id = 2004
title = "do_guest_openat /proc interposition doesn't work for openat"
state = "opened"
created_at = "2023-11-24T17:09:30.952Z"
closed_at = "n/a"
labels = ["linux-user"]
url = "https://gitlab.com/qemu-project/qemu/-/issues/2004"
host-os = "All"
host-arch = "All"
qemu-version = "8.1.2"
guest-os = "Linux"
guest-arch = "All"
description = """For instance, trying with hppa emulated on top of x86:

```
$ hppa-linux-gnu-gcc test.c -o test
$ qemu-hppa-static ./test
```

One gets the host cpu information:

```
processor\t: 0
vendor_id\t: GenuineIntel
cpu family\t: 6
model\t\t: 142
model name\t: Intel(R) Core(TM) i5-10210U CPU @ 1.60GHz
[...]
```

while we would want to see the guest cpu information, like the test program does when `#if 0` is turned into `#if 1`:

```
processor\t: 0            
cpu family\t: PA-RISC 1.1e
cpu\t\t: PA7300LC (PCX-L2)
capabilities\t: os32
model\t\t: 9000/778/B160L - Merlin L2 160 QEMU (9000/778/B160L)
```

This is because `do_guest_openat` only checks for the path, and does not look at `dirfd`, so it doesn't recognize that `openat(dirfd, "cpuinfo", O_RDONLY)` is actually opening a file in `/proc`.

We could probably, when `dirfd` is not `AT_FDCWD`, try to `fstat()` it, open `/proc` with `O_DIRECTORY` and `fstat()` that too, and compare their `st_dev` and `st_ino`?"""
reproduce = "n/a"
additional = "n/a"