source: src/libcfa/exception.c @ 36982fc

aaron-thesisarm-ehcleanup-dtorsdeferred_resndemanglerjacob/cs343-translationjenkins-sandboxnew-astnew-ast-unique-exprnew-envno_listpersistent-indexerresolv-newwith_gc
Last change on this file since 36982fc was 36982fc, checked in by Thierry Delisle <tdelisle@…>, 4 years ago

Renamed internal stuff to cfaabi_...

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1//
2// Cforall Version 1.0.0 Copyright (C) 2016 University of Waterloo
3//
4// The contents of this file are covered under the licence agreement in the
5// file "LICENCE" distributed with Cforall.
6//
7// exception.c --
8//
9// Author           : Andrew Beach
10// Created On       : Mon Jun 26 15:13:00 2017
11// Last Modified By : Andrew Beach
12// Last Modified On : Thr Aug 17 15:45:00 2017
13// Update Count     : 7
14//
15
16#include <stddef.h> // for size_t
17
18#include "exception.h"
19
20// Implementation of the secret header.
21
22#include <stdlib.h>
23#include <stdio.h>
24#include <unwind.h>
25#include <libhdr/libdebug.h>
26
27// FIX ME: temporary hack to keep ARM build working
28#ifndef _URC_FATAL_PHASE1_ERROR
29#define _URC_FATAL_PHASE1_ERROR 2
30#endif // ! _URC_FATAL_PHASE1_ERROR
31#ifndef _URC_FATAL_PHASE2_ERROR
32#define _URC_FATAL_PHASE2_ERROR 2
33#endif // ! _URC_FATAL_PHASE2_ERROR
34
35#include "lsda.h"
36
37
38// Base exception vtable is abstract, you should not have base exceptions.
39struct __cfaabi_ehm__base_exception_t_vtable
40                ___cfaabi_ehm__base_exception_t_vtable_instance = {
41        .parent = NULL,
42        .size = 0,
43        .copy = NULL,
44        .free = NULL,
45        .msg = NULL
46};
47
48
49// Temperary global exception context. Does not work with concurency.
50struct exception_context_t {
51    struct __cfaabi_ehm__try_resume_node * top_resume;
52    struct __cfaabi_ehm__try_resume_node * current_resume;
53
54    exception * current_exception;
55    int current_handler_index;
56} shared_stack = {NULL, NULL, 0, 0};
57
58// Get the current exception context.
59// There can be a single global until multithreading occurs, then each stack
60// needs its own. It will have to be updated to handle that.
61struct exception_context_t * this_exception_context() {
62        return &shared_stack;
63}
64//#define SAVE_EXCEPTION_CONTEXT(to_name)
65//struct exception_context_t * to_name = this_exception_context();
66//exception * this_exception() {
67//    return this_exception_context()->current_exception;
68//}
69
70
71// This macro should be the only thing that needs to change across machines.  Used in the personality function, way down
72// in termination.
73// struct _Unwind_Context * -> _Unwind_Reason_Code(*)(exception *)
74#define MATCHER_FROM_CONTEXT(ptr_to_context) \
75        (*(_Unwind_Reason_Code(**)(exception*))(_Unwind_GetCFA(ptr_to_context) + 8))
76
77
78// RESUMPTION ================================================================
79
80void __cfaabi_ehm__throw_resume(exception * except) {
81
82        __cfaabi_dbg_print_safe("Throwing resumption exception\n");
83
84        struct __cfaabi_ehm__try_resume_node * original_head = shared_stack.current_resume;
85        struct __cfaabi_ehm__try_resume_node * current =
86                (original_head) ? original_head->next : shared_stack.top_resume;
87
88        for ( ; current ; current = current->next) {
89                shared_stack.current_resume = current;
90                if (current->handler(except)) {
91                        shared_stack.current_resume = original_head;
92                        return;
93                }
94        }
95
96        __cfaabi_dbg_print_safe("Unhandled exception\n");
97        shared_stack.current_resume = original_head;
98
99        // Fall back to termination:
100        __cfaabi_ehm__throw_terminate(except);
101        // TODO: Default handler for resumption.
102}
103
104// Do we control where exceptions get thrown even with concurency?  If not these are not quite thread safe, the cleanup
105// hook has to be added after the node is built but before it is made the top node.
