874 lines
24 KiB
C
874 lines
24 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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#include "runtime.h"
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/* These constants are documented here:
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https://refspecs.linuxfoundation.org/LSB_3.0.0/LSB-PDA/LSB-PDA/dwarfext.html
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*/
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#define DW_EH_PE_omit 0xff
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#define DW_EH_PE_absptr 0x00
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#define DW_EH_PE_uleb128 0x01
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#define DW_EH_PE_udata2 0x02
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#define DW_EH_PE_udata4 0x03
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#define DW_EH_PE_udata8 0x04
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#define DW_EH_PE_sleb128 0x09
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#define DW_EH_PE_sdata2 0x0A
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#define DW_EH_PE_sdata4 0x0B
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#define DW_EH_PE_sdata8 0x0C
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#define DW_EH_PE_pcrel 0x10
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#define DW_EH_PE_textrel 0x20
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#define DW_EH_PE_datarel 0x30
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#define DW_EH_PE_funcrel 0x40
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#define DW_EH_PE_aligned 0x50
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#define DW_EH_PE_indirect 0x80
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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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/* Rethrow an exception. */
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void rethrowException (void) __asm__(GOSYM_PREFIX "runtime.rethrowException");
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void
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rethrowException ()
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{
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struct _Unwind_Exception *hdr;
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_Unwind_Reason_Code reason;
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hdr = (struct _Unwind_Exception *) runtime_g()->exception;
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#ifdef __USING_SJLJ_EXCEPTIONS__
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reason = _Unwind_SjLj_Resume_or_Rethrow (hdr);
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#else
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#if defined(_LIBUNWIND_STD_ABI)
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reason = _Unwind_RaiseException (hdr);
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#else
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reason = _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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runtime_printf ("failed to rethrow unwind exception (reason=%d)\n", reason);
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abort();
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}
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/* Return the size of the type that holds an exception header, so that
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it can be allocated by Go code. */
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uintptr unwindExceptionSize(void)
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__asm__ (GOSYM_PREFIX "runtime.unwindExceptionSize");
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uintptr
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unwindExceptionSize ()
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{
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uintptr ret, align;
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ret = sizeof (struct _Unwind_Exception);
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/* Adjust the size fo make sure that we can get an aligned value. */
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align = __alignof__ (struct _Unwind_Exception);
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if (align > __alignof__ (uintptr))
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ret += align - __alignof__ (uintptr);
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return ret;
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}
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/* Throw an exception. This is called with g->exception pointing to
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an uninitialized _Unwind_Exception instance. */
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void throwException (void) __asm__(GOSYM_PREFIX "runtime.throwException");
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void
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throwException ()
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{
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struct _Unwind_Exception *hdr;
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uintptr align;
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_Unwind_Reason_Code reason;
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hdr = (struct _Unwind_Exception *)runtime_g ()->exception;
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/* Make sure the value is correctly aligned. It will be large
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enough, because of unwindExceptionSize. */
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align = __alignof__ (struct _Unwind_Exception);
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hdr = ((struct _Unwind_Exception *)
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(((uintptr) hdr + align - 1) &~ (align - 1)));
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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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#ifdef __USING_SJLJ_EXCEPTIONS__
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reason = _Unwind_SjLj_RaiseException (hdr);
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#else
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reason = _Unwind_RaiseException (hdr);
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#endif
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/* Raising an exception should not return. */
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runtime_printf ("failed to throw unwind exception (reason=%d)\n", reason);
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abort ();
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}
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static inline _Unwind_Ptr
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encoded_value_base (uint8_t encoding, struct _Unwind_Context *context)
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{
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if (encoding == DW_EH_PE_omit)
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return 0;
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switch (encoding & 0x70)
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{
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case DW_EH_PE_absptr:
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case DW_EH_PE_pcrel:
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case DW_EH_PE_aligned:
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return 0;
