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Implement ARM personality routine in Rust.
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Remove the `eh_personality_catch` lang item.
Use a simplified version of `cfg_if!` in libunwind.
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@vadimcn
vadimcn committed Jul 24, 2016
1 parent 2c50f4e commit 6cef93d
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Showing 5 changed files with 314 additions and 270 deletions.
271 changes: 159 additions & 112 deletions src/libpanic_unwind/gcc.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -61,6 +61,8 @@ use core::ptr;
use alloc::boxed::Box;

use unwind as uw;
use libc::{c_int, uintptr_t};
use dwarf::eh::{self, EHContext, EHAction};

#[repr(C)]
struct Exception {
Expand Down Expand Up @@ -106,139 +108,184 @@ fn rust_exception_class() -> uw::_Unwind_Exception_Class {
0x4d4f5a_00_52555354
}

// All targets, except ARM which uses a slightly different ABI (however, iOS goes here as it uses
// SjLj unwinding). Also, 64-bit Windows implementation lives in seh64_gnu.rs
#[cfg(all(any(target_os = "ios", not(target_arch = "arm"))))]
pub mod eabi {
use unwind as uw;
use libc::{c_int, uintptr_t};
use dwarf::eh::{EHContext, EHAction, find_eh_action};

// Register ids were lifted from LLVM's TargetLowering::getExceptionPointerRegister()
// and TargetLowering::getExceptionSelectorRegister() for each architecture,
// then mapped to DWARF register numbers via register definition tables
// (typically <arch>RegisterInfo.td, search for "DwarfRegNum").
// See also http://llvm.org/docs/WritingAnLLVMBackend.html#defining-a-register.
// Register ids were lifted from LLVM's TargetLowering::getExceptionPointerRegister()
// and TargetLowering::getExceptionSelectorRegister() for each architecture,
// then mapped to DWARF register numbers via register definition tables
// (typically <arch>RegisterInfo.td, search for "DwarfRegNum").
// See also http://llvm.org/docs/WritingAnLLVMBackend.html#defining-a-register.

#[cfg(target_arch = "x86")]
const UNWIND_DATA_REG: (i32, i32) = (0, 2); // EAX, EDX
#[cfg(target_arch = "x86")]
const UNWIND_DATA_REG: (i32, i32) = (0, 2); // EAX, EDX

#[cfg(target_arch = "x86_64")]
const UNWIND_DATA_REG: (i32, i32) = (0, 1); // RAX, RDX
#[cfg(target_arch = "x86_64")]
const UNWIND_DATA_REG: (i32, i32) = (0, 1); // RAX, RDX

#[cfg(any(target_arch = "arm", target_arch = "aarch64"))]
const UNWIND_DATA_REG: (i32, i32) = (0, 1); // R0, R1 / X0, X1
#[cfg(any(target_arch = "arm", target_arch = "aarch64"))]
const UNWIND_DATA_REG: (i32, i32) = (0, 1); // R0, R1 / X0, X1

#[cfg(any(target_arch = "mips", target_arch = "mipsel"))]
const UNWIND_DATA_REG: (i32, i32) = (4, 5); // A0, A1
#[cfg(any(target_arch = "mips", target_arch = "mipsel"))]
const UNWIND_DATA_REG: (i32, i32) = (4, 5); // A0, A1

#[cfg(any(target_arch = "powerpc", target_arch = "powerpc64"))]
const UNWIND_DATA_REG: (i32, i32) = (3, 4); // R3, R4 / X3, X4
#[cfg(any(target_arch = "powerpc", target_arch = "powerpc64"))]
const UNWIND_DATA_REG: (i32, i32) = (3, 4); // R3, R4 / X3, X4

// Based on GCC's C and C++ personality routines. For reference, see:
// https://github.com/gcc-mirror/gcc/blob/master/libstdc++-v3/libsupc++/eh_personality.cc
// https://github.com/gcc-mirror/gcc/blob/trunk/libgcc/unwind-c.c
#[lang = "eh_personality"]
#[no_mangle]
#[allow(unused)]
unsafe extern "C" fn rust_eh_personality(version: c_int,
actions: uw::_Unwind_Action,
exception_class: uw::_Unwind_Exception_Class,
exception_object: *mut uw::_Unwind_Exception,
context: *mut uw::_Unwind_Context)
-> uw::_Unwind_Reason_Code {
if version != 1 {
return uw::_URC_FATAL_PHASE1_ERROR;
}
let lsda = uw::_Unwind_GetLanguageSpecificData(context) as *const u8;
let mut ip_before_instr: c_int = 0;
let ip = uw::_Unwind_GetIPInfo(context, &mut ip_before_instr);
let eh_context = EHContext {
// The return address points 1 byte past the call instruction,
// which could be in the next IP range in LSDA range table.
ip: if ip_before_instr != 0 { ip } else { ip - 1 },
func_start: uw::_Unwind_GetRegionStart(context),
get_text_start: &|| uw::_Unwind_GetTextRelBase(context),
get_data_start: &|| uw::_Unwind_GetDataRelBase(context),
};
let eh_action = find_eh_action(lsda, &eh_context);
// The following code is based on GCC's C and C++ personality routines. For reference, see:
// https://github.com/gcc-mirror/gcc/blob/master/libstdc++-v3/libsupc++/eh_personality.cc
// https://github.com/gcc-mirror/gcc/blob/trunk/libgcc/unwind-c.c

