Express the complex conditions in Kconfig rather than Makefiles, since Kconfig
is better suited at expressing dependencies and detecting contradictions.
Cc: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
In my "build everything" tree, changing hw/qdev-properties.h triggers
a recompile of some 2700 out of 6600 objects (not counting tests and
objects that don't depend on qemu/osdep.h).
Many places including hw/qdev-properties.h (directly or via hw/qdev.h)
actually need only hw/qdev-core.h. Include hw/qdev-core.h there
instead.
hw/qdev.h is actually pointless: all it does is include hw/qdev-core.h
and hw/qdev-properties.h, which in turn includes hw/qdev-core.h.
Replace the remaining uses of hw/qdev.h by hw/qdev-properties.h.
While there, delete a few superfluous inclusions of hw/qdev-core.h.
Touching hw/qdev-properties.h now recompiles some 1200 objects.
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Daniel P. Berrangé" <berrange@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Message-Id: <20190812052359.30071-22-armbru@redhat.com>
In my "build everything" tree, changing qemu/main-loop.h triggers a
recompile of some 5600 out of 6600 objects (not counting tests and
objects that don't depend on qemu/osdep.h). It includes block/aio.h,
which in turn includes qemu/event_notifier.h, qemu/notify.h,
qemu/processor.h, qemu/qsp.h, qemu/queue.h, qemu/thread-posix.h,
qemu/thread.h, qemu/timer.h, and a few more.
Include qemu/main-loop.h only where it's needed. Touching it now
recompiles only some 1700 objects. For block/aio.h and
qemu/event_notifier.h, these numbers drop from 5600 to 2800. For the
others, they shrink only slightly.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20190812052359.30071-21-armbru@redhat.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
In my "build everything" tree, changing hw/hw.h triggers a recompile
of some 2600 out of 6600 objects (not counting tests and objects that
don't depend on qemu/osdep.h).
The previous commits have left only the declaration of hw_error() in
hw/hw.h. This permits dropping most of its inclusions. Touching it
now recompiles less than 200 objects.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <20190812052359.30071-19-armbru@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
A Xen public header have been imported into QEMU (by
f65eadb639 "xen: import ring.h from xen"), but there are other header
that depends on ring.h which come from the system when building QEMU.
This patch resolves the issue of having headers from the system
importing a different copie of ring.h.
This patch is prompt by the build issue described in the previous
patch: 'Revert xen/io/ring.h of "Clean up a few header guard symbols"'
ring.h and the new imported headers are moved to
"include/hw/xen/interface" as those describe interfaces with a guest.
The imported headers are cleaned up a bit while importing them: some
part of the file that QEMU doesn't use are removed (description
of how to make hypercall in grant_table.h have been removed).
Other cleanup:
- xen-mapcache.c and xen-legacy-backend.c don't need grant_table.h.
- xenfb.c doesn't need event_channel.h.
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Paul Durrant <paul.durrant@citrix.com>
Message-Id: <20190621105441.3025-3-anthony.perard@citrix.com>
No header includes qemu-common.h after this commit, as prescribed by
qemu-common.h's file comment.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20190523143508.25387-5-armbru@redhat.com>
[Rebased with conflicts resolved automatically, except for
include/hw/arm/xlnx-zynqmp.h hw/arm/nrf51_soc.c hw/arm/msf2-soc.c
block/qcow2-refcount.c block/qcow2-cluster.c block/qcow2-cache.c
target/arm/cpu.h target/lm32/cpu.h target/m68k/cpu.h target/mips/cpu.h
target/moxie/cpu.h target/nios2/cpu.h target/openrisc/cpu.h
target/riscv/cpu.h target/tilegx/cpu.h target/tricore/cpu.h
target/unicore32/cpu.h target/xtensa/cpu.h; bsd-user/main.c and
net/tap-bsd.c fixed up]
Some trace points are attributed to the wrong source file. Happens
when we neglect to update trace-events for code motion, or add events
in the wrong place, or misspell the file name.
Clean up with help of cleanup-trace-events.pl. Same funnies as in the
previous commit, of course. Manually shorten its change to
linux-user/trace-events to */signal.c.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-id: 20190314180929.27722-6-armbru@redhat.com
Message-Id: <20190314180929.27722-6-armbru@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
We spell out sub/dir/ in sub/dir/trace-events' comments pointing to
source files. That's because when trace-events got split up, the
comments were moved verbatim.