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case DW_EH_PE_textrel:
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return _Unwind_GetTextRelBase(context);
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case DW_EH_PE_datarel:
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return _Unwind_GetDataRelBase(context);
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case DW_EH_PE_funcrel:
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return _Unwind_GetRegionStart(context);
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}
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abort ();
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}
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/* Read an unsigned leb128 value. */
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static inline const uint8_t *
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read_uleb128 (const uint8_t *p, _uleb128_t *val)
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{
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unsigned int shift = 0;
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_uleb128_t result = 0;
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uint8_t byte;
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do
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{
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byte = *p++;
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result |= ((_uleb128_t)byte & 0x7f) << shift;
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shift += 7;
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}
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while (byte & 0x80);
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*val = result;
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return p;
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}
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/* Similar, but read a signed leb128 value. */
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static inline const uint8_t *
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read_sleb128 (const uint8_t *p, _sleb128_t *val)
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{
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unsigned int shift = 0;
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_uleb128_t result = 0;
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uint8_t byte;
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do
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{
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byte = *p++;
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result |= ((_uleb128_t)byte & 0x7f) << shift;
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shift += 7;
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}
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while (byte & 0x80);
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/* sign extension */
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if (shift < (8 * sizeof(result)) && (byte & 0x40) != 0)
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result |= (((_uleb128_t)~0) << shift);
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*val = (_sleb128_t)result;
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return p;
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}
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#define ROUND_UP_TO_PVB(x) (x + sizeof(void *) - 1) &- sizeof(void *)
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static inline const uint8_t *
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read_encoded_value (struct _Unwind_Context *context, uint8_t encoding,
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const uint8_t *p, _Unwind_Ptr *val)
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{
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_Unwind_Ptr base = encoded_value_base (encoding, context);
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_Unwind_Internal_Ptr decoded = 0;
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const uint8_t *origp = p;
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if (encoding == DW_EH_PE_aligned)
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{
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_Unwind_Internal_Ptr uip = (_Unwind_Internal_Ptr)p;
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uip = ROUND_UP_TO_PVB (uip);
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decoded = *(_Unwind_Internal_Ptr *)uip;
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p = (const uint8_t *)(uip + sizeof(void *));
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}
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else
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{
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switch (encoding & 0x0f)
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{
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case DW_EH_PE_sdata2:
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{
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int16_t result;
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__builtin_memcpy (&result, p, sizeof(int16_t));
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decoded = result;
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p += sizeof(int16_t);
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break;
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}
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case DW_EH_PE_udata2:
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{
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uint16_t result;
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__builtin_memcpy (&result, p, sizeof(uint16_t));
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decoded = result;
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p += sizeof(uint16_t);
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break;
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}
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case DW_EH_PE_sdata4:
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{
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int32_t result;
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__builtin_memcpy (&result, p, sizeof(int32_t));
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decoded = result;
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p += sizeof(int32_t);
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break;
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}
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case DW_EH_PE_udata4:
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{
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uint32_t result;
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__builtin_memcpy (&result, p, sizeof(uint32_t));
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decoded = result;
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p += sizeof(uint32_t);
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break;
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}
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case DW_EH_PE_sdata8:
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{
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int64_t result;
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__builtin_memcpy (&result, p, sizeof(int64_t));
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decoded = result;
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p += sizeof(int64_t);
