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https://github.com/darlinghq/cctools-port.git
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324 lines
9.1 KiB
C
324 lines
9.1 KiB
C
/**
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* This file is Copyright PathScale 2010. Permission granted to distribute
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* according to the terms of the MIT license (see COPYING.MIT)
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*/
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#include <assert.h>
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#include <stdint.h>
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// _GNU_SOURCE must be defined for unwind.h to expose some of the functions
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// that we want. If it isn't, then we define it and undefine it to make sure
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// that it doesn't impact the rest of the program.
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#ifndef _GNU_SOURCE
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# define _GNU_SOURCE 1
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# include "unwind.h"
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# undef _GNU_SOURCE
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#else
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# include "unwind.h"
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#endif
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/**
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* Type used to store pointers to values computed by DWARF expressions.
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*/
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typedef unsigned char *dw_eh_ptr_t;
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// Flag indicating a signed quantity
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#define DW_EH_PE_signed 0x08
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/// DWARF data encoding types
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enum dwarf_data_encoding
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{
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// Unsigned, little-endian, base 128-encoded (variable length)
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DW_EH_PE_uleb128 = 0x01,
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// uint16
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DW_EH_PE_udata2 = 0x02,
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// uint32
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DW_EH_PE_udata4 = 0x03,
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// uint64
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DW_EH_PE_udata8 = 0x04,
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// Signed versions of the above:
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DW_EH_PE_sleb128 = DW_EH_PE_uleb128 | DW_EH_PE_signed,
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DW_EH_PE_sdata2 = DW_EH_PE_udata2 | DW_EH_PE_signed,
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DW_EH_PE_sdata4 = DW_EH_PE_udata4 | DW_EH_PE_signed,
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DW_EH_PE_sdata8 = DW_EH_PE_udata8 | DW_EH_PE_signed
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};
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static inline enum dwarf_data_encoding get_encoding(unsigned char x)
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{
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return (enum dwarf_data_encoding)(x & 0xf);
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}
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enum dwarf_data_relative
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{
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// Value is omitted
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DW_EH_PE_omit = 0xff,
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// Absolute pointer value
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DW_EH_PE_absptr = 0x00,
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// Value relative to program counter
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DW_EH_PE_pcrel = 0x10,
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// Value relative to the text segment
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DW_EH_PE_textrel = 0x20,
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// Value relative to the data segment
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DW_EH_PE_datarel = 0x30,
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// Value relative to the start of the function
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DW_EH_PE_funcrel = 0x40,
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// Aligned pointer (Not supported yet - are they actually used?)
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DW_EH_PE_aligned = 0x50,
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// Pointer points to address of real value
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DW_EH_PE_indirect = 0x80
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};
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static inline enum dwarf_data_relative get_base(unsigned char x)
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{
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return (enum dwarf_data_relative)(x & 0x70);
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}
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static int is_indirect(unsigned char x)
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{
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return (x & DW_EH_PE_indirect);
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}
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static inline int dwarf_size_of_fixed_size_field(unsigned char type)
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{
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// Low three bits indicate size...
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switch (type & 7)
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{
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case DW_EH_PE_udata2: return 2;
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case DW_EH_PE_udata4: return 4;
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case DW_EH_PE_udata8: return 8;
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case DW_EH_PE_absptr: return sizeof(void*);
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}
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abort();
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}
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/**
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* Read an unsigned, little-endian, base-128, DWARF value. Updates *data to
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* point to the end of the value.
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*/
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static uint64_t read_leb128(unsigned char** data, int *b)
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{
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uint64_t uleb = 0;
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unsigned int bit = 0;
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unsigned char digit = 0;
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// We have to read at least one octet, and keep reading until we get to one
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// with the high bit unset
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do
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{
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// This check is a bit too strict - we should also check the highest
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// bit of the digit.