Delete the sub/dir/ part from these comments. Gets rid of several
misspellings.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20190314180929.27722-3-armbru@redhat.com
Message-Id: <20190314180929.27722-3-armbru@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Yang Zhong <yang.zhong@intel.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20190123065618.3520-42-yang.zhong@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The make_device_config.sh script is replaced by minikconf, which
is modified to support the same command line as its predecessor.
The roots of the parsing are default-configs/*.mak, Kconfig.host and
hw/Kconfig. One difference with make_device_config.sh is that all symbols
have to be defined in a Kconfig file, including those coming from the
configure script. This is the reason for the Kconfig.host file introduced
in the previous patch. Whenever a file in default-configs/*.mak used
$(...) to refer to a config-host.mak symbol, this is replaced by a
Kconfig dependency; this part must be done already in this patch
for bisectability.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Yang Zhong <yang.zhong@intel.com>
Acked-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20190123065618.3520-28-yang.zhong@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The Kconfig files were generated mostly with this script:
for i in `grep -ho CONFIG_[A-Z0-9_]* default-configs/* | sort -u`; do
set fnord `git grep -lw $i -- 'hw/*/Makefile.objs' `
shift
if test $# = 1; then
cat >> $(dirname $1)/Kconfig << EOF
config ${i#CONFIG_}
bool
EOF
git add $(dirname $1)/Kconfig
else
echo $i $*
fi
done
sed -i '$d' hw/*/Kconfig
for i in hw/*; do
if test -d $i && ! test -f $i/Kconfig; then
touch $i/Kconfig
git add $i/Kconfig
fi
done
Whenever a symbol is referenced from multiple subdirectories, the
script prints the list of directories that reference the symbol.
These symbols have to be added manually to the Kconfig files.
Kconfig.host and hw/Kconfig were created manually.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Yang Zhong <yang.zhong@intel.com>
Message-Id: <20190123065618.3520-27-yang.zhong@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The VIRTIO_9P || VIRTFS && XEN condition can be computed in hw/Makefile.objs,
removing an "if" from hw/9pfs/Makefile.objs.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
...and xen_backend.h to xen-legacy-backend.h
Rather than attempting to convert the existing backend infrastructure to
be QOM compliant (which would be hard to do in an incremental fashion),
subsequent patches will introduce a completely new framework for Xen PV
backends. Hence it is necessary to re-name parts of existing code to avoid
name clashes. The re-named 'legacy' infrastructure will be removed once all
backends have been ported to the new framework.
This patch is purely cosmetic. No functional change.
Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Acked-by: Anthony Perard <anthony.perard@citrix.com>
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
The "handle" fsdev backend was deprecated in QEMU 2.12.0 with:
commit db3b3c7281
Author: Greg Kurz <groug@kaod.org>
Date: Mon Jan 8 11:18:23 2018 +0100
9pfs: deprecate handle backend
This backend raise some concerns:
- doesn't support symlinks
- fails +100 tests in the PJD POSIX file system test suite [1]
- requires the QEMU process to run with the CAP_DAC_READ_SEARCH
capability, which isn't recommended for security reasons
This backend should not be used and wil be removed. The 'local'
backend is the recommended alternative.
[1] https://www.tuxera.com/community/posix-test-suite/
Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Daniel P. Berrange <berrange@redhat.com>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
It has passed the two release cooling period without any complaint.
Remove it now.
Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Because it is a recommended coding practice (see HACKING).
Signed-off-by: Greg Kurz <groug@kaod.org>
Acked-by: Anthony PERARD <anthony.perard@citrix.com>
Because it is a recommended coding practice (see HACKING).
Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>
When using the 9P2000.u version of the protocol, the following shell
command line in the guest can cause QEMU to crash:
while true; do rm -rf aa; mkdir -p a/b & touch a/b/c & mv a aa; done
With 9P2000.u, file renaming is handled by the WSTAT command. The
v9fs_wstat() function calls v9fs_complete_rename(), which calls
v9fs_fix_path() for every fid whose path is affected by the change.
