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//===------------------------- EHHeaderParser.hpp -------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
//
//
// Parses ELF .eh_frame_hdr sections.
//
//===----------------------------------------------------------------------===//
#ifndef __EHHEADERPARSER_HPP__
#define __EHHEADERPARSER_HPP__
#include "libunwind.h"
#include "DwarfParser.hpp"
namespace libunwind {
/// \brief EHHeaderParser does basic parsing of an ELF .eh_frame_hdr section.
///
/// See DWARF spec for details:
/// http://refspecs.linuxbase.org/LSB_3.1.0/LSB-Core-generic/LSB-Core-generic/ehframechpt.html
///
template <typename A> class EHHeaderParser {
public:
typedef typename A::pint_t pint_t;
/// Information encoded in the EH frame header.
struct EHHeaderInfo {
pint_t eh_frame_ptr;
size_t fde_count;
pint_t table;
uint8_t table_enc;
};
static void decodeEHHdr(A &addressSpace, pint_t ehHdrStart, pint_t ehHdrEnd,
EHHeaderInfo &ehHdrInfo);
static bool findFDE(A &addressSpace, pint_t pc, pint_t ehHdrStart,
uint32_t sectionLength,
typename CFI_Parser<A>::FDE_Info *fdeInfo,
typename CFI_Parser<A>::CIE_Info *cieInfo);
private:
static bool decodeTableEntry(A &addressSpace, pint_t &tableEntry,
pint_t ehHdrStart, pint_t ehHdrEnd,
uint8_t tableEnc,
typename CFI_Parser<A>::FDE_Info *fdeInfo,
typename CFI_Parser<A>::CIE_Info *cieInfo);
static size_t getTableEntrySize(uint8_t tableEnc);
};
template <typename A>
void EHHeaderParser<A>::decodeEHHdr(A &addressSpace, pint_t ehHdrStart,
pint_t ehHdrEnd, EHHeaderInfo &ehHdrInfo) {
pint_t p = ehHdrStart;
uint8_t version = addressSpace.get8(p++);
if (version != 1)
_LIBUNWIND_ABORT("Unsupported .eh_frame_hdr version");
uint8_t eh_frame_ptr_enc = addressSpace.get8(p++);
uint8_t fde_count_enc = addressSpace.get8(p++);
ehHdrInfo.table_enc = addressSpace.get8(p++);
ehHdrInfo.eh_frame_ptr =
addressSpace.getEncodedP(p, ehHdrEnd, eh_frame_ptr_enc, ehHdrStart);
ehHdrInfo.fde_count =
addressSpace.getEncodedP(p, ehHdrEnd, fde_count_enc, ehHdrStart);
ehHdrInfo.table = p;
}
template <typename A>
bool EHHeaderParser<A>::decodeTableEntry(
A &addressSpace, pint_t &tableEntry, pint_t ehHdrStart, pint_t ehHdrEnd,
uint8_t tableEnc, typename CFI_Parser<A>::FDE_Info *fdeInfo,
typename CFI_Parser<A>::CIE_Info *cieInfo) {
// Have to decode the whole FDE for the PC range anyway, so just throw away
// the PC start.
addressSpace.getEncodedP(tableEntry, ehHdrEnd, tableEnc, ehHdrStart);
pint_t fde =
addressSpace.getEncodedP(tableEntry, ehHdrEnd, tableEnc, ehHdrStart);
const char *message =
CFI_Parser<A>::decodeFDE(addressSpace, fde, fdeInfo, cieInfo);
if (message != NULL) {
_LIBUNWIND_DEBUG_LOG("EHHeaderParser::decodeTableEntry: bad fde: %s",
message);
return false;
}
return true;
}
template <typename A>
bool EHHeaderParser<A>::findFDE(A &addressSpace, pint_t pc, pint_t ehHdrStart,
uint32_t sectionLength,
typename CFI_Parser<A>::FDE_Info *fdeInfo,
typename CFI_Parser<A>::CIE_Info *cieInfo) {
pint_t ehHdrEnd = ehHdrStart + sectionLength;
EHHeaderParser<A>::EHHeaderInfo hdrInfo;
EHHeaderParser<A>::decodeEHHdr(addressSpace, ehHdrStart, ehHdrEnd, hdrInfo);
size_t tableEntrySize = getTableEntrySize(hdrInfo.table_enc);
pint_t tableEntry;
size_t low = 0;
for (size_t len = hdrInfo.fde_count; len > 1;) {
size_t mid = low + (len / 2);
tableEntry = hdrInfo.table + mid * tableEntrySize;
pint_t start = addressSpace.getEncodedP(tableEntry, ehHdrEnd,
hdrInfo.table_enc, ehHdrStart);
if (start == pc) {
low = mid;
break;
} else if (start < pc) {
low = mid;
len -= (len / 2);
} else {
len /= 2;
}
}
tableEntry = hdrInfo.table + low * tableEntrySize;
if (decodeTableEntry(addressSpace, tableEntry, ehHdrStart, ehHdrEnd,
hdrInfo.table_enc, fdeInfo, cieInfo)) {
if (pc >= fdeInfo->pcStart && pc < fdeInfo->pcEnd)
return true;
}
return false;
}
template <typename A>
size_t EHHeaderParser<A>::getTableEntrySize(uint8_t tableEnc) {
switch (tableEnc & 0x0f) {
case DW_EH_PE_sdata2:
case DW_EH_PE_udata2:
return 4;
case DW_EH_PE_sdata4:
case DW_EH_PE_udata4:
return 8;
case DW_EH_PE_sdata8:
case DW_EH_PE_udata8:
return 16;
case DW_EH_PE_sleb128:
case DW_EH_PE_uleb128:
_LIBUNWIND_ABORT("Can't binary search on variable length encoded data.");
case DW_EH_PE_omit:
return 0;
default:
_LIBUNWIND_ABORT("Unknown DWARF encoding for search table.");
}
}
}
#endif
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