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authorHenrik Nord <[email protected]>2014-03-21 16:37:11 +0100
committerHenrik Nord <[email protected]>2014-03-21 16:37:26 +0100
commit9d46875b53ffb21bc55aec4a2c76472133ea5d1c (patch)
tree2e0fa6e8829213470acc239b8885c3a79ced63f0 /lib/hipe/llvm/elf_format.erl
parentbbe92ec2c359373205149dabc61ef0d50784760f (diff)
parentb326df0d935d221574abf58d5e2a3efddd020278 (diff)
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Merge branch 'yiannist/hipe-llvm-backend'
* yiannist/hipe-llvm-backend: Support the LLVM backend in HiPE Implement the LLVM backend Extend RTL API to support the LLVM backend Add support for llvm unique symbols in hipe_gensym Add a BIF that only returns the atom ok Move some common code in hipe_pack_constants Add better specs in hipe_pack_constants and cleanup OTP-11801
Diffstat (limited to 'lib/hipe/llvm/elf_format.erl')
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1 files changed, 790 insertions, 0 deletions
diff --git a/lib/hipe/llvm/elf_format.erl b/lib/hipe/llvm/elf_format.erl
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+%% -*- erlang-indent-level: 2 -*-
+
+%%% @copyright 2011-2014 Yiannis Tsiouris <[email protected]>,
+%%% Chris Stavrakakis <[email protected]>,
+%%% Kostis Sagonas <[email protected]>
+%%% @author Yiannis Tsiouris <[email protected]>
+%%% [http://www.softlab.ntua.gr/~gtsiour/]
+
+%%% @doc This module contains functions for extracting various pieces of
+%%% information from an ELF formated Object file. To fully understand
+%%% the ELF format and the use of these functions please read
+%%% "[http://www.linuxjournal.com/article/1060?page=0,0]" carefully.
+
+-module(elf_format).
+
+-export([get_tab_entries/1,
+ %% Relocations
+ get_rodata_relocs/1,
+ get_text_relocs/1,
+ extract_rela/2,
+ get_rela_addends/1,
+ %% Note
+ extract_note/2,
+ %% Executable code
+ extract_text/1,
+ %% GCC Exception Table
+ get_exn_handlers/1,
+ %% Misc.
+ set_architecture_flag/1,
+ is64bit/0
+ ]).
+
+-include("elf_format.hrl").
+
+%%------------------------------------------------------------------------------
+%% Types
+%%------------------------------------------------------------------------------
+
+-type elf() :: binary().
+
+-type lp() :: non_neg_integer(). % landing pad
+-type num() :: non_neg_integer().
+-type index() :: non_neg_integer().
+-type offset() :: non_neg_integer().
+-type size() :: non_neg_integer().
+-type start() :: non_neg_integer().
+
+-type info() :: index().
+-type nameoff() :: offset().
+-type valueoff() :: offset().
+
+-type name() :: string().
+-type name_size() :: {name(), size()}.
+-type name_sizes() :: [name_size()].
+
+%%------------------------------------------------------------------------------
+%% Abstract Data Types and Accessors for ELF Structures.
+%%------------------------------------------------------------------------------
+
+%% File header
+-record(elf_ehdr, {ident, % ELF identification
+ type, % Object file type
+ machine, % Machine Type
+ version, % Object file version
+ entry, % Entry point address
+ phoff, % Program header offset
+ shoff :: offset(), % Section header offset
+ flags, % Processor-specific flags
+ ehsize :: size(), % ELF header size
+ phentsize :: size(), % Size of program header entry
+ phnum :: num(), % Number of program header entries
+ shentsize :: size(), % Size of section header entry
+ shnum :: num(), % Number of section header entries
+ shstrndx :: index() % Section name string table index
+ }).
+-type elf_ehdr() :: #elf_ehdr{}.
+
+-record(elf_ehdr_ident, {class, % File class
+ data, % Data encoding
+ version, % File version
+ osabi, % OS/ABI identification
+ abiversion, % ABI version
+ pad, % Start of padding bytes
+ nident % Size of e_ident[]
+ }).
+%% -type elf_ehdr_ident() :: #elf_ehdr_ident{}.
+
+%% Section header entries
+-record(elf_shdr, {name, % Section name
+ type, % Section type
+ flags, % Section attributes
+ addr, % Virtual address in memory
+ offset :: offset(), % Offset in file
+ size :: size(), % Size of section
+ link, % Link to other section
+ info, % Miscellaneous information
+ addralign, % Address align boundary
+ entsize % Size of entries, if section has table
+ }).
+%% -type elf_shdr() :: #elf_shdr{}.
+
+%% Symbol table entries
+-record(elf_sym, {name :: nameoff(), % Symbol name
+ info, % Type and Binding attributes
+ other, % Reserved
+ shndx, % Section table index
+ value :: valueoff(), % Symbol value
+ size :: size() % Size of object
+ }).
+-type elf_sym() :: #elf_sym{}.
