stage2 macho: generate a code sig (not valid yet)

1 files changed, 68 insertions, 18 deletions

diff --git a/src/link/MachO/CodeSignature.zig b/src/link/MachO/CodeSignature.zig
index 25b1e9e9ff..813993d02c 100644
--- a/src/link/MachO/CodeSignature.zig
+++ b/src/link/MachO/CodeSignature.zig
@@ -7,19 +7,24 @@ const macho = std.macho;
 const mem = std.mem;
 const testing = std.testing;
 const Allocator = mem.Allocator;
+const Sha256 = std.crypto.hash.sha2.Sha256;
 
 const MachO = @import("../MachO.zig");
 
-const Blob = struct {
+const hash_size: u8 = 32;
+const page_size: u16 = 0x1000;
+
+const CodeDirectory = struct {
     inner: macho.CodeDirectory,
     data: std.ArrayListUnmanaged(u8) = .{},
 
-    fn size(self: Blob) u32 {
+    fn size(self: CodeDirectory) u32 {
         return self.inner.length;
     }
 
-    fn write(self: Blob, buffer: []u8) void {
+    fn write(self: CodeDirectory, buffer: []u8) void {
         assert(buffer.len >= self.inner.length);
+
         mem.writeIntBig(u32, buffer[0..4], self.inner.magic);
         mem.writeIntBig(u32, buffer[4..8], self.inner.length);
         mem.writeIntBig(u32, buffer[8..12], self.inner.version);
@@ -29,10 +34,10 @@ const Blob = struct {
         mem.writeIntBig(u32, buffer[24..28], self.inner.nSpecialSlots);
         mem.writeIntBig(u32, buffer[28..32], self.inner.nCodeSlots);
         mem.writeIntBig(u32, buffer[32..36], self.inner.codeLimit);
-        mem.writeIntBig(u8, buffer[36..37], self.inner.hashSize);
-        mem.writeIntBig(u8, buffer[37..38], self.inner.hashType);
-        mem.writeIntBig(u8, buffer[38..39], self.inner.platform);
-        mem.writeIntBig(u8, buffer[39..40], self.inner.pageSize);
+        buffer[36] = self.inner.hashSize;
+        buffer[37] = self.inner.hashType;
+        buffer[38] = self.inner.platform;
+        buffer[39] = self.inner.pageSize;
         mem.writeIntBig(u32, buffer[40..44], self.inner.spare2);
         mem.writeIntBig(u32, buffer[44..48], self.inner.scatterOffset);
         mem.writeIntBig(u32, buffer[48..52], self.inner.teamOffset);
@@ -41,6 +46,8 @@ const Blob = struct {
         mem.writeIntBig(u64, buffer[64..72], self.inner.execSegBase);
         mem.writeIntBig(u64, buffer[72..80], self.inner.execSegLimit);
         mem.writeIntBig(u64, buffer[80..88], self.inner.execSegFlags);
+
+        mem.copy(u8, buffer[88..], self.data.items);
     }
 };
 
@@ -50,7 +57,7 @@ inner: macho.SuperBlob = .{
     .length = @sizeOf(macho.SuperBlob),
     .count = 0,
 },
-blob: ?Blob = null,
+cdir: ?CodeDirectory = null,
 
 pub fn init(alloc: *Allocator) CodeSignature {
     return .{
@@ -60,10 +67,14 @@ pub fn init(alloc: *Allocator) CodeSignature {
 
