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std: unsafe-wrap gcc::rust_eh_personality and impl
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@workingjubilee
workingjubilee committed Jul 24, 2024
1 parent 6242470 commit d252b6b
Showing 1 changed file with 148 additions and 131 deletions.
279 changes: 148 additions & 131 deletions std/src/sys/personality/gcc.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,7 @@
//!
//! Once stack has been unwound down to the handler frame level, unwinding stops
//! 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 crate::ffi::c_int;
Expand Down Expand Up @@ -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

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.
// https://web.archive.org/web/20190728160938/https://infocenter.arm.com/help/topic/com.arm.doc.ihi0038b/IHI0038B_ehabi.pdf
//
Expand All @@ -104,90 +109,94 @@ cfg_if::cfg_if! {
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 {
unsafe {
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);
}
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;
};
} 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.
// 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);
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,
}
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;
} 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,
}
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 {
uw::_URC_FAILURE
}
}
// defined in libgcc
extern "C" {
fn __gnu_unwind_frame(
// 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;
) -> 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 {
Expand All @@ -200,35 +209,37 @@ cfg_if::cfg_if! {
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 = 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,
unsafe {
if version != 1 {
return uw::_URC_FATAL_PHASE1_ERROR;
}
} else {
match eh_action {
EHAction::None => uw::_URC_CONTINUE_UNWIND,
// 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
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 {
match eh_action {
EHAction::None => uw::_URC_CONTINUE_UNWIND,
// 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,
}
}
}
Expand All @@ -245,13 +256,15 @@ cfg_if::cfg_if! {
contextRecord: *mut uw::CONTEXT,
dispatcherContext: *mut uw::DISPATCHER_CONTEXT,
) -> uw::EXCEPTION_DISPOSITION {
uw::_GCC_specific_handler(
exceptionRecord,
establisherFrame,
contextRecord,
dispatcherContext,
rust_eh_personality_impl,
)
unsafe {
uw::_GCC_specific_handler(
exceptionRecord,
establisherFrame,
contextRecord,
dispatcherContext,
rust_eh_personality_impl,
)
}
}
} else {
// The personality routine for most of our targets.
Expand All @@ -263,32 +276,36 @@ cfg_if::cfg_if! {
exception_object: *mut uw::_Unwind_Exception,
context: *mut uw::_Unwind_Context,
) -> uw::_Unwind_Reason_Code {
rust_eh_personality_impl(
version,
actions,
exception_class,
exception_object,
context,
)
unsafe {
rust_eh_personality_impl(
version,
actions,
exception_class,
exception_object,
context,
)
}
}
}
}
}
}

unsafe fn find_eh_action(context: *mut uw::_Unwind_Context) -> Result<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 = -1` has special meaning, so use wrapping sub to allow for that
ip: if ip_before_instr != 0 { ip } else { ip.wrapping_sub(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)
unsafe {
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 = -1` has special meaning, so use wrapping sub to allow for that
ip: if ip_before_instr != 0 { ip } else { ip.wrapping_sub(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)
}
}

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