+
+%% Relocations
+-record(elf_rel, {r_offset :: offset(), % Address of reference
+ r_info :: info() % Symbol index and type of relocation
+ }).
+-type elf_rel() :: #elf_rel{}.
+
+-record(elf_rela, {r_offset :: offset(), % Address of reference
+ r_info :: info(), % Symbol index and type of relocation
+ r_addend :: offset() % Constant part of expression
+ }).
+-type elf_rela() :: #elf_rela{}.
+
+%% %% Program header table
+%% -record(elf_phdr, {type, % Type of segment
+%% flags, % Segment attributes
+%% offset, % Offset in file
+%% vaddr, % Virtual address in memory
+%% paddr, % Reserved
+%% filesz, % Size of segment in file
+%% memsz, % Size of segment in memory
+%% align % Alignment of segment
+%% }).
+
+%% %% GCC exception table
+%% -record(elf_gccexntab, {lpbenc, % Landing pad base encoding
+%% lpbase, % Landing pad base
+%% ttenc, % Type table encoding
+%% ttoff, % Type table offset
+%% csenc, % Call-site table encoding
+%% cstabsize, % Call-site table size
+%% cstab :: cstab() % Call-site table
+%% }).
+%% -type elf_gccexntab() :: #elf_gccexntab{}.
+
+-record(elf_gccexntab_callsite, {start :: start(), % Call-site start
+ size :: size(), % Call-site size
+ lp :: lp(), % Call-site landing pad
+ % (exception handler)
+ onaction % On action (e.g. cleanup)
+ }).
+%% -type elf_gccexntab_callsite() :: #elf_gccexntab_callsite{}.
+
+%%------------------------------------------------------------------------------
+%% Accessor Functions
+%%------------------------------------------------------------------------------
+
+%% File header
+%% -spec mk_ehdr(...) -> elf_ehrd().
+mk_ehdr(Ident, Type, Machine, Version, Entry, Phoff, Shoff, Flags, Ehsize,
+ Phentsize, Phnum, Shentsize, Shnum, Shstrndx) ->
+ #elf_ehdr{ident = Ident, type = Type, machine = Machine, version = Version,
+ entry = Entry, phoff = Phoff, shoff = Shoff, flags = Flags,
+ ehsize = Ehsize, phentsize = Phentsize, phnum = Phnum,
+ shentsize = Shentsize, shnum = Shnum, shstrndx = Shstrndx}.
+
+%% -spec ehdr_shoff(elf_ehdr()) -> offset().
+%% ehdr_shoff(#elf_ehdr{shoff = Offset}) -> Offset.
+%%
+%% -spec ehdr_shentsize(elf_ehdr()) -> size().
+%% ehdr_shentsize(#elf_ehdr{shentsize = Size}) -> Size.
+%%
+%% -spec ehdr_shnum(elf_ehdr()) -> num().
+%% ehdr_shnum(#elf_ehdr{shnum = Num}) -> Num.
+%%
+%% -spec ehdr_shstrndx(elf_ehdr()) -> index().
+%% ehdr_shstrndx(#elf_ehdr{shstrndx = Index}) -> Index.
+
+
+%%-spec mk_ehdr_ident(...) -> elf_ehdr_ident().
+mk_ehdr_ident(Class, Data, Version, OsABI, AbiVersion, Pad, Nident) ->
+ #elf_ehdr_ident{class = Class, data = Data, version = Version, osabi = OsABI,
+ abiversion = AbiVersion, pad = Pad, nident = Nident}.
+
+%%%-------------------------
+%%% Section header entries
+%%%-------------------------
+mk_shdr(Name, Type, Flags, Addr, Offset, Size, Link, Info, AddrAlign, EntSize) ->
+ #elf_shdr{name = Name, type = Type, flags = Flags, addr = Addr,
+ offset = Offset, size = Size, link = Link, info = Info,
+ addralign = AddrAlign, entsize = EntSize}.
+
+%% -spec shdr_offset(elf_shdr()) -> offset().
+%% shdr_offset(#elf_shdr{offset = Offset}) -> Offset.
+%%
+%% -spec shdr_size(elf_shdr()) -> size().
+%% shdr_size(#elf_shdr{size = Size}) -> Size.
+
+%%%-------------------------
+%%% Symbol Table Entries
+%%%-------------------------
+mk_sym(Name, Info, Other, Shndx, Value, Size) ->
+ #elf_sym{name = Name, info = Info, other = Other,
+ shndx = Shndx, value = Value, size = Size}.
+
+-spec sym_name(elf_sym()) -> nameoff().
+sym_name(#elf_sym{name = Name}) -> Name.
+
+%% -spec sym_value(elf_sym()) -> valueoff().
+%% sym_value(#elf_sym{value = Value}) -> Value.
+%%
+%% -spec sym_size(elf_sym()) -> size().
+%% sym_size(#elf_sym{size = Size}) -> Size.
