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elf: simplify logic for resolving nonalloc relocs on different arches
This commit is contained in:
Jakub Konka
parent
4cde47a169
commit
06c191a4ff
@ -433,7 +433,7 @@ pub fn scanRelocs(self: Atom, elf_file: *Elf, code: ?[]const u8, undefs: anytype
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// While traversing relocations, mark symbols that require special handling such as
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// pointer indirection via GOT, or a stub trampoline via PLT.
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switch (elf_file.getTarget().cpu.arch) {
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switch (cpu_arch) {
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.x86_64 => x86_64.scanReloc(self, elf_file, rel, symbol, code, &it) catch |err| switch (err) {
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error.RelocFailure => has_reloc_errors = true,
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else => |e| return e,
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@ -765,6 +765,7 @@ pub fn resolveRelocsAlloc(self: Atom, elf_file: *Elf, code: []u8) RelocError!voi
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switch (cpu_arch) {
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.x86_64 => x86_64.resolveRelocAlloc(self, elf_file, rel, target, args, &it, code, &stream) catch |err| switch (err) {
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error.RelocFailure,
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error.RelaxFailure,
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error.InvalidInstruction,
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error.CannotEncode,
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@ -880,10 +881,83 @@ fn applyDynamicReloc(value: i64, elf_file: *Elf, writer: anytype) !void {
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pub fn resolveRelocsNonAlloc(self: Atom, elf_file: *Elf, code: []u8, undefs: anytype) !void {
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relocs_log.debug("0x{x}: {s}", .{ self.address(elf_file), self.name(elf_file) });
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switch (elf_file.getTarget().cpu.arch) {
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.x86_64 => try x86_64.resolveRelocsNonAlloc(self, elf_file, code, undefs),
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else => return error.UnsupportedCpuArch,
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const cpu_arch = elf_file.getTarget().cpu.arch;
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const file_ptr = self.file(elf_file).?;
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var stream = std.io.fixedBufferStream(code);
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const rels = self.relocs(elf_file);
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var has_reloc_errors = false;
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var it = RelocsIterator{ .relocs = rels };
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while (it.next()) |rel| {
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const r_kind = relocation.decode(rel.r_type(), cpu_arch);
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if (r_kind == .none) continue;
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const r_offset = std.math.cast(usize, rel.r_offset) orelse return error.Overflow;
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const target_index = switch (file_ptr) {
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.zig_object => |x| x.symbol(rel.r_sym()),
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.object => |x| x.symbols.items[rel.r_sym()],
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else => unreachable,
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};
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const target = elf_file.symbol(target_index);
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// Check for violation of One Definition Rule for COMDATs.
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if (target.file(elf_file) == null) {
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// TODO convert into an error
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log.debug("{}: {s}: {s} refers to a discarded COMDAT section", .{
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file_ptr.fmtPath(),
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self.name(elf_file),
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target.name(elf_file),
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});
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continue;
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}
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// Report an undefined symbol.
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if (try self.reportUndefined(elf_file, target, target_index, rel, undefs)) continue;
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// We will use equation format to resolve relocations:
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// https://intezer.com/blog/malware-analysis/executable-and-linkable-format-101-part-3-relocations/
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//
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const P = @as(i64, @intCast(self.address(elf_file) + rel.r_offset));
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// Addend from the relocation.
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const A = rel.r_addend;
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// Address of the target symbol - can be address of the symbol within an atom or address of PLT stub.
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const S = @as(i64, @intCast(target.address(.{}, elf_file)));
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// Address of the global offset table.
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const GOT = blk: {
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const shndx = if (elf_file.got_plt_section_index) |shndx|
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shndx
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else if (elf_file.got_section_index) |shndx|
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shndx
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else
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null;
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break :blk if (shndx) |index| @as(i64, @intCast(elf_file.shdrs.items[index].sh_addr)) else 0;
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};
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// Address of the dynamic thread pointer.
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const DTP = @as(i64, @intCast(elf_file.dtpAddress()));
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const args = ResolveArgs{ P, A, S, GOT, 0, 0, DTP, 0 };
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relocs_log.debug(" {}: {x}: [{x} => {x}] ({s})", .{
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relocation.fmtRelocType(rel.r_type(), cpu_arch),
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rel.r_offset,
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P,
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S + A,
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target.name(elf_file),
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});
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try stream.seekTo(r_offset);
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switch (cpu_arch) {
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.x86_64 => x86_64.resolveRelocNonAlloc(self, elf_file, rel, target, args, &it, code, &stream) catch |err| switch (err) {
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error.RelocFailure => has_reloc_errors = true,
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else => |e| return e,
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},
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else => return error.UnsupportedCpuArch,
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}
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}
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if (has_reloc_errors) return error.RelocFailure;
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}
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pub fn format(
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@ -1210,98 +1284,48 @@ const x86_64 = struct {
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Elf.R_ZIG_GOT32 => try cwriter.writeInt(u32, @as(u32, @intCast(ZIG_GOT + A)), .little),
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Elf.R_ZIG_GOTPCREL => try cwriter.writeInt(i32, @as(i32, @intCast(ZIG_GOT + A - P)), .little),
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else => {},
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else => try atom.reportUnhandledRelocError(rel, elf_file),
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},
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}
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}
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fn resolveRelocsNonAlloc(atom: Atom, elf_file: *Elf, code: []u8, undefs: anytype) !void {
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const file_ptr = atom.file(elf_file).?;
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var stream = std.io.fixedBufferStream(code);
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fn resolveRelocNonAlloc(
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atom: Atom,
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elf_file: *Elf,
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rel: elf.Elf64_Rela,
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target: *const Symbol,
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args: ResolveArgs,
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it: *RelocsIterator,
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code: []u8,
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stream: anytype,
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) !void {
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_ = code;
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_ = it;
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const r_type: elf.R_X86_64 = @enumFromInt(rel.r_type());
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const cwriter = stream.writer();
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const rels = atom.relocs(elf_file);
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var i: usize = 0;
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while (i < rels.len) : (i += 1) {
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const rel = rels[i];
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const r_type: elf.R_X86_64 = @enumFromInt(rel.r_type());
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if (r_type == .NONE) continue;
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_, const A, const S, const GOT, _, _, const DTP, _ = args;
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const r_offset = std.math.cast(usize, rel.r_offset) orelse return error.Overflow;
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const target_index = switch (file_ptr) {
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.zig_object => |x| x.symbol(rel.r_sym()),
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.object => |x| x.symbols.items[rel.r_sym()],
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else => unreachable,
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};
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const target = elf_file.symbol(target_index);
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// Check for violation of One Definition Rule for COMDATs.
