441 lines
11 KiB
C
441 lines
11 KiB
C
/* go-unwind.c -- unwind the stack for panic/recover.
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Copyright 2010 The Go Authors. All rights reserved.
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Use of this source code is governed by a BSD-style
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license that can be found in the LICENSE file. */
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#include "config.h"
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#include <stdlib.h>
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#include <unistd.h>
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#include "unwind.h"
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#define NO_SIZE_OF_ENCODED_VALUE
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#include "unwind-pe.h"
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#include "runtime.h"
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#include "go-alloc.h"
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#include "go-defer.h"
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#include "go-panic.h"
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/* The code for a Go exception. */
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#ifdef __ARM_EABI_UNWINDER__
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static const _Unwind_Exception_Class __go_exception_class =
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{ 'G', 'N', 'U', 'C', 'G', 'O', '\0', '\0' };
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#else
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static const _Unwind_Exception_Class __go_exception_class =
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((((((((_Unwind_Exception_Class) 'G'
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<< 8 | (_Unwind_Exception_Class) 'N')
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<< 8 | (_Unwind_Exception_Class) 'U')
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<< 8 | (_Unwind_Exception_Class) 'C')
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<< 8 | (_Unwind_Exception_Class) 'G')
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<< 8 | (_Unwind_Exception_Class) 'O')
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<< 8 | (_Unwind_Exception_Class) '\0')
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<< 8 | (_Unwind_Exception_Class) '\0');
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#endif
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/* This function is called by exception handlers used when unwinding
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the stack after a recovered panic. The exception handler looks
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like this:
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__go_check_defer (frame);
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return;
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If we have not yet reached the frame we are looking for, we
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continue unwinding. */
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void
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__go_check_defer (_Bool *frame)
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{
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G *g;
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struct _Unwind_Exception *hdr;
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g = runtime_g ();
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if (g == NULL)
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{
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/* Some other language has thrown an exception. We know there
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are no defer handlers, so there is nothing to do. */
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}
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else if (g->is_foreign)
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{
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struct __go_panic_stack *n;
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_Bool was_recovered;
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/* Some other language has thrown an exception. We need to run
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the local defer handlers. If they call recover, we stop
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unwinding the stack here. */
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n = ((struct __go_panic_stack *)
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__go_alloc (sizeof (struct __go_panic_stack)));
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n->__arg.__type_descriptor = NULL;
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n->__arg.__object = NULL;
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n->__was_recovered = 0;
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n->__is_foreign = 1;
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n->__next = g->panic;
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g->panic = n;
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while (1)
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{
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struct __go_defer_stack *d;
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void (*pfn) (void *);
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d = g->defer;
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if (d == NULL || d->__frame != frame || d->__pfn == NULL)
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break;
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pfn = d->__pfn;
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g->defer = d->__next;
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(*pfn) (d->__arg);
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__go_free (d);
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if (n->__was_recovered)
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{
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/* The recover function caught the panic thrown by some
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other language. */
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break;
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}
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}
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was_recovered = n->__was_recovered;
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g->panic = n->__next;
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__go_free (n);
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if (was_recovered)
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{
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/* Just return and continue executing Go code. */
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*frame = 1;
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return;
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}
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/* We are panicing through this function. */
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*frame = 0;
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}
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else if (g->defer != NULL
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&& g->defer->__pfn == NULL
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&& g->defer->__frame == frame)
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{
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struct __go_defer_stack *d;
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/* This is the defer function which called recover. Simply
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return to stop the stack unwind, and let the Go code continue
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to execute. */
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d = g->defer;
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g->defer = d->__next;
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__go_free (d);
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/* We are returning from this function. */
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*frame = 1;
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return;
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}
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/* This is some other defer function. It was already run by the
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call to panic, or just above. Rethrow the exception. */
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hdr = (struct _Unwind_Exception *) g->exception;
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#ifdef LIBGO_SJLJ_EXCEPTIONS
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_Unwind_SjLj_Resume_or_Rethrow (hdr);
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#else
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#if defined(_LIBUNWIND_STD_ABI)
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_Unwind_RaiseException (hdr);
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#else
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_Unwind_Resume_or_Rethrow (hdr);
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#endif
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#endif
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/* Rethrowing the exception should not return. */
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abort();
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}
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/* Unwind function calls until we reach the one which used a defer
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function which called recover. Each function which uses a defer
