Sergey,

thanks for review. Fixes applied and force-pushed to the same branch.

Sergey

Hi, Sergey!
Thanks for the patch!
Please consider my comments below.

May we add the test [1] to verify that there will be no regression in the
future?

This "test" was for a FAT binary generated by LuaJIT.

With backported patches, FAT (aka Universal Binary) support is gone.

mach-O header is checked by tests in proposed patch.

On 05.07.24, Sergey Bronnikov wrote:

Reported by Sergey Bronnikov.

(cherry picked from commit 7110b935672489afd6ba3eef3e5139d2f3bd05b6)

Previously, LuaJIT generated Mach-O FAT object files for ARM and
ARM64 on macOS. The patch removes support of 32-bit ARM and
FAT object files and now LuaJIT generate Mach-O object files for
ARM64.

I suppose we should mention that no x86/x86_64 objects are generated
now.

$ ./build/gc64/src/luajit -b -o osx -a arm64 empty.lua empty.o
$ file empty.o
empty.o: Mach-O 64-bit arm64 object
$ ./build/gc64/src/luajit -b -o osx -a x64 empty.lua empty.o
$ file empty.o
empty.o: Mach-O 64-bit x86_64 object
$

Anyway, commit message has been updated.

Sergey Bronnikov:
* added the description and the trimmed the test for the problem

Part of tarantool/tarantool#10199
---
 src/jit/bcsave.lua                            | 155 ++-------
 ...-865-cross-generation-mach-o-file.test.lua | 294 +++---------------
 2 files changed, 70 insertions(+), 379 deletions(-)

diff --git a/src/jit/bcsave.lua b/src/jit/bcsave.lua
index 26ec29c6..61953c2d 100644
--- a/src/jit/bcsave.lua
+++ b/src/jit/bcsave.lua

<snipped>

diff --git a/test/tarantool-tests/lj-865-cross-generation-mach-o-file.test.lua b/test/tarantool-tests/lj-865-cross-generation-mach-o-file.test.lua
index f008f3bd..6a58de95 100644
--- a/test/tarantool-tests/lj-865-cross-generation-mach-o-file.test.lua
+++ b/test/tarantool-tests/lj-865-cross-generation-mach-o-file.test.lua
@@ -3,109 +3,11 @@ local test = tap.test('lj-865-cross-generation-mach-o-file')
 local utils = require('utils')
 local ffi = require('ffi')
 
-test:plan(2)
+test:plan(1)
 
 -- The test creates an object file in Mach-O format with LuaJIT
 -- bytecode and checks the validity of the object file fields.
---
--- The original problem is reproduced with LuaJIT, which is built
--- with enabled AVX512F instructions. The support for AVX512F
--- could be checked in `/proc/cpuinfo` on Linux and
--- `sysctl hw.optional.avx512f` on Mac. AVX512F must be
--- implicitly enabled in a C compiler by passing a CPU codename.
--- Please take a look at the GCC Online Documentation [1] for
--- available CPU codenames. Also, see the Wikipedia for CPUs with
--- AVX-512 support [2].
--- Execute command below to detect the CPU codename:
--- `gcc -march=native -Q --help=target | grep march`.
---
--- 1. https://gcc.gnu.org/onlinedocs/gcc/x86-Options.html
--- 2. https://en.wikipedia.org/wiki/AVX-512#CPUs_with_AVX-512
---
--- Manual steps for reproducing are the following:
---
--- $ CC=gcc TARGET_CFLAGS='skylake-avx512' cmake -S . -B build
--- $ cmake --build build --parallel
--- $ echo > test.lua
--- $ LUA_PATH="src/?.lua;;" luajit -b -o osx -a arm test.lua test.o
--- $ file test.o
--- empty.o: DOS executable (block device driver)
 