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break;
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}
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case DW_EH_PE_udata8:
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{
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uint64_t result;
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__builtin_memcpy (&result, p, sizeof(uint64_t));
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decoded = result;
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p += sizeof(uint64_t);
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break;
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}
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case DW_EH_PE_uleb128:
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{
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_uleb128_t value;
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p = read_uleb128 (p, &value);
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decoded = (_Unwind_Internal_Ptr)value;
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break;
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}
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case DW_EH_PE_sleb128:
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{
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_sleb128_t value;
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p = read_sleb128 (p, &value);
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decoded = (_Unwind_Internal_Ptr)value;
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break;
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}
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case DW_EH_PE_absptr:
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__builtin_memcpy (&decoded, (const void *)p, sizeof(const void*));
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p += sizeof(void *);
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break;
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default:
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abort ();
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}
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if (decoded == 0)
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{
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*val = decoded;
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return p;
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}
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if ((encoding & 0x70) == DW_EH_PE_pcrel)
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decoded += ((_Unwind_Internal_Ptr)origp);
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else
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decoded += base;
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if ((encoding & DW_EH_PE_indirect) != 0)
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decoded = *(_Unwind_Internal_Ptr *)decoded;
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}
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*val = decoded;
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return p;
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}
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static inline int
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value_size (uint8_t encoding)
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{
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switch (encoding & 0x0f)
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{
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case DW_EH_PE_sdata2:
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case DW_EH_PE_udata2:
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return 2;
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case DW_EH_PE_sdata4:
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case DW_EH_PE_udata4:
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return 4;
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case DW_EH_PE_sdata8:
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case DW_EH_PE_udata8:
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return 8;
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case DW_EH_PE_absptr:
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return sizeof(uintptr);
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default:
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break;
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}
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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 __ARM_EABI_UNWINDER__
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#define STOP_UNWINDING _URC_FAILURE
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#else
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#define STOP_UNWINDING _URC_NORMAL_STOP
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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, target ("general-regs-only")));
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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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if (state & _UA_FORCE_UNWIND)
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/* We are called from _Unwind_Backtrace. No handler to run. */
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CONTINUE_UNWINDING;
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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)
|
|
action_record = info.action_table + cs_action - 1;
|
|
goto found_something;
|
|
}
|
|
#else
|
|
/* Search the call-site table for the action associated with this IP. */
|
|
while (p < info.action_table)
|
|
{
|
|
_Unwind_Ptr cs_start, cs_len, cs_lp;
|
|
_uleb128_t cs_action;
|
|
|
|
/* Note that all call-site encodings are "absolute" displacements. */
|
|
p = read_encoded_value (0, info.call_site_encoding, p, &cs_start);
|
|
p = read_encoded_value (0, info.call_site_encoding, p, &cs_len);
|
|
p = read_encoded_value (0, info.call_site_encoding, p, &cs_lp);
|
|
p = read_uleb128 (p, &cs_action);
|
|
|
|
/* The table is sorted, so if we've passed the ip, stop. */
|
|
if (ip < info.Start + cs_start)
|
|
p = info.action_table;
|
|
else if (ip < info.Start + cs_start + cs_len)
|
|
{
|
|
if (cs_lp)
|
|
landing_pad = info.LPStart + cs_lp;
|
|
if (cs_action)
|
|
action_record = info.action_table + cs_action - 1;
|
|
goto found_something;
|
|
}
|
|
}
|
|
#endif
|
|
|
|
/* IP is not in table. No associated cleanups. */
|
|
CONTINUE_UNWINDING;
|
|
|
|
found_something:
|
|
if (landing_pad == 0)
|
|
{
|
|
/* IP is present, but has a null landing pad.
|
|
No handler to be run. */
|
|
CONTINUE_UNWINDING;
|
|
}
|
|
|
|
if (actions & _UA_SEARCH_PHASE)
|
|
{
|
|
if (action_record == 0)
|
|
{
|
|
/* This indicates a cleanup rather than an exception
|
|
handler. */
|
|
CONTINUE_UNWINDING;
|
|
}
|
|
|
|
return _URC_HANDLER_FOUND;
|
|
}
|
|
|
|
/* It's possible for g to be NULL here for an exception thrown by a
|
|
language other than Go. */
|
|
g = runtime_g ();
|
|
if (g == NULL)
|
|
{
|
|
if (!is_foreign)
|
|
abort ();
|
|
}
|
|
else
|
|
{
|
|
g->exception = ue_header;
|
|
g->isforeign = is_foreign;
|
|
}
|
|
|
|
_Unwind_SetGR (context, __builtin_eh_return_data_regno (0),
|
|
(_Unwind_Ptr) ue_header);
|
|
_Unwind_SetGR (context, __builtin_eh_return_data_regno (1), 0);
|
|
_Unwind_SetIP (context, landing_pad);
|
|
return _URC_INSTALL_CONTEXT;
|
|
}
|
|
|
|
// A dummy personality function, which doesn't capture any exception
|
|
// and simply passes by. This is used for functions that don't
|
|
// capture exceptions but need LSDA for stack maps.
