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std: unsafe-wrap gcc::rust_eh_personality and impl

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This commit is contained in:
Jubilee Young 2024-07-24 11:42:31 -07:00
parent 2ccafed862
commit 2c7ae388b3
1 changed files with 151 additions and 134 deletions
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285
library/std/src/sys/personality/gcc.rs
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@ -35,6 +35,7 @@
//! //!
//! Once stack has been unwound down to the handler frame level, unwinding stops //! Once stack has been unwound down to the handler frame level, unwinding stops
//! and the last personality routine transfers control to the catch block. //! and the last personality routine transfers control to the catch block.
#![forbid(unsafe_op_in_unsafe_fn)]
use super::dwarf::eh::{self, EHAction, EHContext}; use super::dwarf::eh::{self, EHAction, EHContext};
use crate::ffi::c_int; use crate::ffi::c_int;
@ -92,7 +93,11 @@ const UNWIND_DATA_REG: (i32, i32) = (4, 5); // a0, a1
// https://github.com/gcc-mirror/gcc/blob/trunk/libgcc/unwind-c.c // https://github.com/gcc-mirror/gcc/blob/trunk/libgcc/unwind-c.c
cfg_if::cfg_if! { cfg_if::cfg_if! {
if #[cfg(all(not(all(target_vendor = "apple", not(target_os = "watchos"))), target_arch = "arm", not(target_os = "netbsd")))] { if #[cfg(all(
target_arch = "arm",
not(all(target_vendor = "apple", not(target_os = "watchos"))),
not(target_os = "netbsd"),
))] {
// ARM EHABI personality routine. // ARM EHABI personality routine.
// https://web.archive.org/web/20190728160938/https://infocenter.arm.com/help/topic/com.arm.doc.ihi0038b/IHI0038B_ehabi.pdf // https://web.archive.org/web/20190728160938/https://infocenter.arm.com/help/topic/com.arm.doc.ihi0038b/IHI0038B_ehabi.pdf
// //
@ -104,90 +109,94 @@ cfg_if::cfg_if! {
exception_object: *mut uw::_Unwind_Exception, exception_object: *mut uw::_Unwind_Exception,
context: *mut uw::_Unwind_Context, context: *mut uw::_Unwind_Context,
) -> uw::_Unwind_Reason_Code { ) -> uw::_Unwind_Reason_Code {
let state = state as c_int; unsafe {
let action = state & uw::_US_ACTION_MASK as c_int; let state = state as c_int;
let search_phase = if action == uw::_US_VIRTUAL_UNWIND_FRAME as c_int { let action = state & uw::_US_ACTION_MASK as c_int;
// Backtraces on ARM will call the personality routine with let search_phase = if action == uw::_US_VIRTUAL_UNWIND_FRAME as c_int {
// state == _US_VIRTUAL_UNWIND_FRAME | _US_FORCE_UNWIND. In those cases // Backtraces on ARM will call the personality routine with
// we want to continue unwinding the stack, otherwise all our backtraces // state == _US_VIRTUAL_UNWIND_FRAME | _US_FORCE_UNWIND. In those cases
// would end at __rust_try // we want to continue unwinding the stack, otherwise all our backtraces
if state & uw::_US_FORCE_UNWIND as c_int != 0 { // would end at __rust_try
return continue_unwind(exception_object, context); if state & uw::_US_FORCE_UNWIND as c_int != 0 {
}
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;
};
// 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.
let eh_action = match find_eh_action(context) {
Ok(action) => action,
Err(_) => return uw::_URC_FAILURE,
};
if search_phase {
match eh_action {
EHAction::None | EHAction::Cleanup(_) => {
return continue_unwind(exception_object, context); return continue_unwind(exception_object, context);
} }
EHAction::Catch(_) | EHAction::Filter(_) => { true
// EHABI requires the personality routine to update the } else if action == uw::_US_UNWIND_FRAME_STARTING as c_int {
// SP value in the barrier cache of the exception object. false
(*exception_object).private[5] = } else if action == uw::_US_UNWIND_FRAME_RESUME as c_int {
uw::_Unwind_GetGR(context, uw::UNWIND_SP_REG); return continue_unwind(exception_object, context);
return uw::_URC_HANDLER_FOUND;
}
EHAction::Terminate => return uw::_URC_FAILURE,
}
} else {
match eh_action {
EHAction::None => return continue_unwind(exception_object, context),
EHAction::Filter(_) if state & uw::_US_FORCE_UNWIND as c_int != 0 => return continue_unwind(exception_object, context),
EHAction::Cleanup(lpad) | EHAction::Catch(lpad) | EHAction::Filter(lpad) => {
uw::_Unwind_SetGR(
context,
UNWIND_DATA_REG.0,
exception_object as uw::_Unwind_Ptr,
);
uw::_Unwind_SetGR(context, UNWIND_DATA_REG.1, core::ptr::null());
uw::_Unwind_SetIP(context, lpad);
return uw::_URC_INSTALL_CONTEXT;
}
EHAction::Terminate => return uw::_URC_FAILURE,
}
}
// 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 { } else {
uw::_URC_FAILURE return uw::_URC_FAILURE;
};
// 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.
