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workingjubileeworkingjubilee
committedJul 24, 2024
std: unsafe-wrap gcc::rust_eh_personality and impl
1 parent 6242470 commit d252b6b

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-131
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‎std/src/sys/personality/gcc.rs

+148-131
Original file line numberDiff line numberDiff line change
@@ -35,6 +35,7 @@
3535
//!
3636
//! Once stack has been unwound down to the handler frame level, unwinding stops
3737
//! and the last personality routine transfers control to the catch block.
38+
#![forbid(unsafe_op_in_unsafe_fn)]
3839

3940
use super::dwarf::eh::{self, EHAction, EHContext};
4041
use crate::ffi::c_int;
@@ -92,7 +93,11 @@ const UNWIND_DATA_REG: (i32, i32) = (4, 5); // a0, a1
9293
// https://github.com/gcc-mirror/gcc/blob/trunk/libgcc/unwind-c.c
9394

9495
cfg_if::cfg_if! {
95-
if #[cfg(all(not(all(target_vendor = "apple", not(target_os = "watchos"))), target_arch = "arm", not(target_os = "netbsd")))] {
96+
if #[cfg(all(
97+
target_arch = "arm",
98+
not(all(target_vendor = "apple", not(target_os = "watchos"))),
99+
not(target_os = "netbsd"),
100+
))] {
96101
// ARM EHABI personality routine.
97102
// https://web.archive.org/web/20190728160938/https://infocenter.arm.com/help/topic/com.arm.doc.ihi0038b/IHI0038B_ehabi.pdf
98103
//
@@ -104,90 +109,94 @@ cfg_if::cfg_if! {
104109
exception_object: *mut uw::_Unwind_Exception,
105110
context: *mut uw::_Unwind_Context,
106111
) -> uw::_Unwind_Reason_Code {
107-
let state = state as c_int;
108-
let action = state & uw::_US_ACTION_MASK as c_int;
109-
let search_phase = if action == uw::_US_VIRTUAL_UNWIND_FRAME as c_int {
110-
// Backtraces on ARM will call the personality routine with
111-
// state == _US_VIRTUAL_UNWIND_FRAME | _US_FORCE_UNWIND. In those cases
112-
// we want to continue unwinding the stack, otherwise all our backtraces
113-
// would end at __rust_try
114-
if state & uw::_US_FORCE_UNWIND as c_int != 0 {
112+
unsafe {
113+
let state = state as c_int;
114+
let action = state & uw::_US_ACTION_MASK as c_int;
115+
let search_phase = if action == uw::_US_VIRTUAL_UNWIND_FRAME as c_int {
116+
// Backtraces on ARM will call the personality routine with
117+
// state == _US_VIRTUAL_UNWIND_FRAME | _US_FORCE_UNWIND. In those cases
118+
// we want to continue unwinding the stack, otherwise all our backtraces
119+
// would end at __rust_try
120+
if state & uw::_US_FORCE_UNWIND as c_int != 0 {
121+
return continue_unwind(exception_object, context);
122+
}
123+
true
124+
} else if action == uw::_US_UNWIND_FRAME_STARTING as c_int {
125+
false
126+
} else if action == uw::_US_UNWIND_FRAME_RESUME as c_int {
115127
return continue_unwind(exception_object, context);
116-
}
117-
true
118-
} else if action == uw::_US_UNWIND_FRAME_STARTING as c_int {
119-
false
120-
} else if action == uw::_US_UNWIND_FRAME_RESUME as c_int {
121-
return continue_unwind(exception_object, context);
122-
} else {
123-
return uw::_URC_FAILURE;
124-
};
128+
} else {
129+
return uw::_URC_FAILURE;
130+
};
125131