|
|
_Unwind_Reason_Code
|
|
__gccgo_personality_dummy (int, _Unwind_Action, _Unwind_Exception_Class,
|
|
struct _Unwind_Exception *, struct _Unwind_Context *)
|
|
__attribute__ ((no_split_stack));
|
|
|
|
_Unwind_Reason_Code
|
|
#ifdef __ARM_EABI_UNWINDER__
|
|
__attribute__ ((target ("general-regs-only")))
|
|
#endif
|
|
__gccgo_personality_dummy (int version __attribute__ ((unused)),
|
|
_Unwind_Action actions __attribute__ ((unused)),
|
|
_Unwind_Exception_Class exception_class __attribute__ ((unused)),
|
|
struct _Unwind_Exception *ue_header __attribute__ ((unused)),
|
|
struct _Unwind_Context *context __attribute__ ((unused)))
|
|
{
|
|
CONTINUE_UNWINDING;
|
|
}
|
|
|
|
// A sentinel value for Go functions.
|
|
// A function is a Go function if it has LSDA, which has type info,
|
|
// and the first (dummy) landing pad's type info is a pointer to
|
|
// this value.
|
|
#define GO_FUNC_SENTINEL ((uint64)'G' | ((uint64)'O'<<8) | \
|
|
((uint64)'.'<<16) | ((uint64)'.'<<24) | \
|
|
((uint64)'F'<<32) | ((uint64)'U'<<40) | \
|
|
((uint64)'N'<<48) | ((uint64)'C'<<56))
|
|
|
|
struct _stackmap {
|
|
uint32 len;
|
|
uint8 data[1]; // variabe length
|
|
};
|
|
|
|
extern void
|
|
runtime_scanstackblockwithmap (uintptr ip, uintptr sp, uintptr size, uint8 *ptrmask, void* gcw)
|
|
__asm__ (GOSYM_PREFIX "runtime.scanstackblockwithmap");
|
|
|
|
#define FOUND 0
|
|
#define NOTFOUND_OK 1
|
|
#define NOTFOUND_BAD 2
|
|
|
|
// Helper function to search for stack maps in the unwinding records of a frame.
|
|
// If found, populate ip, sp, and stackmap. Returns the #define'd values above.
|
|
static int
|
|
findstackmaps (struct _Unwind_Context *context, _Unwind_Ptr *ip, _Unwind_Ptr *sp, struct _stackmap **stackmap)
|
|
{
|
|
lsda_header_info info;
|
|
const unsigned char *language_specific_data, *p, *action_record;
|
|
bool first;
|
|
struct _stackmap *stackmap1;
|
|
_Unwind_Ptr ip1;
|
|
int ip_before_insn = 0;
|
|
_sleb128_t index;
|
|
int size;
|
|
|
|
#ifdef HAVE_GETIPINFO
|
|
ip1 = _Unwind_GetIPInfo (context, &ip_before_insn);
|
|
#else
|
|
ip1 = _Unwind_GetIP (context);
|
|
#endif
|
|
if (! ip_before_insn)
|
|
--ip1;
|
|
|
|
if (ip != NULL)
|
|
*ip = ip1;
|
|
if (sp != NULL)
|
|
*sp = _Unwind_GetCFA (context);
|
|
|
|
#ifdef __ARM_EABI_UNWINDER__
|
|
{
|
|
_Unwind_Control_Block *ucbp;
|
|
ucbp = (_Unwind_Control_Block *) _Unwind_GetGR (context, 12);
|
|
if (*ucbp->pr_cache.ehtp & (1u << 31))
|
|
// The "compact" model is used, with one of the predefined
|
|
// personality functions. It doesn't have standard LSDA.