let eh_action = match find_eh_action(context) {
Ok(action) => action,
Err(_) => return uw::_URC_FAILURE,
};
if search_phase {
match eh_action {
EHAction::None | EHAction::Cleanup(_) => {
return continue_unwind(exception_object, context);
}
EHAction::Catch(_) | EHAction::Filter(_) => {
// EHABI requires the personality routine to update the
// SP value in the barrier cache of the exception object.
(*exception_object).private[5] =
uw::_Unwind_GetGR(context, uw::UNWIND_SP_REG);
return uw::_URC_HANDLER_FOUND;
}
EHAction::Terminate => return uw::_URC_FAILURE,
}
} else {
match eh_action {
EHAction::None => return continue_unwind(exception_object, context),
EHAction::Filter(_) if state & uw::_US_FORCE_UNWIND as c_int != 0 => return continue_unwind(exception_object, context),
EHAction::Cleanup(lpad) | EHAction::Catch(lpad) | EHAction::Filter(lpad) => {
uw::_Unwind_SetGR(
context,
UNWIND_DATA_REG.0,
exception_object as uw::_Unwind_Ptr,
);
uw::_Unwind_SetGR(context, UNWIND_DATA_REG.1, core::ptr::null());
uw::_Unwind_SetIP(context, lpad);
return uw::_URC_INSTALL_CONTEXT;
}
EHAction::Terminate => return uw::_URC_FAILURE,
}
} }
}
// defined in libgcc // On ARM EHABI the personality routine is responsible for actually
extern "C" { // unwinding a single stack frame before returning (ARM EHABI Sec. 6.1).
fn __gnu_unwind_frame( unsafe fn continue_unwind(
exception_object: *mut uw::_Unwind_Exception, exception_object: *mut uw::_Unwind_Exception,
context: *mut uw::_Unwind_Context, context: *mut uw::_Unwind_Context,
) -> uw::_Unwind_Reason_Code; ) -> uw::_Unwind_Reason_Code {
unsafe {
if __gnu_unwind_frame(exception_object, context) == uw::_URC_NO_REASON {
uw::_URC_CONTINUE_UNWIND
} else {
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;
}
} }
} }
} else { } else {
@ -200,35 +209,37 @@ cfg_if::cfg_if! {
exception_object: *mut uw::_Unwind_Exception, exception_object: *mut uw::_Unwind_Exception,
context: *mut uw::_Unwind_Context, context: *mut uw::_Unwind_Context,
) -> uw::_Unwind_Reason_Code { ) -> uw::_Unwind_Reason_Code {
if version != 1 { unsafe {
return uw::_URC_FATAL_PHASE1_ERROR; if version != 1 {
} return uw::_URC_FATAL_PHASE1_ERROR;
let eh_action = match find_eh_action(context) {
Ok(action) => action,
Err(_) => return uw::_URC_FATAL_PHASE1_ERROR,
};
if actions as i32 & uw::_UA_SEARCH_PHASE as i32 != 0 {
match eh_action {
EHAction::None | EHAction::Cleanup(_) => uw::_URC_CONTINUE_UNWIND,
EHAction::Catch(_) | EHAction::Filter(_) => uw::_URC_HANDLER_FOUND,
EHAction::Terminate => uw::_URC_FATAL_PHASE1_ERROR,
} }
} else { let eh_action = match find_eh_action(context) {
match eh_action { Ok(action) => action,
EHAction::None => uw::_URC_CONTINUE_UNWIND, Err(_) => return uw::_URC_FATAL_PHASE1_ERROR,
// Forced unwinding hits a terminate action. };
EHAction::Filter(_) if actions as i32 & uw::_UA_FORCE_UNWIND as i32 != 0 => uw::_URC_CONTINUE_UNWIND, if actions as i32 & uw::_UA_SEARCH_PHASE as i32 != 0 {
EHAction::Cleanup(lpad) | EHAction::Catch(lpad) | EHAction::Filter(lpad) => { match eh_action {
uw::_Unwind_SetGR( EHAction::None | EHAction::Cleanup(_) => uw::_URC_CONTINUE_UNWIND,
context, EHAction::Catch(_) | EHAction::Filter(_) => uw::_URC_HANDLER_FOUND,
UNWIND_DATA_REG.0, EHAction::Terminate => uw::_URC_FATAL_PHASE1_ERROR,
exception_object.cast(), }
); } else {
uw::_Unwind_SetGR(context, UNWIND_DATA_REG.1, core::ptr::null()); match eh_action {
uw::_Unwind_SetIP(context, lpad); EHAction::None => uw::_URC_CONTINUE_UNWIND,
uw::_URC_INSTALL_CONTEXT // Forced unwinding hits a terminate action.