+
+%%%-------------------------
+%%% Relocations
+%%%-------------------------
+-spec mk_rel(offset(), info()) -> elf_rel().
+mk_rel(Offset, Info) ->
+ #elf_rel{r_offset = Offset, r_info = Info}.
+
+%% The following two functions capitalize on the fact that the two kinds of
+%% relocation records (for 32- and 64-bit architectures have similar structure.
+
+-spec r_offset(elf_rel() | elf_rela()) -> offset().
+r_offset(#elf_rel{r_offset = Offset}) -> Offset;
+r_offset(#elf_rela{r_offset = Offset}) -> Offset.
+
+-spec r_info(elf_rel() | elf_rela()) -> info().
+r_info(#elf_rel{r_info = Info}) -> Info;
+r_info(#elf_rela{r_info = Info}) -> Info.
+
+-spec mk_rela(offset(), info(), offset()) -> elf_rela().
+mk_rela(Offset, Info, Addend) ->
+ #elf_rela{r_offset = Offset, r_info = Info, r_addend = Addend}.
+
+-spec rela_addend(elf_rela()) -> offset().
+rela_addend(#elf_rela{r_addend = Addend}) -> Addend.
+
+%% %%%-------------------------
+%% %%% GCC exception table
+%% %%%-------------------------
+%% -type cstab() :: [elf_gccexntab_callsite()].
+%%
+%% mk_gccexntab(LPbenc, LPbase, TTenc, TToff, CSenc, CStabsize, CStab) ->
+%% #elf_gccexntab{lpbenc = LPbenc, lpbase = LPbase, ttenc = TTenc,
+%% ttoff = TToff, csenc = CSenc, cstabsize = CStabsize,
+%% cstab = CStab}.
+%%
+%% -spec gccexntab_cstab(elf_gccexntab()) -> cstab().
+%% gccexntab_cstab(#elf_gccexntab{cstab = CSTab}) -> CSTab.
+
+mk_gccexntab_callsite(Start, Size, LP, Action) ->
+ #elf_gccexntab_callsite{start = Start, size=Size, lp=LP, onaction=Action}.
+
+%% -spec gccexntab_callsite_start(elf_gccexntab_callsite()) -> start().
+%% gccexntab_callsite_start(#elf_gccexntab_callsite{start = Start}) -> Start.
+%%
+%% -spec gccexntab_callsite_size(elf_gccexntab_callsite()) -> size().
+%% gccexntab_callsite_size(#elf_gccexntab_callsite{size = Size}) -> Size.
+%%
+%% -spec gccexntab_callsite_lp(elf_gccexntab_callsite()) -> lp().
+%% gccexntab_callsite_lp(#elf_gccexntab_callsite{lp = LP}) -> LP.
+
+%%------------------------------------------------------------------------------
+%% Functions to manipulate the ELF File Header
+%%------------------------------------------------------------------------------
+
+%% @doc Extracts the File Header from an ELF formatted object file. Also sets
+%% the ELF class variable in the process dictionary (used by many functions
+%% in this and hipe_llvm_main modules).
+-spec extract_header(elf()) -> elf_ehdr().
+extract_header(Elf) ->
+ Ehdr_bin = get_binary_segment(Elf, 0, ?ELF_EHDR_SIZE),
+ << %% Structural pattern matching on fields.
+ Ident_bin:?E_IDENT_SIZE/binary,
+ Type:?bits(?E_TYPE_SIZE)/integer-little,
+ Machine:?bits(?E_MACHINE_SIZE)/integer-little,
+ Version:?bits(?E_VERSION_SIZE)/integer-little,
+ Entry:?bits(?E_ENTRY_SIZE)/integer-little,
+ Phoff:?bits(?E_PHOFF_SIZE)/integer-little,
+ Shoff:?bits(?E_SHOFF_SIZE)/integer-little,
+ Flags:?bits(?E_FLAGS_SIZE)/integer-little,
+ Ehsize:?bits(?E_EHSIZE_SIZE)/integer-little,
+ Phentsize:?bits(?E_PHENTSIZE_SIZE)/integer-little,
+ Phnum:?bits(?E_PHNUM_SIZE)/integer-little,
+ Shentsize:?bits(?E_SHENTSIZE_SIZE)/integer-little,
+ Shnum:?bits(?E_SHENTSIZE_SIZE)/integer-little,
+ Shstrndx:?bits(?E_SHSTRNDX_SIZE)/integer-little
+ >> = Ehdr_bin,
+ <<16#7f, $E, $L, $F, Class, Data, Version, Osabi, Abiversion,
+ Pad:6/binary, Nident
+ >> = Ident_bin,
+ Ident = mk_ehdr_ident(Class, Data, Version, Osabi,
+ Abiversion, Pad, Nident),
+ mk_ehdr(Ident, Type, Machine, Version, Entry, Phoff, Shoff, Flags,
+ Ehsize, Phentsize, Phnum, Shentsize, Shnum, Shstrndx).
