A later commit will need to lookup a subset of these opcodes. To
avoid duplicating code, pull out a table.

The shift opcodes won't be needed by that later commit, but they're
already duplicated, so fold them into the table anyway.
Signed-off-by: Brendan Jackman <jackmanb@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20210114181751.768687-4-jackmanb@google.com

The JIT case for encoding atomic ops is about to get more
complicated. In order to make the review & resulting code easier,
let's factor out some shared helpers.
Signed-off-by: Brendan Jackman <jackmanb@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20210114181751.768687-3-jackmanb@google.com

The case for JITing atomics is about to get more complicated. Let's
factor out some common code to make the review and result more
readable.

NB the atomics code doesn't yet use the new helper - a subsequent
patch will add its use as a side-effect of other changes.
Signed-off-by: Brendan Jackman <jackmanb@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20210114181751.768687-2-jackmanb@google.com

No additional warnings are generated by enabling this, but having it
enabled will help avoid regressions.
Signed-off-by: Ian Rogers <irogers@google.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20210113223609.3358812-2-irogers@google.com

Add inline to __always_inline making it match the linux/compiler.h.
Adding this avoids an unused function warning on bpf_tail_call_static
when compining with -Wall.
Signed-off-by: Ian Rogers <irogers@google.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210113223609.3358812-1-irogers@google.com

Jean-Philippe Brucker says:

====================

A few fixes for cross-building the sefltests out of tree. This will
enable wider automated testing on various Arm hardware.

Changes since v1 [1]:
* Use wildcard in patch 5
* Move the MAKE_DIRS declaration in patch 1

[1] https://lore.kernel.org/bpf/20210112135959.649075-1-jean-philippe@linaro.org/
====================
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

The btf_dump test cannot access the original source files for comparison
when running the selftests out of tree, causing several failures:

awk: btf_dump_test_case_syntax.c: No such file or directory
...

Add those files to $(TEST_FILES) to have "make install" pick them up.
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210113163319.1516382-6-jean-philippe@linaro.org

For out-of-tree builds, $(TEST_CUSTOM_PROGS) require the $(OUTPUT)
prefix, otherwise the kselftest lib doesn't know how to install them:

rsync: [sender] link_stat "tools/testing/selftests/bpf/urandom_read" failed: No such file or directory (2)
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210113163319.1516382-5-jean-philippe@linaro.org

During an out-of-tree build, attempting to install the $(TEST_FILES)
into the $(OUTPUT) directory fails, because the objects were already
generated into $(OUTPUT):

rsync: [sender] link_stat "tools/testing/selftests/bpf/test_lwt_ip_encap.o" failed: No such file or directory (2)
rsync: [sender] link_stat "tools/testing/selftests/bpf/test_tc_edt.o" failed: No such file or directory (2)

Use $(TEST_GEN_FILES) instead.
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210113163319.1516382-4-jean-philippe@linaro.org

When building out-of-tree, the .skel.h files are generated into the
$(OUTPUT) directory, rather than $(CURDIR). Add $(OUTPUT) to the include
paths.
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210113163319.1516382-3-jean-philippe@linaro.org

Build bpftool and resolve_btfids using the host toolchain when
cross-compiling, since they are executed during build to generate the
selftests. Add a host build directory in order to build both host and
target version of libbpf. Build host tools using $(HOSTCC) defined in
Makefile.include.
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210113163319.1516382-2-jean-philippe@linaro.org

Andrii Nakryiko says:

====================

Add support for using kernel module global variables (__ksym externs in BPF
program). BPF verifier will now support ldimm64 with src_reg=BPF_PSEUDO_BTF_ID
and non-zero insn[1].imm field, specifying module BTF's FD. In such case,
module BTF object, similarly to BPF maps referenced from ldimm64 with
src_reg=BPF_PSEUDO_MAP_FD, will be recorded in bpf_progran's auxiliary data
and refcnt will be increased for both BTF object itself and its kernel module.
This makes sure kernel module won't be unloaded from under active attached BPF
program. These refcounts will be dropped when BPF program is unloaded.

New selftest validates all this is working as intended. bpf_testmod.ko is
extended with per-CPU variable. Selftests expects the latest pahole changes
(soon to be released as v1.20) to generate per-CPU variable BTF info for
kernel module.

v2->v3:
  - added comments, addressed feedack (Yonghong, Hao);
v1->v2:
  - fixed few compiler warnings, posted as separate pre-patches;
rfc->v1:
  - use sys_membarrier(MEMBARRIER_CMD_GLOBAL) (Alexei).

