Re: [Qemu-devel] [PATCH v10 3/3] linux-user: Add support for statx() syscall

[Jim Wilson]

On 6/7/19 3:35 AM, Aleksandar Markovic wrote:
> Implement support for translation of system call statx().

I also need these patches for 32-bit RISC-V linux user mode support.

glibc ld.so calls statx if fstatat is not supported.  Apparently new 
linux architecture ports aren't allowed to define __ARCH_WANT_NEW_STAT 
which enables fstatat because this is already obsolete.  64-bit RISC-V 
linux does have fstatat, but apparently this was a mistake which we 
can't fix now because the ABI is already frozen.  The 32-bit RISC-V ABI 
is not frozen yet, so it won't have fstatat.  Anyways, without statx, 
ld.so doesn't work, which makes user mode qemu pretty useless, so we do 
need this emulated in qemu to make the 32-bit RISC-V linux user mode 
support work properly.

I started with the August 2018 version of the patch a few weeks ago, and 
just noticed that it has been resubmitted.  I had to modify the patch 
slightly to apply to current sources, and had to fix one bug to make it 
work.  The line
+                if (ret != TARGET_ENOSYS) {
needs to instead be
+                if (ret != -TARGET_ENOSYS) {
I see that Laurent has already pointed that out.

Incidentally, I also have strace patches for statx that work on top of 
this patch, since I didn't see that in the nanomips patch set I started 
with.  That helped me debug the 32-bit RISC-V user mode support.

I've tested this on Ubuntu 16.04 (no host statx) and Ubuntu 19.10 (with 
host statx) and it worked well for me running the gcc testsuite for a 
riscv32-linux target.  I haven't tried testing the latest version of the 
patch yet.  I can do that if this is helpful.

Jim