source: libcfa/src/exception.c @ 3b9c674

arm-ehjacob/cs343-translationjenkins-sandboxnew-astnew-ast-unique-expr
Last change on this file since 3b9c674 was 3b9c674, checked in by Andrew Beach <ajbeach@…>, 20 months ago

Expections now supported in position independent code.

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File size: 18.9 KB
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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 : Peter A. Buhr
12// Last Modified On : Thu Feb 22 18:17:34 2018
13// Update Count     : 11
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 <bits/debug.hfa>
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_t * 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.
72// Used in the personality function, way down in termination.
73// struct _Unwind_Context * -> _Unwind_Reason_Code(*)(exception_t *)
74#define MATCHER_FROM_CONTEXT(ptr_to_context) \
75        (*(_Unwind_Reason_Code(**)(exception_t *))(_Unwind_GetCFA(ptr_to_context) + 8))
76
77
78// RESUMPTION ================================================================
79
80void __cfaabi_ehm__throw_resume(exception_t * 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?
105// If not these are not quite thread safe, the cleanup hook has to
106// be added after the node is built but before it is made the top node.
107
108void __cfaabi_ehm__try_resume_setup(struct __cfaabi_ehm__try_resume_node * node,
109                        _Bool (*handler)(exception_t * except)) {
110        node->next = shared_stack.top_resume;
111        node->handler = handler;
112        shared_stack.top_resume = node;
113}
114
115void __cfaabi_ehm__try_resume_cleanup(struct __cfaabi_ehm__try_resume_node * node) {
116        shared_stack.top_resume = node->next;
117}
118
119
120// TERMINATION ===============================================================
121
122// MEMORY MANAGEMENT (still for integers)
123// May have to move to cfa for constructors and destructors (references).
124
125struct __cfaabi_ehm__node {
126        struct __cfaabi_ehm__node * next;
127};
128
129#define NODE_TO_EXCEPT(node) ((exception_t *)(1 + (node)))
130#define EXCEPT_TO_NODE(except) ((struct __cfaabi_ehm__node *)(except) - 1)
131
132// Creates a copy of the indicated exception and sets current_exception to it.
133static void __cfaabi_ehm__allocate_exception( exception_t * except ) {
134        struct exception_context_t * context = this_exception_context();
135
136        // Allocate memory for the exception.
137        struct __cfaabi_ehm__node * store = malloc(
138                sizeof( struct __cfaabi_ehm__node ) + except->virtual_table->size );
139
140        if ( ! store ) {
141                // Failure: cannot allocate exception. Terminate thread.
142                abort(); // <- Although I think it might be the process.
143        }
144
145        // Add the node to the list:
146        store->next = EXCEPT_TO_NODE(context->current_exception);
147        context->current_exception = NODE_TO_EXCEPT(store);
148
149        // Copy the exception to storage.
150        except->virtual_table->copy( context->current_exception, except );
151}
152
153// Delete the provided exception, unsetting current_exception if relivant.
154static void __cfaabi_ehm__delete_exception( exception_t * except ) {
155        struct exception_context_t * context = this_exception_context();
156
157        __cfaabi_dbg_print_safe("Deleting Exception\n");
158
159        // Remove the exception from the list.
160        struct __cfaabi_ehm__node * to_free = EXCEPT_TO_NODE(except);
161        struct __cfaabi_ehm__node * node;
162
163        if ( context->current_exception == except ) {
164                node = to_free->next;
165                context->current_exception = (node) ? NODE_TO_EXCEPT(node) : 0;
166        } else {
167                node = EXCEPT_TO_NODE(context->current_exception);
168                // It may always be in the first or second position.
169                while( to_free != node->next ) {
170                        node = node->next;
171                }
172                node->next = to_free->next;
173        }
174
175        // Free the old exception node.
176        except->virtual_table->free( except );
177        free( to_free );
178}
179
180// If this isn't a rethrow (*except==0), delete the provided exception.
