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macho: write out stubs for new externs only

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This commit is contained in:
Jakub Konka
2021-01-08 22:26:18 +01:00
parent 2f7cd71193
commit 44a052a65f
2 changed files with 64 additions and 51 deletions
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30
src/codegen.zig
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@@ -1862,18 +1862,28 @@ fn Function(comptime arch: std.Target.Cpu.Arch) type {
} else if (func_value.castTag(.extern_fn)) |func_payload| {
const decl = func_payload.data;
const decl_name = try std.fmt.allocPrint(self.bin_file.allocator, "_{s}", .{decl.name});
defer self.bin_file.allocator.free(decl_name);
const name = try macho_file.makeString(decl_name);
const symbol = macho_file.undef_symbols.items.len;
try macho_file.undef_symbols.append(self.bin_file.allocator, .{
.n_strx = name,
.n_type = std.macho.N_UNDF | std.macho.N_EXT,
.n_sect = 0,
.n_desc = std.macho.REFERENCE_FLAG_UNDEFINED_NON_LAZY | std.macho.N_SYMBOL_RESOLVER,
.n_value = 0,
});
const exists: bool = macho_file.externs.contains(decl_name);
const symbol: u32 = blk: {
if (macho_file.externs.get(decl_name)) |index| {
self.bin_file.allocator.free(decl_name);
break :blk index;
} else {
const extern_index = @intCast(u32, macho_file.undef_symbols.items.len - 1); // TODO
try macho_file.externs.putNoClobber(self.bin_file.allocator, decl_name, extern_index);
const name = try macho_file.makeString(decl_name);
try macho_file.undef_symbols.append(self.bin_file.allocator, .{
.n_strx = name,
.n_type = std.macho.N_UNDF | std.macho.N_EXT,
.n_sect = 0,
.n_desc = std.macho.REFERENCE_FLAG_UNDEFINED_NON_LAZY | std.macho.N_SYMBOL_RESOLVER,
.n_value = 0,
});
break :blk extern_index;
}
};
try macho_file.stub_fixups.append(self.bin_file.allocator, .{
.symbol = symbol,
.exists = exists,
.start = self.code.items.len,
.len = 4,
});