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if (target.file(elf_file) == null) {
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// TODO convert into an error
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log.debug("{}: {s}: {s} refers to a discarded COMDAT section", .{
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file_ptr.fmtPath(),
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atom.name(elf_file),
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target.name(elf_file),
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});
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continue;
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}
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// Report an undefined symbol.
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if (try atom.reportUndefined(elf_file, target, target_index, rel, undefs)) continue;
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// We will use equation format to resolve relocations:
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// https://intezer.com/blog/malware-analysis/executable-and-linkable-format-101-part-3-relocations/
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//
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const P = @as(i64, @intCast(atom.address(elf_file) + rel.r_offset));
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// Addend from the relocation.
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const A = rel.r_addend;
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// Address of the target symbol - can be address of the symbol within an atom or address of PLT stub.
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const S = @as(i64, @intCast(target.address(.{}, elf_file)));
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// Address of the global offset table.
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const GOT = blk: {
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const shndx = if (elf_file.got_plt_section_index) |shndx|
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shndx
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else if (elf_file.got_section_index) |shndx|
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shndx
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else
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null;
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break :blk if (shndx) |index| @as(i64, @intCast(elf_file.shdrs.items[index].sh_addr)) else 0;
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};
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// Address of the dynamic thread pointer.
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const DTP = @as(i64, @intCast(elf_file.dtpAddress()));
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relocs_log.debug(" {}: {x}: [{x} => {x}] ({s})", .{
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relocation.fmtRelocType(rel.r_type(), .x86_64),
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rel.r_offset,
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P,
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S + A,
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target.name(elf_file),
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});
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try stream.seekTo(r_offset);
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switch (r_type) {
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.NONE => unreachable,
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.@"8" => try cwriter.writeInt(u8, @as(u8, @bitCast(@as(i8, @intCast(S + A)))), .little),
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.@"16" => try cwriter.writeInt(u16, @as(u16, @bitCast(@as(i16, @intCast(S + A)))), .little),
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.@"32" => try cwriter.writeInt(u32, @as(u32, @bitCast(@as(i32, @intCast(S + A)))), .little),
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.@"32S" => try cwriter.writeInt(i32, @as(i32, @intCast(S + A)), .little),
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.@"64" => try cwriter.writeInt(i64, S + A, .little),
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.DTPOFF32 => try cwriter.writeInt(i32, @as(i32, @intCast(S + A - DTP)), .little),
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.DTPOFF64 => try cwriter.writeInt(i64, S + A - DTP, .little),
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.GOTOFF64 => try cwriter.writeInt(i64, S + A - GOT, .little),
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.GOTPC64 => try cwriter.writeInt(i64, GOT + A, .little),
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.SIZE32 => {
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const size = @as(i64, @intCast(target.elfSym(elf_file).st_size));
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try cwriter.writeInt(u32, @as(u32, @bitCast(@as(i32, @intCast(size + A)))), .little);
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},
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.SIZE64 => {
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const size = @as(i64, @intCast(target.elfSym(elf_file).st_size));
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try cwriter.writeInt(i64, @as(i64, @intCast(size + A)), .little);
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},
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else => try atom.reportUnhandledRelocError(rel, elf_file),
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}
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switch (r_type) {
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.NONE => unreachable,
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.@"8" => try cwriter.writeInt(u8, @as(u8, @bitCast(@as(i8, @intCast(S + A)))), .little),
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.@"16" => try cwriter.writeInt(u16, @as(u16, @bitCast(@as(i16, @intCast(S + A)))), .little),
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.@"32" => try cwriter.writeInt(u32, @as(u32, @bitCast(@as(i32, @intCast(S + A)))), .little),
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.@"32S" => try cwriter.writeInt(i32, @as(i32, @intCast(S + A)), .little),
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.@"64" => try cwriter.writeInt(i64, S + A, .little),
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.DTPOFF32 => try cwriter.writeInt(i32, @as(i32, @intCast(S + A - DTP)), .little),
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.DTPOFF64 => try cwriter.writeInt(i64, S + A - DTP, .little),
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.GOTOFF64 => try cwriter.writeInt(i64, S + A - GOT, .little),
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.GOTPC64 => try cwriter.writeInt(i64, GOT + A, .little),
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.SIZE32 => {
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const size = @as(i64, @intCast(target.elfSym(elf_file).st_size));
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try cwriter.writeInt(u32, @as(u32, @bitCast(@as(i32, @intCast(size + A)))), .little);
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},
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.SIZE64 => {
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const size = @as(i64, @intCast(target.elfSym(elf_file).st_size));
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try cwriter.writeInt(i64, @as(i64, @intCast(size + A)), .little);
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},
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else => try atom.reportUnhandledRelocError(rel, elf_file),
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}
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}
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