fn __rust_abort() {
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::sys::abort_internal();
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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use core::array::FixedSizeArray;
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use mem::MaybeUninit;
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use {mem, ptr};
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// The below test verifies that the bytes of initialized RWLock are the ones
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// we use in libunwind.
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// If they change we need to update src/UnwindRustSgx.h in libunwind.
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#[test]
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fn test_c_rwlock_initializer() {
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const RWLOCK_INIT: &[u8] = &[
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0x1, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
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0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
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0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
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0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
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0x3, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
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0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
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0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
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0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
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0x1, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
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0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
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0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
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0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
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0x3, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
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0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
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0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
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0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
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];
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let mut init = MaybeUninit::<RWLock>::zeroed();
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init.set(RWLock::new());
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assert_eq!(
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mem::transmute::<_, [u8; 128]>(init.into_inner()).as_slice(),
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RWLOCK_INIT
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);
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}
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}
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@ -26,10 +26,7 @@
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cfg_if! {
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if #[cfg(target_env = "msvc")] {
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// no extra unwinder support needed
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} else if #[cfg(any(
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all(target_arch = "wasm32", not(target_os = "emscripten")),
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target_env = "sgx"
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))] {
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} else if #[cfg(all(target_arch = "wasm32", not(target_os = "emscripten")))] {
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// no unwinder on the system!
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} else {
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extern crate libc;
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