Index: libcfa/src/exception.c =================================================================== --- libcfa/src/exception.c (revision 98d6965d977b39416143b988d932952fb731637a) +++ libcfa/src/exception.c (revision 332bd3303d25cdb1960e2fe79243496df86ebe8b) @@ -69,6 +69,6 @@ -// This macro should be the only thing that needs to change across machines. Used in the personality function, way down -// in termination. +// This macro should be the only thing that needs to change across machines. +// Used in the personality function, way down in termination. // struct _Unwind_Context * -> _Unwind_Reason_Code(*)(exception_t *) #define MATCHER_FROM_CONTEXT(ptr_to_context) \ @@ -102,6 +102,7 @@ } -// Do we control where exceptions get thrown even with concurency? If not these are not quite thread safe, the cleanup -// hook has to be added after the node is built but before it is made the top node. +// Do we control where exceptions get thrown even with concurency? +// If not these are not quite thread safe, the cleanup hook has to +// be added after the node is built but before it is made the top node. void __cfaabi_ehm__try_resume_setup(struct __cfaabi_ehm__try_resume_node * node, @@ -212,13 +213,14 @@ _Unwind_Reason_Code ret = _Unwind_RaiseException( &this_exception_storage ); - // If we reach here it means something happened. For resumption to work we need to find a way to return back to - // here. Most of them will probably boil down to setting a global flag and making the phase 1 either stop or - // fail. Causing an error on purpose may help avoiding unnecessary work but it might have some weird side - // effects. If we just pretend no handler was found that would work but may be expensive for no reason since we - // will always search the whole stack. + // If we reach here it means something happened. For resumption to work we need to find a way + // to return back to here. Most of them will probably boil down to setting a global flag and + // making the phase 1 either stop or fail. Causing an error on purpose may help avoiding + // unnecessary work but it might have some weird side effects. If we just pretend no handler + // was found that would work but may be expensive for no reason since we will always search + // the whole stack. if( ret == _URC_END_OF_STACK ) { - // No proper handler was found. This can be handled in several way. C++ calls std::terminate Here we - // force unwind the stack, basically raising a cancellation. + // No proper handler was found. This can be handled in many ways, C++ calls std::terminate. + // Here we force unwind the stack, basically raising a cancellation. printf("Uncaught exception %p\n", &this_exception_storage); @@ -228,5 +230,5 @@ } - // We did not simply reach the end of the stack without finding a handler. Something wen't wrong + // We did not simply reach the end of the stack without finding a handler. This is an error. printf("UNWIND ERROR %d after raise exception\n", ret); abort(); @@ -254,7 +256,8 @@ abort(); } -#else -// This is our personality routine. For every stack frame anotated with ".cfi_personality 0x3,__gcfa_personality_v0". -// This function will be called twice when unwinding. Once in the search phased and once in the cleanup phase. +#else // PIC +// This is our personality routine. For every stack frame annotated with +// ".cfi_personality 0x3,__gcfa_personality_v0" this function will be called twice when unwinding. +// Once in the search phase and once in the cleanup phase. _Unwind_Reason_Code __gcfa_personality_v0 ( int version, _Unwind_Action actions, unsigned long long exceptionClass, @@ -264,5 +267,6 @@ //__cfaabi_dbg_print_safe("CFA: 0x%lx\n", _Unwind_GetCFA(context)); - __cfaabi_dbg_print_safe("Personality function (%d, %x, %llu, %p, %p):", version, actions, exceptionClass, unwind_exception, context); + __cfaabi_dbg_print_safe("Personality function (%d, %x, %llu, %p, %p):", + version, actions, exceptionClass, unwind_exception, context); // If we've reached the end of the stack then there is nothing much we can do... @@ -291,5 +295,5 @@ // Get the instuction pointer and a reading pointer into the exception table lsda_header_info lsd_info; - const unsigned char * cur_ptr = parse_lsda_header( context, lsd, &lsd_info); + const unsigned char * cur_ptr = parse_lsda_header(context, lsd, &lsd_info); _Unwind_Ptr instruction_ptr = _Unwind_GetIP( context ); @@ -302,8 +306,8 @@ // Decode the common stuff we have in here - cur_ptr = read_encoded_value (0, lsd_info.call_site_encoding, cur_ptr, &callsite_start); - cur_ptr = read_encoded_value (0, lsd_info.call_site_encoding, cur_ptr, &callsite_len); - cur_ptr = read_encoded_value (0, lsd_info.call_site_encoding, cur_ptr, &callsite_landing_pad); - cur_ptr = read_uleb128 (cur_ptr, &callsite_action); + cur_ptr = read_encoded_value(0, lsd_info.call_site_encoding, cur_ptr, &callsite_start); + cur_ptr = read_encoded_value(0, lsd_info.call_site_encoding, cur_ptr, &callsite_len); + cur_ptr = read_encoded_value(0, lsd_info.call_site_encoding, cur_ptr, &callsite_landing_pad); + cur_ptr = read_uleb128(cur_ptr, &callsite_action); // Have we reach the correct frame info yet? @@ -316,10 +320,11 @@ void * ep = (void*)lsd_info.Start + callsite_start + callsite_len; void * ip = (void*)instruction_ptr; - __cfaabi_dbg_print_safe("\nfound %p - %p (%p, %p, %p), looking for %p\n", bp, ep, ls, cs, cl, ip); + __cfaabi_dbg_print_safe("\nfound %p - %p (%p, %p, %p), looking for %p\n", + bp, ep, ls, cs, cl, ip); #endif // __CFA_DEBUG_PRINT__ continue; } - // Have we gone too far + // Have we gone too far? if( lsd_info.Start + callsite_start > instruction_ptr ) { printf(" gone too far"); @@ -331,8 +336,8 @@ // Which phase are we in if (actions & _UA_SEARCH_PHASE) { - // Search phase, this means we probably found a potential handler and must check if it is a match - - // If we have arbitrarily decided that 0 means nothing to do and 1 means there is a potential handler - // This doesn't seem to conflict the gcc default behavior + // In search phase, these means we found a potential handler we must check. + + // We have arbitrarily decided that 0 means nothing to do and 1 means there is + // a potential handler. This doesn't seem to conflict the gcc default behavior. if (callsite_action != 0) { // Now we want to run some code to see if the handler matches @@ -351,9 +356,6 @@ // The current apprach uses one exception table entry per try block _uleb128_t imatcher; - // Get the relative offset to the - cur_ptr = read_uleb128 (cur_ptr, &imatcher); - - // Get a function pointer from the relative offset and call it - // _Unwind_Reason_Code (*matcher)() = (_Unwind_Reason_Code (*)())lsd_info.LPStart + imatcher; + // Get the relative offset to the {...}? + cur_ptr = read_uleb128(cur_ptr, &imatcher); _Unwind_Reason_Code (*matcher)(exception_t *) = @@ -414,6 +416,6 @@ } -// Try statements are hoisted out see comments for details. With this could probably be unique and simply linked from -// libcfa but there is one problem left, see the exception table for details +// Try statements are hoisted out see comments for details. While this could probably be unique +// and simply linked from libcfa but there is one problem left, see the exception table for details __attribute__((noinline)) void __cfaabi_ehm__try_terminate(void (*try_block)(), @@ -428,7 +430,6 @@ // assembly works. - // Setup the personality routine + // Setup the personality routine and exception table. asm volatile (".cfi_personality 0x3,__gcfa_personality_v0"); - // Setup the exception table asm volatile (".cfi_lsda 0x3, .LLSDACFA2"); @@ -442,5 +443,5 @@ asm volatile goto ("" : : : : CATCH ); - // Normal return + // Normal return for when there is no throw. return; @@ -459,26 +460,33 @@ } -// Exception table data we need to generate. While this is almost generic, the custom data refers to foo_try_match try -// 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. +// Exception table data we need to generate. While this is almost generic, the custom data refers +// to {*}try_terminate, which is no way generic. Some more works need to be done if we want to +// have a single call to the try routine. #if defined( __i386 ) || defined( __x86_64 ) asm ( - //HEADER + // HEADER ".LFECFA1:\n" " .globl __gcfa_personality_v0\n" " .section .gcc_except_table,\"a\",@progbits\n" - ".LLSDACFA2:\n" //TABLE header + // TABLE HEADER (important field is the BODY length at the end) + ".LLSDACFA2:\n" " .byte 0xff\n" " .byte 0xff\n" " .byte 0x1\n" - " .uleb128 .LLSDACSECFA2-.LLSDACSBCFA2\n" // BODY length - // Body uses language specific data and therefore could be modified arbitrarily - ".LLSDACSBCFA2:\n" // BODY start - " .uleb128 .TRYSTART-__cfaabi_ehm__try_terminate\n" // Handled area start (relative to start of function) - " .uleb128 .TRYEND-.TRYSTART\n" // Handled area length - " .uleb128 .CATCH-__cfaabi_ehm__try_terminate\n" // Hanlder landing pad adress (relative to start of function) - " .uleb128 1\n" // Action code, gcc seems to use always 0 - ".LLSDACSECFA2:\n" // BODY end - " .text\n" // TABLE footer + " .uleb128 .LLSDACSECFA2-.LLSDACSBCFA2\n" + // BODY (language specific data) + ".LLSDACSBCFA2:\n" + // Handled area start (relative to start of function) + " .uleb128 .TRYSTART-__cfaabi_ehm__try_terminate\n" + // Handled area length + " .uleb128 .TRYEND-.TRYSTART\n" + // Handler landing pad address (relative to start of function) + " .uleb128 .CATCH-__cfaabi_ehm__try_terminate\n" + // Action code, gcc seems to always use 0. + " .uleb128 1\n" + // TABLE FOOTER + ".LLSDACSECFA2:\n" + " .text\n" " .size __cfaabi_ehm__try_terminate, .-__cfaabi_ehm__try_terminate\n" " .ident \"GCC: (Ubuntu 6.2.0-3ubuntu11~16.04) 6.2.0 20160901\"\n" @@ -486,3 +494,3 @@ ); #endif // __i386 || __x86_64 -#endif //PIC +#endif // PIC