126-
// The DWARF unwinder assumes that _Unwind_Context holds things like the function
127-
// and LSDA pointers, however ARM EHABI places them into the exception object.
128-
// To preserve signatures of functions like _Unwind_GetLanguageSpecificData(), which
129-
// take only the context pointer, GCC personality routines stash a pointer to
130-
// exception_object in the context, using location reserved for ARM's
131-
// "scratch register" (r12).
132-
uw::_Unwind_SetGR(context, uw::UNWIND_POINTER_REG, exception_object as uw::_Unwind_Ptr);
133-
// ...A more principled approach would be to provide the full definition of ARM's
134-
// _Unwind_Context in our libunwind bindings and fetch the required data from there
135-
// directly, bypassing DWARF compatibility functions.
132+
// The DWARF unwinder assumes that _Unwind_Context holds things like the function
133+
// and LSDA pointers, however ARM EHABI places them into the exception object.
134+
// To preserve signatures of functions like _Unwind_GetLanguageSpecificData(), which
135+
// take only the context pointer, GCC personality routines stash a pointer to
136+
// exception_object in the context, using location reserved for ARM's
137+
// "scratch register" (r12).
138+
uw::_Unwind_SetGR(context, uw::UNWIND_POINTER_REG, exception_object as uw::_Unwind_Ptr);
139+
// ...A more principled approach would be to provide the full definition of ARM's
140+
// _Unwind_Context in our libunwind bindings and fetch the required data from there
141+
// directly, bypassing DWARF compatibility functions.
136142

137-
let eh_action = match find_eh_action(context) {
138-
Ok(action) => action,
139-
Err(_) => return uw::_URC_FAILURE,
140-
};
141-
if search_phase {
142-
match eh_action {
143-
EHAction::None | EHAction::Cleanup(_) => {
144-
return continue_unwind(exception_object, context);
143+
let eh_action = match find_eh_action(context) {
144+
Ok(action) => action,
145+
Err(_) => return uw::_URC_FAILURE,
146+
};
147+
if search_phase {
148+
match eh_action {
149+
EHAction::None | EHAction::Cleanup(_) => {
150+
return continue_unwind(exception_object, context);
151+
}
152+
EHAction::Catch(_) | EHAction::Filter(_) => {
153+
// EHABI requires the personality routine to update the
154+
// SP value in the barrier cache of the exception object.
155+
(*exception_object).private[5] =
156+
uw::_Unwind_GetGR(context, uw::UNWIND_SP_REG);
157+
return uw::_URC_HANDLER_FOUND;
158+
}
159+
EHAction::Terminate => return uw::_URC_FAILURE,
145160
}
146-
EHAction::Catch(_) | EHAction::Filter(_) => {
147-
// EHABI requires the personality routine to update the
148-
// SP value in the barrier cache of the exception object.
149-
(*exception_object).private[5] =
150-
uw::_Unwind_GetGR(context, uw::UNWIND_SP_REG);
151-
return uw::_URC_HANDLER_FOUND;
152-
}
153-
EHAction::Terminate => return uw::_URC_FAILURE,
154-
}
155-
} else {
156-
match eh_action {
157-
EHAction::None => return continue_unwind(exception_object, context),
158-
EHAction::Filter(_) if state & uw::_US_FORCE_UNWIND as c_int != 0 => return continue_unwind(exception_object, context),
159-
EHAction::Cleanup(lpad) | EHAction::Catch(lpad) | EHAction::Filter(lpad) => {
160-
uw::_Unwind_SetGR(
161-
context,
162-
UNWIND_DATA_REG.0,
163-
exception_object as uw::_Unwind_Ptr,
164-
);
165-
uw::_Unwind_SetGR(context, UNWIND_DATA_REG.1, core::ptr::null());
166-
uw::_Unwind_SetIP(context, lpad);
167-
return uw::_URC_INSTALL_CONTEXT;
161+
} else {
162+
match eh_action {
163+
EHAction::None => return continue_unwind(exception_object, context),
164+
EHAction::Filter(_) if state & uw::_US_FORCE_UNWIND as c_int != 0 => return continue_unwind(exception_object, context),
165+
EHAction::Cleanup(lpad) | EHAction::Catch(lpad) | EHAction::Filter(lpad) => {
166+
uw::_Unwind_SetGR(
167+
context,
168+
UNWIND_DATA_REG.0,
169+
exception_object as uw::_Unwind_Ptr,
170+
);
171+
uw::_Unwind_SetGR(context, UNWIND_DATA_REG.1, core::ptr::null());
172+
uw::_Unwind_SetIP(context, lpad);
173+
return uw::_URC_INSTALL_CONTEXT;
174+
}
175+
EHAction::Terminate => return uw::_URC_FAILURE,
168176
}
169-
EHAction::Terminate => return uw::_URC_FAILURE,
170177
}
171-
}
172178

