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macho: store source section address of relocs in context

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This is particularly relevant for x86_64 and C++ when relocating
StaticInit sections containing static initializers machine code.
Then, in case of SIGNED_X relocations, it is necessary to have the
full image of the VM address layout of the sections in the object
file as this is how the addend needs to be adjusted for non-extern
relocations.
This commit is contained in:
Jakub Konka 2021-09-07 23:21:08 +02:00
parent 159e55dfd9
commit e229202cb8
2 changed files with 18 additions and 14 deletions
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9
src/link/MachO/Object.zig
View File

@ -425,7 +425,8 @@ const TextBlockParser = struct {
}
try block.parseRelocs(self.relocs, .{
.base_addr = start_addr,
.base_addr = self.section.addr,
.base_offset = start_addr,
.allocator = context.allocator,
.object = context.object,
.macho_file = context.macho_file,
@ -583,7 +584,8 @@ pub fn parseTextBlocks(
}
try block.parseRelocs(relocs, .{
.base_addr = 0,
.base_addr = sect.addr,
.base_offset = 0,
.allocator = allocator,
.object = self,
.macho_file = macho_file,
@ -689,7 +691,8 @@ pub fn parseTextBlocks(
}
try block.parseRelocs(relocs, .{
.base_addr = 0,
.base_addr = sect.addr,
.base_offset = 0,
.allocator = allocator,
.object = self,
.macho_file = macho_file,

23
src/link/MachO/TextBlock.zig
View File

@ -479,13 +479,13 @@ pub const Relocation = struct {
pub const Signed = struct {
addend: i64,
correction: i4,
correction: u3,
pub fn resolve(self: Signed, args: ResolveArgs) !void {
const target_addr = @intCast(i64, args.target_addr) + self.addend;
const displacement = try math.cast(
i32,
target_addr - @intCast(i64, args.source_addr) - self.correction - 4,
target_addr - @intCast(i64, args.source_addr + self.correction + 4),
);
mem.writeIntLittle(u32, args.block.code.items[args.offset..][0..4], @bitCast(u32, displacement));
}
@ -613,6 +613,7 @@ pub fn freeListEligible(self: TextBlock, macho_file: MachO) bool {
const RelocContext = struct {
base_addr: u64 = 0,
base_offset: u64 = 0,
allocator: *Allocator,
object: *Object,
macho_file: *MachO,
@ -620,7 +621,7 @@ const RelocContext = struct {
fn initRelocFromObject(rel: macho.relocation_info, context: RelocContext) !Relocation {
var parsed_rel = Relocation{
.offset = @intCast(u32, @intCast(u64, rel.r_address) - context.base_addr),
.offset = @intCast(u32, @intCast(u64, rel.r_address) - context.base_offset),
.where = undefined,
.where_index = undefined,
.payload = undefined,
@ -684,7 +685,7 @@ fn initRelocFromObject(rel: macho.relocation_info, context: RelocContext) !Reloc
}
pub fn parseRelocs(self: *TextBlock, relocs: []macho.relocation_info, context: RelocContext) !void {
const filtered_relocs = filterRelocs(relocs, context.base_addr, context.base_addr + self.size);
const filtered_relocs = filterRelocs(relocs, context.base_offset, context.base_offset + self.size);
var it = RelocIterator{
.buffer = filtered_relocs,
};
@ -956,9 +957,9 @@ fn parseUnsigned(
mem.readIntLittle(i32, self.code.items[out.offset..][0..4]);
if (rel.r_extern == 0) {
const source_seg = context.object.load_commands.items[context.object.segment_cmd_index.?].Segment;
const source_sect_base_addr = source_seg.sections.items[rel.r_symbolnum - 1].addr;
addend -= @intCast(i64, source_sect_base_addr);
const seg = context.object.load_commands.items[context.object.segment_cmd_index.?].Segment;
const target_sect_base_addr = seg.sections.items[rel.r_symbolnum - 1].addr;
addend -= @intCast(i64, target_sect_base_addr);
}
out.payload = .{
@ -1043,7 +1044,7 @@ fn parseSigned(self: TextBlock, rel: macho.relocation_info, out: *Relocation, co
assert(rel.r_length == 2);
const rel_type = @intToEnum(macho.reloc_type_x86_64, rel.r_type);
const correction: i4 = switch (rel_type) {
const correction: u3 = switch (rel_type) {
.X86_64_RELOC_SIGNED => 0,
.X86_64_RELOC_SIGNED_1 => 1,
.X86_64_RELOC_SIGNED_2 => 2,
@ -1053,9 +1054,9 @@ fn parseSigned(self: TextBlock, rel: macho.relocation_info, out: *Relocation, co
var addend: i64 = mem.readIntLittle(i32, self.code.items[out.offset..][0..4]) + correction;
if (rel.r_extern == 0) {
const source_seg = context.object.load_commands.items[context.object.segment_cmd_index.?].Segment;
const source_sect_base_addr = source_seg.sections.items[rel.r_symbolnum - 1].addr;
addend = @intCast(i64, out.offset) + addend - @intCast(i64, source_sect_base_addr) + 4 + correction;
const seg = context.object.load_commands.items[context.object.segment_cmd_index.?].Segment;
const target_sect_base_addr = seg.sections.items[rel.r_symbolnum - 1].addr;
addend += @intCast(i64, context.base_addr + out.offset + correction + 4) - @intCast(i64, target_sect_base_addr);
}
out.payload = .{