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Register individual FDEs for musl libc.

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When targeting musl, libunwind is used for the `__register_frame`
implementation.

Unlike when targeting libgcc which expects an entire frame table, the libunwind
implementation expects a single FDE.

This change ensures Wasmtime registers each individual FDE when targeting musl.

Fixes #1904.
This commit is contained in:
Peter Huene
2020-06-23 13:45:18 -07:00
parent 9751b96c5e
commit 4087fcee65
1 changed files with 24 additions and 24 deletions
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48
crates/jit/src/unwind/systemv.rs
View File

@@ -90,8 +90,10 @@ impl UnwindRegistry {
let mut eh_frame = EhFrame(EndianVec::new(RunTimeEndian::default()));
table.write_eh_frame(&mut eh_frame).unwrap();
// GCC expects a terminating "empty" length, so write a 0 length at the end of the table.
eh_frame.0.write_u32(0).unwrap();
if cfg!(all(target_os = "linux", target_env = "gnu")) {
// libgcc expects a terminating "empty" length, so write a 0 length at the end of the table.
eh_frame.0.write_u32(0).unwrap();
}
self.frame_table = eh_frame.0.into_vec();
@@ -99,31 +101,29 @@ impl UnwindRegistry {
}
unsafe fn register_frames(&mut self) {
cfg_if::cfg_if! {
if #[cfg(target_os = "macos")] {
// On macOS, `__register_frame` takes a pointer to a single FDE
let start = self.frame_table.as_ptr();
let end = start.add(self.frame_table.len());
let mut current = start;
if cfg!(all(target_os = "linux", target_env = "gnu")) {
// On gnu (libgcc), `__register_frame` will walk the FDEs until an entry of length 0
let ptr = self.frame_table.as_ptr();
__register_frame(ptr);
self.registrations.push(ptr as usize);
} else {
// For libunwind, `__register_frame` takes a pointer to a single FDE
let start = self.frame_table.as_ptr();
let end = start.add(self.frame_table.len());
let mut current = start;
// Walk all of the entries in the frame table and register them
while current < end {
let len = std::ptr::read::<u32>(current as *const u32) as usize;
// Walk all of the entries in the frame table and register them
while current < end {
let len = std::ptr::read::<u32>(current as *const u32) as usize;
// Skip over the CIE
if current != start {
__register_frame(current);
self.registrations.push(current as usize);
}
// Move to the next table entry (+4 because the length itself is not inclusive)
current = current.add(len + 4);
// Skip over the CIE
if current != start {
__register_frame(current);
self.registrations.push(current as usize);
}
} else {
// On other platforms, `__register_frame` will walk the FDEs until an entry of length 0
let ptr = self.frame_table.as_ptr();
__register_frame(ptr);
self.registrations.push(ptr as usize);
// Move to the next table entry (+4 because the length itself is not inclusive)
current = current.add(len + 4);
}
}
}