106
107void __cfaabi_ehm__try_resume_setup(struct __cfaabi_ehm__try_resume_node * node,
108                        _Bool (*handler)(exception * except)) {
109        node->next = shared_stack.top_resume;
110        node->handler = handler;
111        shared_stack.top_resume = node;
112}
113
114void __cfaabi_ehm__try_resume_cleanup(struct __cfaabi_ehm__try_resume_node * node) {
115        shared_stack.top_resume = node->next;
116}
117
118
119// TERMINATION ===============================================================
120
121// MEMORY MANAGEMENT (still for integers)
122// May have to move to cfa for constructors and destructors (references).
123
124struct __cfaabi_ehm__node {
125        struct __cfaabi_ehm__node * next;
126};
127
128#define NODE_TO_EXCEPT(node) ((exception *)(1 + (node)))
129#define EXCEPT_TO_NODE(except) ((struct __cfaabi_ehm__node *)(except) - 1)
130
131// Creates a copy of the indicated exception and sets current_exception to it.
132static void __cfaabi_ehm__allocate_exception( exception * except ) {
133        struct exception_context_t * context = this_exception_context();
134
135        // Allocate memory for the exception.
136        struct __cfaabi_ehm__node * store = malloc(
137                sizeof( struct __cfaabi_ehm__node ) + except->virtual_table->size );
138
139        if ( ! store ) {
140                // Failure: cannot allocate exception. Terminate thread.
141                abort(); // <- Although I think it might be the process.
142        }
143
144        // Add the node to the list:
145        store->next = EXCEPT_TO_NODE(context->current_exception);
146        context->current_exception = NODE_TO_EXCEPT(store);
147
148        // Copy the exception to storage.
149        except->virtual_table->copy( context->current_exception, except );
150}
151
152// Delete the provided exception, unsetting current_exception if relivant.
153static void __cfaabi_ehm__delete_exception( exception * except ) {
154        struct exception_context_t * context = this_exception_context();
155
156        __cfaabi_dbg_print_safe("Deleting Exception\n");
157
158        // Remove the exception from the list.
159        struct __cfaabi_ehm__node * to_free = EXCEPT_TO_NODE(except);
160        struct __cfaabi_ehm__node * node;
161
162        if ( context->current_exception == except ) {
163                node = to_free->next;
164                context->current_exception = (node) ? NODE_TO_EXCEPT(node) : 0;
165        } else {
166                node = EXCEPT_TO_NODE(context->current_exception);
167                // It may always be in the first or second position.
168                while( to_free != node->next ) {
169                        node = node->next;
170                }
171                node->next = to_free->next;
172        }
173
174        // Free the old exception node.
175        except->virtual_table->free( except );
176        free( to_free );
177}
178
179// If this isn't a rethrow (*except==0), delete the provided exception.
180void __cfaabi_ehm__cleanup_terminate( void * except ) {
181        if ( *(void**)except ) __cfaabi_ehm__delete_exception( *(exception**)except );
182}
183
184
185// We need a piece of storage to raise the exception
186struct _Unwind_Exception this_exception_storage;
187
188// Function needed by force unwind
189// It basically says to unwind the whole stack and then exit when we reach the end of the stack
190static _Unwind_Reason_Code _Stop_Fn(
191                int version,
192                _Unwind_Action actions,
193                _Unwind_Exception_Class exceptionClass,
194                struct _Unwind_Exception * unwind_exception,
195                struct _Unwind_Context * context,
196                void * some_param) {
197        if( actions & _UA_END_OF_STACK  ) exit(1);
198        if( actions & _UA_CLEANUP_PHASE ) return _URC_NO_REASON;
199
200        return _URC_FATAL_PHASE2_ERROR;
201}
202
203// The exception that is being thrown must already be stored.
204__attribute__((noreturn)) void __cfaabi_ehm__begin_unwind(void) {
205        if ( ! this_exception_context()->current_exception ) {
206                printf("UNWIND ERROR missing exception in begin unwind\n");
207                abort();
208        }
209
210
211        // Call stdlibc to raise the exception
212        _Unwind_Reason_Code ret = _Unwind_RaiseException( &this_exception_storage );
213
214        // If we reach here it means something happened.  For resumption to work we need to find a way to return back to
215        // here.  Most of them will probably boil down to setting a global flag and making the phase 1 either stop or
216        // fail.  Causing an error on purpose may help avoiding unnecessary work but it might have some weird side
217        // effects.  If we just pretend no handler was found that would work but may be expensive for no reason since we
218        // will always search the whole stack.