+
+%%------------------------------------------------------------------------------
+%% Functions to manipulate Section Header Entries
+%%------------------------------------------------------------------------------
+
+%% @doc Extracts the Section Header Table from an ELF formated Object File.
+extract_shdrtab(Elf) ->
+ %% Extract File Header to get info about Section Header Offset (in bytes),
+ %% Entry Size (in bytes) and Number of entries
+ #elf_ehdr{shoff = ShOff, shentsize = ShEntsize, shnum = ShNum} =
+ extract_header(Elf),
+ %% Get actual Section header table (binary)
+ ShdrBin = get_binary_segment(Elf, ShOff, ShNum * ShEntsize),
+ get_shdrtab_entries(ShdrBin, []).
+
+get_shdrtab_entries(<<>>, Acc) ->
+ lists:reverse(Acc);
+get_shdrtab_entries(ShdrBin, Acc) ->
+ <<%% Structural pattern matching on fields.
+ Name:?bits(?SH_NAME_SIZE)/integer-little,
+ Type:?bits(?SH_TYPE_SIZE)/integer-little,
+ Flags:?bits(?SH_FLAGS_SIZE)/integer-little,
+ Addr:?bits(?SH_ADDR_SIZE)/integer-little,
+ Offset:?bits(?SH_OFFSET_SIZE)/integer-little,
+ Size:?bits(?SH_SIZE_SIZE)/integer-little,
+ Link:?bits(?SH_LINK_SIZE)/integer-little,
+ Info:?bits(?SH_INFO_SIZE)/integer-little,
+ Addralign:?bits(?SH_ADDRALIGN_SIZE)/integer-little,
+ Entsize:?bits(?SH_ENTSIZE_SIZE)/integer-little,
+ MoreShdrE/binary
+ >> = ShdrBin,
+ ShdrE = mk_shdr(Name, Type, Flags, Addr, Offset,
+ Size, Link, Info, Addralign, Entsize),
+ get_shdrtab_entries(MoreShdrE, [ShdrE | Acc]).
+
+%% @doc Extracts a specific Entry of a Section Header Table. This function
+%% takes as argument the Section Header Table (`SHdrTab') and the entry's
+%% serial number (`EntryNum') and returns the entry (`shdr').
+get_shdrtab_entry(SHdrTab, EntryNum) ->
+ lists:nth(EntryNum + 1, SHdrTab).
+
+%%------------------------------------------------------------------------------
+%% Functions to manipulate Section Header String Table
+%%------------------------------------------------------------------------------
+
+%% @doc Extracts the Section Header String Table. This section is not a known
+%% ELF Object File section. It is just a "hidden" table storing the
+%% names of all sections that exist in current object file.
+-spec extract_shstrtab(elf()) -> [name()].
+extract_shstrtab(Elf) ->
+ %% Extract Section Name String Table Index
+ #elf_ehdr{shstrndx = ShStrNdx} = extract_header(Elf),
+ ShHdrTab = extract_shdrtab(Elf),
+ %% Extract Section header entry and get actual Section-header String Table
+ #elf_shdr{offset = ShStrOffset, size = ShStrSize} =
+ get_shdrtab_entry(ShHdrTab, ShStrNdx),
+ case get_binary_segment(Elf, ShStrOffset, ShStrSize) of
+ <<>> -> %% Segment empty
+ [];
+ ShStrTab -> %% Convert to string table
+ [Name || {Name, _Size} <- get_names(ShStrTab)]
+ end.
+
+%%------------------------------------------------------------------------------
+
+-spec get_tab_entries(elf()) -> [{name(), valueoff(), size()}].
+get_tab_entries(Elf) ->
+ SymTab = extract_symtab(Elf),
+ Ts = [{Name, Value, Size div ?ELF_XWORD_SIZE}
+ || #elf_sym{name = Name, value = Value, size = Size} <- SymTab,
+ Name =/= 0],
+ {NameIndices, ValueOffs, Sizes} = lists:unzip3(Ts),
+ %% Find the names of the symbols.
+ %% Get string table entries ([{Name, Offset in strtab section}]). Keep only
+ %% relevant entries:
+ StrTab = extract_strtab(Elf),
+ Relevant = [get_strtab_entry(StrTab, Off) || Off <- NameIndices],
+ %% Zip back to {Name, ValueOff, Size}
+ lists:zip3(Relevant, ValueOffs, Sizes).
+
+%%------------------------------------------------------------------------------
+%% Functions to manipulate Symbol Table
+%%------------------------------------------------------------------------------
+
+%% @doc Function that extracts Symbol Table from an ELF Object file.
+extract_symtab(Elf) ->
+ Symtab_bin = extract_segment_by_name(Elf, ?SYMTAB),
+ get_symtab_entries(Symtab_bin, []).
