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-rw-r--r--library/backtrace/src/backtrace/libunwind.rs267
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diff --git a/library/backtrace/src/backtrace/libunwind.rs b/library/backtrace/src/backtrace/libunwind.rs
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+//! Backtrace support using libunwind/gcc_s/etc APIs.
+//!
+//! This module contains the ability to unwind the stack using libunwind-style
+//! APIs. Note that there's a whole bunch of implementations of the
+//! libunwind-like API, and this is just trying to be compatible with most of
+//! them all at once instead of being picky.
+//!
+//! The libunwind API is powered by `_Unwind_Backtrace` and is in practice very
+//! reliable at generating a backtrace. It's not entirely clear how it does it
+//! (frame pointers? eh_frame info? both?) but it seems to work!
+//!
+//! Most of the complexity of this module is handling the various platform
+//! differences across libunwind implementations. Otherwise this is a pretty
+//! straightforward Rust binding to the libunwind APIs.
+//!
+//! This is the default unwinding API for all non-Windows platforms currently.
+
+use super::super::Bomb;
+use core::ffi::c_void;
+
+pub enum Frame {
+ Raw(*mut uw::_Unwind_Context),
+ Cloned {
+ ip: *mut c_void,
+ sp: *mut c_void,
+ symbol_address: *mut c_void,
+ },
+}
+
+// With a raw libunwind pointer it should only ever be access in a readonly
+// threadsafe fashion, so it's `Sync`. When sending to other threads via `Clone`
+// we always switch to a version which doesn't retain interior pointers, so we
+// should be `Send` as well.
+unsafe impl Send for Frame {}
+unsafe impl Sync for Frame {}
+
+impl Frame {
+ pub fn ip(&self) -> *mut c_void {
+ let ctx = match *self {
+ Frame::Raw(ctx) => ctx,
+ Frame::Cloned { ip, .. } => return ip,
+ };
+ unsafe { uw::_Unwind_GetIP(ctx) as *mut c_void }
+ }
+
+ pub fn sp(&self) -> *mut c_void {
+ match *self {
+ Frame::Raw(ctx) => unsafe { uw::get_sp(ctx) as *mut c_void },
+ Frame::Cloned { sp, .. } => sp,
+ }
+ }
+
+ pub fn symbol_address(&self) -> *mut c_void {
+ if let Frame::Cloned { symbol_address, .. } = *self {
+ return symbol_address;
+ }
+
+ // The macOS linker emits a "compact" unwind table that only includes an
+ // entry for a function if that function either has an LSDA or its
+ // encoding differs from that of the previous entry. Consequently, on
+ // macOS, `_Unwind_FindEnclosingFunction` is unreliable (it can return a
+ // pointer to some totally unrelated function). Instead, we just always
+ // return the ip.
+ //
+ // https://github.com/rust-lang/rust/issues/74771#issuecomment-664056788
+ //
+ // Note the `skip_inner_frames.rs` test is skipped on macOS due to this
+ // clause, and if this is fixed that test in theory can be run on macOS!
+ if cfg!(target_os = "macos") || cfg!(target_os = "ios") {
+ self.ip()
+ } else {
+ unsafe { uw::_Unwind_FindEnclosingFunction(self.ip()) }
+ }
+ }
+
+ pub fn module_base_address(&self) -> Option<*mut c_void> {
+ None
+ }
+}
+
+impl Clone for Frame {
+ fn clone(&self) -> Frame {
+ Frame::Cloned {
+ ip: self.ip(),
+ sp: self.sp(),
+ symbol_address: self.symbol_address(),
+ }
+ }
+}
+
+#[inline(always)]
+pub unsafe fn trace(mut cb: &mut dyn FnMut(&super::Frame) -> bool) {
+ uw::_Unwind_Backtrace(trace_fn, &mut cb as *mut _ as *mut _);
+
+ extern "C" fn trace_fn(
+ ctx: *mut uw::_Unwind_Context,
+ arg: *mut c_void,
+ ) -> uw::_Unwind_Reason_Code {
+ let cb = unsafe { &mut *(arg as *mut &mut dyn FnMut(&super::Frame) -> bool) };
+ let cx = super::Frame {
+ inner: Frame::Raw(ctx),
+ };
+
+ let mut bomb = Bomb { enabled: true };
+ let keep_going = cb(&cx);
+ bomb.enabled = false;
+
+ if keep_going {
+ uw::_URC_NO_REASON
+ } else {
+ uw::_URC_FAILURE
+ }
+ }
+}
+
+/// Unwind library interface used for backtraces
+///
+/// Note that dead code is allowed as here are just bindings
+/// iOS doesn't use all of them it but adding more
+/// platform-specific configs pollutes the code too much
+#[allow(non_camel_case_types)]
+#[allow(non_snake_case)]
+#[allow(dead_code)]
+mod uw {
+ pub use self::_Unwind_Reason_Code::*;
+
+ use core::ffi::c_void;
+
+ #[repr(C)]
+ pub enum _Unwind_Reason_Code {
+ _URC_NO_REASON = 0,
+ _URC_FOREIGN_EXCEPTION_CAUGHT = 1,
+ _URC_FATAL_PHASE2_ERROR = 2,
+ _URC_FATAL_PHASE1_ERROR = 3,
+ _URC_NORMAL_STOP = 4,
+ _URC_END_OF_STACK = 5,
+ _URC_HANDLER_FOUND = 6,
+ _URC_INSTALL_CONTEXT = 7,
+ _URC_CONTINUE_UNWIND = 8,
+ _URC_FAILURE = 9, // used only by ARM EABI
+ }
+
+ pub enum _Unwind_Context {}
+
+ pub type _Unwind_Trace_Fn =
+ extern "C" fn(ctx: *mut _Unwind_Context, arg: *mut c_void) -> _Unwind_Reason_Code;
+
+ extern "C" {
+ pub fn _Unwind_Backtrace(
+ trace: _Unwind_Trace_Fn,
+ trace_argument: *mut c_void,
+ ) -> _Unwind_Reason_Code;
+ }
+
+ cfg_if::cfg_if! {
+ // available since GCC 4.2.0, should be fine for our purpose
+ if #[cfg(all(
+ not(all(target_os = "android", target_arch = "arm")),
+ not(all(target_os = "freebsd", target_arch = "arm")),
+ not(all(target_os = "linux", target_arch = "arm")),
+ not(all(target_os = "horizon", target_arch = "arm"))
+ ))] {
+ extern "C" {
+ pub fn _Unwind_GetIP(ctx: *mut _Unwind_Context) -> libc::uintptr_t;
+ pub fn _Unwind_FindEnclosingFunction(pc: *mut c_void) -> *mut c_void;
+
+ #[cfg(not(all(target_os = "linux", target_arch = "s390x")))]
+ // This function is a misnomer: rather than getting this frame's
+ // Canonical Frame Address (aka the caller frame's SP) it
+ // returns this frame's SP.