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assert(bit < sizeof(uint64_t) * 8);
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// Get the base 128 digit
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digit = (**data) & 0x7f;
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// Add it to the current value
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uleb += digit << bit;
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// Increase the shift value
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bit += 7;
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// Proceed to the next octet
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(*data)++;
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// Terminate when we reach a value that does not have the high bit set
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// (i.e. which was not modified when we mask it with 0x7f)
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} while ((*(*data - 1)) != digit);
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*b = bit;
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return uleb;
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}
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static int64_t read_uleb128(unsigned char** data)
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{
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int b;
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return read_leb128(data, &b);
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}
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static int64_t read_sleb128(unsigned char** data)
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{
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int bits;
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// Read as if it's signed
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uint64_t uleb = read_leb128(data, &bits);
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// If the most significant bit read is 1, then we need to sign extend it
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if (uleb >> (bits-1) == 1)
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{
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// Sign extend by setting all bits in front of it to 1
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uleb |= ((int64_t)-1) << bits;
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}
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return (int64_t)uleb;
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}
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static uint64_t read_value(char encoding, unsigned char **data)
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{
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enum dwarf_data_encoding type = get_encoding(encoding);
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uint64_t v;
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switch ((int)type)
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{
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// Read fixed-length types
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#define READ(dwarf, type) \
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case dwarf:\
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v = (uint64_t)(*(type*)(*data));\
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*data += sizeof(type);\
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break;
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READ(DW_EH_PE_udata2, uint16_t)
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READ(DW_EH_PE_udata4, uint32_t)
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READ(DW_EH_PE_udata8, uint64_t)
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READ(DW_EH_PE_sdata2, int16_t)
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READ(DW_EH_PE_sdata4, int32_t)
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READ(DW_EH_PE_sdata8, int64_t)
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case DW_EH_PE_absptr:
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v = (uint64_t)(*(intptr_t*)(*data));
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*data += sizeof(intptr_t);
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break;
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//READ(DW_EH_PE_absptr, intptr_t)
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#undef READ
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case DW_EH_PE_sleb128:
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v = read_sleb128(data);
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break;
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case DW_EH_PE_uleb128:
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v = read_uleb128(data);
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break;
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default: abort();
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}
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return v;
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}
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static uint64_t resolve_indirect_value(struct _Unwind_Context *c, unsigned char encoding, int64_t v, dw_eh_ptr_t start)
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{
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switch (get_base(encoding))
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{
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case DW_EH_PE_pcrel:
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v += (uint64_t)(uintptr_t)start;
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break;
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case DW_EH_PE_textrel:
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v += (uint64_t)(uintptr_t)_Unwind_GetTextRelBase(c);
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break;
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case DW_EH_PE_datarel:
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v += (uint64_t)(uintptr_t)_Unwind_GetDataRelBase(c);
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break;
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case DW_EH_PE_funcrel:
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v += (uint64_t)(uintptr_t)_Unwind_GetRegionStart(c);
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default:
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break;
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}
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// If this is an indirect value, then it is really the address of the real
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// value
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// TODO: Check whether this should really always be a pointer - it seems to
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// be a GCC extensions, so not properly documented...
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if (is_indirect(encoding))
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{
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v = (uint64_t)(uintptr_t)*(void**)(uintptr_t)v;
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}
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return v;
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}
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static inline void read_value_with_encoding(struct _Unwind_Context *context,
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dw_eh_ptr_t *data,
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uint64_t *out)
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{
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dw_eh_ptr_t start = *data;
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unsigned char encoding = *((*data)++);
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// If this value is omitted, skip it and don't touch the output value
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if (encoding == DW_EH_PE_omit) { return; }
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*out = read_value(encoding, data);
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*out = resolve_indirect_value(context, encoding, *out, start);
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}
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struct dwarf_eh_lsda
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{
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dw_eh_ptr_t region_start;
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dw_eh_ptr_t landing_pads;
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dw_eh_ptr_t type_table;
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unsigned char type_table_encoding;
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dw_eh_ptr_t call_site_table;
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dw_eh_ptr_t action_table;
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unsigned char callsite_encoding;
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};
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static inline struct dwarf_eh_lsda parse_lsda(struct _Unwind_Context *context, unsigned char *data)
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{
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struct dwarf_eh_lsda lsda;
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lsda.region_start = (dw_eh_ptr_t)(uintptr_t)_Unwind_GetRegionStart(context);
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// If the landing pads are relative to anything other than the start of
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// this region, find out where. This is @LPStart in the spec, although the
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// encoding that GCC uses does not quite match the spec.