181void __cfaabi_ehm__cleanup_terminate( void * except ) {
182        if ( *(void**)except ) __cfaabi_ehm__delete_exception( *(exception_t **)except );
183}
184
185
186// We need a piece of storage to raise the exception
187struct _Unwind_Exception this_exception_storage;
188
189// Function needed by force unwind
190// It basically says to unwind the whole stack and then exit when we reach the end of the stack
191static _Unwind_Reason_Code _Stop_Fn(
192                int version,
193                _Unwind_Action actions,
194                _Unwind_Exception_Class exceptionClass,
195                struct _Unwind_Exception * unwind_exception,
196                struct _Unwind_Context * context,
197                void * some_param) {
198        if( actions & _UA_END_OF_STACK  ) exit(1);
199        if( actions & _UA_CLEANUP_PHASE ) return _URC_NO_REASON;
200
201        return _URC_FATAL_PHASE2_ERROR;
202}
203
204// The exception that is being thrown must already be stored.
205__attribute__((noreturn)) void __cfaabi_ehm__begin_unwind(void) {
206        if ( ! this_exception_context()->current_exception ) {
207                printf("UNWIND ERROR missing exception in begin unwind\n");
208                abort();
209        }
210
211
212        // Call stdlibc to raise the exception
213        _Unwind_Reason_Code ret = _Unwind_RaiseException( &this_exception_storage );
214
215        // If we reach here it means something happened. For resumption to work we need to find a way
216        // to return back to here. Most of them will probably boil down to setting a global flag and
217        // making the phase 1 either stop or fail. Causing an error on purpose may help avoiding
218        // unnecessary work but it might have some weird side effects. If we just pretend no handler
219        // was found that would work but may be expensive for no reason since we will always search
220        // the whole stack.
221
222        if( ret == _URC_END_OF_STACK ) {
223                // No proper handler was found. This can be handled in many ways, C++ calls std::terminate.
224                // Here we force unwind the stack, basically raising a cancellation.
225                printf("Uncaught exception %p\n", &this_exception_storage);
226
227                ret = _Unwind_ForcedUnwind( &this_exception_storage, _Stop_Fn, (void*)0x22 );
228                printf("UNWIND ERROR %d after force unwind\n", ret);
229                abort();
230        }
231
232        // We did not simply reach the end of the stack without finding a handler. This is an error.
233        printf("UNWIND ERROR %d after raise exception\n", ret);
234        abort();
235}
236
237void __cfaabi_ehm__throw_terminate( exception_t * val ) {
238        __cfaabi_dbg_print_safe("Throwing termination exception\n");
239
240        __cfaabi_ehm__allocate_exception( val );
241        __cfaabi_ehm__begin_unwind();
242}
243
244void __cfaabi_ehm__rethrow_terminate(void) {
245        __cfaabi_dbg_print_safe("Rethrowing termination exception\n");
246
247        __cfaabi_ehm__begin_unwind();
248}
249
250#pragma GCC push_options
251#pragma GCC optimize("O0")
252
253// This is our personality routine. For every stack frame annotated with
254// ".cfi_personality 0x3,__gcfa_personality_v0" this function will be called twice when unwinding.
255//  Once in the search phase and once in the cleanup phase.
256_Unwind_Reason_Code __gcfa_personality_v0 (
257                int version, _Unwind_Action actions, unsigned long long exceptionClass,
258                struct _Unwind_Exception* unwind_exception,
259                struct _Unwind_Context* context)
260{
261
262        //__cfaabi_dbg_print_safe("CFA: 0x%lx\n", _Unwind_GetCFA(context));
263        __cfaabi_dbg_print_safe("Personality function (%d, %x, %llu, %p, %p):",
264                        version, actions, exceptionClass, unwind_exception, context);
265
266        // If we've reached the end of the stack then there is nothing much we can do...
