Merge pull request #12940 from danielnachun/patch_prefix2

Binary patching of build prefixes

Library/Homebrew/formula_installer.rb

@@ -1228,6 +1228,14 @@ class FormulaInstaller
     keg = Keg.new(formula.prefix)
     skip_linkage = formula.bottle_specification.skip_relocation?
     keg.replace_placeholders_with_locations tab.changed_files, skip_linkage: skip_linkage
+
+    cellar = formula.bottle_specification.tag_to_cellar(Utils::Bottles.tag)
+    return if [:any, :any_skip_relocation].include?(cellar)
+
+    prefix = Pathname(cellar).parent.to_s
+    return if cellar == HOMEBREW_CELLAR.to_s && prefix == HOMEBREW_PREFIX.to_s
+
+    keg.relocate_build_prefix(keg, prefix, HOMEBREW_PREFIX)
   end
 
   sig { params(output: T.nilable(String)).void }

Library/Homebrew/keg.rb

@@ -529,6 +529,8 @@ class Keg
     elf_files
   end
 
+  def codesign_patched_binary(_binary_file); end
+
   private
 
   def resolve_any_conflicts(dst, dry_run: false, verbose: false, overwrite: false)

Library/Homebrew/keg_relocate.rb

@@ -165,6 +165,45 @@ class Keg
     changed_files
   end
 
+  def relocate_build_prefix(keg, old_prefix, new_prefix)
+    each_unique_file_matching(old_prefix) do |file|
+      # Skip files which are not binary, as they do not need null padding.
+      next unless keg.binary_file?(file)
+
+      # Skip sharballs, which appear to break if patched.
+      next if file.text_executable?
+
+      # Split binary by null characters into array and substitute new prefix for old prefix.
+      # Null padding is added if the new string is too short.
+      file.ensure_writable do
+        binary = File.binread file
+        odebug "Replacing build prefix in: #{file}"
+        binary_strings = binary.split(/#{NULL_BYTE}/o, -1)
+        match_indices = binary_strings.each_index.select { |i| binary_strings[i].include?(old_prefix) }
+
+        # Only perform substitution on strings which match prefix regex.
+        match_indices.each do |i|
+          s = binary_strings[i]
+          binary_strings[i] = s.gsub(old_prefix, new_prefix)
+                               .ljust(s.size, NULL_BYTE)
+        end
+
+        # Rejoin strings by null bytes.
+        patched_binary = binary_strings.join(NULL_BYTE)
+        if patched_binary.size != binary.size
+          raise <<~EOS
+            Patching failed!  Original and patched binary sizes do not match.
+            Original size: #{binary.size}
+            Patched size: #{patched_binary.size}
+          EOS
+        end
+
+        file.atomic_write patched_binary
+      end
+      codesign_patched_binary(file)
+    end
+  end
+
   def detect_cxx_stdlibs(_options = {})
     []
   end

Library/Homebrew/software_spec.rb

@@ -473,6 +473,8 @@ class Bottle
 end
 
 class BottleSpecification
+  RELOCATABLE_CELLARS = [:any, :any_skip_relocation].freeze
+
   extend T::Sig
 
   attr_rw :rebuild
@@ -518,12 +520,15 @@ class BottleSpecification
   def compatible_locations?(tag: Utils::Bottles.tag)
     cellar = tag_to_cellar(tag)
 
-    return true if [:any, :any_skip_relocation].include?(cellar)
+    return true if RELOCATABLE_CELLARS.include?(cellar)
 
     prefix = Pathname(cellar).parent.to_s
 
-    compatible_cellar = cellar == HOMEBREW_CELLAR.to_s
-    compatible_prefix = prefix == HOMEBREW_PREFIX.to_s
+    cellar_relocatable = cellar.size >= HOMEBREW_CELLAR.to_s.size && ENV["HOMEBREW_RELOCATE_BUILD_PREFIX"]
+    prefix_relocatable = prefix.size >= HOMEBREW_PREFIX.to_s.size && ENV["HOMEBREW_RELOCATE_BUILD_PREFIX"]
+
+    compatible_cellar = cellar == HOMEBREW_CELLAR.to_s || cellar_relocatable
+    compatible_prefix = prefix == HOMEBREW_PREFIX.to_s || prefix_relocatable
 
     compatible_cellar && compatible_prefix
   end

Library/Homebrew/test/keg_relocate/binary_relocation_spec.rb

@@ -0,0 +1,44 @@
+# typed: false
+# frozen_string_literal: true
+
+require "keg_relocate"
+
+describe Keg do
+  subject(:keg) { described_class.new(HOMEBREW_CELLAR/"foo/1.0.0") }
+
+  let(:dir) { HOMEBREW_CELLAR/"foo/1.0.0" }
+  let(:newdir) { HOMEBREW_CELLAR/"foo" }
+  let(:binary_file) { dir/"file.bin" }
+
+  before do
+    dir.mkpath
+  end
+
+  def setup_binary_file
+    binary_file.atomic_write <<~EOS
+      \x00#{dir}\x00
+    EOS
+  end
+
+  describe "#relocate_build_prefix" do
+    specify "replace prefix in binary files" do
+      setup_binary_file
+
+      keg.relocate_build_prefix(keg, dir, newdir)
+
+      old_prefix_matches = Set.new
+      keg.each_unique_file_matching(dir) do |file|
+        old_prefix_matches << file
+      end
+
+      expect(old_prefix_matches.size).to eq 0
+
+      new_prefix_matches = Set.new
+      keg.each_unique_file_matching(newdir) do |file|
+        new_prefix_matches << file
+      end
+
+      expect(new_prefix_matches.size).to eq 1
+    end
+  end
+end