85
src/link/MachO.zig
View File

@@ -167,9 +167,11 @@ last_text_block: ?*TextBlock = null,
pie_fixups: std.ArrayListUnmanaged(PieFixup) = .{},
stub_fixups: std.ArrayListUnmanaged(StubFixup) = .{},
externs: std.StringHashMapUnmanaged(u32) = .{},
pub const StubFixup = struct {
symbol: usize,
symbol: u32,
exists: bool,
start: usize,
len: usize,
};
@@ -1263,56 +1265,57 @@ pub fn updateDecl(self: *MachO, module: *Module, decl: *Module.Decl) !void {
const stub_h = &text_segment.sections.items[self.stub_helper_section_index.?];
const data_segment = &self.load_commands.items[self.data_segment_cmd_index.?].Segment;
const la_ptr = &data_segment.sections.items[self.la_symbol_ptr_section_index.?];
for (self.stub_fixups.items) |fixup, idx| {
const i = @intCast(u32, idx);
for (self.stub_fixups.items) |fixup| {
// TODO increment offset for stub writing
const stub_addr = stubs.addr + i * stubs.reserved2;
const stub_addr = stubs.addr + fixup.symbol * stubs.reserved2;
const text_addr = symbol.n_value + fixup.start;
const displacement = @intCast(u32, stub_addr - text_addr);
var placeholder = code_buffer.items[fixup.start..][0..fixup.len];
mem.writeIntSliceLittle(u32, placeholder, aarch64.Instruction.bl(@intCast(i28, displacement)).toU32());
const end = stub_h.addr + self.next_stub_helper_off.? - stub_h.offset;
var buf: [@sizeOf(u64)]u8 = undefined;
mem.writeIntLittle(u64, &buf, end);
try self.base.file.?.pwriteAll(&buf, la_ptr.offset + i * @sizeOf(u64));
if (!fixup.exists) {
const end = stub_h.addr + self.next_stub_helper_off.? - stub_h.offset;
var buf: [@sizeOf(u64)]u8 = undefined;
mem.writeIntLittle(u64, &buf, end);
try self.base.file.?.pwriteAll(&buf, la_ptr.offset + fixup.symbol * @sizeOf(u64));
const la_ptr_addr = la_ptr.addr + i * @sizeOf(u64);
const displacement2 = la_ptr_addr - stub_addr;
var ccode: [2 * @sizeOf(u32)]u8 = undefined;
mem.writeIntLittle(u32, ccode[0..4], aarch64.Instruction.ldr(.x16, .{
.literal = @intCast(u19, displacement2 / 4),
}).toU32());
mem.writeIntLittle(u32, ccode[4..8], aarch64.Instruction.br(.x16).toU32());
try self.base.file.?.pwriteAll(&ccode, stubs.offset + i * stubs.reserved2);
const la_ptr_addr = la_ptr.addr + fixup.symbol * @sizeOf(u64);
const displacement2 = la_ptr_addr - stub_addr;
var ccode: [2 * @sizeOf(u32)]u8 = undefined;
mem.writeIntLittle(u32, ccode[0..4], aarch64.Instruction.ldr(.x16, .{
.literal = @intCast(u19, displacement2 / 4),
}).toU32());
mem.writeIntLittle(u32, ccode[4..8], aarch64.Instruction.br(.x16).toU32());
try self.base.file.?.pwriteAll(&ccode, stubs.offset + fixup.symbol * stubs.reserved2);
const displacement3 = @intCast(i64, stub_h.addr) - @intCast(i64, end + 4);
var cccode: [3 * @sizeOf(u32)]u8 = undefined;
mem.writeIntLittle(u32, cccode[0..4], aarch64.Instruction.ldr(.w16, .{
.literal = 0x2,
}).toU32());
mem.writeIntLittle(u32, cccode[4..8], aarch64.Instruction.b(@intCast(i28, displacement3)).toU32());
mem.writeIntLittle(u32, cccode[8..12], i * 0xd);
try self.base.file.?.pwriteAll(&cccode, self.next_stub_helper_off.?);
self.next_stub_helper_off = self.next_stub_helper_off.? + 3 * @sizeOf(u32);
const displacement3 = @intCast(i64, stub_h.addr) - @intCast(i64, end + 4);
var cccode: [3 * @sizeOf(u32)]u8 = undefined;
mem.writeIntLittle(u32, cccode[0..4], aarch64.Instruction.ldr(.w16, .{
.literal = 0x2,
}).toU32());
mem.writeIntLittle(u32, cccode[4..8], aarch64.Instruction.b(@intCast(i28, displacement3)).toU32());
mem.writeIntLittle(u32, cccode[8..12], fixup.symbol * 0xd);
try self.base.file.?.pwriteAll(&cccode, self.next_stub_helper_off.?);
self.next_stub_helper_off = self.next_stub_helper_off.? + 3 * @sizeOf(u32);
try self.rebase_info_table.symbols.append(self.base.allocator, .{
.segment = 3,
.offset = i * stubs.reserved2,
});
self.rebase_info_dirty = true;
try self.rebase_info_table.symbols.append(self.base.allocator, .{
.segment = 3,
.offset = fixup.symbol * stubs.reserved2,
});
self.rebase_info_dirty = true;
const sym = self.undef_symbols.items[fixup.symbol];
const name_str = self.getString(sym.n_strx);
var name = try self.base.allocator.alloc(u8, name_str.len);
mem.copy(u8, name, name_str);
try self.lazy_binding_info_table.symbols.append(self.base.allocator, .{
.segment = 3,
.offset = i * @sizeOf(u64),
.dylib_ordinal = 1,
.name = name,
});
self.lazy_binding_info_dirty = true;
const sym = self.undef_symbols.items[fixup.symbol + 1];
const name_str = self.getString(sym.n_strx);
var name = try self.base.allocator.alloc(u8, name_str.len);
mem.copy(u8, name, name_str);
try self.lazy_binding_info_table.symbols.append(self.base.allocator, .{
.segment = 3,
.offset = fixup.symbol * @sizeOf(u64),
.dylib_ordinal = 1,
.name = name,
});
self.lazy_binding_info_dirty = true;
}
}
self.stub_fixups.shrinkRetainingCapacity(0);