The involved calls to v9fs_path_copy() may race with any other access
to the fid path performed by some worker thread, causing a crash like
shown below:
Thread 12 "qemu-system-x86" received signal SIGSEGV, Segmentation fault.
0x0000555555a25da2 in local_open_nofollow (fs_ctx=0x555557d958b8, path=0x0,
flags=65536, mode=0) at hw/9pfs/9p-local.c:59
59 while (*path && fd != -1) {
(gdb) bt
#0 0x0000555555a25da2 in local_open_nofollow (fs_ctx=0x555557d958b8,
path=0x0, flags=65536, mode=0) at hw/9pfs/9p-local.c:59
#1 0x0000555555a25e0c in local_opendir_nofollow (fs_ctx=0x555557d958b8,
path=0x0) at hw/9pfs/9p-local.c:92
#2 0x0000555555a261b8 in local_lstat (fs_ctx=0x555557d958b8,
fs_path=0x555556b56858, stbuf=0x7fff84830ef0) at hw/9pfs/9p-local.c:185
#3 0x0000555555a2b367 in v9fs_co_lstat (pdu=0x555557d97498,
path=0x555556b56858, stbuf=0x7fff84830ef0) at hw/9pfs/cofile.c:53
#4 0x0000555555a1e9e2 in v9fs_stat (opaque=0x555557d97498)
at hw/9pfs/9p.c:1083
#5 0x0000555555e060a2 in coroutine_trampoline (i0=-669165424, i1=32767)
at util/coroutine-ucontext.c:116
#6 0x00007fffef4f5600 in __start_context () at /lib64/libc.so.6
#7 0x0000000000000000 in ()
(gdb)
The fix is to take the path write lock when calling v9fs_complete_rename(),
like in v9fs_rename().
Impact: DoS triggered by unprivileged guest users.
Fixes: CVE-2018-19489
Cc: P J P <ppandit@redhat.com>
Reported-by: zhibin hu <noirfate@gmail.com>
Reviewed-by: Prasad J Pandit <pjp@fedoraproject.org>
Signed-off-by: Greg Kurz <groug@kaod.org>
Recent commit 5b76ef50f6 fixed a race where v9fs_co_open2() could
possibly overwrite a fid path with v9fs_path_copy() while it is being
accessed by some other thread, ie, use-after-free that can be detected
by ASAN with a custom 9p client.
It turns out that the same can happen at several locations where
v9fs_path_copy() is used to set the fid path. The fix is again to
take the write lock.
Fixes CVE-2018-19364.
Cc: P J P <ppandit@redhat.com>
Reported-by: zhibin hu <noirfate@gmail.com>
Reviewed-by: Prasad J Pandit <pjp@fedoraproject.org>
Signed-off-by: Greg Kurz <groug@kaod.org>
The assumption that the fid cannot be used by any other operation is
wrong. At least, nothing prevents a misbehaving client to create a
file with a given fid, and to pass this fid to some other operation
at the same time (ie, without waiting for the response to the creation
request). The call to v9fs_path_copy() performed by the worker thread
after the file was created can race with any access to the fid path
performed by some other thread. This causes use-after-free issues that
can be detected by ASAN with a custom 9p client.
Unlike other operations that only read the fid path, v9fs_co_open2()
does modify it. It should hence take the write lock.
Cc: P J P <ppandit@redhat.com>
Reported-by: zhibin hu <noirfate@gmail.com>
Signed-off-by: Greg Kurz <groug@kaod.org>
Calling error_report() from within a function that takes an Error **
argument is suspicious. qemu_fsdev_add() does that, and its caller
fsdev_init_func() then fails without setting an error. Its caller
main(), via qemu_opts_foreach(), is fine with it, but clean it up
anyway.
Cc: Greg Kurz <groug@kaod.org>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Acked-by: Greg Kurz <groug@kaod.org>
Message-Id: <20181017082702.5581-32-armbru@redhat.com>
Calling error_report() in a function that takes an Error ** argument
is suspicious. 9p-handle.c's handle_parse_opts() does that, and then
fails without setting an error. Wrong. Its caller crashes when it
tries to report the error:
$ qemu-system-x86_64 -nodefaults -fsdev id=foo,fsdriver=handle
qemu-system-x86_64: -fsdev id=foo,fsdriver=handle: warning: handle backend is deprecated
qemu-system-x86_64: -fsdev id=foo,fsdriver=handle: fsdev: No path specified
Segmentation fault (core dumped)
Screwed up when commit 91cda4e8f3 (v2.12.0) converted the function to
Error. Fix by calling error_setg() instead of error_report().