+ //
+ // https://github.com/libunwind/libunwind/blob/d32956507cf29d9b1a98a8bce53c78623908f4fe/src/unwind/GetCFA.c#L28-L35
+ #[link_name = "_Unwind_GetCFA"]
+ pub fn get_sp(ctx: *mut _Unwind_Context) -> libc::uintptr_t;
+
+ }
+
+ // s390x uses a biased CFA value, therefore we need to use
+ // _Unwind_GetGR to get the stack pointer register (%r15)
+ // instead of relying on _Unwind_GetCFA.
+ #[cfg(all(target_os = "linux", target_arch = "s390x"))]
+ pub unsafe fn get_sp(ctx: *mut _Unwind_Context) -> libc::uintptr_t {
+ extern "C" {
+ pub fn _Unwind_GetGR(ctx: *mut _Unwind_Context, index: libc::c_int) -> libc::uintptr_t;
+ }
+ _Unwind_GetGR(ctx, 15)
+ }
+ } else {
+ // On android and arm, the function `_Unwind_GetIP` and a bunch of
+ // others are macros, so we define functions containing the
+ // expansion of the macros.
+ //
+ // TODO: link to the header file that defines these macros, if you
+ // can find it. (I, fitzgen, cannot find the header file that some
+ // of these macro expansions were originally borrowed from.)
+ #[repr(C)]
+ enum _Unwind_VRS_Result {
+ _UVRSR_OK = 0,
+ _UVRSR_NOT_IMPLEMENTED = 1,
+ _UVRSR_FAILED = 2,
+ }
+ #[repr(C)]
+ enum _Unwind_VRS_RegClass {
+ _UVRSC_CORE = 0,
+ _UVRSC_VFP = 1,
+ _UVRSC_FPA = 2,
+ _UVRSC_WMMXD = 3,
+ _UVRSC_WMMXC = 4,
+ }
+ #[repr(C)]
+ enum _Unwind_VRS_DataRepresentation {
+ _UVRSD_UINT32 = 0,
+ _UVRSD_VFPX = 1,
+ _UVRSD_FPAX = 2,
+ _UVRSD_UINT64 = 3,
+ _UVRSD_FLOAT = 4,
+ _UVRSD_DOUBLE = 5,
+ }
+
+ type _Unwind_Word = libc::c_uint;
+ extern "C" {
+ fn _Unwind_VRS_Get(
+ ctx: *mut _Unwind_Context,
+ klass: _Unwind_VRS_RegClass,
+ word: _Unwind_Word,
+ repr: _Unwind_VRS_DataRepresentation,
+ data: *mut c_void,
+ ) -> _Unwind_VRS_Result;
+ }
+
+ pub unsafe fn _Unwind_GetIP(ctx: *mut _Unwind_Context) -> libc::uintptr_t {
+ let mut val: _Unwind_Word = 0;
+ let ptr = &mut val as *mut _Unwind_Word;
+ let _ = _Unwind_VRS_Get(
+ ctx,
+ _Unwind_VRS_RegClass::_UVRSC_CORE,
+ 15,
+ _Unwind_VRS_DataRepresentation::_UVRSD_UINT32,
+ ptr as *mut c_void,
+ );
+ (val & !1) as libc::uintptr_t
+ }
+
+ // R13 is the stack pointer on arm.
+ const SP: _Unwind_Word = 13;
+
+ pub unsafe fn get_sp(ctx: *mut _Unwind_Context) -> libc::uintptr_t {
+ let mut val: _Unwind_Word = 0;
+ let ptr = &mut val as *mut _Unwind_Word;
+ let _ = _Unwind_VRS_Get(
+ ctx,
+ _Unwind_VRS_RegClass::_UVRSC_CORE,
+ SP,
+ _Unwind_VRS_DataRepresentation::_UVRSD_UINT32,
+ ptr as *mut c_void,
+ );
+ val as libc::uintptr_t
+ }
+
+ // This function also doesn't exist on Android or ARM/Linux, so make it
+ // a no-op.
+ pub unsafe fn _Unwind_FindEnclosingFunction(pc: *mut c_void) -> *mut c_void {
+ pc
+ }
+ }
+ }
+}
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