Cc: Hao Luo <haoluo@google.com>
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Add per-CPU variable to bpf_testmod.ko and use those from new selftest to
validate it works end-to-end.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Hao Luo <haoluo@google.com>
Link: https://lore.kernel.org/bpf/20210112075520.4103414-8-andrii@kernel.org

Add support for searching for ksym externs not just in vmlinux BTF, but across
all module BTFs, similarly to how it's done for CO-RE relocations. Kernels
that expose module BTFs through sysfs are assumed to support new ldimm64
instruction extension with BTF FD provided in insn[1].imm field, so no extra
feature detection is performed.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Hao Luo <haoluo@google.com>
Link: https://lore.kernel.org/bpf/20210112075520.4103414-7-andrii@kernel.org

Add support for directly accessing kernel module variables from BPF programs
using special ldimm64 instructions. This functionality builds upon vmlinux
ksym support, but extends ldimm64 with src_reg=BPF_PSEUDO_BTF_ID to allow
specifying kernel module BTF's FD in insn[1].imm field.

During BPF program load time, verifier will resolve FD to BTF object and will
take reference on BTF object itself and, for module BTFs, corresponding module
as well, to make sure it won't be unloaded from under running BPF program. The
mechanism used is similar to how bpf_prog keeps track of used bpf_maps.

One interesting change is also in how per-CPU variable is determined. The
logic is to find .data..percpu data section in provided BTF, but both vmlinux
and module each have their own .data..percpu entries in BTF. So for module's
case, the search for DATASEC record needs to look at only module's added BTF
types. This is implemented with custom search function.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Hao Luo <haoluo@google.com>
Link: https://lore.kernel.org/bpf/20210112075520.4103414-6-andrii@kernel.org

If some of the subtests use module BTFs through ksyms, they will cause
bpf_prog to take a refcount on bpf_testmod module, which will prevent it from
successfully unloading. Module's refcnt is decremented when bpf_prog is freed,
which generally happens in RCU callback. So we need to trigger
syncronize_rcu() in the kernel, which can be achieved nicely with
membarrier(MEMBARRIER_CMD_SHARED) or membarrier(MEMBARRIER_CMD_GLOBAL) syscall.
So do that in kernel_sync_rcu() and make it available to other test inside the
test_progs. This synchronize_rcu() is called before attempting to unload
bpf_testmod.

Fixes: 9f7fa225 ("selftests/bpf: Add bpf_testmod kernel module for testing")
Suggested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Hao Luo <haoluo@google.com>
Link: https://lore.kernel.org/bpf/20210112075520.4103414-5-andrii@kernel.org

__bpf_free_used_maps() is always defined in kernel/bpf/core.c, while
include/linux/bpf.h is guarding it behind CONFIG_BPF_SYSCALL. Move it out of
that guard region and fix compiler warning.

Fixes: a2ea0746 ("bpf: Fix missing prog untrack in release_maps")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20210112075520.4103414-4-andrii@kernel.org

BPF interpreter uses extra input argument, so re-casts __bpf_call_base into
__bpf_call_base_args. Avoid compiler warning about incompatible function
prototypes by casting to void * first.

Fixes: 1ea47e01 ("bpf: add support for bpf_call to interpreter")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20210112075520.4103414-3-andrii@kernel.org

Add bpf_patch_call_args() prototype. This function is called from BPF verifier
and only if CONFIG_BPF_JIT_ALWAYS_ON is not defined. This fixes compiler
warning about missing prototype in some kernel configurations.

Fixes: 1ea47e01 ("bpf: add support for bpf_call to interpreter")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20210112075520.4103414-2-andrii@kernel.org

Extend existing cgroup bind4/bind6 tests to add coverage for setting and
retrieving SO_MARK, SO_PRIORITY and SO_BINDTOIFINDEX at the bind hook.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/384fdc90e5fa83f8335a37aa90fa2f5f3661929c.1610406333.git.daniel@iogearbox.net

The _bpf_setsockopt() is able to set some of the SOL_SOCKET level options,
however, _bpf_getsockopt() has little support to actually retrieve them.
This small patch adds few misc options such as SO_MARK, SO_PRIORITY and
SO_BINDTOIFINDEX. For the latter getter and setter are added. The mark and
priority in particular allow to retrieve the options from BPF cgroup hooks
to then implement custom behavior / settings on the syscall hooks compared
to other sockets that stick to the defaults, for example.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/cba44439b801e5ddc1170e5be787f4dc93a2d7f9.1610406333.git.daniel@iogearbox.net