|
|
return NOTFOUND_OK;
|
|
}
|
|
#endif
|
|
|
|
language_specific_data = (const unsigned char *)
|
|
_Unwind_GetLanguageSpecificData (context);
|
|
|
|
/* If no LSDA, then there is no stack maps. */
|
|
if (! language_specific_data)
|
|
return NOTFOUND_OK;
|
|
|
|
p = parse_lsda_header (context, language_specific_data, &info);
|
|
|
|
if (info.TType == NULL)
|
|
return NOTFOUND_OK;
|
|
|
|
size = value_size (info.ttype_encoding);
|
|
|
|
action_record = NULL;
|
|
first = true;
|
|
|
|
/* Search the call-site table for the action associated with this IP. */
|
|
while (p < info.action_table)
|
|
{
|
|
_Unwind_Ptr cs_start, cs_len, cs_lp;
|
|
_uleb128_t cs_action;
|
|
|
|
/* Note that all call-site encodings are "absolute" displacements. */
|
|
p = read_encoded_value (0, info.call_site_encoding, p, &cs_start);
|
|
p = read_encoded_value (0, info.call_site_encoding, p, &cs_len);
|
|
p = read_encoded_value (0, info.call_site_encoding, p, &cs_lp);
|
|
p = read_uleb128 (p, &cs_action);
|
|
|
|
if (first)
|
|
{
|
|
// For a Go function, the first entry points to the sentinel value.
|
|
// Check this here.
|
|
const unsigned char *p1, *action1;
|
|
uint64 *x;
|
|
|
|
if (!cs_action)
|
|
return NOTFOUND_OK;
|
|
|
|
action1 = info.action_table + cs_action - 1;
|
|
read_sleb128 (action1, &index);
|
|
p1 = info.TType - index*size;
|
|
read_encoded_value (context, info.ttype_encoding, p1, (_Unwind_Ptr*)&x);
|
|
if (x == NULL || *x != GO_FUNC_SENTINEL)
|
|
return NOTFOUND_OK;
|
|
|
|
first = false;
|
|
continue;
|
|
}
|
|
|
|
/* The table is sorted, so if we've passed the ip, stop. */
|
|
if (ip1 < info.Start + cs_start)
|
|
return NOTFOUND_BAD;
|
|
else if (ip1 < info.Start + cs_start + cs_len)
|
|
{
|
|
if (cs_action)
|
|
action_record = info.action_table + cs_action - 1;
|
|
break;
|
|
}
|
|
}
|
|
|
|
if (action_record == NULL)
|
|
return NOTFOUND_BAD;
|
|
|
|
read_sleb128 (action_record, &index);
|
|
p = info.TType - index*size;
|
|
read_encoded_value (context, info.ttype_encoding, p, (_Unwind_Ptr*)&stackmap1);
|
|
if (stackmap1 == NULL)
|
|
return NOTFOUND_BAD;
|
|
|
|
if (stackmap != NULL)
|
|
*stackmap = stackmap1;
|
|
return FOUND;
|
|
}
|
|
|
|
struct scanstate {
|
|
void* gcw; // the GC worker, passed into scanstackwithmap_callback
|
|
uintptr lastsp; // the last (outermost) SP of Go function seen in a traceback, set by the callback
|
|
};
|
|
|
|
// Callback function to scan a stack frame with stack maps.
|
|
// It skips non-Go functions.