--- LuaJIT can generate so called Universal Binary with Lua
--- bytecode. The Universal Binary format is a format for
--- executable files that run natively on hardware platforms with
--- different hardware architectures. This concept is more
--- generally known as a fat binary.
---
--- The format of the Mach-O is described in the document
--- "OS X ABI Mach-O File Format Reference", published by Apple
--- company. The copy of the (now removed) official documentation
--- can be found here [1]. Yet another source of truth is
--- XNU headers, see the definition of C-structures in:
--- [2] (`nlist_64`), [3] (`fat_arch` and `fat_header`).
---
--- There is a good visual representation of Universal Binary
--- in "Mac OS X Internals" book (pages 67-68) [5] and in the [6].
--- Below is the schematic structure of Universal Binary, which
--- includes two executables for PowerPC and Intel i386 (omitted):
---
---   0x0000000 ---------------------------------------
---             |
--- struct      | 0xcafebabe  FAT_MAGIC                 magic
--- fat_header  | -------------------------------------
---             | 0x00000003                            nfat_arch
---             ---------------------------------------
---             | 0x00000012  CPU_TYPE_POWERPC          cputype
---             | -------------------------------------
---             | 0x00000000  CPU_SUBTYPE_POWERPC_ALL   cpusubtype
--- struct      | -------------------------------------
--- fat_arch    | 0x00001000  4096 bytes                offset
---             | -------------------------------------
---             | 0x00004224  16932 bytes               size
---             | -------------------------------------
---             | 0x0000000c  2^12 = 4096 bytes         align
---             ---------------------------------------
---             ---------------------------------------
---             | 0x00000007  CPU_TYPE_I386             cputype
---             | -------------------------------------
---             | 0x00000003  CPU_SUBTYPE_I386_ALL      cpusubtype
--- struct      | -------------------------------------
--- fat_arch    | 0x00006000  24576 bytes               offset
---             | -------------------------------------
---             | 0x0000292c  10540 bytes               size
---             | -------------------------------------
---             | 0x0000000c  2^12 = 4096 bytes         align
---             ---------------------------------------
---               Unused
--- 0x00001000  ---------------------------------------
---             | 0xfeedface  MH_MAGIC                  magic
---             | ------------------------------------
---             | 0x00000012  CPU_TYPE_POWERPC          cputype
---             | ------------------------------------
--- struct      | 0x00000000  CPU_SUBTYPE_POWERPC_ALL   cpusubtype
--- mach_header | ------------------------------------
---             | 0x00000002  MH_EXECUTE                filetype
---             | ------------------------------------
---             | 0x0000000b  10 load commands          ncmds
---             | ------------------------------------
---             | 0x00000574  1396 bytes                sizeofcmds
---             | ------------------------------------
---             | 0x00000085  DYLDLINK TWOLEVEL         flags
---             --------------------------------------
---               Load commands
---             ---------------------------------------
---               Data
---             ---------------------------------------
---
---               < x86 executable >
---
--- 1. https://github.com/aidansteele/osx-abi-macho-file-format-reference
--- 2. https://github.com/apple-oss-distributions/xnu/blob/xnu-10002.1.13/EXTERNAL_HEADERS/mach-o/nlist.h
--- 3. https://github.com/apple-oss-distributions/xnu/blob/xnu-10002.1.13/EXTERNAL_HEADERS/mach-o/fat.h
--- 4. https://developer.apple.com/documentation/apple-silicon/addressing-architectural-differences-in-your-macos-code
--- 5. https://reverseengineering.stackexchange.com/a/6357/46029
--- 6. http://formats.kaitai.io/mach_o/index.html

I prefer to keep the non-FAT part of this comment since it is very
useful.

reverted:

diff --git a/build/src/luajit b/build/src/luajit
deleted file mode 100755
index bd10e09a..00000000
Binary files a/build/src/luajit and /dev/null differ
diff --git a/test/tarantool-tests/lj-865-cross-generation-mach-o-file.test.lua b/test/tarantool-tests/lj-865-cross-generation-mach-o-file.test.lua
index 6a58de95..f9ca6e38 100644
--- a/test/tarantool-tests/lj-865-cross-generation-mach-o-file.test.lua
+++ b/test/tarantool-tests/lj-865-cross-generation-mach-o-file.test.lua
@@ -68,6 +68,62 @@ end
 