+
+get_symtab_entries(<<>>, Acc) ->
+ lists:reverse(Acc);
+get_symtab_entries(Symtab_bin, Acc) ->
+ <<SymE_bin:?ELF_SYM_SIZE/binary, MoreSymE/binary>> = Symtab_bin,
+ case is64bit() of
+ true ->
+ <<%% Structural pattern matching on fields.
+ Name:?bits(?ST_NAME_SIZE)/integer-little,
+ Info:?bits(?ST_INFO_SIZE)/integer-little,
+ Other:?bits(?ST_OTHER_SIZE)/integer-little,
+ Shndx:?bits(?ST_SHNDX_SIZE)/integer-little,
+ Value:?bits(?ST_VALUE_SIZE)/integer-little,
+ Size:?bits(?ST_SIZE_SIZE)/integer-little
+ >> = SymE_bin;
+ false ->
+ << %% Same fields in different order:
+ Name:?bits(?ST_NAME_SIZE)/integer-little,
+ Value:?bits(?ST_VALUE_SIZE)/integer-little,
+ Size:?bits(?ST_SIZE_SIZE)/integer-little,
+ Info:?bits(?ST_INFO_SIZE)/integer-little,
+ Other:?bits(?ST_OTHER_SIZE)/integer-little,
+ Shndx:?bits(?ST_SHNDX_SIZE)/integer-little
+ >> = SymE_bin
+ end,
+ SymE = mk_sym(Name, Info, Other, Shndx, Value, Size),
+ get_symtab_entries(MoreSymE, [SymE | Acc]).
+
+%% @doc Extracts a specific entry from the Symbol Table (as binary).
+%% This function takes as arguments the Symbol Table (`SymTab')
+%% and the entry's serial number and returns that entry (`sym').
+get_symtab_entry(SymTab, EntryNum) ->
+ lists:nth(EntryNum + 1, SymTab).
+
+%%------------------------------------------------------------------------------
+%% Functions to manipulate String Table
+%%------------------------------------------------------------------------------
+
+%% @doc Extracts String Table from an ELF formated Object File.
+-spec extract_strtab(elf()) -> [{string(), offset()}].
+extract_strtab(Elf) ->
+ Strtab_bin = extract_segment_by_name(Elf, ?STRTAB),
+ NamesSizes = get_names(Strtab_bin),
+ make_offsets(NamesSizes).
+
+%% @doc Returns the name of the symbol at the given offset. The string table
+%% contains entries of the form {Name, Offset}. If no such offset exists
+%% returns the empty string (`""').
+%% XXX: There might be a bug here because of the "compact" saving the ELF
+%% format uses: e.g. only stores ".rela.text" for ".rela.text" and ".text".
+get_strtab_entry(Strtab, Offset) ->
+ case lists:keyfind(Offset, 2, Strtab) of
+ {Name, Offset} -> Name;
+ false -> ""
+ end.
+
+%%------------------------------------------------------------------------------
+%% Functions to manipulate Relocations
+%%------------------------------------------------------------------------------
+
+%% @doc This function gets as argument an ELF binary file and returns a list
+%% with all .rela.rodata labels (i.e. constants and literals in code)
+%% or an empty list if no ".rela.rodata" section exists in code.
+-spec get_rodata_relocs(elf()) -> [offset()].
+get_rodata_relocs(Elf) ->
+ case is64bit() of
+ true ->
+ %% Only care about the addends (== offsets):
+ get_rela_addends(extract_rela(Elf, ?RODATA));
+ false ->
+ %% Find offsets hardcoded in ".rodata" entry
+ %%XXX: Treat all 0s as padding and skip them!
+ [SkipPadding || SkipPadding <- extract_rodata(Elf), SkipPadding =/= 0]
+ end.
+
+-spec get_rela_addends([elf_rela()]) -> [offset()].
+get_rela_addends(RelaEntries) ->
+ [rela_addend(E) || E <- RelaEntries].
+
+%% @doc Extract a list of the form `[{SymbolName, Offset}]' with all relocatable
+%% symbols and their offsets in the code from the ".text" section.
+-spec get_text_relocs(elf()) -> [{name(), offset()}].
+get_text_relocs(Elf) ->
+ %% Only care about the symbol table index and the offset:
+ NameOffsetTemp = [{?ELF_R_SYM(r_info(E)), r_offset(E)}
+ || E <- extract_rela(Elf, ?TEXT)],
+ {NameIndices, ActualOffsets} = lists:unzip(NameOffsetTemp),
+ %% Find the names of the symbols:
+ %%
+ %% Get those symbol table entries that are related to Text relocs:
+ Symtab = extract_symtab(Elf),
+ SymtabEs = [get_symtab_entry(Symtab, Index) || Index <- NameIndices],
+ %XXX: not zero-indexed!
+ %% Symbol table entries contain the offset of the name of the symbol in
+ %% String Table:
+ SymtabEs2 = [sym_name(E) || E <- SymtabEs], %XXX: Do we need to sort SymtabE?