219
220        if( ret == _URC_END_OF_STACK ) {
221                // No proper handler was found.  This can be handled in several way.  C++ calls std::terminate Here we
222                // force unwind the stack, basically raising a cancellation.
223                printf("Uncaught exception %p\n", &this_exception_storage);
224
225                ret = _Unwind_ForcedUnwind( &this_exception_storage, _Stop_Fn, (void*)0x22 );
226                printf("UNWIND ERROR %d after force unwind\n", ret);
227                abort();
228        }
229
230        // We did not simply reach the end of the stack without finding a handler.  Something wen't wrong
231        printf("UNWIND ERROR %d after raise exception\n", ret);
232        abort();
233}
234
235void __cfaabi_ehm__throw_terminate( exception * val ) {
236        __cfaabi_dbg_print_safe("Throwing termination exception\n");
237
238        __cfaabi_ehm__allocate_exception( val );
239        __cfaabi_ehm__begin_unwind();
240}
241
242void __cfaabi_ehm__rethrow_terminate(void) {
243        __cfaabi_dbg_print_safe("Rethrowing termination exception\n");
244
245        __cfaabi_ehm__begin_unwind();
246}
247
248// This is our personality routine.  For every stack frame anotated with ".cfi_personality 0x3,__gcfa_personality_v0".
249// This function will be called twice when unwinding.  Once in the search phased and once in the cleanup phase.
250_Unwind_Reason_Code __gcfa_personality_v0 (
251                int version, _Unwind_Action actions, unsigned long long exceptionClass,
252                struct _Unwind_Exception* unwind_exception,
253                struct _Unwind_Context* context)
254{
255
256        //__cfaabi_dbg_print_safe("CFA: 0x%lx\n", _Unwind_GetCFA(context));
257        __cfaabi_dbg_print_safe("Personality function (%d, %x, %llu, %p, %p):", version, actions, exceptionClass, unwind_exception, context);
258
259        // If we've reached the end of the stack then there is nothing much we can do...
260        if( actions & _UA_END_OF_STACK ) return _URC_END_OF_STACK;
261
262        if (actions & _UA_SEARCH_PHASE) {
263                __cfaabi_dbg_print_safe(" lookup phase");
264        }
265        else if (actions & _UA_CLEANUP_PHASE) {
266                __cfaabi_dbg_print_safe(" cleanup phase");
267        }
268        // Just in case, probably can't actually happen
269        else {
270                printf(" error\n");
271                return _URC_FATAL_PHASE1_ERROR;
272        }
273
274        // Get a pointer to the language specific data from which we will read what we need
275        const unsigned char * lsd = (const unsigned char*) _Unwind_GetLanguageSpecificData( context );
276
277        if( !lsd ) {    //Nothing to do, keep unwinding
278                printf(" no LSD");
279                goto UNWIND;
280        }
281
282        // Get the instuction pointer and a reading pointer into the exception table
283        lsda_header_info lsd_info;
284        const unsigned char * cur_ptr = parse_lsda_header( context, lsd, &lsd_info);
285        _Unwind_Ptr instruction_ptr = _Unwind_GetIP( context );
286
287        // Linearly search the table for stuff to do
288        while( cur_ptr < lsd_info.action_table ) {
289                _Unwind_Ptr callsite_start;
290                _Unwind_Ptr callsite_len;
291                _Unwind_Ptr callsite_landing_pad;
292                _uleb128_t  callsite_action;
293
294                // Decode the common stuff we have in here
295                cur_ptr = read_encoded_value (0, lsd_info.call_site_encoding, cur_ptr, &callsite_start);
296                cur_ptr = read_encoded_value (0, lsd_info.call_site_encoding, cur_ptr, &callsite_len);
297                cur_ptr = read_encoded_value (0, lsd_info.call_site_encoding, cur_ptr, &callsite_landing_pad);
298                cur_ptr = read_uleb128 (cur_ptr, &callsite_action);
299
300                // Have we reach the correct frame info yet?