 -- Parses a buffer in the Mach-O format and returns its fields
 -- in a table.
+-- The test creates an object file in Mach-O format with LuaJIT
+-- bytecode and checks the validity of the object file fields.
+---
+--- The original problem is reproduced with LuaJIT, which is built
+--- with enabled AVX512F instructions. The support for AVX512F
+--- could be checked in `/proc/cpuinfo` on Linux and
+--- `sysctl hw.optional.avx512f` on Mac. AVX512F must be
+--- implicitly enabled in a C compiler by passing a CPU codename.
+--- Please take a look at the GCC Online Documentation [1] for
+--- available CPU codenames. Also, see the Wikipedia for CPUs with
+--- AVX-512 support [2].
+--- Execute command below to detect the CPU codename:
+--- `gcc -march=native -Q --help=target | grep march`.
+---
+--- 1. https://gcc.gnu.org/onlinedocs/gcc/x86-Options.html
+--- 2. https://en.wikipedia.org/wiki/AVX-512#CPUs_with_AVX-512
+---
+--- Manual steps for reproducing are the following:
+---
+--- $ CC=gcc TARGET_CFLAGS='skylake-avx512' cmake -S . -B build
+--- $ cmake --build build --parallel
+--- $ echo > test.lua
+--- $ LUA_PATH="src/?.lua;;" luajit -b -o osx -a arm test.lua test.o
+--- $ file test.o
+--- empty.o: DOS executable (block device driver)
+
+--- The format of the Mach-O is described in the document
+--- "OS X ABI Mach-O File Format Reference", published by Apple
+--- company. The copy of the (now removed) official documentation
+--- can be found here [1]. There is a good visual representation
+--- of Mach-O format in "Mac OS X Internals" book (pages 67-68)
+--- [2] and in the [3].
+--
+--- 0x0000000  ---------------------------------------
+---             | 0xfeedface  MH_MAGIC                  magic
+---             | ------------------------------------
+---             | 0x00000012  CPU_TYPE_POWERPC          cputype
+---             | ------------------------------------
+--- struct      | 0x00000000  CPU_SUBTYPE_POWERPC_ALL   cpusubtype
+--- mach_header | ------------------------------------
+---             | 0x00000002  MH_EXECUTE                filetype
+---             | ------------------------------------
+---             | 0x0000000b  10 load commands          ncmds
+---             | ------------------------------------
+---             | 0x00000574  1396 bytes                sizeofcmds
+---             | ------------------------------------
+---             | 0x00000085  DYLDLINK TWOLEVEL         flags
+---             --------------------------------------
+---               Load commands
+---             ---------------------------------------
+---               Data
+---             ---------------------------------------
+---
+--- 1. https://github.com/aidansteele/osx-abi-macho-file-format-reference
+--- 2. https://reverseengineering.stackexchange.com/a/6357/46029
+--- 3. http://formats.kaitai.io/mach_o/index.html
 local function read_mach_o(buf, hw_arch)
   local is64 = hw_arch == 'arm64'
 

---
 -- Using the same declarations as defined in <src/jit/bcsave.lua>.
 ffi.cdef[[

<snipped>

 local function create_obj_file(name, arch)
@@ -212,108 +66,37 @@ local function create_obj_file(name, arch)
   return mach_o_path
 end
 
--- Parses a buffer in the Mach-O format and returns the FAT magic
--- number and `nfat_arch`.
+-- Parses a buffer in the Mach-O format and returns its fields
+-- in a table.
 local function read_mach_o(buf, hw_arch)

I suggest renaming it to `read_mach_o_hdr()` and returning only the
header without any additional wrapping in the table.

Updated:

diff --git a/build/src/luajit b/build/src/luajit
deleted file mode 100755
index bd10e09a..00000000
Binary files a/build/src/luajit and /dev/null differ
diff --git a/test/tarantool-tests/lj-865-cross-generation-mach-o-file.test.lua b/test/tarantool-tests/lj-865-cross-generation-mach-o-file.test.lua
index 6a58de95..0f269a8c 100644
--- a/test/tarantool-tests/lj-865-cross-generation-mach-o-file.test.lua
+++ b/test/tarantool-tests/lj-865-cross-generation-mach-o-file.test.lua
@@ -78,15 +134,7 @@ local function read_mach_o(buf, hw_arch)
   -- Mach-O object header.
   local mach_header = obj.hdr
 
-  return {
-    header = {
-      magic = mach_header.magic,
-      cputype = mach_header.cputype,
-      cpusubtype = mach_header.cpusubtype,
-      filetype = mach_header.filetype,
-      ncmds = mach_header.ncmds,
-    },
-  }
+  return mach_header
 end
 
 -- The function builds Mach-O object file and retrieves
@@ -104,22 +152,22 @@ local function build_and_check_mach_o(subtest)
   local mach_o_buf = utils.tools.read_file(mach_o_obj_path)
   assert(mach_o_buf ~= nil and #mach_o_buf ~= 0, 'cannot read an object file')
 