|
|
static _Unwind_Reason_Code
|
|
scanstackwithmap_callback (struct _Unwind_Context *context, void *arg)
|
|
{
|
|
struct _stackmap *stackmap;
|
|
_Unwind_Ptr ip, sp;
|
|
G* gp;
|
|
struct scanstate* state = (struct scanstate*) arg;
|
|
void *gcw;
|
|
|
|
gp = runtime_g ();
|
|
gcw = state->gcw;
|
|
|
|
switch (findstackmaps (context, &ip, &sp, &stackmap))
|
|
{
|
|
case NOTFOUND_OK:
|
|
// Not a Go function. Skip this frame.
|
|
return _URC_NO_REASON;
|
|
case NOTFOUND_BAD:
|
|
{
|
|
// No stack map found.
|
|
// If we're scanning from the signal stack, the goroutine
|
|
// may be not stopped at a safepoint. Allow this case.
|
|
if (gp != gp->m->gsignal)
|
|
{
|
|
// TODO: print gp, pc, sp
|
|
runtime_throw ("no stack map");
|
|
}
|
|
return STOP_UNWINDING;
|
|
}
|
|
case FOUND:
|
|
break;
|
|
default:
|
|
abort ();
|
|
}
|
|
|
|
state->lastsp = sp;
|
|
runtime_scanstackblockwithmap (ip, sp, (uintptr)(stackmap->len) * sizeof(uintptr), stackmap->data, gcw);
|
|
|
|
return _URC_NO_REASON;
|
|
}
|
|
|
|
// Scan the stack with stack maps. Return whether the scan
|
|
// succeeded.
|
|
bool
|
|
scanstackwithmap (void *gcw)
|
|
{
|
|
_Unwind_Reason_Code code;
|
|
bool ret;
|
|
struct scanstate state;
|
|
G* gp;
|
|
G* curg;
|
|
|
|
state.gcw = gcw;
|
|
state.lastsp = 0;
|
|
gp = runtime_g ();
|
|
curg = gp->m->curg;
|
|
|
|
runtime_xadd (&__go_runtime_in_callers, 1);
|
|
code = _Unwind_Backtrace (scanstackwithmap_callback, (void*)&state);
|
|
runtime_xadd (&__go_runtime_in_callers, -1);
|
|
ret = (code == _URC_END_OF_STACK);
|
|
if (ret && gp == gp->m->gsignal)
|
|
{
|
|
// For signal-triggered scan, the unwinder may not be able to unwind
|
|
// the whole stack while it still reports _URC_END_OF_STACK (e.g.
|
|
// signal is delivered in vdso). Check that we actually reached the
|
|
// the end of the stack, that is, the SP on entry.
|
|
if (state.lastsp != curg->entrysp)
|
|
ret = false;
|
|
}
|
|
return ret;
|
|
}
|
|
|
|
// Returns whether stack map is enabled.
|
|
bool
|
|
usestackmaps ()
|
|
{
|
|
return runtime_usestackmaps;
|
|
}
|
|
|
|
// Callback function to probe if a stack frame has stack maps.
|
|
static _Unwind_Reason_Code
|
|
probestackmaps_callback (struct _Unwind_Context *context,
|
|
void *arg __attribute__ ((unused)))
|
|
{
|
|
switch (findstackmaps (context, NULL, NULL, NULL))
|
|
{
|
|
case NOTFOUND_OK:
|
|
case NOTFOUND_BAD:
|
|
return _URC_NO_REASON;
|
|
case FOUND:
|
|
break;
|
|
default:
|
|
abort ();
|
|
}
|
|
|
|
// Found a stack map. No need to keep unwinding.
|
|
runtime_usestackmaps = true;
|
|
return STOP_UNWINDING;
|
|
}
|
|
|
|
// Try to find a stack map, store the result in global variable runtime_usestackmaps.
|
|
// Called in start-up time from Go code, so there is a Go frame on the stack.
|
|
bool
|
|
probestackmaps ()
|
|
{
|
|
runtime_usestackmaps = false;
|
|
_Unwind_Backtrace (probestackmaps_callback, NULL);
|
|
return runtime_usestackmaps;
|
|
}
|