if actions as i32 & uw::_UA_SEARCH_PHASE as i32 != 0 {
match eh_action {
EHAction::None | EHAction::Cleanup(_) => return uw::_URC_CONTINUE_UNWIND,
EHAction::Catch(_) => return uw::_URC_HANDLER_FOUND,
EHAction::Terminate => return uw::_URC_FATAL_PHASE1_ERROR,
}
} else {
match eh_action {
EHAction::None => return uw::_URC_CONTINUE_UNWIND,
EHAction::Cleanup(lpad) | EHAction::Catch(lpad) => {
uw::_Unwind_SetGR(context, UNWIND_DATA_REG.0, exception_object as uintptr_t);
uw::_Unwind_SetGR(context, UNWIND_DATA_REG.1, 0);
uw::_Unwind_SetIP(context, lpad);
return uw::_URC_INSTALL_CONTEXT;
}
EHAction::Terminate => return uw::_URC_FATAL_PHASE2_ERROR,
// The personality routine for most of our targets, except ARM, which has a slightly different ABI
// (however, iOS goes here as it uses SjLj unwinding). Also, the 64-bit Windows implementation
// lives in seh64_gnu.rs
#[cfg(all(any(target_os = "ios", not(target_arch = "arm"))))]
#[lang = "eh_personality"]
#[no_mangle]
#[allow(unused)]
unsafe extern "C" fn rust_eh_personality(version: c_int,
actions: uw::_Unwind_Action,
exception_class: uw::_Unwind_Exception_Class,
exception_object: *mut uw::_Unwind_Exception,
context: *mut uw::_Unwind_Context)
-> uw::_Unwind_Reason_Code {
if version != 1 {
return uw::_URC_FATAL_PHASE1_ERROR;
}
let eh_action = find_eh_action(context);
if actions as i32 & uw::_UA_SEARCH_PHASE as i32 != 0 {
match eh_action {
EHAction::None | EHAction::Cleanup(_) => return uw::_URC_CONTINUE_UNWIND,
EHAction::Catch(_) => return uw::_URC_HANDLER_FOUND,
EHAction::Terminate => return uw::_URC_FATAL_PHASE1_ERROR,
}
} else {
match eh_action {
EHAction::None => return uw::_URC_CONTINUE_UNWIND,
EHAction::Cleanup(lpad) | EHAction::Catch(lpad) => {
uw::_Unwind_SetGR(context, UNWIND_DATA_REG.0, exception_object as uintptr_t);
uw::_Unwind_SetGR(context, UNWIND_DATA_REG.1, 0);
uw::_Unwind_SetIP(context, lpad);
return uw::_URC_INSTALL_CONTEXT;
}
EHAction::Terminate => return uw::_URC_FATAL_PHASE2_ERROR,
}
}

#[cfg(stage0)]
#[lang = "eh_personality_catch"]
#[no_mangle]
pub unsafe extern "C" fn rust_eh_personality_catch(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 {
rust_eh_personality(version, actions, exception_class, ue_header, context)
}
}

// ARM EHABI uses a slightly different personality routine signature,
// but otherwise works the same.
// ARM EHABI personality routine.
// http://infocenter.arm.com/help/topic/com.arm.doc.ihi0038b/IHI0038B_ehabi.pdf
#[cfg(all(target_arch = "arm", not(target_os = "ios")))]
pub mod eabi {
use unwind as uw;
use libc::c_int;
#[lang = "eh_personality"]
#[no_mangle]
unsafe extern "C" fn rust_eh_personality(state: uw::_Unwind_State,
exception_object: *mut uw::_Unwind_Exception,
context: *mut uw::_Unwind_Context)
-> uw::_Unwind_Reason_Code {
let state = state as c_int;
let action = state & uw::_US_ACTION_MASK as c_int;
let search_phase = if action == uw::_US_VIRTUAL_UNWIND_FRAME as c_int {
// Backtraces on ARM will call the personality routine with
// state == _US_VIRTUAL_UNWIND_FRAME | _US_FORCE_UNWIND. In those cases
// we want to continue unwinding the stack, otherwise all our backtraces
// would end at __rust_try
if state & uw::_US_FORCE_UNWIND as c_int != 0 {
return continue_unwind(exception_object, context)
}
true
} else if action == uw::_US_UNWIND_FRAME_STARTING as c_int {
false
} else if action == uw::_US_UNWIND_FRAME_RESUME as c_int {
return continue_unwind(exception_object, context);
} else {
return uw::_URC_FAILURE;
};

