zig

commit 705cd64080a5555425de7d13a9fbc6c19af65bde (tree)
parent 8bd0687713855a41578605a3e1a6c9686a702bfe
Author: Jakub Konka <kubkon@jakubkonka.com>
Date:   Fri, 27 Aug 2021 10:45:56 +0200

macho: preactively add zerofill sections in correct order

The required order on macOS nowadays is:
* __data
* __thread_vars
* __thread_data
* __thread_bss
* __bss

Diffstat:
M
src/link/MachO.zig
 | 
106
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-

1 file changed, 105 insertions(+), 1 deletion(-)
diff --git a/src/link/MachO.zig b/src/link/MachO.zig
@@ -780,7 +780,7 @@ pub fn flush(self: *MachO, comp: *Compilation) !void {
             }
 
             try self.parseTextBlocks();
-            try self.sortSections();
+            // try self.sortSections();
             try self.allocateTextSegment();
             try self.allocateDataConstSegment();
             try self.allocateDataSegment();
@@ -4163,6 +4163,110 @@ pub fn populateMissingMetadata(self: *MachO) !void {
         self.load_commands_dirty = true;
     }
 
+    if (self.tlv_section_index == null) {
+        const data_segment = &self.load_commands.items[self.data_segment_cmd_index.?].Segment;
+        self.tlv_section_index = @intCast(u16, data_segment.sections.items.len);
+
+        const needed_size = @sizeOf(u64) * self.base.options.symbol_count_hint;
+        const off = data_segment.findFreeSpace(needed_size, @alignOf(u64), null);
+        assert(off + needed_size <= data_segment.inner.fileoff + data_segment.inner.filesize); // TODO Must expand __DATA segment.
+
+        log.debug("found __thread_vars section free space 0x{x} to 0x{x}", .{ off, off + needed_size });
+
+        try data_segment.addSection(self.base.allocator, "__thread_vars", .{
+            .addr = data_segment.inner.vmaddr + off - data_segment.inner.fileoff,
+            .size = needed_size,
+            .offset = @intCast(u32, off),
+            .@"align" = 3, // 2^3 = @sizeOf(u64)
+            .flags = macho.S_THREAD_LOCAL_VARIABLES,
+        });
+        const match = MatchingSection{
+            .seg = self.data_segment_cmd_index.?,
+            .sect = self.tlv_section_index.?,
+        };
+        _ = try self.section_ordinals.getOrPut(self.base.allocator, match);
+        try self.block_free_lists.putNoClobber(self.base.allocator, match, .{});
+        self.load_commands_dirty = true;
+    }
+
+    if (self.tlv_data_section_index == null) {
+        const data_segment = &self.load_commands.items[self.data_segment_cmd_index.?].Segment;
+        self.tlv_data_section_index = @intCast(u16, data_segment.sections.items.len);
+
+        const needed_size = @sizeOf(u64) * self.base.options.symbol_count_hint;
+        const off = data_segment.findFreeSpace(needed_size, @alignOf(u64), null);
+        assert(off + needed_size <= data_segment.inner.fileoff + data_segment.inner.filesize); // TODO Must expand __DATA segment.
+
+        log.debug("found __thread_data section free space 0x{x} to 0x{x}", .{ off, off + needed_size });
+
+        try data_segment.addSection(self.base.allocator, "__thread_data", .{
+            .addr = data_segment.inner.vmaddr + off - data_segment.inner.fileoff,
+            .size = needed_size,
+            .offset = @intCast(u32, off),
+            .@"align" = 3, // 2^3 = @sizeOf(u64)
+            .flags = macho.S_THREAD_LOCAL_REGULAR,
+        });
+        const match = MatchingSection{
+            .seg = self.data_segment_cmd_index.?,
+            .sect = self.tlv_data_section_index.?,
+        };
+        _ = try self.section_ordinals.getOrPut(self.base.allocator, match);
+        try self.block_free_lists.putNoClobber(self.base.allocator, match, .{});
+        self.load_commands_dirty = true;
+    }
+
+    if (self.tlv_bss_section_index == null) {
+        const data_segment = &self.load_commands.items[self.data_segment_cmd_index.?].Segment;
+        self.tlv_bss_section_index = @intCast(u16, data_segment.sections.items.len);
+
+        const needed_size = @sizeOf(u64) * self.base.options.symbol_count_hint;
+        const off = data_segment.findFreeSpace(needed_size, @alignOf(u64), null);
+        assert(off + needed_size <= data_segment.inner.fileoff + data_segment.inner.filesize); // TODO Must expand __DATA segment.
+
+        log.debug("found __thread_bss section free space 0x{x} to 0x{x}", .{ off, off + needed_size });
+
+        try data_segment.addSection(self.base.allocator, "__thread_bss", .{
+            .addr = data_segment.inner.vmaddr + off - data_segment.inner.fileoff,
+            .size = needed_size,
+            .offset = @intCast(u32, off),
+            .@"align" = 3, // 2^3 = @sizeOf(u64)
+            .flags = macho.S_THREAD_LOCAL_ZEROFILL,
+        });
+        const match = MatchingSection{
+            .seg = self.data_segment_cmd_index.?,
+            .sect = self.tlv_bss_section_index.?,
+        };
+        _ = try self.section_ordinals.getOrPut(self.base.allocator, match);
+        try self.block_free_lists.putNoClobber(self.base.allocator, match, .{});
+        self.load_commands_dirty = true;
+    }
+
+    if (self.bss_section_index == null) {
+        const data_segment = &self.load_commands.items[self.data_segment_cmd_index.?].Segment;
+        self.bss_section_index = @intCast(u16, data_segment.sections.items.len);
+
+        const needed_size = @sizeOf(u64) * self.base.options.symbol_count_hint;
+        const off = data_segment.findFreeSpace(needed_size, @alignOf(u64), null);
+        assert(off + needed_size <= data_segment.inner.fileoff + data_segment.inner.filesize); // TODO Must expand __DATA segment.
+
+        log.debug("found __bss section free space 0x{x} to 0x{x}", .{ off, off + needed_size });
+
+        try data_segment.addSection(self.base.allocator, "__bss", .{
+            .addr = data_segment.inner.vmaddr + off - data_segment.inner.fileoff,
+            .size = 0,
+            .offset = @intCast(u32, off),
+            .@"align" = 3, // 2^3 = @sizeOf(u64)
+            .flags = macho.S_ZEROFILL,
+        });
+        const match = MatchingSection{
+            .seg = self.data_segment_cmd_index.?,
+            .sect = self.bss_section_index.?,
+        };
+        _ = try self.section_ordinals.getOrPut(self.base.allocator, match);
+        try self.block_free_lists.putNoClobber(self.base.allocator, match, .{});
+        self.load_commands_dirty = true;
+    }
+
     if (self.linkedit_segment_cmd_index == null) {
         self.linkedit_segment_cmd_index = @intCast(u16, self.load_commands.items.len);
         const address_and_offset = self.nextSegmentAddressAndOffset();