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Rollup merge of #124748 - madsmtm:fix-32bit-watchos-unwind, r=Mark-Simulacrum

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Fix unwinding on 32-bit watchOS ARM (v2)

This PR is identical to https://github.com/rust-lang/rust/pull/124494, which was approved and merged but then removed from master by a force-push due to a [CI bug](https://rust-lang.zulipchat.com/#narrow/stream/242791-t-infra/topic/ci.20broken.3F).

r? Mark-Simulacrum

Original PR description:

---

Found while doing https://github.com/rust-lang/rust/pull/124491, I wanted to unify the code under `target_vendor = "apple"`, and found that [Clang actually specifies that watchOS ARM 32-bit does not use SjLj](https://github.com/llvm/llvm-project/blob/llvmorg-18.1.4/clang/lib/Driver/ToolChains/Darwin.cpp#L3107-L3119).

I don't have an Apple Watch from that generation at hand to test this myself (series 1 to 3), and I don't think it will be sufficient to test it in the simulator (as it's architecture-specific), so maybe someone else could do so?

N.B. The code is written in a way to support 32-bit iOS and tvOS ARM devices (which do use SjLj) for future compatibility even though we currently only have a target for 32-bit iOS ARM (if you think that's excessive, then I'll change it).

`@rustbot` label O-watchos
This commit is contained in:
Guillaume Gomez 2024-05-05 16:42:47 +02:00 committed by GitHub
commit 3b8eba9747
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3 changed files with 23 additions and 15 deletions
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9
library/std/src/sys/personality/dwarf/eh.rs
View File

@ -54,7 +54,14 @@ pub enum EHAction {
Terminate,
}
pub const USING_SJLJ_EXCEPTIONS: bool = cfg!(all(target_os = "ios", target_arch = "arm"));
/// 32-bit Apple ARM uses SjLj exceptions, except for watchOS.
///
/// I.e. iOS and tvOS, as those are the only Apple OSes that used 32-bit ARM
/// devices.
///
/// <https://github.com/llvm/llvm-project/blob/llvmorg-18.1.4/clang/lib/Driver/ToolChains/Darwin.cpp#L3107-L3119>
pub const USING_SJLJ_EXCEPTIONS: bool =
cfg!(all(target_vendor = "apple", not(target_os = "watchos"), target_arch = "arm"));
pub unsafe fn find_eh_action(lsda: *const u8, context: &EHContext<'_>) -> Result<EHAction, ()> {
if lsda.is_null() {

5
library/std/src/sys/personality/gcc.rs
View File

@ -92,11 +92,12 @@ const UNWIND_DATA_REG: (i32, i32) = (4, 5); // a0, a1
// https://github.com/gcc-mirror/gcc/blob/trunk/libgcc/unwind-c.c
cfg_if::cfg_if! {
if #[cfg(all(target_arch = "arm", not(target_os = "ios"), not(target_os = "tvos"), not(target_os = "watchos"), not(target_os = "visionos"), not(target_os = "netbsd")))] {
if #[cfg(all(not(all(target_vendor = "apple", not(target_os = "watchos"))), target_arch = "arm", not(target_os = "netbsd")))] {
// ARM EHABI personality routine.
// https://web.archive.org/web/20190728160938/https://infocenter.arm.com/help/topic/com.arm.doc.ihi0038b/IHI0038B_ehabi.pdf
//
// iOS uses the default routine instead since it uses SjLj unwinding.
// Apple 32-bit ARM (but not watchOS) uses the default routine instead
// since it uses SjLj unwinding.
#[lang = "eh_personality"]
unsafe extern "C" fn rust_eh_personality(
state: uw::_Unwind_State,

24
library/unwind/src/libunwind.rs
View File

@ -33,10 +33,10 @@ pub const unwinder_private_data_size: usize = 2;
#[cfg(all(target_arch = "x86_64", target_os = "windows"))]
pub const unwinder_private_data_size: usize = 6;
#[cfg(all(target_arch = "arm", not(any(target_os = "ios", target_os = "watchos"))))]
#[cfg(all(target_arch = "arm", not(all(target_vendor = "apple", not(target_os = "watchos")))))]
pub const unwinder_private_data_size: usize = 20;
#[cfg(all(target_arch = "arm", any(target_os = "ios", target_os = "watchos")))]
#[cfg(all(target_arch = "arm", all(target_vendor = "apple", not(target_os = "watchos"))))]
pub const unwinder_private_data_size: usize = 5;
#[cfg(all(target_arch = "aarch64", target_pointer_width = "64", not(target_os = "windows")))]
@ -123,7 +123,7 @@ extern "C" {
}
cfg_if::cfg_if! {
if #[cfg(any(target_os = "ios", target_os = "tvos", target_os = "watchos", target_os = "visionos", target_os = "netbsd", not(target_arch = "arm")))] {
if #[cfg(any(all(target_vendor = "apple", not(target_os = "watchos")), target_os = "netbsd", not(target_arch = "arm")))] {
// Not ARM EHABI
#[repr(C)]
#[derive(Copy, Clone, PartialEq)]
@ -258,8 +258,15 @@ if #[cfg(any(target_os = "ios", target_os = "tvos", target_os = "watchos", targe
} // cfg_if!
cfg_if::cfg_if! {
if #[cfg(not(all(target_os = "ios", target_arch = "arm")))] {
// Not 32-bit iOS
if #[cfg(all(target_vendor = "apple", not(target_os = "watchos"), target_arch = "arm"))] {
// 32-bit ARM Apple (except for watchOS) uses SjLj and does not provide
// _Unwind_Backtrace()
extern "C-unwind" {
pub fn _Unwind_SjLj_RaiseException(e: *mut _Unwind_Exception) -> _Unwind_Reason_Code;
}
pub use _Unwind_SjLj_RaiseException as _Unwind_RaiseException;
} else {
#[cfg_attr(
all(feature = "llvm-libunwind", any(target_os = "fuchsia", target_os = "linux", target_os = "xous")),
link(name = "unwind", kind = "static", modifiers = "-bundle")
@ -276,13 +283,6 @@ if #[cfg(not(all(target_os = "ios", target_arch = "arm")))] {
trace_argument: *mut c_void)
-> _Unwind_Reason_Code;
}
} else {
// 32-bit iOS uses SjLj and does not provide _Unwind_Backtrace()
extern "C-unwind" {
pub fn _Unwind_SjLj_RaiseException(e: *mut _Unwind_Exception) -> _Unwind_Reason_Code;
}
pub use _Unwind_SjLj_RaiseException as _Unwind_RaiseException;
}
} // cfg_if!