Unfortunately there is no kernel API which we can use on the host to say "give me inodes and offsets which will fit into a 32 bit field". The 'getdents' syscall uses the "unsigned long" type for the d_ino and d_off fields, so on a 64-bit host these will be the same size as the ino64_t and off64_t used by 'getdents64', and you will still have the "trying to fit a quart into a pint pot" problem.
The only way to fix this is to fix the host kernel to provide the API QEMU needs for this (see discussion in the kernel thread linked to in comment #5). -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1805913 Title: readdir() returns NULL (errno=EOVERFLOW) for 32-bit user-static qemu on 64-bit host Status in QEMU: New Bug description: This can be simply reproduced by compiling and running the attached C code (readdir-bug.c) under 32-bit user-static qemu, such as qemu-arm- static: # Setup docker for user-static binfmt docker run --rm --privileged multiarch/qemu-user-static:register --reset # Compile the code and run (readdir for / is fine, so create a new directory /test). docker run -v /path/to/qemu-arm-static:/usr/bin/qemu-arm-static -v /path/to/readdir-bug.c:/tmp/readdir-bug.c -it --rm arm32v7/ubuntu:18.10 bash -c '{ apt update && apt install -y gcc; } >&/dev/null && mkdir -p /test && cd /test && gcc /tmp/readdir-bug.c && ./a.out' dir=0xff5b4150 readdir(dir)=(nil) errno=75: Value too large for defined data type Do remember to replace the /path/to/qemu-arm-static and /path/to /readdir-bug.c to the actual paths of the files. The root cause is in glibc: https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/getdents.c;h=6d09a5be7057e2792be9150d3a2c7b293cf6fc34;hb=a5275ba5378c9256d18e582572b4315e8edfcbfb#l87 By C standard, the return type of readdir() is DIR*, in which the inode number and offset are 32-bit integers, therefore, glibc calls getdents64() and check if the inode number and offset fits the 32-bit range, and reports EOVERFLOW if not. The problem here is for 32-bit user-static qemu running on 64-bit host, getdents64 simply passing through the inode number and offset from underlying getdents64 syscall (from 64-bit kernel), which is very likely to not fit into 32-bit range. On real hardware, the 32-bit kernel creates 32-bit inode numbers, therefore works properly. The glibc code makes sense to do the check to be conformant with C standard, therefore ideally it should be a fix on qemu side. I admit this is difficult because qemu has to maintain a mapping between underlying 64-bit inode numbers and 32-bit inode numbers, which would severely hurt the performance. I don't expect this could be fix anytime soon (or even there would be a fix), but it would be worthwhile to surface this issue. To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1805913/+subscriptions