173-
// On ARM EHABI the personality routine is responsible for actually
174-
// unwinding a single stack frame before returning (ARM EHABI Sec. 6.1).
175-
unsafe fn continue_unwind(
176-
exception_object: *mut uw::_Unwind_Exception,
177-
context: *mut uw::_Unwind_Context,
178-
) -> uw::_Unwind_Reason_Code {
179-
if __gnu_unwind_frame(exception_object, context) == uw::_URC_NO_REASON {
180-
uw::_URC_CONTINUE_UNWIND
181-
} else {
182-
uw::_URC_FAILURE
183-
}
184-
}
185-
// defined in libgcc
186-
extern "C" {
187-
fn __gnu_unwind_frame(
179+
// On ARM EHABI the personality routine is responsible for actually
180+
// unwinding a single stack frame before returning (ARM EHABI Sec. 6.1).
181+
unsafe fn continue_unwind(
188182
exception_object: *mut uw::_Unwind_Exception,
189183
context: *mut uw::_Unwind_Context,
190-
) -> uw::_Unwind_Reason_Code;
184+
) -> uw::_Unwind_Reason_Code {
185+
unsafe {
186+
if __gnu_unwind_frame(exception_object, context) == uw::_URC_NO_REASON {
187+
uw::_URC_CONTINUE_UNWIND
188+
} else {
189+
uw::_URC_FAILURE
190+
}
191+
}
192+
}
193+
// defined in libgcc
194+
extern "C" {
195+
fn __gnu_unwind_frame(
196+
exception_object: *mut uw::_Unwind_Exception,
197+
context: *mut uw::_Unwind_Context,
198+
) -> uw::_Unwind_Reason_Code;
199+
}
191200
}
192201
}
193202
} else {
@@ -200,35 +209,37 @@ cfg_if::cfg_if! {
200209
exception_object: *mut uw::_Unwind_Exception,
201210
context: *mut uw::_Unwind_Context,
202211
) -> uw::_Unwind_Reason_Code {
203-
if version != 1 {
204-
return uw::_URC_FATAL_PHASE1_ERROR;
205-
}
206-
let eh_action = match find_eh_action(context) {
207-
Ok(action) => action,
208-
Err(_) => return uw::_URC_FATAL_PHASE1_ERROR,
209-
};
210-
if actions as i32 & uw::_UA_SEARCH_PHASE as i32 != 0 {
211-
match eh_action {
212-
EHAction::None | EHAction::Cleanup(_) => uw::_URC_CONTINUE_UNWIND,
213-
EHAction::Catch(_) | EHAction::Filter(_) => uw::_URC_HANDLER_FOUND,
214-
EHAction::Terminate => uw::_URC_FATAL_PHASE1_ERROR,
212+
unsafe {
213+
if version != 1 {
214+
return uw::_URC_FATAL_PHASE1_ERROR;
215215
}
216-
} else {
217-
match eh_action {
218-
EHAction::None => uw::_URC_CONTINUE_UNWIND,
219-
// Forced unwinding hits a terminate action.
220-
EHAction::Filter(_) if actions as i32 & uw::_UA_FORCE_UNWIND as i32 != 0 => uw::_URC_CONTINUE_UNWIND,
221-
EHAction::Cleanup(lpad) | EHAction::Catch(lpad) | EHAction::Filter(lpad) => {
222-
uw::_Unwind_SetGR(
223-
context,
224-
UNWIND_DATA_REG.0,
225-
exception_object.cast(),
226-
);
227-
uw::_Unwind_SetGR(context, UNWIND_DATA_REG.1, core::ptr::null());
228-
uw::_Unwind_SetIP(context, lpad);
229-
uw::_URC_INSTALL_CONTEXT
216+
let eh_action = match find_eh_action(context) {
217+
Ok(action) => action,
218+
Err(_) => return uw::_URC_FATAL_PHASE1_ERROR,
219+
};
220+
if actions as i32 & uw::_UA_SEARCH_PHASE as i32 != 0 {
221+
match eh_action {
222+
EHAction::None | EHAction::Cleanup(_) => uw::_URC_CONTINUE_UNWIND,
223+
EHAction::Catch(_) | EHAction::Filter(_) => uw::_URC_HANDLER_FOUND,
224+
EHAction::Terminate => uw::_URC_FATAL_PHASE1_ERROR,
225+
}
226+
} else {
227+
match eh_action {
228+
EHAction::None => uw::_URC_CONTINUE_UNWIND,
229+
// Forced unwinding hits a terminate action.
230+
EHAction::Filter(_) if actions as i32 & uw::_UA_FORCE_UNWIND as i32 != 0 => uw::_URC_CONTINUE_UNWIND,
231+
EHAction::Cleanup(lpad) | EHAction::Catch(lpad) | EHAction::Filter(lpad) => {
232+
uw::_Unwind_SetGR(
233+
context,
234+
UNWIND_DATA_REG.0,
235+
exception_object.cast(),
236+
);
237+
uw::_Unwind_SetGR(context, UNWIND_DATA_REG.1, core::ptr::null());
238+
uw::_Unwind_SetIP(context, lpad);
239+
uw::_URC_INSTALL_CONTEXT
240+
}
241+
EHAction::Terminate => uw::_URC_FATAL_PHASE2_ERROR,
230242
}
231-
EHAction::Terminate => uw::_URC_FATAL_PHASE2_ERROR,
232243
}
233244
}
234245
}
@@ -245,13 +256,15 @@ cfg_if::cfg_if! {
245256
contextRecord: *mut uw::CONTEXT,
246257
dispatcherContext: *mut uw::DISPATCHER_CONTEXT,
247258
) -> uw::EXCEPTION_DISPOSITION {
248-
uw::_GCC_specific_handler(
249-
exceptionRecord,
250-
establisherFrame,
251-
contextRecord,
252-
dispatcherContext,
253-
rust_eh_personality_impl,
254-
)
259+
unsafe {
260+
uw::_GCC_specific_handler(
261+
exceptionRecord,
262+
establisherFrame,
263+
contextRecord,
264+
dispatcherContext,
265+
rust_eh_personality_impl,
266+
)
267+
}
255268
}
256269
} else {
257270
// The personality routine for most of our targets.
@@ -263,32 +276,36 @@ cfg_if::cfg_if! {
263276
exception_object: *mut uw::_Unwind_Exception,
264277
context: *mut uw::_Unwind_Context,
265278
) -> uw::_Unwind_Reason_Code {
266-
rust_eh_personality_impl(
267-
version,
268-
actions,
269-
exception_class,
270-
exception_object,
271-
context,
272-
)
279+
unsafe {
280+
rust_eh_personality_impl(
281+
version,
282+
actions,
283+
exception_class,
284+
exception_object,
285+
context,
286+
)
287+
}
273288
}
274289
}
275290
}
276291
}
277292
}
278293