EHAction::Filter(_) if actions as i32 & uw::_UA_FORCE_UNWIND as i32 != 0 => uw::_URC_CONTINUE_UNWIND,
EHAction::Cleanup(lpad) | EHAction::Catch(lpad) | EHAction::Filter(lpad) => {
uw::_Unwind_SetGR(
context,
UNWIND_DATA_REG.0,
exception_object.cast(),
);
uw::_Unwind_SetGR(context, UNWIND_DATA_REG.1, core::ptr::null());
uw::_Unwind_SetIP(context, lpad);
uw::_URC_INSTALL_CONTEXT
}
EHAction::Terminate => uw::_URC_FATAL_PHASE2_ERROR,
} }
EHAction::Terminate => uw::_URC_FATAL_PHASE2_ERROR,
} }
} }
} }
@ -245,13 +256,15 @@ cfg_if::cfg_if! {
contextRecord: *mut uw::CONTEXT, contextRecord: *mut uw::CONTEXT,
dispatcherContext: *mut uw::DISPATCHER_CONTEXT, dispatcherContext: *mut uw::DISPATCHER_CONTEXT,
) -> uw::EXCEPTION_DISPOSITION { ) -> uw::EXCEPTION_DISPOSITION {
uw::_GCC_specific_handler( unsafe {
exceptionRecord, uw::_GCC_specific_handler(
establisherFrame, exceptionRecord,
contextRecord, establisherFrame,
dispatcherContext, contextRecord,
rust_eh_personality_impl, dispatcherContext,
) rust_eh_personality_impl,
)
}
} }
} else { } else {
// The personality routine for most of our targets. // The personality routine for most of our targets.
@ -263,13 +276,15 @@ cfg_if::cfg_if! {
exception_object: *mut uw::_Unwind_Exception, exception_object: *mut uw::_Unwind_Exception,
context: *mut uw::_Unwind_Context, context: *mut uw::_Unwind_Context,
) -> uw::_Unwind_Reason_Code { ) -> uw::_Unwind_Reason_Code {
rust_eh_personality_impl( unsafe {
version, rust_eh_personality_impl(
actions, version,
exception_class, actions,
exception_object, exception_class,
context, exception_object,
) context,
)
}
} }
} }
} }
@ -277,18 +292,20 @@ cfg_if::cfg_if! {
} }
unsafe fn find_eh_action(context: *mut uw::_Unwind_Context) -> Result<EHAction, ()> { unsafe fn find_eh_action(context: *mut uw::_Unwind_Context) -> Result<EHAction, ()> {
let lsda = uw::_Unwind_GetLanguageSpecificData(context) as *const u8; unsafe {
let mut ip_before_instr: c_int = 0; let lsda = uw::_Unwind_GetLanguageSpecificData(context) as *const u8;
let ip = uw::_Unwind_GetIPInfo(context, &mut ip_before_instr); let mut ip_before_instr: c_int = 0;
let eh_context = EHContext { let ip = uw::_Unwind_GetIPInfo(context, &mut ip_before_instr);
// The return address points 1 byte past the call instruction, let eh_context = EHContext {
// which could be in the next IP range in LSDA range table. // The return address points 1 byte past the call instruction,
// // which could be in the next IP range in LSDA range table.
// `ip = -1` has special meaning, so use wrapping sub to allow for that //
ip: if ip_before_instr != 0 { ip } else { ip.wrapping_sub(1) }, // `ip = -1` has special meaning, so use wrapping sub to allow for that
func_start: uw::_Unwind_GetRegionStart(context), ip: if ip_before_instr != 0 { ip } else { ip.wrapping_sub(1) },
get_text_start: &|| uw::_Unwind_GetTextRelBase(context), func_start: uw::_Unwind_GetRegionStart(context),
get_data_start: &|| uw::_Unwind_GetDataRelBase(context), get_text_start: &|| uw::_Unwind_GetTextRelBase(context),
}; get_data_start: &|| uw::_Unwind_GetDataRelBase(context),
eh::find_eh_action(lsda, &eh_context) };
eh::find_eh_action(lsda, &eh_context)
}
} }