267        if( actions & _UA_END_OF_STACK ) return _URC_END_OF_STACK;
268
269        if (actions & _UA_SEARCH_PHASE) {
270                __cfaabi_dbg_print_safe(" lookup phase");
271        }
272        else if (actions & _UA_CLEANUP_PHASE) {
273                __cfaabi_dbg_print_safe(" cleanup phase");
274        }
275        // Just in case, probably can't actually happen
276        else {
277                printf(" error\n");
278                return _URC_FATAL_PHASE1_ERROR;
279        }
280
281        // Get a pointer to the language specific data from which we will read what we need
282        const unsigned char * lsd = (const unsigned char*) _Unwind_GetLanguageSpecificData( context );
283
284        if( !lsd ) {    //Nothing to do, keep unwinding
285                printf(" no LSD");
286                goto UNWIND;
287        }
288
289        // Get the instuction pointer and a reading pointer into the exception table
290        lsda_header_info lsd_info;
291        const unsigned char * cur_ptr = parse_lsda_header(context, lsd, &lsd_info);
292        _Unwind_Ptr instruction_ptr = _Unwind_GetIP( context );
293
294        // Linearly search the table for stuff to do
295        while( cur_ptr < lsd_info.action_table ) {
296                _Unwind_Ptr callsite_start;
297                _Unwind_Ptr callsite_len;
298                _Unwind_Ptr callsite_landing_pad;
299                _uleb128_t  callsite_action;
300
301                // Decode the common stuff we have in here
302                cur_ptr = read_encoded_value(0, lsd_info.call_site_encoding, cur_ptr, &callsite_start);
303                cur_ptr = read_encoded_value(0, lsd_info.call_site_encoding, cur_ptr, &callsite_len);
304                cur_ptr = read_encoded_value(0, lsd_info.call_site_encoding, cur_ptr, &callsite_landing_pad);
305                cur_ptr = read_uleb128(cur_ptr, &callsite_action);
306
307                // Have we reach the correct frame info yet?
308                if( lsd_info.Start + callsite_start + callsite_len < instruction_ptr ) {
309#ifdef __CFA_DEBUG_PRINT__
310                        void * ls = (void*)lsd_info.Start;
311                        void * cs = (void*)callsite_start;
312                        void * cl = (void*)callsite_len;
313                        void * bp = (void*)lsd_info.Start + callsite_start;
314                        void * ep = (void*)lsd_info.Start + callsite_start + callsite_len;
315                        void * ip = (void*)instruction_ptr;
316                        __cfaabi_dbg_print_safe("\nfound %p - %p (%p, %p, %p), looking for %p\n",
317                                        bp, ep, ls, cs, cl, ip);
318#endif // __CFA_DEBUG_PRINT__
319                        continue;
320                }
321
322                // Have we gone too far?
323                if( lsd_info.Start + callsite_start > instruction_ptr ) {
324                        printf(" gone too far");
325                        break;
326                }
327
328                // Something to do?
329                if( callsite_landing_pad ) {
330                        // Which phase are we in
331                        if (actions & _UA_SEARCH_PHASE) {
332                                // In search phase, these means we found a potential handler we must check.
333
334                                // We have arbitrarily decided that 0 means nothing to do and 1 means there is
335                                // a potential handler. This doesn't seem to conflict the gcc default behavior.
336                                if (callsite_action != 0) {
337                                        // Now we want to run some code to see if the handler matches
338                                        // This is the tricky part where we want to the power to run arbitrary code
339                                        // However, generating a new exception table entry and try routine every time
340                                        // is way more expansive than we might like
341                                        // The information we have is :
342                                        //  - The GR (Series of registers)
343                                        //    GR1=GP Global Pointer of frame ref by context
344                                        //  - The instruction pointer
345                                        //  - The instruction pointer info (???)
346                                        //  - The CFA (Canonical Frame Address)
347                                        //  - The BSP (Probably the base stack pointer)
348
349
350                                        // The current apprach uses one exception table entry per try block
351                                        _uleb128_t imatcher;
352                                        // Get the relative offset to the {...}?