+ %% Get string table entries ([{Name, Offset in strtab section}]). Keep only
+ %% relevant entries:
+ Strtab = extract_strtab(Elf),
+ Relevant = [get_strtab_entry(Strtab, Off) || Off <- SymtabEs2],
+ %% Zip back with actual offsets:
+ lists:zip(Relevant, ActualOffsets).
+
+%% @doc Extract the Relocations segment for section `Name' (that is passed
+%% as second argument) from an ELF formated Object file binary.
+-spec extract_rela(elf(), name()) -> [elf_rel() | elf_rela()].
+extract_rela(Elf, Name) ->
+ SegName =
+ case is64bit() of
+ true -> ?RELA(Name); % ELF-64 uses ".rela"
+ false -> ?REL(Name) % ...while ELF-32 uses ".rel"
+ end,
+ Rela_bin = extract_segment_by_name(Elf, SegName),
+ get_rela_entries(Rela_bin, []).
+
+get_rela_entries(<<>>, Acc) ->
+ lists:reverse(Acc);
+get_rela_entries(Bin, Acc) ->
+ E = case is64bit() of
+ true ->
+ <<%% Structural pattern matching on fields of a Rela Entry.
+ Offset:?bits(?R_OFFSET_SIZE)/integer-little,
+ Info:?bits(?R_INFO_SIZE)/integer-little,
+ Addend:?bits(?R_ADDEND_SIZE)/integer-little,
+ Rest/binary
+ >> = Bin,
+ mk_rela(Offset, Info, Addend);
+ false ->
+ <<%% Structural pattern matching on fields of a Rel Entry.
+ Offset:?bits(?R_OFFSET_SIZE)/integer-little,
+ Info:?bits(?R_INFO_SIZE)/integer-little,
+ Rest/binary
+ >> = Bin,
+ mk_rel(Offset, Info)
+ end,
+ get_rela_entries(Rest, [E | Acc]).
+
+%% %% @doc Extract the `EntryNum' (serial number) Relocation Entry.
+%% get_rela_entry(Rela, EntryNum) ->
+%% lists:nth(EntryNum + 1, Rela).
+
+%%------------------------------------------------------------------------------
+%% Functions to manipulate Executable Code segment
+%%------------------------------------------------------------------------------
+
+%% @doc This function gets as arguments an ELF formated binary file and
+%% returns the Executable Code (".text" segment) or an empty binary if it
+%% is not found.
+-spec extract_text(elf()) -> binary().
+extract_text(Elf) ->
+ extract_segment_by_name(Elf, ?TEXT).
+
+%%------------------------------------------------------------------------------
+%% Functions to manipulate Note Section
+%%------------------------------------------------------------------------------
+
+%% @doc Extract specific Note Section from an ELF Object file. The function
+%% takes as first argument the object file (`Elf') and the `Name' of the
+%% wanted Note Section (<b>without</b> the ".note" prefix!). It returns
+%% the specified binary segment or an empty binary if no such section
+%% exists.
+-spec extract_note(elf(), string()) -> binary().
+extract_note(Elf, Name) ->
+ extract_segment_by_name(Elf, ?NOTE(Name)).
+
+%%------------------------------------------------------------------------------
+%% Functions to manipulate GCC Exception Table segment
+%%------------------------------------------------------------------------------
+
+%% A description for the C++ exception table formats can be found at Exception
+%% Handling Tables (http://www.codesourcery.com/cxx-abi/exceptions.pdf).
+
+%% A list with `{Start, End, HandlerOffset}' for all call sites in the code
+-spec get_exn_handlers(elf()) -> [{start(), start(), lp()}].
+get_exn_handlers(Elf) ->
+ CallSites = extract_gccexntab_callsites(Elf),
+ [{Start, Start + Size, LP}
+ || #elf_gccexntab_callsite{start = Start, size = Size, lp = LP} <- CallSites].
+
+%% @doc This function gets as argument an ELF binary file and returns
+%% the table (list) of call sites which is stored in GCC
+%% Exception Table (".gcc_except_table") section.
+%% It returns an empty list if the Exception Table is not found.
+%% XXX: Assumes there is *no* Action Record Table.
+extract_gccexntab_callsites(Elf) ->
+ case extract_segment_by_name(Elf, ?GCC_EXN_TAB) of
+ <<>> ->
+ [];
+ ExnTab ->
+ %% First byte of LSDA is Landing Pad base encoding.
+ <<LBenc:8, More/binary>> = ExnTab,
+ %% Second byte is the Landing Pad base (if its encoding is not
+ %% DW_EH_PE_omit) (optional).
+ {_LPBase, LSDACont} =
+ case LBenc =:= ?DW_EH_PE_omit of
+ true -> % No landing pad base byte. (-1 denotes that)
+ {-1, More};
+ false -> % Landing pad base.
+ <<Base:8, More2/binary>> = More,
+ {Base, More2}
+ end,
+ %% Next byte of LSDA is the encoding of the Type Table.