Fixes: 91cda4e8f3
Cc: Greg Kurz <groug@kaod.org>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Acked-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20181017082702.5581-9-armbru@redhat.com>
From include/qapi/error.h:
* Pass an existing error to the caller with the message modified:
* error_propagate(errp, err);
* error_prepend(errp, "Could not frobnicate '%s': ", name);
Fei Li pointed out that doing error_propagate() first doesn't work
well when @errp is &error_fatal or &error_abort: the error_prepend()
is never reached.
Since I doubt fixing the documentation will stop people from getting
it wrong, introduce error_propagate_prepend(), in the hope that it
lures people away from using its constituents in the wrong order.
Update the instructions in error.h accordingly.
Convert existing error_prepend() next to error_propagate to
error_propagate_prepend(). If any of these get reached with
&error_fatal or &error_abort, the error messages improve. I didn't
check whether that's the case anywhere.
Cc: Fei Li <fli@suse.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20181017082702.5581-2-armbru@redhat.com>
Comparisons of mode_t with -1 require an explicit cast, since mode_t
is unsigned on Darwin.
Signed-off-by: Keno Fischer <keno@juliacomputing.com>
Signed-off-by: Greg Kurz <groug@kaod.org>
strchrnul is a GNU extension and thus unavailable on a number of targets.
In the review for a commit removing strchrnul from 9p, I was asked to
create a qemu_strchrnul helper to factor out this functionality.
Do so, and use it in a number of other places in the code base that inlined
the replacement pattern in a place where strchrnul could be used.
Signed-off-by: Keno Fischer <keno@juliacomputing.com>
Acked-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Greg Kurz <groug@kaod.org>
As with unlinkat, these flags come from the client and need to
be translated to their host values. The protocol values happen
to match linux, but that need not be true in general.
Signed-off-by: Keno Fischer <keno@juliacomputing.com>
Signed-off-by: Greg Kurz <groug@kaod.org>
The 9p-local code previously relied on P9_DOTL_AT_REMOVEDIR and AT_REMOVEDIR
having the same numerical value and deferred any errorchecking to the
syscall itself. However, while the former assumption is true on Linux,
it is not true in general. 9p-handle did this properly however. Move
the translation code to the generic 9p server code and add an error
if unrecognized flags are passed.
Signed-off-by: Keno Fischer <keno@juliacomputing.com>
Signed-off-by: Greg Kurz <groug@kaod.org>
Both `stbuf` and `local_ioc_getversion` where unused when
FS_IOC_GETVERSION was not defined, causing a compiler warning.
Reorganize the code to avoid this warning.
Signed-off-by: Keno Fischer <keno@juliacomputing.com>
Signed-off-by: Greg Kurz <groug@kaod.org>
If the size returned from llistxattr/lgetxattr is 0, we skipped
the malloc call, leaving xattr.value uninitialized. However, this
value is later passed to `g_free` without any further checks,
causing an error. Fix that by always calling g_malloc unconditionally.
If `size` is 0, it will return NULL, which is safe to pass to g_free.
Signed-off-by: Keno Fischer <keno@juliacomputing.com>
Signed-off-by: Greg Kurz <groug@kaod.org>
These functions will need custom implementations on Darwin. Since the
implementation is very similar among all of them, and 9p-util already
has the _nofollow version of fgetxattrat, let's move them all there.
Signed-off-by: Keno Fischer <keno@juliacomputing.com>
Signed-off-by: Greg Kurz <groug@kaod.org>
In the review of
9p: Avoid warning if FS_IOC_GETVERSION is not defined
Grep Kurz noted this error path was failing to set errp.
Fix that.
Signed-off-by: Keno Fischer <keno@juliacomputing.com>
[added local: to commit title, Greg Kurz]
Signed-off-by: Greg Kurz <groug@kaod.org>
The size to pass to the `connect` call is the size of the entire
`struct sockaddr_un`. Passing anything shorter than this causes errors
on darwin.
