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https://github.com/ziglang/zig.git
synced 2026-01-25 16:55:22 +00:00
macho: resolve special section/segment boundary symbols
Boundary symbols have a special name prefix: * section$start$segname$sectname * section$stop$segname$sectname * segment$start$segname * segment$stop$segname and will resolve to either start or end of the respective section/segment if found. If not found, we return an error stating we couldn't find the requested section/segment rather than silently failing and resolving the address to 0 which seems to be the case with Apple's ld64.
This commit is contained in:
Jakub Konka
parent
03adafd802
commit
0f2489d8fc
@ -1416,6 +1416,51 @@ pub fn allocateSpecialSymbols(self: *MachO) !void {
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seg.segName(),
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});
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}
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for (self.globals.items) |global| {
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const sym = self.getSymbolPtr(global);
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if (sym.n_desc != N_BOUNDARY) continue;
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if (self.getSectionBoundarySymbol(global)) |bsym| {
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const sect_id = self.getSectionByName(bsym.segname, bsym.sectname) orelse {
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try self.reportUnresolvedBoundarySymbol(self.getSymbolName(global), "section not found: {s},{s}", .{
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bsym.segname, bsym.sectname,
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});
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continue;
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};
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const sect = self.sections.items(.header)[sect_id];
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sym.n_sect = sect_id + 1;
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sym.n_value = switch (bsym.kind) {
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.start => sect.addr,
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.stop => sect.addr + sect.size,
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};
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log.debug("allocating {s} at @0x{x} sect({d})", .{
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self.getSymbolName(global),
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sym.n_value,
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sym.n_sect,
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});
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continue;
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}
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if (self.getSegmentBoundarySymbol(global)) |bsym| {
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const seg_id = self.getSegmentByName(bsym.segname) orelse {
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try self.reportUnresolvedBoundarySymbol(self.getSymbolName(global), "segment not found: {s}", .{
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bsym.segname,
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});
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continue;
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};
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const seg = self.segments.items[seg_id];
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sym.n_value = switch (bsym.kind) {
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.start => seg.vmaddr,
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.stop => seg.vmaddr + seg.vmsize,
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};
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log.debug("allocating {s} at @0x{x} ", .{ self.getSymbolName(global), sym.n_value });
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continue;
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}
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}
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}
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const CreateAtomOpts = struct {
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@ -1442,6 +1487,7 @@ pub fn createTentativeDefAtoms(self: *MachO) !void {
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const sym = self.getSymbolPtr(global);
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if (!sym.tentative()) continue;
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if (sym.n_desc == N_DEAD) continue;
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if (sym.n_desc == N_BOUNDARY) continue;
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log.debug("creating tentative definition for ATOM(%{d}, '{s}') in object({?})", .{
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global.sym_index, self.getSymbolName(global), global.file,
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@ -1630,6 +1676,13 @@ pub fn resolveSymbols(self: *MachO) !void {
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try self.createMhExecuteHeaderSymbol();
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try self.createDsoHandleSymbol();
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try self.resolveSymbolsAtLoading();
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// Final stop, check if unresolved contain any of the special magic boundary symbols
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// * section$start$
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// * section$stop$
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// * segment$start$
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// * segment$stop$
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try self.resolveBoundarySymbols();
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}
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fn resolveGlobalSymbol(self: *MachO, current: SymbolWithLoc) !void {
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@ -1845,6 +1898,34 @@ fn resolveSymbolsAtLoading(self: *MachO) !void {
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}
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}
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fn resolveBoundarySymbols(self: *MachO) !void {
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var next_sym: usize = 0;
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while (next_sym < self.unresolved.count()) {
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const global_index = self.unresolved.keys()[next_sym];
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const global = &self.globals.items[global_index];
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if (self.getSectionBoundarySymbol(global.*) != null or self.getSegmentBoundarySymbol(global.*) != null) {
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const sym_index = try self.allocateSymbol();
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const sym_loc = SymbolWithLoc{ .sym_index = sym_index };
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const sym = self.getSymbolPtr(sym_loc);
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sym.* = .{
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.n_strx = try self.strtab.insert(self.base.allocator, self.getSymbolName(global.*)),
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.n_type = macho.N_SECT | macho.N_EXT,
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.n_sect = 0,
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.n_desc = N_BOUNDARY,
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.n_value = 0,
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};
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if (global.getFile()) |file| {
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const global_object = &self.objects.items[file];
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global_object.globals_lookup[global.sym_index] = global_index;
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}
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global.* = sym_loc;
