bug#61386: [PATCH] cp,mv,install: Disable sparse copy on macOS

[George Valkov]

Due to a bug in macOS, sparse copies are corrupted on virtual disks
formatted with APFS. HFS is not affected. Affected are coreutils
install, and gcp when compiled with SEEK_HOLE, as well as macOS Finder.

While reading the entire file returns valid data, scanning for
allocated segments may return holes where valid data is present.
In this case a sparse copy does not contain these segments and returns
zeroes instead. Once the virtual disk is dismounted and then
mounted again, a sparse copy produces correct results.

This breaks OpenWRT build on macOS. Details:
https://github.com/openwrt/openwrt/pull/11960
https://github.com/openwrt/openwrt/pull/11960#issuecomment-1423185579

Signed-off-by: Georgi Valkov <gvalkov@gmail.com>
---
 src/copy.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/copy.c b/src/copy.c
index e16fedb28..4f56138a6 100644
--- a/src/copy.c
+++ b/src/copy.c
@@ -1065,7 +1065,7 @@ infer_scantype (int fd, struct stat const *sb,
       return PLAIN_SCANTYPE;
     }
 
-#ifdef SEEK_HOLE
+#if defined(SEEK_HOLE) && !defined(__APPLE__)
   scan_inference->ext_start = lseek (fd, 0, SEEK_DATA);
   if (0 <= scan_inference->ext_start || errno == ENXIO)
     return LSEEK_SCANTYPE;
-- 
2.39.1


The issue is most likely within APFS, So we need to bring it to Apple's 
attention.
Since it is triggered by building `gcc`, it would be helpful
if they can shine some light how their tools are build
and what trigger this, in order to create PoC code.

**steps to reproduce**

_Create a sparse disk image with APFS_
- open Disk Utility
- press Command-N to create a new virtual disk
- Image Format: sparse disk image
- save as: ~/vhd/test
- Name: test
- Size: 50 GB
- Format: APFS (Case-sensitive)
- Encryption: none
- Partitions: Single partition - GUID Partition Map
- Save
- the image is mounted under `/Volumes/test`

_clone and build coreutils_
``` bash
cd /Volumes/test
# patched with sparse support disabled on macOS
git clone https://github.com/httpstorm/coreutils.git
mv coreutils coreutils-no-sparse
cd coreutils-no-sparse
git checkout macos_disable-sparse-copy
git submodule foreach git pull origin master
./bootstrap
make -j 16
cd ..

# original code
git clone https://github.com/coreutils/coreutils.git
cd coreutils
git submodule foreach git pull origin master
./bootstrap
make -j 16
```

_download OpenWRT and build gcc_
``` bash
cd /Volumes/test
git clone https://github.com/openwrt/openwrt.git
cd openwrt
./scripts/feeds update -a
./scripts/feeds install -a
make defconfig
make menuconfig
# Target System (Marvell EBU Armada)
# Target Profile (Linksys WRT3200ACM)
# Save, Exit
make tools/compile -j 16
make toolchain/gcc/initial/compile -j 16
```

proof of concept
``` bash
cd /Volumes/test/openwrt
cd 
build_dir/toolchain-arm_cortex-a9+vfpv3-d16_gcc-12.2.0_musl_eabi/gcc-12.2.0-initial/gcc

/Volumes/test/coreutils/src/cp cc1 cc1-ori
./cc1-ori --help
-bash: ./cc1-ori: cannot execute binary file: Exec format error

/Volumes/test/coreutils-no-sparse/src/cp cc1 cc1-fix
./cc1-fix --help
# works correctly

sha1sum cc1
# fcf5d9458f54d5588efc5a76a89388925ca04eda  cc1
sha1sum cc1-fix 
# fcf5d9458f54d5588efc5a76a89388925ca04eda  cc1-fix
sha1sum cc1-ori
# 7b447132f56f3b549ef62a4780945e82d26f7d2c  cc1-ori
```


Kind regards,

Georgi Valkov
httpstorm.com
nano RTOS