Signed-off-by: Keno Fischer <keno@juliacomputing.com>
Signed-off-by: Greg Kurz <groug@kaod.org>
This is only half of the work, because the proxy devices (virtio-*-pci,
virtio-*-ccw, etc.) are still included unconditionally. It is still a
move in the right direction.
Based-on: <20180522194943.24871-1-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Now that helpers are available in xen_backend, use them throughout all
Xen PV backends.
Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Acked-by: Anthony Perard <anthony.perard@citrix.com>
Signed-off-by: Stefano Stabellini <sstabellini@kernel.org>
Don't print the tv_nsec part of atime and mtime, to stay below the 10
argument limit of trace events.
Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Leak found thanks to ASAN:
Direct leak of 8 byte(s) in 1 object(s) allocated from:
#0 0x55995789ac90 in __interceptor_malloc (/home/elmarco/src/qemu/build/x86_64-softmmu/qemu-system-x86_64+0x1510c90)
#1 0x7f0a91190f0c in g_malloc /home/elmarco/src/gnome/glib/builddir/../glib/gmem.c:94
#2 0x5599580a281c in v9fs_path_copy /home/elmarco/src/qemu/hw/9pfs/9p.c:196:17
#3 0x559958f9ec5d in coroutine_trampoline /home/elmarco/src/qemu/util/coroutine-ucontext.c:116:9
#4 0x7f0a8766ebbf (/lib64/libc.so.6+0x50bbf)
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Greg Kurz <groug@kaod.org>
lhs/rhs doesn't tell much about how argument are handled, dst/src is
and const arguments is clearer in my mind. Use g_memdup() while at it.
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Greg Kurz <groug@kaod.org>
qemu-common.h includes qemu/option.h, but most places that include the
former don't actually need the latter. Drop the include, and add it
to the places that actually need it.
While there, drop superfluous includes of both headers, and
separate #include from file comment with a blank line.
This cleanup makes the number of objects depending on qemu/option.h
drop from 4545 (out of 4743) to 284 in my "build everything" tree.
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20180201111846.21846-20-armbru@redhat.com>
[Semantic conflict with commit bdd6a90a9e in block/nvme.c resolved]
This cleanup makes the number of objects depending on qapi/error.h
drop from 1910 (out of 4743) to 1612 in my "build everything" tree.
While there, separate #include from file comment with a blank line,
and drop a useless comment on why qemu/osdep.h is included first.
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20180201111846.21846-5-armbru@redhat.com>
[Semantic conflict with commit 34e304e975 resolved, OSX breakage fixed]
The idea is to send a victim request that will possibly block in the
server and to send a flush request to cancel the victim request.
This patch adds two test to verifiy that:
- the server does not reply to a victim request that was actually
cancelled
- the server replies to the flush request after replying to the
victim request if it could not cancel it
9p request cancellation reference:
http://man.cat-v.org/plan_9/5/flush
Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
(groug, change the test to only write a single byte to avoid
any alignment or endianess consideration)
Trivial test of a successful write.
Signed-off-by: Greg Kurz <groug@kaod.org>
(groug, handle potential overflow when computing request size,
add missing g_free(buf),
backend handles one written byte at a time to validate
the server doesn't do short-reads)
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
The purpose of virtio-9p-test is to test the virtio-9p device, especially
the 9p server state machine. We don't really care what fsdev backend we're
using. Moreover, if we want to be able to test the flush request or a
device reset with in-flights I/O, it is close to impossible to achieve
with a physical backend because we cannot ask it reliably to put an I/O
on hold at a specific point in time.
Fortunately, we can do that with the synthetic backend, which allows to
register callbacks on read/write accesses to a specific file. This will
be used by a later patch to test the 9P flush request.
The walk request test is converted to using the synth backend.
Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
# Background
I was investigating spurious non-deterministic EINTR returns from
various 9p file system operations in a Linux guest served from the
qemu 9p server.
## EINTR, ERESTARTSYS and the linux kernel
When a signal arrives that the Linux kernel needs to deliver to user-space
while a given thread is blocked (in the 9p case waiting for a reply to its
request in 9p_client_rpc -> wait_event_interruptible), it asks whatever
driver is currently running to abort its current operation (in the 9p case
causing the submission of a TFLUSH message) and return to user space.
