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Implement unwinding for Win64.
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The original trick used to trigger unwinds would not work with GCC's implementation of SEH, so I had to invent a new one: rust_try now consists of two routines: the outer one, whose handler triggers unwinds, and the inner one, that stops unwinds by having a landing pad that swallows exceptions and passes them on to the outer routine via a normal return.
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@vadimcn
vadimcn committed Aug 5, 2014
1 parent a12b235 commit 5a24ee8
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Showing 3 changed files with 146 additions and 35 deletions.
2 changes: 1 addition & 1 deletion src/librustrt/libunwind.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -60,7 +60,7 @@ pub type _Unwind_Word = libc::uintptr_t;
pub static unwinder_private_data_size: uint = 5;

#[cfg(target_arch = "x86_64")]
pub static unwinder_private_data_size: uint = 2;
pub static unwinder_private_data_size: uint = 6;

#[cfg(target_arch = "arm", not(target_os = "ios"))]
pub static unwinder_private_data_size: uint = 20;
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145 changes: 120 additions & 25 deletions src/librustrt/unwind.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -227,7 +227,7 @@ fn rust_exception_class() -> uw::_Unwind_Exception_Class {
// This is achieved by overriding the return value in search phase to always
// say "catch!".

#[cfg(not(target_arch = "arm"), not(test))]
#[cfg(not(target_arch = "arm"), not(windows, target_arch = "x86_64"), not(test))]
#[doc(hidden)]
#[allow(visible_private_types)]
pub mod eabi {
Expand All @@ -244,7 +244,8 @@ pub mod eabi {
}

#[lang="eh_personality"]
extern fn eh_personality(
#[no_mangle] // referenced from rust_try.ll
extern fn rust_eh_personality(
version: c_int,
actions: uw::_Unwind_Action,
exception_class: uw::_Unwind_Exception_Class,
Expand All @@ -260,21 +261,19 @@ pub mod eabi {

#[no_mangle] // referenced from rust_try.ll
pub extern "C" fn rust_eh_personality_catch(
version: c_int,
_version: c_int,
actions: uw::_Unwind_Action,
exception_class: uw::_Unwind_Exception_Class,
ue_header: *mut uw::_Unwind_Exception,
context: *mut uw::_Unwind_Context
_exception_class: uw::_Unwind_Exception_Class,
_ue_header: *mut uw::_Unwind_Exception,
_context: *mut uw::_Unwind_Context
) -> uw::_Unwind_Reason_Code
{

if (actions as c_int & uw::_UA_SEARCH_PHASE as c_int) != 0 { // search phase
uw::_URC_HANDLER_FOUND // catch!
}
else { // cleanup phase
unsafe {
__gcc_personality_v0(version, actions, exception_class, ue_header,
context)
}
uw::_URC_INSTALL_CONTEXT
}
}
}
Expand All @@ -299,7 +298,7 @@ pub mod eabi {
}

#[lang="eh_personality"]
#[no_mangle] // so we can reference it by name from middle/trans/base.rs
#[no_mangle] // referenced from rust_try.ll
pub extern "C" fn rust_eh_personality(
version: c_int,
actions: uw::_Unwind_Action,
Expand All @@ -316,29 +315,26 @@ pub mod eabi {

#[no_mangle] // referenced from rust_try.ll
pub extern "C" fn rust_eh_personality_catch(
version: c_int,
_version: c_int,
actions: uw::_Unwind_Action,
exception_class: uw::_Unwind_Exception_Class,
ue_header: *mut uw::_Unwind_Exception,
context: *mut uw::_Unwind_Context
_exception_class: uw::_Unwind_Exception_Class,
_ue_header: *mut uw::_Unwind_Exception,
_context: *mut uw::_Unwind_Context
) -> uw::_Unwind_Reason_Code
{
if (actions as c_int & uw::_UA_SEARCH_PHASE as c_int) != 0 { // search phase
uw::_URC_HANDLER_FOUND // catch!
}
else { // cleanup phase
unsafe {
__gcc_personality_sj0(version, actions, exception_class, ue_header,
context)
}
uw::_URC_INSTALL_CONTEXT
}
}
}


// ARM EHABI uses a slightly different personality routine signature,
// but otherwise works the same.
#[cfg(target_arch = "arm", not(test), not(target_os = "ios"))]
#[cfg(target_arch = "arm", not(target_os = "ios", not(test)))]
#[allow(visible_private_types)]
pub mod eabi {
use uw = libunwind;
Expand All @@ -352,7 +348,8 @@ pub mod eabi {
}

#[lang="eh_personality"]
extern "C" fn eh_personality(
#[no_mangle] // referenced from rust_try.ll
extern "C" fn rust_eh_personality(
state: uw::_Unwind_State,
ue_header: *mut uw::_Unwind_Exception,
context: *mut uw::_Unwind_Context
Expand All @@ -366,19 +363,117 @@ pub mod eabi {
#[no_mangle] // referenced from rust_try.ll
pub extern "C" fn rust_eh_personality_catch(
state: uw::_Unwind_State,
ue_header: *mut uw::_Unwind_Exception,
context: *mut uw::_Unwind_Context
_ue_header: *mut uw::_Unwind_Exception,
_context: *mut uw::_Unwind_Context
) -> uw::_Unwind_Reason_Code
{
if (state as c_int & uw::_US_ACTION_MASK as c_int)
== uw::_US_VIRTUAL_UNWIND_FRAME as c_int { // search phase
uw::_URC_HANDLER_FOUND // catch!
}
else { // cleanup phase
unsafe {
__gcc_personality_v0(state, ue_header, context)
uw::_URC_INSTALL_CONTEXT
}
}
}

// Win64 SEH (see http://msdn.microsoft.com/en-us/library/1eyas8tf.aspx)
//
// This looks a bit convoluted because rather than implementing a native SEH handler,
// GCC reuses the same personality routine as for the other architectures by wrapping it
// with an "API translator" layer (_GCC_specific_handler).