The error message here is misleading, the argument will be rejected unless
it is a known constant.
Signed-off-by: Brendan Jackman <jackmanb@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210112123913.2016804-1-jackmanb@google.com

When the buffer is too small to contain the input string, these helpers
return the length of the buffer, not the length of the original string.
This tries to make the docs totally clear about that, since "the length
of the [copied ]string" could also refer to the length of the input.
Signed-off-by: Brendan Jackman <jackmanb@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: KP Singh <kpsingh@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20210112123422.2011234-1-jackmanb@google.com

Add comments clarifying that USER variants of CO-RE reading macro are still
only going to work with kernel types, defined in kernel or kernel module BTF.
This should help preventing invalid use of those macro to read user-defined
types (which doesn't work with CO-RE).
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210108194408.3468860-1-andrii@kernel.org

'unistd.h' included in 'selftests/bpf/prog_tests/test_lsm.c' is
duplicated.
Signed-off-by: Menglong Dong <dong.menglong@zte.com.cn>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20210105152047.6070-1-dong.menglong@zte.com.cnSigned-off-by: Alexei Starovoitov <ast@kernel.org>

Introduce xdp_prepare_buff utility routine to initialize per-descriptor
xdp_buff fields (e.g. xdp_buff pointers). Rely on xdp_prepare_buff() in
all XDP capable drivers.
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Shay Agroskin <shayagr@amazon.com>
Acked-by: Martin Habets <habetsm.xilinx@gmail.com>
Acked-by: Camelia Groza <camelia.groza@nxp.com>
Acked-by: Marcin Wojtas <mw@semihalf.com>
Link: https://lore.kernel.org/bpf/45f46f12295972a97da8ca01990b3e71501e9d89.1608670965.git.lorenzo@kernel.orgSigned-off-by: Alexei Starovoitov <ast@kernel.org>

Introduce xdp_init_buff utility routine to initialize xdp_buff fields
const over NAPI iterations (e.g. frame_sz or rxq pointer). Rely on
xdp_init_buff in all XDP capable drivers.
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Shay Agroskin <shayagr@amazon.com>
Acked-by: Martin Habets <habetsm.xilinx@gmail.com>
Acked-by: Camelia Groza <camelia.groza@nxp.com>
Acked-by: Marcin Wojtas <mw@semihalf.com>
Link: https://lore.kernel.org/bpf/7f8329b6da1434dc2b05a77f2e800b29628a8913.1608670965.git.lorenzo@kernel.orgSigned-off-by: Alexei Starovoitov <ast@kernel.org>

The function sockfd_lookup uses fget on the value that is stored in
the file field of the returned structure, so fput should ultimately
be applied to this value. This can be done directly, but it seems
better to use the specific macro sockfd_put, which does the same
thing.

The cleanup was done using the following semantic patch:
    (http://www.emn.fr/x-info/coccinelle/)

    // <smpl>
    @@
    expression s;
    @@

       s = sockfd_lookup(...)
       ...
    +  sockfd_put(s);
    ?- fput(s->file);
    // </smpl>
Signed-off-by: Zheng Yongjun <zhengyongjun3@huawei.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20201229134834.22962-1-zhengyongjun3@huawei.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

This program does not use argp (which is a glibcism). Instead include <errno.h>
directly, which was pulled in by <argp.h>.
Signed-off-by: Leah Neukirchen <leah@vuxu.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20201216100306.30942-1-leah@vuxu.orgSigned-off-by: Alexei Starovoitov <ast@kernel.org>

Add selftests validating that newly added variations of BPF_CORE_READ(), for
use with user-space addresses and for non-CO-RE reads, work as expected.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20201218235614.2284956-4-andrii@kernel.orgSigned-off-by: Alexei Starovoitov <ast@kernel.org>

BPF_CORE_READ(), in addition to handling CO-RE relocations, also allows much
nicer way to read data structures with nested pointers. Instead of writing
a sequence of bpf_probe_read() calls to follow links, one can just write
BPF_CORE_READ(a, b, c, d) to effectively do a->b->c->d read. This is a welcome
ability when porting BCC code, which (in most cases) allows exactly the
intuitive a->b->c->d variant.