+ <<TTenc:8, More3/binary>> = LSDACont,
+ %% Next byte is the Types Table offset encoded in U-LEB128 (optional).
+ {_TTOff, LSDACont2} =
+ case TTenc =:= ?DW_EH_PE_omit of
+ true -> % There is no Types Table pointer. (-1 denotes that)
+ {-1, More3};
+ false -> % The byte offset from this field to the start of the Types
+ % Table used for exception matching.
+ leb128_decode(More3)
+ end,
+ %% Next byte of LSDA is the encoding of the fields in the Call-site Table.
+ <<_CSenc:8, More4/binary>> = LSDACont2,
+ %% Sixth byte is the size (in bytes) of the Call-site Table encoded in
+ %% U-LEB128.
+ {_CSTabSize, CSTab} = leb128_decode(More4),
+ %% Extract all call site information
+ get_gccexntab_callsites(CSTab, [])
+ end.
+
+get_gccexntab_callsites(<<>>, Acc) ->
+ lists:reverse(Acc);
+get_gccexntab_callsites(CSTab, Acc) ->
+ %% We are only interested in the Landing Pad of every entry.
+ <<Start:32/integer-little, Size:32/integer-little,
+ LP:32/integer-little, OnAction:8, More/binary
+ >> = CSTab,
+ GccCS = mk_gccexntab_callsite(Start, Size, LP, OnAction),
+ get_gccexntab_callsites(More, [GccCS | Acc]).
+
+%%------------------------------------------------------------------------------
+%% Functions to manipulate Read-only Data (.rodata)
+%%------------------------------------------------------------------------------
+extract_rodata(Elf) ->
+ Rodata_bin = extract_segment_by_name(Elf, ?RODATA),
+ get_rodata_entries(Rodata_bin, []).
+
+get_rodata_entries(<<>>, Acc) ->
+ lists:reverse(Acc);
+get_rodata_entries(Rodata_bin, Acc) ->
+ <<Num:?bits(?ELF_ADDR_SIZE)/integer-little, More/binary>> = Rodata_bin,
+ get_rodata_entries(More, [Num | Acc]).
+
+%%------------------------------------------------------------------------------
+%% Helper functions
+%%------------------------------------------------------------------------------
+
+%% @doc Returns the binary segment starting at `Offset' with length `Size'
+%% (bytes) from a binary file. If `Offset' is bigger than the byte size of
+%% the binary, an empty binary (`<<>>') is returned.
+-spec get_binary_segment(binary(), offset(), size()) -> binary().
+get_binary_segment(Bin, Offset, _Size) when Offset > byte_size(Bin) ->
+ <<>>;
+get_binary_segment(Bin, Offset, Size) ->
+ <<_Hdr:Offset/binary, BinSeg:Size/binary, _More/binary>> = Bin,
+ BinSeg.
+
+%% @doc This function gets as arguments an ELF formated binary object and
+%% a string with the segments' name and returns the specified segment or
+%% an empty binary (`<<>>') if there exists no segment with that name.
+%% There are handy macros defined in elf_format.hrl for all Standard
+%% Section Names.
+-spec extract_segment_by_name(elf(), string()) -> binary().
+extract_segment_by_name(Elf, SectionName) ->
+ %% Extract Section Header Table and Section Header String Table from binary
+ SHdrTable = extract_shdrtab(Elf),
+ Names = extract_shstrtab(Elf),
+ %% Zip to a list of (Name,ShdrE)
+ [_Zero | ShdrEs] = lists:keysort(2, SHdrTable), % Skip first entry (zeros).
+ L = lists:zip(Names, ShdrEs),
+ %% Find Section Header Table entry by name
+ case lists:keyfind(SectionName, 1, L) of
+ {SectionName, ShdrE} -> %% Note: Same name.
+ #elf_shdr{offset = Offset, size = Size} = ShdrE,
+ get_binary_segment(Elf, Offset, Size);
+ false -> %% Not found.
+ <<>>
+ end.
+
+%% @doc Extracts a list of strings with (zero-separated) names from a binary.
+%% Returns tuples of `{Name, Size}'.
+%% XXX: Skip trailing 0.
+-spec get_names(<<_:8,_:_*8>>) -> name_sizes().
+get_names(<<0, Bin/binary>>) ->
+ NamesSizes = get_names(Bin, []),
+ fix_names(NamesSizes, []).
+
+get_names(<<>>, Acc) ->
+ lists:reverse(Acc);
+get_names(Bin, Acc) ->
+ {Name, MoreNames} = bin_get_string(Bin),
+ get_names(MoreNames, [{Name, length(Name)} | Acc]).
+
+%% @doc Fix names:
+%% e.g. If ".rela.text" exists, ".text" does not. Same goes for
+%% ".rel.text". In that way, the Section Header String Table is more
+%% compact. Add ".text" just *before* the corresponding rela-field,
+%% etc.
+-spec fix_names(name_sizes(), name_sizes()) -> name_sizes().