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_ = self.unresolved.swapRemove(global_index);
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continue;
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}
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}
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}
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pub fn deinit(self: *MachO) void {
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const gpa = self.base.allocator;
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@ -3565,6 +3646,7 @@ fn collectRebaseData(self: *MachO, rebase: *Rebase) !void {
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const atom = self.getAtom(atom_index);
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const sym = self.getSymbol(atom.getSymbolWithLoc());
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if (sym.n_desc == N_DEAD) continue;
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if (sym.n_desc == N_BOUNDARY) continue;
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const sect_id = sym.n_sect - 1;
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const section = self.sections.items(.header)[sect_id];
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@ -3719,6 +3801,7 @@ fn collectBindData(self: *MachO, bind: anytype, raw_bindings: anytype) !void {
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const atom = self.getAtom(atom_index);
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const sym = self.getSymbol(atom.getSymbolWithLoc());
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if (sym.n_desc == N_DEAD) continue;
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if (sym.n_desc == N_BOUNDARY) continue;
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const sect_id = sym.n_sect - 1;
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const section = self.sections.items(.header)[sect_id];
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@ -3819,6 +3902,7 @@ fn collectExportData(self: *MachO, trie: *Trie) !void {
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if (sym.undf()) continue;
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assert(sym.ext());
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if (sym.n_desc == N_DEAD) continue;
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if (sym.n_desc == N_BOUNDARY) continue;
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const sym_name = self.getSymbolName(global);
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log.debug(" (putting '{s}' defined at 0x{x})", .{ sym_name, sym.n_value });
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@ -3953,7 +4037,8 @@ const asc_u64 = std.sort.asc(u64);
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fn addSymbolToFunctionStarts(self: *MachO, sym_loc: SymbolWithLoc, addresses: *std.ArrayList(u64)) !void {
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const sym = self.getSymbol(sym_loc);
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if (sym.n_strx == 0) return;
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if (sym.n_desc == MachO.N_DEAD) return;
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if (sym.n_desc == N_DEAD) return;
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if (sym.n_desc == N_BOUNDARY) return;
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if (self.symbolIsTemp(sym_loc)) return;
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try addresses.append(sym.n_value);
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}
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@ -4061,7 +4146,8 @@ pub fn writeDataInCode(self: *MachO) !void {
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for (object.exec_atoms.items) |atom_index| {
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const atom = self.getAtom(atom_index);
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const sym = self.getSymbol(atom.getSymbolWithLoc());
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if (sym.n_desc == MachO.N_DEAD) continue;
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if (sym.n_desc == N_DEAD) continue;
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if (sym.n_desc == N_BOUNDARY) return;
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const source_addr = if (object.getSourceSymbol(atom.sym_index)) |source_sym|
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source_sym.n_value
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@ -4119,7 +4205,8 @@ fn writeSymtabs(self: *MachO) !void {
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fn addLocalToSymtab(self: *MachO, sym_loc: SymbolWithLoc, locals: *std.ArrayList(macho.nlist_64)) !void {
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const sym = self.getSymbol(sym_loc);
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if (sym.n_strx == 0) return; // no name, skip
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if (sym.n_desc == MachO.N_DEAD) return; // garbage-collected, skip
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if (sym.n_desc == N_DEAD) return; // garbage-collected, skip
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if (sym.n_desc == N_BOUNDARY) return; // boundary symbol, skip
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if (sym.ext()) return; // an export lands in its own symtab section, skip
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if (self.symbolIsTemp(sym_loc)) return; // local temp symbol, skip
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var out_sym = sym;
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@ -4157,6 +4244,7 @@ fn writeSymtab(self: *MachO) !SymtabCtx {
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const sym = self.getSymbol(global);
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if (sym.undf()) continue; // import, skip
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if (sym.n_desc == N_DEAD) continue;
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if (sym.n_desc == N_BOUNDARY) continue;
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var out_sym = sym;
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out_sym.n_strx = try self.strtab.insert(gpa, self.getSymbolName(global));
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try exports.append(out_sym);
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@ -4172,6 +4260,7 @@ fn writeSymtab(self: *MachO) !SymtabCtx {
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if (sym.n_strx == 0) continue; // no name, skip
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if (!sym.undf()) continue; // not an import, skip
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if (sym.n_desc == N_DEAD) continue;
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if (sym.n_desc == N_BOUNDARY) continue;
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const new_index = @as(u32, @intCast(imports.items.len));
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var out_sym = sym;
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out_sym.n_strx = try self.strtab.insert(gpa, self.getSymbolName(global));
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@ -4842,6 +4931,55 @@ pub fn getSymbolName(self: *const MachO, sym_with_loc: SymbolWithLoc) []const u8
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}
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}
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const BoundarySymbolKind = enum {
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start,
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stop,
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};
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const SectionBoundarySymbol = struct {
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kind: BoundarySymbolKind,
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segname: []const u8,
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sectname: []const u8,
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};
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pub fn getSectionBoundarySymbol(self: *const MachO, sym_with_loc: SymbolWithLoc) ?SectionBoundarySymbol {
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const sym_name = self.getSymbolName(sym_with_loc);
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if (mem.startsWith(u8, sym_name, "section$")) {