 pub fn calcAdhocSignature(self: *CodeSignature, bin_file: *const MachO) !void {
     const text_segment = bin_file.load_commands.items[bin_file.text_segment_cmd_index.?].Segment;
+    const data_segment = bin_file.load_commands.items[bin_file.data_segment_cmd_index.?].Segment;
+    const linkedit_segment = bin_file.load_commands.items[bin_file.linkedit_segment_cmd_index.?].Segment;
+    const symtab = bin_file.load_commands.items[bin_file.symtab_cmd_index.?].Symtab;
+
     const execSegBase: u64 = text_segment.fileoff;
     const execSegLimit: u64 = text_segment.filesize;
-    const execSegFlags: u64 = text_segment.flags;
-    var blob = Blob{
+    const execSegFlags: u64 = if (bin_file.base.options.output_mode == .Exe) macho.CS_EXECSEG_MAIN_BINARY else 0;
+    var cdir = CodeDirectory{
         .inner = .{
             .magic = macho.CSMAGIC_CODEDIRECTORY,
             .length = @sizeOf(macho.CodeDirectory),
@@ -74,10 +85,10 @@ pub fn calcAdhocSignature(self: *CodeSignature, bin_file: *const MachO) !void {
             .nSpecialSlots = 0,
             .nCodeSlots = 0,
             .codeLimit = 0,
-            .hashSize = 0,
-            .hashType = 0,
+            .hashSize = hash_size,
+            .hashType = macho.CS_HASHTYPE_SHA256,
             .platform = 0,
-            .pageSize = 0,
+            .pageSize = @truncate(u8, std.math.log2(page_size)),
             .spare2 = 0,
             .scatterOffset = 0,
             .teamOffset = 0,
@@ -88,9 +99,48 @@ pub fn calcAdhocSignature(self: *CodeSignature, bin_file: *const MachO) !void {
             .execSegFlags = execSegFlags,
         },
     };
-    self.inner.length += @sizeOf(macho.BlobIndex) + blob.size();
+
+    const file_size = symtab.stroff + symtab.strsize;
+    const total_pages = mem.alignForward(file_size, page_size) / page_size;
+    log.debug("Total file size: {}; total number of pages: {}\n", .{ file_size, total_pages });
+
+    var hash: [hash_size]u8 = undefined;
+    var buffer = try bin_file.base.allocator.alloc(u8, page_size);
+    defer bin_file.base.allocator.free(buffer);
+    const macho_file = bin_file.base.file.?;
+
+    const id = bin_file.base.options.emit.?.sub_path;
+    try cdir.data.ensureCapacity(self.alloc, total_pages * hash_size + id.len + 1);
+
+    // 1. Save the identifier and update offsets
+    cdir.inner.identOffset = cdir.inner.length;
+    cdir.data.appendSliceAssumeCapacity(id);
+    cdir.data.appendAssumeCapacity(0);
+
+    // 2. Calculate hash for each page (in file) and write it to the buffer
+    // TODO figure out how we can cache several hashes since we won't update
+    // every page during incremental linking
+    cdir.inner.hashOffset = cdir.inner.identOffset + @intCast(u32, id.len) + 1;
+    var i: usize = 0;
+    while (i < total_pages) : (i += 1) {
+        const fstart = i * page_size;
+        const fsize = if (fstart + page_size > file_size) file_size - fstart else page_size;
+        const len = try macho_file.preadAll(buffer, fstart);
+        assert(fsize <= len);
+
+        Sha256.hash(buffer[0..fsize], &hash, .{});
+        log.debug("Calculated hash for page 0x{x}-0x{x}: 0x{x}\n", .{ fstart, fstart + fsize, hash[0..] });
+
+        cdir.data.appendSliceAssumeCapacity(hash[0..]);
+        cdir.inner.nCodeSlots += 1;
+    }
+
+    // 3. Update CodeDirectory length
+    cdir.inner.length += @intCast(u32, cdir.data.items.len);
+
+    self.inner.length += @sizeOf(macho.BlobIndex) + cdir.size();
     self.inner.count = 1;
-    self.blob = blob;
+    self.cdir = cdir;
 }
 
 pub fn size(self: CodeSignature) u32 {
@@ -102,12 +152,12 @@ pub fn write(self: CodeSignature, buffer: []u8) void {
     self.writeHeader(buffer);
     const offset: u32 = @sizeOf(macho.SuperBlob) + @sizeOf(macho.BlobIndex);
     writeBlobIndex(macho.CSSLOT_CODEDIRECTORY, offset, buffer[@sizeOf(macho.SuperBlob)..]);
-    self.blob.?.write(buffer[offset..]);
+    self.cdir.?.write(buffer[offset..]);
 }
 
 pub fn deinit(self: *CodeSignature) void {
-    if (self.blob) |*b| {
-        b.data.deinit(self.alloc);
+    if (self.cdir) |*cdir| {
+        cdir.data.deinit(self.alloc);
     }
 }