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uint64_t v = (uint64_t)(uintptr_t)lsda.region_start;
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read_value_with_encoding(context, &data, &v);
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lsda.landing_pads = (dw_eh_ptr_t)(uintptr_t)v;
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// If there is a type table, find out where it is. This is @TTBase in the
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// spec. Note: we find whether there is a type table pointer by checking
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// whether the leading byte is DW_EH_PE_omit (0xff), which is not what the
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// spec says, but does seem to be how G++ indicates this.
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lsda.type_table = 0;
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lsda.type_table_encoding = *data++;
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if (lsda.type_table_encoding != DW_EH_PE_omit)
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{
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v = read_uleb128(&data);
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dw_eh_ptr_t type_table = data;
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type_table += v;
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lsda.type_table = type_table;
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//lsda.type_table = (uintptr_t*)(data + v);
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}
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lsda.callsite_encoding = (enum dwarf_data_encoding)(*(data++));
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// Action table is immediately after the call site table
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lsda.action_table = data;
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uintptr_t callsite_size = (uintptr_t)read_uleb128(&data);
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lsda.action_table = data + callsite_size;
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// Call site table is immediately after the header
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lsda.call_site_table = (dw_eh_ptr_t)data;
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return lsda;
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}
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struct dwarf_eh_action
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{
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dw_eh_ptr_t landing_pad;
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dw_eh_ptr_t action_record;
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};
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/**
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* Look up the landing pad that corresponds to the current invoke.
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*/
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__attribute__((unused))
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static struct dwarf_eh_action
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dwarf_eh_find_callsite(struct _Unwind_Context *context, struct dwarf_eh_lsda *lsda)
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{
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struct dwarf_eh_action result = { 0, 0 };
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uint64_t ip = _Unwind_GetIP(context) - _Unwind_GetRegionStart(context);
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unsigned char *callsite_table = (unsigned char*)lsda->call_site_table;
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while (callsite_table <= lsda->action_table)
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{
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// Once again, the layout deviates from the spec.
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uint64_t call_site_start, call_site_size, landing_pad, action;
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call_site_start = read_value(lsda->callsite_encoding, &callsite_table);
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call_site_size = read_value(lsda->callsite_encoding, &callsite_table);
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// Call site entries are started
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if (call_site_start > ip) { break; }
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landing_pad = read_value(lsda->callsite_encoding, &callsite_table);
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action = read_uleb128(&callsite_table);
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if (call_site_start <= ip && ip <= call_site_start + call_site_size)
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{
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if (action)
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{
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// Action records are 1-biased so both no-record and zeroth
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// record can be stored.
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result.action_record = lsda->action_table + action - 1;
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}
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// No landing pad means keep unwinding.
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if (landing_pad)
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{
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// Landing pad is the offset from the value in the header
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result.landing_pad = lsda->landing_pads + landing_pad;
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}
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break;
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}
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}
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return result;
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}
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#define EXCEPTION_CLASS(a,b,c,d,e,f,g,h) ((((uint64_t)a) << 56) + (((uint64_t)b) << 48) + (((uint64_t)c) << 40) + (((uint64_t)d) << 32) + (((uint64_t)e) << 24) + (((uint64_t)f) << 16) + (((uint64_t)g) << 8) + (((uint64_t)h)))
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