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statement will have an exception handler, as shown above. */
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void
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__go_unwind_stack ()
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{
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struct _Unwind_Exception *hdr;
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hdr = ((struct _Unwind_Exception *)
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__go_alloc (sizeof (struct _Unwind_Exception)));
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__builtin_memcpy (&hdr->exception_class, &__go_exception_class,
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sizeof hdr->exception_class);
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hdr->exception_cleanup = NULL;
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runtime_g ()->exception = hdr;
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#ifdef __USING_SJLJ_EXCEPTIONS__
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_Unwind_SjLj_RaiseException (hdr);
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#else
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_Unwind_RaiseException (hdr);
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#endif
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/* Raising an exception should not return. */
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abort ();
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}
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/* The rest of this code is really similar to gcc/unwind-c.c and
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libjava/exception.cc. */
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typedef struct
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{
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_Unwind_Ptr Start;
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_Unwind_Ptr LPStart;
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_Unwind_Ptr ttype_base;
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const unsigned char *TType;
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const unsigned char *action_table;
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unsigned char ttype_encoding;
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unsigned char call_site_encoding;
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} lsda_header_info;
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static const unsigned char *
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parse_lsda_header (struct _Unwind_Context *context, const unsigned char *p,
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lsda_header_info *info)
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{
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_uleb128_t tmp;
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unsigned char lpstart_encoding;
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info->Start = (context ? _Unwind_GetRegionStart (context) : 0);
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/* Find @LPStart, the base to which landing pad offsets are relative. */
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lpstart_encoding = *p++;
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if (lpstart_encoding != DW_EH_PE_omit)
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p = read_encoded_value (context, lpstart_encoding, p, &info->LPStart);
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else
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info->LPStart = info->Start;
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/* Find @TType, the base of the handler and exception spec type data. */
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info->ttype_encoding = *p++;
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if (info->ttype_encoding != DW_EH_PE_omit)
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{
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p = read_uleb128 (p, &tmp);
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info->TType = p + tmp;
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}
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else
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info->TType = 0;
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/* The encoding and length of the call-site table; the action table
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immediately follows. */
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info->call_site_encoding = *p++;
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p = read_uleb128 (p, &tmp);
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info->action_table = p + tmp;
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return p;
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}
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/* The personality function is invoked when unwinding the stack due to
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a panic. Its job is to find the cleanup and exception handlers to
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run. We can't split the stack here, because we won't be able to
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unwind from that split. */
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#ifdef __ARM_EABI_UNWINDER__
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/* ARM EABI personality routines must also unwind the stack. */
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#define CONTINUE_UNWINDING \
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do \
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{ \
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if (__gnu_unwind_frame (ue_header, context) != _URC_OK) \
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return _URC_FAILURE; \
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return _URC_CONTINUE_UNWIND; \
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} \
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while (0)
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#else
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#define CONTINUE_UNWINDING return _URC_CONTINUE_UNWIND
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#endif
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#ifdef __USING_SJLJ_EXCEPTIONS__
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#define PERSONALITY_FUNCTION __gccgo_personality_sj0
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#define __builtin_eh_return_data_regno(x) x
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#else
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#define PERSONALITY_FUNCTION __gccgo_personality_v0
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#endif
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#ifdef __ARM_EABI_UNWINDER__
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_Unwind_Reason_Code
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PERSONALITY_FUNCTION (_Unwind_State, struct _Unwind_Exception *,
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struct _Unwind_Context *)
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__attribute__ ((no_split_stack, flatten));
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_Unwind_Reason_Code
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PERSONALITY_FUNCTION (_Unwind_State state,
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struct _Unwind_Exception * ue_header,
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struct _Unwind_Context * context)
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#else
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_Unwind_Reason_Code
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PERSONALITY_FUNCTION (int, _Unwind_Action, _Unwind_Exception_Class,
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struct _Unwind_Exception *, struct _Unwind_Context *)
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__attribute__ ((no_split_stack, flatten));
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_Unwind_Reason_Code
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PERSONALITY_FUNCTION (int version,
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_Unwind_Action actions,
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_Unwind_Exception_Class exception_class,
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struct _Unwind_Exception *ue_header,
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struct _Unwind_Context *context)
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#endif
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{
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lsda_header_info info;
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const unsigned char *language_specific_data, *p, *action_record;
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_Unwind_Ptr landing_pad, ip;
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int ip_before_insn = 0;
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_Bool is_foreign;
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G *g;
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#ifdef __ARM_EABI_UNWINDER__
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_Unwind_Action actions;
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switch (state & _US_ACTION_MASK)
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{
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case _US_VIRTUAL_UNWIND_FRAME:
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actions = _UA_SEARCH_PHASE;
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break;
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case _US_UNWIND_FRAME_STARTING:
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actions = _UA_CLEANUP_PHASE;
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if (!(state & _US_FORCE_UNWIND)