+fix_names([], Acc) ->
+ lists:reverse(Acc);
+fix_names([{Name, Size}=T | Names], Acc) ->
+ case is64bit() of
+ true ->
+ case string:str(Name, ".rela") =:= 1 of
+ true -> %% Name starts with ".rela":
+ Section = string:substr(Name, 6),
+ fix_names(Names, [{Section, Size - 5}
+ | [T | Acc]]); % XXX: Is order ok? (".text"
+ % always before ".rela.text")
+ false -> %% Name does not start with ".rela":
+ fix_names(Names, [T | Acc])
+ end;
+ false ->
+ case string:str(Name, ".rel") =:= 1 of
+ true -> %% Name starts with ".rel":
+ Section = string:substr(Name, 5),
+ fix_names(Names, [{Section, Size - 4}
+ | [T | Acc]]); % XXX: Is order ok? (".text"
+ % always before ".rela.text")
+ false -> %% Name does not start with ".rel":
+ fix_names(Names, [T | Acc])
+ end
+ end.
+
+
+%% @doc A function that byte-reverses a binary. This might be needed because of
+%% little (fucking!) endianess.
+-spec bin_reverse(binary()) -> binary().
+bin_reverse(Bin) when is_binary(Bin) ->
+ bin_reverse(Bin, <<>>).
+
+-spec bin_reverse(binary(), binary()) -> binary().
+bin_reverse(<<>>, Acc) ->
+ Acc;
+bin_reverse(<<Head, More/binary>>, Acc) ->
+ bin_reverse(More, <<Head, Acc/binary>>).
+
+%% @doc A function that extracts a null-terminated string from a binary. It
+%% returns the found string along with the rest of the binary.
+-spec bin_get_string(binary()) -> {string(), binary()}.
+bin_get_string(Bin) ->
+ bin_get_string(Bin, <<>>).
+
+bin_get_string(<<>>, BinAcc) ->
+ Bin = bin_reverse(BinAcc), % little endian!
+ {binary_to_list(Bin), <<>>};
+bin_get_string(<<0, MoreBin/binary>>, BinAcc) ->
+ Bin = bin_reverse(BinAcc), % little endian!
+ {binary_to_list(Bin), MoreBin};
+bin_get_string(<<Letter, Tail/binary>>, BinAcc) ->
+ bin_get_string(Tail, <<Letter, BinAcc/binary>>).
+
+%% @doc
+make_offsets(NamesSizes) ->
+ {Names, Sizes} = lists:unzip(NamesSizes),
+ Offsets = make_offsets_from_sizes(Sizes, 1, []),
+ lists:zip(Names, Offsets).
+
+make_offsets_from_sizes([], _, Acc) ->
+ lists:reverse(Acc);
+make_offsets_from_sizes([Size | Sizes], Cur, Acc) ->
+ make_offsets_from_sizes(Sizes, Size+Cur+1, [Cur | Acc]). % For the "."!
+
+%% @doc Little-Endian Base 128 (LEB128) Decoder
+%% This function extracts the <b>first</b> LEB128-encoded integer in a
+%% binary and returns that integer along with the remaining binary. This is
+%% done because a LEB128 number has variable bit-size and that is a way of
+%% extracting only one number in a binary and continuing parsing the binary
+%% for other kind of data (e.g. different encoding).
+%% FIXME: Only decodes unsigned data!
+-spec leb128_decode(binary()) -> {integer(), binary()}.
+leb128_decode(LebNum) ->
+ leb128_decode(LebNum, 0, <<>>).
+
+-spec leb128_decode(binary(), integer(), binary()) -> {integer(), binary()}.
+leb128_decode(LebNum, NoOfBits, Acc) ->
+ <<Sentinel:1/bits, NextBundle:7/bits, MoreLebNums/bits>> = LebNum,
+ case Sentinel of
+ <<1:1>> -> % more bytes to follow
+ leb128_decode(MoreLebNums, NoOfBits+7, <<NextBundle:7/bits, Acc/bits>>);
+ <<0:1>> -> % byte bundle stop
+ Size = NoOfBits+7,
+ <<Num:Size/integer>> = <<NextBundle:7/bits, Acc/bits>>,
+ {Num, MoreLebNums}
+ end.
+
+%% @doc Extract ELF Class from ELF header and export symbol to process
+%% dictionary.
+-spec set_architecture_flag(elf()) -> 'ok'.
+set_architecture_flag(Elf) ->
+ %% Extract information about ELF Class from ELF Header
+ <<16#7f, $E, $L, $F, EI_Class, _MoreHeader/binary>>
+ = get_binary_segment(Elf, 0, ?ELF_EHDR_SIZE),
+ put(elf_class, EI_Class),
+ ok.
+
+%% @doc Read from object file header if the file class is ELF32 or ELF64.
+-spec is64bit() -> boolean().
+is64bit() ->
+ case get(elf_class) of
+ ?ELFCLASS64 -> true;
+ ?ELFCLASS32 -> false
+ end.