QEMU fails to honor O_TMPFILE

[Thiago Macieira]

When making a call like

  open("/tmp", O_TMPFILE | O_RDWR);

under QEMU, we ged -EISDIR.

Under any kernel 3.11 or later, we are supposed to get an unnamed file in /tmp. In case the filesystem for /tmp does not support unnamed files, we are supposed to get EOPNOTSUPP.

[I don't know the QEMU version, since this happened in a system I don't have access to]

[Riku Voipio (riku-voipio)]

Hi Thiago,

What is the version of glibc on the targets you are building to? There was an O_TMPFILE bug in older glibc's:

https://sourceware.org/bugzilla/show_bug.cgi?id=17912

[Riku Voipio (riku-voipio)]

On Mon, Aug 07, 2017 at 08:18:04PM -0000, Thiago Macieira wrote:
> Public bug reported:
>
> When making a call like
>
> open("/tmp", O_TMPFILE | O_RDWR);
>
> under QEMU, we ged -EISDIR.
>
> Under any kernel 3.11 or later, we are supposed to get an unnamed file
> in /tmp. In case the filesystem for /tmp does not support unnamed files,
> we are supposed to get EOPNOTSUPP.

Actually, -EISDIR is valid error when underlying system doesn't support O_TMPFILE.
See man openat or the kernel definition for O_TMPFILE.

Regardless, I'm submitting a patch to properly translate the O_TMPFILE.

Riku

[Riku Voipio (riku-voipio)]

Since O_TMPFILE might differ between guest and host,
add it to the bitmask_transtbl. While at it, fix the definitions
of O_DIRECTORY etc on arm64, which are identical to arm32 according
to kernel sources.

This fixes open14 and openat03 ltp testcases.

Fixes: https://bugs.launchpad.net/qemu/+bug/1709170

---
 linux-user/strace.c | 4 ++++
 linux-user/syscall.c | 3 +++
 linux-user/syscall_defs.h | 8 +++++++-
 3 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/linux-user/strace.c b/linux-user/strace.c
index d821d165ff..bd897a3f20 100644
--- a/linux-user/strace.c
+++ b/linux-user/strace.c
@@ -838,6 +838,10 @@ UNUSED static struct flags open_flags[] = {
 #ifdef O_PATH
     FLAG_TARGET(O_PATH),
 #endif
+#ifdef O_TMPFILE
+ FLAG_TARGET(O_TMPFILE),
+ FLAG_TARGET(__O_TMPFILE),
+#endif
     FLAG_END,
 };

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 54343c06be..b3aa8099b4 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -342,6 +342,9 @@ static bitmask_transtbl fcntl_flags_tbl[] = {
 #if defined(O_PATH)
   { TARGET_O_PATH, TARGET_O_PATH, O_PATH, O_PATH },
 #endif
+#if defined(O_TMPFILE)
+ { TARGET_O_TMPFILE, TARGET_O_TMPFILE, O_TMPFILE, O_TMPFILE },
+#endif
   /* Don't terminate the list prematurely on 64-bit host+guest. */
 #if TARGET_O_LARGEFILE != 0 || O_LARGEFILE != 0
   { TARGET_O_LARGEFILE, TARGET_O_LARGEFILE, O_LARGEFILE, O_LARGEFILE, },
diff --git a/linux-user/syscall_defs.h b/linux-user/syscall_defs.h
index 40c5027e93..6e2287e918 100644
--- a/linux-user/syscall_defs.h
+++ b/linux-user/syscall_defs.h
@@ -2416,7 +2416,7 @@ struct target_statfs64 {
 #define TARGET_O_CLOEXEC 010000000
 #define TARGET___O_SYNC 000100000
 #define TARGET_O_PATH 020000000
-#elif defined(TARGET_ARM) || defined(TARGET_M68K)
+#elif defined(TARGET_ARM) || defined(TARGET_M68K) || defined(TARGET_AARCH64)
 #define TARGET_O_DIRECTORY 040000 /* must be a directory */
 #define TARGET_O_NOFOLLOW 0100000 /* don't follow links */
 #define TARGET_O_DIRECT 0200000 /* direct disk access hint */
@@ -2513,6 +2513,12 @@ struct target_statfs64 {
 #ifndef TARGET_O_PATH
 #define TARGET_O_PATH 010000000
 #endif
+#ifndef TARGET___O_TMPFILE
+#define TARGET___O_TMPFILE 020000000
+#endif
+#ifndef TARGET_O_TMPFILE
+#define TARGET_O_TMPFILE (TARGET___O_TMPFILE | TARGET_O_DIRECTORY)
+#endif
 #ifndef TARGET_O_NDELAY
 #define TARGET_O_NDELAY TARGET_O_NONBLOCK
 #endif
--
2.11.0

[Thiago Macieira (thiago-kde)]

It was a Yocto 2.0 sysroot running on an Ubuntu 16.04 host.

[Thomas Huth (th-huth)]

Fix has been released with QEMU 2.11:
https://git.qemu.org/?p=qemu.git;a=commitdiff;h=5f9cee46cd4ec4600e1a