This patch adds non-CO-RE variants of BPF_CORE_READ() family of macros for
cases where CO-RE is not supported (e.g., old kernels). In such cases, the
property of shortening a sequence of bpf_probe_read()s to a simple
BPF_PROBE_READ(a, b, c, d) invocation is still desirable, especially when
porting BCC code to libbpf. Yet, no CO-RE relocation is going to be emitted.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20201218235614.2284956-3-andrii@kernel.orgSigned-off-by: Alexei Starovoitov <ast@kernel.org>

Add BPF_CORE_READ_USER(), BPF_CORE_READ_USER_STR() and their _INTO()
variations to allow reading CO-RE-relocatable kernel data structures from the
user-space. One of such cases is reading input arguments of syscalls, while
reaping the benefits of CO-RE relocations w.r.t. handling 32/64 bit
conversions and handling missing/new fields in UAPI data structs.
Suggested-by: Gilad Reti <gilad.reti@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20201218235614.2284956-2-andrii@kernel.orgSigned-off-by: Alexei Starovoitov <ast@kernel.org>

Trivial conflict in CAN on file rename.

Conflicts:
	drivers/net/can/m_can/tcan4x5x-core.c
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Pull more networking fixes from Jakub Kicinski:
 "Slightly lighter pull request to get back into the Thursday cadence.

  Current release - always broken:

   - can: mcp251xfd: fix Tx/Rx ring buffer driver race conditions

   - dsa: hellcreek: fix led_classdev build errors

  Previous releases - regressions:

   - ipv6: fib: flush exceptions when purging route to avoid netdev
     reference leak

   - ip_tunnels: fix pmtu check in nopmtudisc mode

   - ip: always refragment ip defragmented packets to avoid MTU issues
     when forwarding through tunnels, correct "packet too big" message
     is prohibitively tricky to generate

   - s390/qeth: fix locking for discipline setup / removal and during
     recovery to prevent both deadlocks and races

   - mlx5: Use port_num 1 instead of 0 when delete a RoCE address

  Previous releases - always broken:

   - cdc_ncm: correct overhead calculation in delayed_ndp_size to
     prevent out of bound accesses with Huawei 909s-120 LTE module

   - fix stmmac dwmac-sun8i suspend/resume:
           - PHY being left powered off
           - MAC syscon configuration being reset
           - reference to the reset controller being improperly dropped

   - qrtr: fix null-ptr-deref in qrtr_ns_remove

   - can: tcan4x5x: fix bittiming const, use common bittiming from m_can
     driver

   - mlx5e: CT: Use per flow counter when CT flow accounting is enabled

   - mlx5e: Fix SWP offsets when vlan inserted by driver

  Misc:

   - bpf: Fix a task_iter bug caused by a bpf -> net merge conflict
     resolution

  And the usual many fixes to various error paths"

* tag 'net-5.11-rc3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net: (69 commits)
  net: dsa: lantiq_gswip: Exclude RMII from modes that report 1 GbE
  s390/qeth: fix L2 header access in qeth_l3_osa_features_check()
  s390/qeth: fix locking for discipline setup / removal
  s390/qeth: fix deadlock during recovery
  selftests: fib_nexthops: Fix wrong mausezahn invocation
  nexthop: Bounce NHA_GATEWAY in FDB nexthop groups
  nexthop: Unlink nexthop group entry in error path
  nexthop: Fix off-by-one error in error path
  octeontx2-af: fix memory leak of lmac and lmac->name
  chtls: Fix chtls resources release sequence
  chtls: Added a check to avoid NULL pointer dereference
  chtls: Replace skb_dequeue with skb_peek
  chtls: Avoid unnecessary freeing of oreq pointer
  chtls: Fix panic when route to peer not configured
  chtls: Remove invalid set_tcb call
  chtls: Fix hardware tid leak
  net: ip: always refragment ip defragmented packets
  net: fix pmtu check in nopmtudisc mode
  selftests: netfilter: add selftest for ipip pmtu discovery with enabled connection tracking
  docs: octeontx2: tune rst markup
  ...

Pull crypto fixes from Herbert Xu:
 "This fixes a functional bug in arm/chacha-neon as well as a potential
  buffer overflow in ecdh"

* 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6:
  crypto: ecdh - avoid buffer overflow in ecdh_set_secret()
  crypto: arm/chacha-neon - add missing counter increment

The kernel test robot reported a -5.8% performance regression on the
"poll2" test of will-it-scale, and bisected it to commit d55564cf
("x86: Make __put_user() generate an out-of-line call").

I didn't expect an out-of-line __put_user() to matter, because no normal
core code should use that non-checking legacy version of user access any
more.  But I had overlooked the very odd poll() usage, which does a
__put_user() to update the 'revents' values of the poll array.

Now, Al Viro correctly points out that instead of updating just the
'revents' field, it would be much simpler to just copy the _whole_
pollfd entry, and then we could just use "copy_to_user()" on the whole
array of entries, the same way we use "copy_from_user()" a few lines
earlier to get the original values.