353                                        cur_ptr = read_uleb128(cur_ptr, &imatcher);
354
355                                        _Unwind_Reason_Code (*matcher)(exception_t *) =
356                                                MATCHER_FROM_CONTEXT(context);
357                                        int index = matcher(shared_stack.current_exception);
358                                        _Unwind_Reason_Code ret = (0 == index)
359                                                ? _URC_CONTINUE_UNWIND : _URC_HANDLER_FOUND;
360                                        shared_stack.current_handler_index = index;
361
362                                        // Based on the return value, check if we matched the exception
363                                        if( ret == _URC_HANDLER_FOUND) {
364                                                __cfaabi_dbg_print_safe(" handler found\n");
365                                        } else {
366                                                __cfaabi_dbg_print_safe(" no handler\n");
367                                        }
368                                        return ret;
369                                }
370
371                                // This is only a cleanup handler, ignore it
372                                __cfaabi_dbg_print_safe(" no action");
373                        }
374                        else if (actions & _UA_CLEANUP_PHASE) {
375
376                                if( (callsite_action != 0) && !(actions & _UA_HANDLER_FRAME) ){
377                                        // If this is a potential exception handler
378                                        // but not the one that matched the exception in the seach phase,
379                                        // just ignore it
380                                        goto UNWIND;
381                                }
382
383                                // We need to run some clean-up or a handler
384                                // These statment do the right thing but I don't know any specifics at all
385                                _Unwind_SetGR( context, __builtin_eh_return_data_regno(0), (_Unwind_Ptr) unwind_exception );
386                                _Unwind_SetGR( context, __builtin_eh_return_data_regno(1), 0 );
387
388                                // I assume this sets the instruction pointer to the adress of the landing pad
389                                // It doesn't actually set it, it only state the value that needs to be set once we return _URC_INSTALL_CONTEXT
390                                _Unwind_SetIP( context, ((lsd_info.LPStart) + (callsite_landing_pad)) );
391
392                                __cfaabi_dbg_print_safe(" action\n");
393
394                                // Return have some action to run
395                                return _URC_INSTALL_CONTEXT;
396                        }
397                }
398
399                // Nothing to do, move along
400                __cfaabi_dbg_print_safe(" no landing pad");
401        }
402        // No handling found
403        __cfaabi_dbg_print_safe(" table end reached\n");
404
405        UNWIND:
406        __cfaabi_dbg_print_safe(" unwind\n");
407
408        // Keep unwinding the stack
409        return _URC_CONTINUE_UNWIND;
410}
411
412// Try statements are hoisted out see comments for details. While this could probably be unique
413// and simply linked from libcfa but there is one problem left, see the exception table for details
414__attribute__((noinline))
415void __cfaabi_ehm__try_terminate(void (*try_block)(),
416                void (*catch_block)(int index, exception_t * except),
417                __attribute__((unused)) int (*match_block)(exception_t * except)) {
418        //! volatile int xy = 0;
419        //! printf("%p %p %p %p\n", &try_block, &catch_block, &match_block, &xy);
420
421        // Setup statments: These 2 statments won't actually result in any code, they only setup global tables.
422        // However, they clobber gcc cancellation support from gcc.  We can replace the personality routine but
423        // replacing the exception table gcc generates is not really doable, it generates labels based on how the
424        // assembly works.
425
426        // Setup the personality routine and exception table.
427#ifdef __PIC__
428        asm volatile (".cfi_personality 0x9b,CFA.ref.__gcfa_personality_v0");
429        asm volatile (".cfi_lsda 0x1b, .LLSDACFA2");
430#else
431        asm volatile (".cfi_personality 0x3,__gcfa_personality_v0");
432        asm volatile (".cfi_lsda 0x3, .LLSDACFA2");
433#endif
434
435        // Label which defines the start of the area for which the handler is setup.
436        asm volatile (".TRYSTART:");
437
438        // The actual statements of the try blocks
439        try_block();
440
441        // asm statement to prevent deadcode removal
442        asm volatile goto ("" : : : : CATCH );
443
444        // Normal return for when there is no throw.
445        return;
446
447        // Exceptionnal path
448        CATCH : __attribute__(( unused ));
449        // Label which defines the end of the area for which the handler is setup.
450        asm volatile (".TRYEND:");
451        // Label which defines the start of the exception landing pad.  Basically what is called when the exception is
452        // caught.  Note, if multiple handlers are given, the multiplexing should be done by the generated code, not the
453        // exception runtime.
454        asm volatile (".CATCH:");
455
456        // Exception handler
457        catch_block( shared_stack.current_handler_index,
458                     shared_stack.current_exception );
459}
460
461// Exception table data we need to generate. While this is almost generic, the custom data refers
462// to {*}try_terminate, which is no way generic. Some more works need to be done if we want to
463// have a single call to the try routine.