301                if( lsd_info.Start + callsite_start + callsite_len < instruction_ptr ) {
302#ifdef __CFA_DEBUG_PRINT__
303                        void * ls = (void*)lsd_info.Start;
304                        void * cs = (void*)callsite_start;
305                        void * cl = (void*)callsite_len;
306                        void * bp = (void*)lsd_info.Start + callsite_start;
307                        void * ep = (void*)lsd_info.Start + callsite_start + callsite_len;
308                        void * ip = (void*)instruction_ptr;
309                        __cfaabi_dbg_print_safe("\nfound %p - %p (%p, %p, %p), looking for %p\n", bp, ep, ls, cs, cl, ip);
310#endif // __CFA_DEBUG_PRINT__
311                        continue;
312                }
313
314                // Have we gone too far
315                if( lsd_info.Start + callsite_start > instruction_ptr ) {
316                        printf(" gone too far");
317                        break;
318                }
319
320                // Something to do?
321                if( callsite_landing_pad ) {
322                        // Which phase are we in
323                        if (actions & _UA_SEARCH_PHASE) {
324                                // Search phase, this means we probably found a potential handler and must check if it is a match
325
326                                // If we have arbitrarily decided that 0 means nothing to do and 1 means there is a potential handler
327                                // This doesn't seem to conflict the gcc default behavior
328                                if (callsite_action != 0) {
329                                        // Now we want to run some code to see if the handler matches
330                                        // This is the tricky part where we want to the power to run arbitrary code
331                                        // However, generating a new exception table entry and try routine every time
332                                        // is way more expansive than we might like
333                                        // The information we have is :
334                                        //  - The GR (Series of registers)
335                                        //    GR1=GP Global Pointer of frame ref by context
336                                        //  - The instruction pointer
337                                        //  - The instruction pointer info (???)
338                                        //  - The CFA (Canonical Frame Address)
339                                        //  - The BSP (Probably the base stack pointer)
340
341
342                                        // The current apprach uses one exception table entry per try block
343                                        _uleb128_t imatcher;
344                                        // Get the relative offset to the
345                                        cur_ptr = read_uleb128 (cur_ptr, &imatcher);
346
347                                        // Get a function pointer from the relative offset and call it
348                                        // _Unwind_Reason_Code (*matcher)() = (_Unwind_Reason_Code (*)())lsd_info.LPStart + imatcher;
349
350                                        _Unwind_Reason_Code (*matcher)(exception *) =
351                                                MATCHER_FROM_CONTEXT(context);
352                                        int index = matcher(shared_stack.current_exception);
353                                        _Unwind_Reason_Code ret = (0 == index)
354                                                ? _URC_CONTINUE_UNWIND : _URC_HANDLER_FOUND;
355                                        shared_stack.current_handler_index = index;
356
357                                        // Based on the return value, check if we matched the exception
358                                        if( ret == _URC_HANDLER_FOUND) {
359                                                __cfaabi_dbg_print_safe(" handler found\n");
360                                        } else {
361                                                __cfaabi_dbg_print_safe(" no handler\n");
362                                        }
363                                        return ret;
364                                }
365
366                                // This is only a cleanup handler, ignore it
367                                __cfaabi_dbg_print_safe(" no action");
368                        }
369                        else if (actions & _UA_CLEANUP_PHASE) {
370
371                                if( (callsite_action != 0) && !(actions & _UA_HANDLER_FRAME) ){
372                                        // If this is a potential exception handler
373                                        // but not the one that matched the exception in the seach phase,
374                                        // just ignore it
375                                        goto UNWIND;
376                                }
377
378                                // We need to run some clean-up or a handler
379                                // These statment do the right thing but I don't know any specifics at all
380                                _Unwind_SetGR( context, __builtin_eh_return_data_regno(0), (_Unwind_Ptr) unwind_exception );
381                                _Unwind_SetGR( context, __builtin_eh_return_data_regno(1), 0 );
382
383                                // I assume this sets the instruction pointer to the adress of the landing pad
384                                // It doesn't actually set it, it only state the value that needs to be set once we return _URC_INSTALL_CONTEXT
385                                _Unwind_SetIP( context, ((lsd_info.LPStart) + (callsite_landing_pad)) );
386
387                                __cfaabi_dbg_print_safe(" action\n");
388
389                                // Return have some action to run
390                                return _URC_INSTALL_CONTEXT;
391                        }
392                }
393
394                // Nothing to do, move along
395                __cfaabi_dbg_print_safe(" no landing pad");
396        }
397        // No handling found
398        __cfaabi_dbg_print_safe(" table end reached\n");
399
400        UNWIND:
401        __cfaabi_dbg_print_safe(" unwind\n");
402
403        // Keep unwinding the stack
404        return _URC_CONTINUE_UNWIND;
405}
406
407// Try statements are hoisted out see comments for details.  With this could probably be unique and simply linked from
408// libcfa but there is one problem left, see the exception table for details
409__attribute__((noinline))
410void __cfaabi_ehm__try_terminate(void (*try_block)(),
411                void (*catch_block)(int index, exception * except),
412                __attribute__((unused)) int (*match_block)(exception * except)) {
413        //! volatile int xy = 0;
414        //! printf("%p %p %p %p\n", &try_block, &catch_block, &match_block, &xy);
415
416        // Setup statments: These 2 statments won't actually result in any code, they only setup global tables.