#[cfg(windows, target_arch = "x86_64", not(test))]
#[allow(visible_private_types)]
#[allow(non_camel_case_types)]
#[allow(unused_variable)]
#[allow(uppercase_variables)]
pub mod eabi {
use uw = libunwind;
use libc::{c_void, c_int};

struct EXCEPTION_RECORD;
struct CONTEXT;
struct DISPATCHER_CONTEXT;

#[repr(C)]
enum EXCEPTION_DISPOSITION {
ExceptionContinueExecution,
ExceptionContinueSearch,
ExceptionNestedException,
ExceptionCollidedUnwind
}

type _Unwind_Personality_Fn =
extern "C" fn(
version: c_int,
actions: uw::_Unwind_Action,
exception_class: uw::_Unwind_Exception_Class,
ue_header: *mut uw::_Unwind_Exception,
context: *mut uw::_Unwind_Context
) -> uw::_Unwind_Reason_Code;

extern "C" {
fn __gcc_personality_seh0(
exceptionRecord: *mut EXCEPTION_RECORD,
establisherFrame: *mut c_void,
contextRecord: *mut CONTEXT,
dispatcherContext: *mut DISPATCHER_CONTEXT
) -> EXCEPTION_DISPOSITION;

fn _GCC_specific_handler(
exceptionRecord: *mut EXCEPTION_RECORD,
establisherFrame: *mut c_void,
contextRecord: *mut CONTEXT,
dispatcherContext: *mut DISPATCHER_CONTEXT,
personality: _Unwind_Personality_Fn
) -> EXCEPTION_DISPOSITION;
}

#[lang="eh_personality"]
#[no_mangle] // referenced from rust_try.ll
extern "C" fn rust_eh_personality(
exceptionRecord: *mut EXCEPTION_RECORD,
establisherFrame: *mut c_void,
contextRecord: *mut CONTEXT,
dispatcherContext: *mut DISPATCHER_CONTEXT
) -> EXCEPTION_DISPOSITION
{
unsafe {
__gcc_personality_seh0(exceptionRecord, establisherFrame,
contextRecord, dispatcherContext)
}
}

#[no_mangle] // referenced from rust_try.ll
pub extern "C" fn rust_eh_personality_catch(
exceptionRecord: *mut EXCEPTION_RECORD,
establisherFrame: *mut c_void,
contextRecord: *mut CONTEXT,
dispatcherContext: *mut DISPATCHER_CONTEXT
) -> EXCEPTION_DISPOSITION
{
extern "C" fn inner(
_version: c_int,
actions: uw::_Unwind_Action,
_exception_class: uw::_Unwind_Exception_Class,
_ue_header: *mut uw::_Unwind_Exception,
_context: *mut uw::_Unwind_Context
) -> uw::_Unwind_Reason_Code
{
if (actions as c_int & uw::_UA_SEARCH_PHASE as c_int) != 0 { // search phase
uw::_URC_HANDLER_FOUND // catch!
}
else { // cleanup phase
uw::_URC_INSTALL_CONTEXT
}
}

unsafe {
_GCC_specific_handler(exceptionRecord, establisherFrame,
contextRecord, dispatcherContext,
inner)
}
}
}

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34 changes: 25 additions & 9 deletions src/rt/rust_try.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -11,24 +11,40 @@
; Rust's try-catch
; When f(...) returns normally, the return value is null.
; When f(...) throws, the return value is a pointer to the caught exception object.
; See also: libstd/rt/unwind.rs
; See also: librustrt/unwind.rs

define i8* @rust_try(void (i8*,i8*)* %f, i8* %fptr, i8* %env) {

invoke void %f(i8* %fptr, i8* %env)
to label %normal
unwind label %catch
%1 = invoke i8* @rust_try_inner(void (i8*,i8*)* %f, i8* %fptr, i8* %env)
to label %normal
unwind label %catch

normal:
ret i8* null
ret i8* %1

catch:
%1 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @rust_eh_personality_catch to i8*)
catch i8* null ; catch everything
landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @rust_eh_personality_catch to i8*)
catch i8* null
; execution will never reach here because rust_try_inner's landing pad does not resume unwinds
ret i8* null
}

define internal i8* @rust_try_inner(void (i8*,i8*)* %f, i8* %fptr, i8* %env) {

invoke void %f(i8* %fptr, i8* %env)
to label %normal
unwind label %catch

; extract and return pointer to the exception object
normal:
ret i8* null

catch:
%1 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @rust_eh_personality to i8*)
catch i8* null
; extract and return pointer to the exception object
%2 = extractvalue { i8*, i32 } %1, 0
ret i8* %2
ret i8* %2
}

declare i32 @rust_eh_personality(...)
declare i32 @rust_eh_personality_catch(...)

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