464
465#ifdef __PIC__
466#if defined( __i386 ) || defined( __x86_64 )
467asm (
468        // HEADER
469        ".LFECFA1:\n"
470        "       .globl  __gcfa_personality_v0\n"
471        "       .section        .gcc_except_table,\"a\",@progbits\n"
472        // TABLE HEADER (important field is the BODY length at the end)
473        ".LLSDACFA2:\n"
474        "       .byte   0xff\n"
475        "       .byte   0xff\n"
476        "       .byte   0x1\n"
477        "       .uleb128 .LLSDACSECFA2-.LLSDACSBCFA2\n"
478        // BODY (language specific data)
479        // This uses language specific data and can be modified arbitrarily
480        // We use handled area offset, handled area length,
481        // handler landing pad offset and 1 (action code, gcc seems to use 0).
482        ".LLSDACSBCFA2:\n"
483        "       .uleb128 .TRYSTART-__cfaabi_ehm__try_terminate\n"
484        "       .uleb128 .TRYEND-.TRYSTART\n"
485        "       .uleb128 .CATCH-__cfaabi_ehm__try_terminate\n"
486        "       .uleb128 1\n"
487        ".LLSDACSECFA2:\n"
488        // TABLE FOOTER
489        "       .text\n"
490        "       .size   __cfaabi_ehm__try_terminate, .-__cfaabi_ehm__try_terminate\n"
491);
492
493// Somehow this piece of helps with the resolution of debug symbols.
494__attribute__((unused)) static const int dummy = 0;
495
496asm (
497        // Add a hidden symbol which points at the function.
498        "       .hidden CFA.ref.__gcfa_personality_v0\n"
499        "       .weak   CFA.ref.__gcfa_personality_v0\n"
500        // No clue what this does specifically
501        "       .section        .data.rel.local.CFA.ref.__gcfa_personality_v0,\"awG\",@progbits,CFA.ref.__gcfa_personality_v0,comdat\n"
502        "       .align 8\n"
503        "       .type CFA.ref.__gcfa_personality_v0, @object\n"
504        "       .size CFA.ref.__gcfa_personality_v0, 8\n"
505        "CFA.ref.__gcfa_personality_v0:\n"
506#if defined( __x86_64 )
507        "       .quad __gcfa_personality_v0\n"
508#else // then __i386
509        "   .long __gcfa_personality_v0\n"
510#endif
511);
512#else
513#error Exception Handling: unknown architecture for position independent code.
514#endif // __i386 || __x86_64
515#else // __PIC__
516#if defined( __i386 ) || defined( __x86_64 )
517asm (
518        // HEADER
519        ".LFECFA1:\n"
520        "       .globl  __gcfa_personality_v0\n"
521        "       .section        .gcc_except_table,\"a\",@progbits\n"
522        // TABLE HEADER (important field is the BODY length at the end)
523        ".LLSDACFA2:\n"
524        "       .byte   0xff\n"
525        "       .byte   0xff\n"
526        "       .byte   0x1\n"
527        "       .uleb128 .LLSDACSECFA2-.LLSDACSBCFA2\n"
528        // BODY (language specific data)
529        ".LLSDACSBCFA2:\n"
530        //      Handled area start (relative to start of function)
531        "       .uleb128 .TRYSTART-__cfaabi_ehm__try_terminate\n"
532        //      Handled area length
533        "       .uleb128 .TRYEND-.TRYSTART\n"
534        //      Handler landing pad address (relative to start of function)
535        "       .uleb128 .CATCH-__cfaabi_ehm__try_terminate\n"
536        //      Action code, gcc seems to always use 0.
537        "       .uleb128 1\n"
538        // TABLE FOOTER
539        ".LLSDACSECFA2:\n"
540        "       .text\n"
541        "       .size   __cfaabi_ehm__try_terminate, .-__cfaabi_ehm__try_terminate\n"
542        "       .ident  \"GCC: (Ubuntu 6.2.0-3ubuntu11~16.04) 6.2.0 20160901\"\n"
543        "       .section        .note.GNU-stack,\"x\",@progbits\n"
544);
545#else
546#error Exception Handling: unknown architecture for position dependent code.
547#endif // __i386 || __x86_64
548#endif // __PIC__
549
550#pragma GCC pop_options
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