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&& ue_header->barrier_cache.sp == _Unwind_GetGR(context, 13))
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actions |= _UA_HANDLER_FRAME;
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break;
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case _US_UNWIND_FRAME_RESUME:
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CONTINUE_UNWINDING;
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break;
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default:
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abort();
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}
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actions |= state & _US_FORCE_UNWIND;
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is_foreign = 0;
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/* The dwarf unwinder assumes the context structure holds things like the
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function and LSDA pointers. The ARM implementation caches these in
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the exception header (UCB). To avoid rewriting everything we make the
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virtual IP register point at the UCB. */
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ip = (_Unwind_Ptr) ue_header;
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_Unwind_SetGR (context, 12, ip);
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#else
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if (version != 1)
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return _URC_FATAL_PHASE1_ERROR;
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is_foreign = exception_class != __go_exception_class;
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#endif
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language_specific_data = (const unsigned char *)
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_Unwind_GetLanguageSpecificData (context);
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/* If no LSDA, then there are no handlers or cleanups. */
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if (! language_specific_data)
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CONTINUE_UNWINDING;
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/* Parse the LSDA header. */
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p = parse_lsda_header (context, language_specific_data, &info);
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#ifdef HAVE_GETIPINFO
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ip = _Unwind_GetIPInfo (context, &ip_before_insn);
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#else
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ip = _Unwind_GetIP (context);
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#endif
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if (! ip_before_insn)
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--ip;
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landing_pad = 0;
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action_record = NULL;
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#ifdef __USING_SJLJ_EXCEPTIONS__
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/* The given "IP" is an index into the call-site table, with two
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exceptions -- -1 means no-action, and 0 means terminate. But
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since we're using uleb128 values, we've not got random access
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to the array. */
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if ((int) ip <= 0)
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return _URC_CONTINUE_UNWIND;
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else
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{
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_uleb128_t cs_lp, cs_action;
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do
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{
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p = read_uleb128 (p, &cs_lp);
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p = read_uleb128 (p, &cs_action);
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}
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while (--ip);
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/* Can never have null landing pad for sjlj -- that would have
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been indicated by a -1 call site index. */
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landing_pad = (_Unwind_Ptr)cs_lp + 1;
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if (cs_action)
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action_record = info.action_table + cs_action - 1;
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goto found_something;
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}
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#else
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/* Search the call-site table for the action associated with this IP. */
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while (p < info.action_table)
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{
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_Unwind_Ptr cs_start, cs_len, cs_lp;
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_uleb128_t cs_action;
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/* Note that all call-site encodings are "absolute" displacements. */
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p = read_encoded_value (0, info.call_site_encoding, p, &cs_start);
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p = read_encoded_value (0, info.call_site_encoding, p, &cs_len);
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p = read_encoded_value (0, info.call_site_encoding, p, &cs_lp);
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p = read_uleb128 (p, &cs_action);
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/* The table is sorted, so if we've passed the ip, stop. */
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if (ip < info.Start + cs_start)
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p = info.action_table;
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else if (ip < info.Start + cs_start + cs_len)
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{
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if (cs_lp)
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landing_pad = info.LPStart + cs_lp;
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if (cs_action)
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action_record = info.action_table + cs_action - 1;
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goto found_something;
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}
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}
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#endif
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/* IP is not in table. No associated cleanups. */
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CONTINUE_UNWINDING;
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found_something:
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if (landing_pad == 0)
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{
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/* IP is present, but has a null landing pad.
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No handler to be run. */
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CONTINUE_UNWINDING;
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}
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if (actions & _UA_SEARCH_PHASE)
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{
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if (action_record == 0)
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{
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/* This indicates a cleanup rather than an exception
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handler. */
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CONTINUE_UNWINDING;
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}
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return _URC_HANDLER_FOUND;
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}
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/* It's possible for g to be NULL here for an exception thrown by a
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language other than Go. */
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g = runtime_g ();
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if (g == NULL)
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{
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if (!is_foreign)
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abort ();
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}
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else
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{
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g->exception = ue_header;
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g->is_foreign = is_foreign;
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}
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_Unwind_SetGR (context, __builtin_eh_return_data_regno (0),
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(_Unwind_Ptr) ue_header);
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_Unwind_SetGR (context, __builtin_eh_return_data_regno (1), 0);
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_Unwind_SetIP (context, landing_pad);
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return _URC_INSTALL_CONTEXT;
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}
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