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const trailing = sym_name["section$".len..];
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const kind: BoundarySymbolKind = kind: {
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if (mem.startsWith(u8, trailing, "start$")) break :kind .start;
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if (mem.startsWith(u8, trailing, "stop$")) break :kind .stop;
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return null;
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};
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const names = trailing[@tagName(kind).len + 1 ..];
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const sep_idx = mem.indexOf(u8, names, "$") orelse return null;
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const segname = names[0..sep_idx];
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const sectname = names[sep_idx + 1 ..];
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return .{ .kind = kind, .segname = segname, .sectname = sectname };
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}
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return null;
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}
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const SegmentBoundarySymbol = struct {
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kind: BoundarySymbolKind,
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segname: []const u8,
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};
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pub fn getSegmentBoundarySymbol(self: *const MachO, sym_with_loc: SymbolWithLoc) ?SegmentBoundarySymbol {
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const sym_name = self.getSymbolName(sym_with_loc);
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if (mem.startsWith(u8, sym_name, "segment$")) {
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const trailing = sym_name["segment$".len..];
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const kind: BoundarySymbolKind = kind: {
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if (mem.startsWith(u8, trailing, "start$")) break :kind .start;
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if (mem.startsWith(u8, trailing, "stop$")) break :kind .stop;
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return null;
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};
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const segname = trailing[@tagName(kind).len + 1 ..];
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return .{ .kind = kind, .segname = segname };
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}
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return null;
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}
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/// Returns pointer to the global entry for `name` if one exists.
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pub fn getGlobalPtr(self: *MachO, name: []const u8) ?*SymbolWithLoc {
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const global_index = self.resolver.get(name) orelse return null;
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@ -5137,6 +5275,23 @@ pub fn reportParseError(
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});
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}
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pub fn reportUnresolvedBoundarySymbol(
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self: *MachO,
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sym_name: []const u8,
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comptime format: []const u8,
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args: anytype,
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) error{OutOfMemory}!void {
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const gpa = self.base.allocator;
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try self.misc_errors.ensureUnusedCapacity(gpa, 1);
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var notes = try gpa.alloc(File.ErrorMsg, 1);
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errdefer gpa.free(notes);
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notes[0] = .{ .msg = try std.fmt.allocPrint(gpa, "while resolving {s}", .{sym_name}) };
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self.misc_errors.appendAssumeCapacity(.{
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.msg = try std.fmt.allocPrint(gpa, format, args),
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.notes = notes,
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});
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}
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pub fn reportUndefined(self: *MachO) error{OutOfMemory}!void {
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const gpa = self.base.allocator;
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const count = self.unresolved.count();
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@ -5340,7 +5495,8 @@ pub fn logSymtab(self: *MachO) void {
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for (self.globals.items, 0..) |global, i| {
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const sym = self.getSymbol(global);
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if (sym.undf()) continue;
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if (sym.n_desc == MachO.N_DEAD) continue;
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if (sym.n_desc == N_DEAD) continue;
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if (sym.n_desc == N_BOUNDARY) continue;
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scoped_log.debug(" %{d}: {s} @{x} in sect({d}), {s} (def in object({?}))", .{
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i,
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self.getSymbolName(global),
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@ -5355,7 +5511,8 @@ pub fn logSymtab(self: *MachO) void {
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for (self.globals.items, 0..) |global, i| {
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const sym = self.getSymbol(global);
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if (!sym.undf()) continue;
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if (sym.n_desc == MachO.N_DEAD) continue;
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if (sym.n_desc == N_DEAD) continue;
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if (sym.n_desc == N_BOUNDARY) continue;
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const ord = @divTrunc(sym.n_desc, macho.N_SYMBOL_RESOLVER);
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scoped_log.debug(" %{d}: {s} @{x} in ord({d}), {s}", .{
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i,
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@ -5466,6 +5623,7 @@ pub fn logAtom(self: *MachO, atom_index: Atom.Index, logger: anytype) void {
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pub const base_tag: File.Tag = File.Tag.macho;
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pub const N_DEAD: u16 = @as(u16, @bitCast(@as(i16, -1)));
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pub const N_BOUNDARY: u16 = @as(u16, @bitCast(@as(i16, -2)));
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/// Mode of operation of the linker.
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pub const Mode = enum {
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@ -50,6 +50,7 @@ fn collectRoots(macho_file: *MachO, roots: *AtomTable) !void {
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for (macho_file.globals.items) |global| {
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const sym = macho_file.getSymbol(global);
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if (sym.undf()) continue;
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if (sym.n_desc == MachO.N_BOUNDARY) continue;
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if (global.getFile()) |file| {
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try addRoot(macho_file, roots, file, global);
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