extern "C" {
fn __gcc_personality_v0(state: uw::_Unwind_State,
ue_header: *mut uw::_Unwind_Exception,
context: *mut uw::_Unwind_Context)
-> uw::_Unwind_Reason_Code;
}
// The DWARF unwinder assumes that _Unwind_Context holds things like the function
// and LSDA pointers, however ARM EHABI places them into the exception object.
// To preserve signatures of functions like _Unwind_GetLanguageSpecificData(), which
// take only the context pointer, GCC personality routines stash a pointer to exception_object
// in the context, using location reserved for ARM's "scratch register" (r12).
uw::_Unwind_SetGR(context, uw::UNWIND_POINTER_REG, exception_object as uw::_Unwind_Ptr);
// ...A more principled approach would be to provide the full definition of ARM's
// _Unwind_Context in our libunwind bindings and fetch the required data from there directly,
// bypassing DWARF compatibility functions.

#[lang = "eh_personality"]
#[no_mangle]
extern "C" fn rust_eh_personality(state: uw::_Unwind_State,
ue_header: *mut uw::_Unwind_Exception,
context: *mut uw::_Unwind_Context)
-> uw::_Unwind_Reason_Code {
unsafe { __gcc_personality_v0(state, ue_header, context) }
let eh_action = find_eh_action(context);
if search_phase {
match eh_action {
EHAction::None |
EHAction::Cleanup(_) => return continue_unwind(exception_object, context),
EHAction::Catch(_) => return uw::_URC_HANDLER_FOUND,
EHAction::Terminate => return uw::_URC_FAILURE,
}
} else {
match eh_action {
EHAction::None => return continue_unwind(exception_object, context),
EHAction::Cleanup(lpad) | EHAction::Catch(lpad) => {
uw::_Unwind_SetGR(context, UNWIND_DATA_REG.0, exception_object as uintptr_t);
uw::_Unwind_SetGR(context, UNWIND_DATA_REG.1, 0);
uw::_Unwind_SetIP(context, lpad);
return uw::_URC_INSTALL_CONTEXT;
}
EHAction::Terminate => return uw::_URC_FAILURE,
}
}

#[lang = "eh_personality_catch"]
#[no_mangle]
pub extern "C" fn rust_eh_personality_catch(state: uw::_Unwind_State,
ue_header: *mut uw::_Unwind_Exception,
context: *mut uw::_Unwind_Context)
-> uw::_Unwind_Reason_Code {
// Backtraces on ARM will call the personality routine with
// state == _US_VIRTUAL_UNWIND_FRAME | _US_FORCE_UNWIND. In those cases
// we want to continue unwinding the stack, otherwise all our backtraces
// would end at __rust_try.
if (state as c_int & uw::_US_ACTION_MASK as c_int) ==
uw::_US_VIRTUAL_UNWIND_FRAME as c_int &&
(state as c_int & uw::_US_FORCE_UNWIND as c_int) == 0 {
// search phase
uw::_URC_HANDLER_FOUND // catch!
// On ARM EHABI the personality routine is responsible for actually
// unwinding a single stack frame before returning (ARM EHABI Sec. 6.1).
unsafe fn continue_unwind(exception_object: *mut uw::_Unwind_Exception,
context: *mut uw::_Unwind_Context)
-> uw::_Unwind_Reason_Code {
if __gnu_unwind_frame(exception_object, context) == uw::_URC_NO_REASON {
uw::_URC_CONTINUE_UNWIND
} else {
// cleanup phase
unsafe { __gcc_personality_v0(state, ue_header, context) }
uw::_URC_FAILURE
}
}
// defined in libgcc
extern "C" {
fn __gnu_unwind_frame(exception_object: *mut uw::_Unwind_Exception,
context: *mut uw::_Unwind_Context)
-> uw::_Unwind_Reason_Code;
}
}

unsafe fn find_eh_action(context: *mut uw::_Unwind_Context) -> EHAction {
let lsda = uw::_Unwind_GetLanguageSpecificData(context) as *const u8;
let mut ip_before_instr: c_int = 0;
let ip = uw::_Unwind_GetIPInfo(context, &mut ip_before_instr);
let eh_context = EHContext {
// The return address points 1 byte past the call instruction,
// which could be in the next IP range in LSDA range table.
ip: if ip_before_instr != 0 { ip } else { ip - 1 },
func_start: uw::_Unwind_GetRegionStart(context),
get_text_start: &|| uw::_Unwind_GetTextRelBase(context),
get_data_start: &|| uw::_Unwind_GetDataRelBase(context),
};
eh::find_eh_action(lsda, &eh_context)
}