-  local mach_o = read_mach_o(mach_o_buf, hw_arch)
+  local mach_o = read_mach_o_hdr(mach_o_buf, hw_arch)
 
   -- Teardown.
   assert(os.remove(mach_o_obj_path), 'remove an object file')
 
-  local magic_str = string.format('%#x', mach_o.header.magic)
+  local magic_str = string.format('%#x', mach_o.magic)
   subtest:is(magic_str, '0xfeedfacf',
              'magic is correct in Mach-O')
-  local cputype_str = string.format('%#x', mach_o.header.cputype)
+  local cputype_str = string.format('%#x', mach_o.cputype)
   subtest:is(cputype_str, '0x100000c',
              'cputype is correct in Mach-O')
-  subtest:is(mach_o.header.cpusubtype, 0,
+  subtest:is(mach_o.cpusubtype, 0,
              'cpusubtype is correct in Mach-O')
-  subtest:is(mach_o.header.filetype, 1,
+  subtest:is(mach_o.filetype, 1,
              'filetype is correct in Mach-O')
-  subtest:is(mach_o.header.ncmds, 2,
+  subtest:is(mach_o.ncmds, 2,
              'ncmds is correct in Mach-O')
 end
 

-  local res = {
-    header = {
-      magic = 0,
-      nfat_arch = 0,
-    },
-    fat_arch = {},
-  }
-
   local is64 = hw_arch == 'arm64'

Maybe it is better to use assert here, like we do for the
`build_and_check_mach_o()` routine?

 
-  -- Mach-O FAT object.
-  local mach_fat_obj_type = ffi.typeof(is64 and
-                                       'mach_fat_obj_64 *' or
-                                       'mach_fat_obj *')
-  local obj = ffi.cast(mach_fat_obj_type, buf)
+  -- Mach-O object.
+  local mach_obj_type = ffi.typeof(is64 and 'mach_obj_64 *')

Maybe just use mach_obj_64 since there is no alternative?

+  local obj = ffi.cast(mach_obj_type, buf)
 
-  -- Mach-O FAT object header.
-  local mach_fat_header = obj.fat
-  -- Mach-O FAT is BE, target arch is LE.
-  local be32 = bit.bswap
-  res.header.magic = be32(mach_fat_header.magic)
-  res.header.nfat_arch = be32(mach_fat_header.nfat_arch)
+  -- Mach-O object header.
+  local mach_header = obj.hdr
 
-  -- Mach-O FAT object arches.
-  for i = 0, res.header.nfat_arch - 1 do
-    local fat_arch = obj.fat_arch[i]
-    local arch = {
-      cputype = be32(fat_arch.cputype),
-      cpusubtype = be32(fat_arch.cpusubtype),
-    }
-    table.insert(res.fat_arch, arch)
-  end
-
-  return res
+  return {
+    header = {
+      magic = mach_header.magic,
+      cputype = mach_header.cputype,
+      cpusubtype = mach_header.cpusubtype,
+      filetype = mach_header.filetype,
+      ncmds = mach_header.ncmds,
+    },
+  }
 end
 
--- Universal Binary can contain executables for more than one
--- CPU architecture. For simplicity, the test compares the *sum*
--- of CPU types and CPU subtypes.
---
--- <src/jit/bcsave.lua:bcsave_machobj> has the definitions of the
--- numbers below. The original XNU source code may be found in
--- <osfmk/mach/machine.h> [1].
---
--- 1. https://opensource.apple.com/source/xnu/xnu-4570.41.2/osfmk/mach/machine.h.auto.html
---
-local SUM_CPUTYPE = {
-  -- x86 + arm.
-  arm = 7 + 12,
-  -- x64 + arm64.
-  arm64 = 0x01000007 + 0x0100000c,
-}
-local SUM_CPUSUBTYPE = {
-  -- x86 + arm.
-  arm = 3 + 9,
-  -- x64 + arm64.
-  arm64 = 3 + 0,
-}
-
--- The function builds Mach-O FAT object file and retrieves
--- its header fields (magic and nfat_arch) and fields of each arch
--- (cputype, cpusubtype).
---
--- The Mach-O FAT object header can be retrieved with `otool` on
--- macOS:
---
--- $ otool -f empty.o
--- Fat headers
--- fat_magic 0xcafebabe
--- nfat_arch 2
--- <snipped>
---
--- CPU type and subtype can be retrieved with `lipo` on macOS:
---
--- $ luajit -b -o osx -a arm empty.lua empty.o
--- $ lipo -archs empty.o
--- i386 armv7
--- $ luajit -b -o osx -a arm64 empty.lua empty.o
--- $ lipo -archs empty.o
--- x86_64 arm64
+-- The function builds Mach-O object file and retrieves
+-- its header fields.
 local function build_and_check_mach_o(subtest)
   local hw_arch = subtest.name
-  assert(hw_arch == 'arm' or hw_arch == 'arm64')
+  -- LuaJIT always generate 64-bit non-FAT Mach-O object files.