In these situations, the error message reported is generally ERESTARTSYS.
If the userspace processes specified SA_RESTART, this means that the
system call will get restarted upon completion of the signal handler
delivery (assuming the signal handler doesn't modify the process state
in complicated ways not relevant here). If SA_RESTART is not specified,
ERESTARTSYS gets translated to EINTR and user space is expected to handle
the restart itself.
## The 9p TFLUSH command
The 9p TFLUSH commands requests that the server abort an ongoing operation.
The man page [1] specifies:
```
If it recognizes oldtag as the tag of a pending transaction, it should
abort any pending response and discard that tag.
[...]
When the client sends a Tflush, it must wait to receive the corresponding
Rflush before reusing oldtag for subsequent messages. If a response to the
flushed request is received before the Rflush, the client must honor the
response as if it had not been flushed, since the completed request may
signify a state change in the server
```
In particular, this means that the server must not send a reply with the
orignal tag in response to the cancellation request, because the client is
obligated to interpret such a reply as a coincidental reply to the original
request.
# The bug
When qemu receives a TFlush request, it sets the `cancelled` flag on the
relevant pdu. This flag is periodically checked, e.g. in
`v9fs_co_name_to_path`, and if set, the operation is aborted and the error
is set to EINTR. However, the server then violates the spec, by returning
to the client an Rerror response, rather than discarding the message
entirely. As a result, the client is required to assume that said Rerror
response is a result of the original request, not a result of the
cancellation and thus passes the EINTR error back to user space.
This is not the worst thing it could do, however as discussed above, the
correct error code would have been ERESTARTSYS, such that user space
programs with SA_RESTART set get correctly restarted upon completion of
the signal handler.
Instead, such programs get spurious EINTR results that they were not
expecting to handle.
It should be noted that there are plenty of user space programs that do not
set SA_RESTART and do not correctly handle EINTR either. However, that is
then a userspace bug. It should also be noted that this bug has been
mitigated by a recent commit to the Linux kernel [2], which essentially
prevents the kernel from sending Tflush requests unless the process is about
to die (in which case the process likely doesn't care about the response).
Nevertheless, for older kernels and to comply with the spec, I believe this
change is beneficial.
# Implementation
The fix is fairly simple, just skipping notification of a reply if
the pdu was previously cancelled. We do however, also notify the transport
layer that we're doing this, so it can clean up any resources it may be
holding. I also added a new trace event to distinguish
operations that caused an error reply from those that were cancelled.
One complication is that we only omit sending the message on EINTR errors in
order to avoid confusing the rest of the code (which may assume that a
client knows about a fid if it sucessfully passed it off to pud_complete
without checking for cancellation status). This does mean that if the server
acts upon the cancellation flag, it always needs to set err to EINTR. I
believe this is true of the current code.
[1] https://9fans.github.io/plan9port/man/man9/flush.html
[2] https://github.com/torvalds/linux/commit/9523feac272ccad2ad8186ba4fcc891
Signed-off-by: Keno Fischer <keno@juliacomputing.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
[groug, send a zero-sized reply instead of detaching the buffer]
Signed-off-by: Greg Kurz <groug@kaod.org>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
No good reasons to do this outside of v9fs_device_realize_common().
Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
This backend raise some concerns:
- doesn't support symlinks
- fails +100 tests in the PJD POSIX file system test suite [1]
- requires the QEMU process to run with the CAP_DAC_READ_SEARCH
capability, which isn't recommended for security reasons
This backend should not be used and wil be removed. The 'local'
backend is the recommended alternative.
[1] https://www.tuxera.com/community/posix-test-suite/
Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Daniel P. Berrange <berrange@redhat.com>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
This patch changes some error messages in the backend init code and
convert backends to propagate QEMU Error objects instead of calling
error_report().
One notable improvement is that the local backend now provides a more
detailed error report when it fails to open the shared directory.
Signed-off-by: Greg Kurz <groug@kaod.org>
This patch changes some error messages in the backend opts parsing
code and convert backends to propagate QEMU Error objects instead
of calling error_report().
Signed-off-by: Greg Kurz <groug@kaod.org>