// *** Delete after a new snapshot ***
#[cfg(all(stage0, any(target_os = "ios", not(target_arch = "arm"))))]
#[lang = "eh_personality_catch"]
#[no_mangle]
pub unsafe extern "C" fn rust_eh_personality_catch(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 {
rust_eh_personality(version, actions, exception_class, ue_header, context)
}

// *** Delete after a new snapshot ***
#[cfg(all(stage0, target_arch = "arm", not(target_os = "ios")))]
#[lang = "eh_personality_catch"]
#[no_mangle]
pub unsafe extern "C" fn rust_eh_personality_catch(state: uw::_Unwind_State,
ue_header: *mut uw::_Unwind_Exception,
context: *mut uw::_Unwind_Context)
-> uw::_Unwind_Reason_Code {
rust_eh_personality(state, ue_header, context)
}

// See docs in the `unwind` module.
Expand Down
1 change: 1 addition & 0 deletions src/libpanic_unwind/seh64_gnu.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -81,6 +81,7 @@ pub unsafe fn cleanup(ptr: *mut u8) -> Box<Any + Send> {
// This is considered acceptable, because the behavior of throwing exceptions
// through a C ABI boundary is undefined.

// *** Delete after a new snapshot ***
#[cfg(stage0)]
#[lang = "eh_personality_catch"]
#[cfg(not(test))]
Expand Down
1 change: 0 additions & 1 deletion src/librustc/middle/lang_items.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -359,7 +359,6 @@ language_item_table! {
StartFnLangItem, "start", start_fn;

EhPersonalityLangItem, "eh_personality", eh_personality;
EhPersonalityCatchLangItem, "eh_personality_catch", eh_personality_catch;
EhUnwindResumeLangItem, "eh_unwind_resume", eh_unwind_resume;
MSVCTryFilterLangItem, "msvc_try_filter", msvc_try_filter;

Expand Down
19 changes: 1 addition & 18 deletions src/librustc_trans/intrinsic.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -19,7 +19,6 @@ use rustc::ty::subst;
use rustc::ty::subst::FnSpace;
use abi::{Abi, FnType};
use adt;
use attributes;
use base::*;
use build::*;
use callee::{self, Callee};
Expand All @@ -37,7 +36,6 @@ use machine;
use type_::Type;
use rustc::ty::{self, Ty};
use Disr;
use rustc::ty::subst::Substs;
use rustc::hir;
use syntax::ast;
use syntax::ptr::P;
Expand Down Expand Up @@ -1172,7 +1170,6 @@ fn trans_gnu_try<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
dloc: DebugLoc) -> Block<'blk, 'tcx> {
let llfn = get_rust_try_fn(bcx.fcx, &mut |bcx| {
let ccx = bcx.ccx();
let tcx = ccx.tcx();
let dloc = DebugLoc::None;

// Translates the shims described above:
Expand All @@ -1192,20 +1189,6 @@ fn trans_gnu_try<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
// expected to be `*mut *mut u8` for this to actually work, but that's
// managed by the standard library.

attributes::emit_uwtable(bcx.fcx.llfn, true);
let target = &bcx.sess().target.target;
let catch_pers = if target.arch == "arm" && target.target_os != "ios" {
// Only ARM still uses a separate catch personality (for now)
match tcx.lang_items.eh_personality_catch() {
Some(did) => {
Callee::def(ccx, did, tcx.mk_substs(Substs::empty())).reify(ccx).val
}
None => bug!("eh_personality_catch not defined"),
}
} else {
bcx.fcx.eh_personality()
};

let then = bcx.fcx.new_temp_block("then");
let catch = bcx.fcx.new_temp_block("catch");

Expand All @@ -1223,7 +1206,7 @@ fn trans_gnu_try<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
// rust_try ignores the selector.
let lpad_ty = Type::struct_(ccx, &[Type::i8p(ccx), Type::i32(ccx)],
false);
let vals = LandingPad(catch, lpad_ty, catch_pers, 1);
let vals = LandingPad(catch, lpad_ty, bcx.fcx.eh_personality(), 1);
AddClause(catch, vals, C_null(Type::i8p(ccx)));
let ptr = ExtractValue(catch, vals, 0);
Store(catch, ptr, BitCast(catch, local_ptr, Type::i8p(ccx).ptr_to()));
Expand Down
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