417        // However, they clobber gcc cancellation support from gcc.  We can replace the personality routine but
418        // replacing the exception table gcc generates is not really doable, it generates labels based on how the
419        // assembly works.
420
421        // Setup the personality routine
422        asm volatile (".cfi_personality 0x3,__gcfa_personality_v0");
423        // Setup the exception table
424        asm volatile (".cfi_lsda 0x3, .LLSDACFA2");
425
426        // Label which defines the start of the area for which the handler is setup.
427        asm volatile (".TRYSTART:");
428
429        // The actual statements of the try blocks
430        try_block();
431
432        // asm statement to prevent deadcode removal
433        asm volatile goto ("" : : : : CATCH );
434
435        // Normal return
436        return;
437
438        // Exceptionnal path
439        CATCH : __attribute__(( unused ));
440        // Label which defines the end of the area for which the handler is setup.
441        asm volatile (".TRYEND:");
442        // Label which defines the start of the exception landing pad.  Basically what is called when the exception is
443        // caught.  Note, if multiple handlers are given, the multiplexing should be done by the generated code, not the
444        // exception runtime.
445        asm volatile (".CATCH:");
446
447        // Exception handler
448        catch_block( shared_stack.current_handler_index,
449                     shared_stack.current_exception );
450}
451
452// Exception table data we need to generate.  While this is almost generic, the custom data refers to foo_try_match try
453// match, which is no way generic.  Some more works need to be done if we want to have a single call to the try routine.
454
455#if defined( __x86_64__ ) || defined( __i386__ )
456asm (
457        //HEADER
458        ".LFECFA1:\n"
459        "       .globl  __gcfa_personality_v0\n"
460        "       .section        .gcc_except_table,\"a\",@progbits\n"
461        ".LLSDACFA2:\n"                                                 //TABLE header
462        "       .byte   0xff\n"
463        "       .byte   0xff\n"
464        "       .byte   0x1\n"
465        "       .uleb128 .LLSDACSECFA2-.LLSDACSBCFA2\n"         // BODY length
466        // Body uses language specific data and therefore could be modified arbitrarily
467        ".LLSDACSBCFA2:\n"                                              // BODY start
468        "       .uleb128 .TRYSTART-__cfaabi_ehm__try_terminate\n"               // Handled area start  (relative to start of function)
469        "       .uleb128 .TRYEND-.TRYSTART\n"                           // Handled area length
470        "       .uleb128 .CATCH-__cfaabi_ehm__try_terminate\n"                          // Hanlder landing pad adress  (relative to start of function)
471        "       .uleb128 1\n"                                           // Action code, gcc seems to use always 0
472        ".LLSDACSECFA2:\n"                                              // BODY end
473        "       .text\n"                                                        // TABLE footer
474        "       .size   __cfaabi_ehm__try_terminate, .-__cfaabi_ehm__try_terminate\n"
475        "       .ident  \"GCC: (Ubuntu 6.2.0-3ubuntu11~16.04) 6.2.0 20160901\"\n"
476//      "       .section        .note.GNU-stack,\"x\",@progbits\n"
477);
478#endif // __x86_64__ || __i386__
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