279294
unsafe fn find_eh_action(context: *mut uw::_Unwind_Context) -> Result<EHAction, ()> {
280-
let lsda = uw::_Unwind_GetLanguageSpecificData(context) as *const u8;
281-
let mut ip_before_instr: c_int = 0;
282-
let ip = uw::_Unwind_GetIPInfo(context, &mut ip_before_instr);
283-
let eh_context = EHContext {
284-
// The return address points 1 byte past the call instruction,
285-
// which could be in the next IP range in LSDA range table.
286-
//
287-
// `ip = -1` has special meaning, so use wrapping sub to allow for that
288-
ip: if ip_before_instr != 0 { ip } else { ip.wrapping_sub(1) },
289-
func_start: uw::_Unwind_GetRegionStart(context),
290-
get_text_start: &|| uw::_Unwind_GetTextRelBase(context),
291-
get_data_start: &|| uw::_Unwind_GetDataRelBase(context),
292-
};
293-
eh::find_eh_action(lsda, &eh_context)
295+
unsafe {
296+
let lsda = uw::_Unwind_GetLanguageSpecificData(context) as *const u8;
297+
let mut ip_before_instr: c_int = 0;
298+
let ip = uw::_Unwind_GetIPInfo(context, &mut ip_before_instr);
299+
let eh_context = EHContext {
300+
// The return address points 1 byte past the call instruction,
301+
// which could be in the next IP range in LSDA range table.
302+
//
303+
// `ip = -1` has special meaning, so use wrapping sub to allow for that
304+
ip: if ip_before_instr != 0 { ip } else { ip.wrapping_sub(1) },
305+
func_start: uw::_Unwind_GetRegionStart(context),
306+
get_text_start: &|| uw::_Unwind_GetTextRelBase(context),
307+
get_data_start: &|| uw::_Unwind_GetDataRelBase(context),
308+
};
309+
eh::find_eh_action(lsda, &eh_context)
310+
}
294311
}

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