The fact that these files are generated only for M1 CPUs looks worth
mentioning.

+  assert(hw_arch == 'arm64')
 
-  subtest:plan(4)
-  -- FAT_MAGIC is an integer containing the value 0xCAFEBABE in
-  -- big-endian byte order format. On a big-endian host CPU,
-  -- this can be validated using the constant FAT_MAGIC;
-  -- on a little-endian host CPU, it can be validated using
-  -- the constant FAT_CIGAM.
-  --
-  -- FAT_NARCH is an integer specifying the number of fat_arch
-  -- data structures that follow. This is the number of
-  -- architectures contained in this binary.
-  --
-  -- See the aforementioned "OS X ABI Mach-O File Format
-  -- Reference".

The similar comment about Mach-O format will be appretiated.

-  local FAT_MAGIC = '0xffffffffcafebabe'
-  local FAT_NARCH = 2
+  subtest:plan(5)
 
   local MODULE_NAME = 'lango_team'
 
@@ -327,24 +110,19 @@ local function build_and_check_mach_o(subtest)
   assert(os.remove(mach_o_obj_path), 'remove an object file')
 
   local magic_str = string.format('%#x', mach_o.header.magic)
-  subtest:is(magic_str, FAT_MAGIC,
-             'fat_magic is correct in Mach-O')
-  subtest:is(mach_o.header.nfat_arch, FAT_NARCH,
-             'nfat_arch is correct in Mach-O')
-
-  local total_cputype = 0
-  local total_cpusubtype = 0
-  for i = 1, FAT_NARCH do
-    total_cputype = total_cputype + mach_o.fat_arch[i].cputype
-    total_cpusubtype = total_cpusubtype + mach_o.fat_arch[i].cpusubtype
-  end
-  subtest:is(total_cputype, SUM_CPUTYPE[hw_arch],
+  subtest:is(magic_str, '0xfeedfacf',

Please use MH_MAGIC_64 named constant for this magic string.

+             'magic is correct in Mach-O')

Looks like this line may be joined with the previous one.

+  local cputype_str = string.format('%#x', mach_o.header.cputype)
+  subtest:is(cputype_str, '0x100000c',

Please use the named constant CPU_TYPE_ARM64 for this magic string.

              'cputype is correct in Mach-O')

Looks like this line may be joined with the previous one.

-  subtest:is(total_cpusubtype, SUM_CPUSUBTYPE[hw_arch],
+  subtest:is(mach_o.header.cpusubtype, 0,

Please use the named constant CPU_SUBTYPE_ARM64 for this magic constant.

              'cpusubtype is correct in Mach-O')

Looks like this line may be joined with the previous one.

+  subtest:is(mach_o.header.filetype, 1,

What does the 1 filetype mean?
Please use the named constant.

MH_OBJECT, added

 * The file type MH_OBJECT is a compact format intended as output of the
 * assembler and input (and possibly output) of the link editor (the .o
 * format).  All sections are in one unnamed segment with no segment padding. 
 * This format is used as an executable format when the file is so small the
 * segment padding greatly increases it's size.
 
https://opensource.apple.com/source/xnu/xnu-344/EXTERNAL_HEADERS/mach-o/loader.h.auto.html

+             'filetype is correct in Mach-O')

Looks like this line may be joined with the previous one.

+  subtest:is(mach_o.header.ncmds, 2,

Why there are 2 commands for Mach-O format?
Please use the named constant.

+             'ncmds is correct in Mach-O')

Looks like this line may be joined with the previous one.

 end
 
-test:test('arm', build_and_check_mach_o)
 test:test('arm64', build_and_check_mach_o)
 
 test:done(true)
-- 
2.34.1

[1]: https://github.com/LuaJIT/LuaJIT/issues/1181#issue-2202788411