But that is not what we've traditionally done, and I worry that threaded
applications might be concurrently modifying the other fields of the
pollfd array.  So while Al's suggestion is simpler - and perhaps worth
trying in the future - this instead keeps the "just update revents"
model.

To fix the performance regression, use the modern "unsafe_put_user()"
instead of __put_user(), with the proper "user_write_access_begin()"
guarding in place. This improves code generation enormously.

Link: https://lore.kernel.org/lkml/20210107134723.GA28532@xsang-OptiPlex-9020/Reported-by: kernel test robot <oliver.sang@intel.com>
Tested-by: Oliver Sang <oliver.sang@intel.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: David Laight <David.Laight@aculab.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This reverts commit 757055ae.

The commit caused that ttynull was used as the default console
on several systems[1][2][3]. As a result, the console was
blank even when a better alternative existed.

It happened when there was no console configured
on the command line and ttynull_init() was the first initcall
calling register_console().

Or it happened when /dev/ did not exist when console_on_rootfs()
was called. It was not able to open /dev/console even though
a console driver was registered. It tried to add ttynull console
but it obviously did not help. But ttynull became the preferred
console and was used by /dev/console when it was available later.

The commit tried to fix a historical problem that have been there
for ages. The primary motivation was the commit 3cffa06a
("printk/console: Allow to disable console output by using console=""
 or console=null"). It provided a clean solution for a workaround
 that was widely used and worked only by chance.

This revert causes that the console="" or console=null command line
options will again work only by chance. These options will cause that
a particular console will be preferred and the default (tty) ones
will not get enabled. There will be no console registered at
all. As a result there won't be stdin, stdout, and stderr for
the init process. But it worked exactly this way even before.

The proper solution has to fulfill many conditions:

  + Register ttynull only when explicitly required or as
    the ultimate fallback.

  + ttynull should get associated with /dev/console but it must
    not become preferred console when used as a fallback.
    Especially, it must still be possible to replace it
    by a better console later.

Such a change requires clean up of the register_console() code.
Otherwise, it would be even harder to follow. Especially, the use
of has_preferred_console and CON_CONSDEV flag is tricky. The clean
up is risky. The ordering of consoles is not well defined. And
any changes tend to break existing user settings.

Do the revert at the least risky solution for now.

[1] https://lore.kernel.org/linux-kselftest/20201221144302.GR4077@smile.fi.intel.com/
[2] https://lore.kernel.org/lkml/d2a3b3c0-e548-7dd1-730f-59bc5c04e191@synopsys.com/
[3] https://patchwork.ozlabs.org/project/linux-um/patch/20210105120128.10854-1-thomas@m3y3r.de/Reported-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reported-by: Vineet Gupta <vgupta@synopsys.com>
Reported-by: Thomas Meyer <thomas@m3y3r.de>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Saeed Mahameed says:

====================
mlx5 fixes 2021-01-07

* tag 'mlx5-fixes-2021-01-07' of git://git.kernel.org/pub/scm/linux/kernel/git/saeed/linux:
  net/mlx5e: Fix memleak in mlx5e_create_l2_table_groups
  net/mlx5e: Fix two double free cases
  net/mlx5: Release devlink object if adev fails
  net/mlx5e: ethtool, Fix restriction of autoneg with 56G
  net/mlx5e: In skb build skip setting mark in switchdev mode
  net/mlx5: E-Switch, fix changing vf VLANID
  net/mlx5e: Fix SWP offsets when vlan inserted by driver
  net/mlx5e: CT: Use per flow counter when CT flow accounting is enabled
  net/mlx5: Use port_num 1 instead of 0 when delete a RoCE address
  net/mlx5e: Add missing capability check for uplink follow
  net/mlx5: Check if lag is supported before creating one
====================

Link: https://lore.kernel.org/r/20210107202845.470205-1-saeed@kernel.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

Exclude RMII from modes that report 1 GbE support. Reduced MII supports
up to 100 MbE.

Fixes: 14fceff4 ("net: dsa: Add Lantiq / Intel DSA driver for vrx200")
Signed-off-by: Aleksander Jan Bajkowski <olek2@wp.pl>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20210107195818.3878-1-olek2@wp.plSigned-off-by: Jakub Kicinski <kuba@kernel.org>

Julian Wiedmann says:

====================
s390/qeth: fixes 2021-01-07

This brings two locking fixes for the device control path.
Also one fix for a path where our .ndo_features_check() attempts to
access a non-existent L2 header.
====================

Link: https://lore.kernel.org/r/20210107172442.1737-1-jwi@linux.ibm.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>