Support VF device IDs used by the Hyper-V hypervisor.
Reviewed-by: Vasundhara Volam <vasundhara-v.volam@broadcom.com>
Reviewed-by: Andy Gospodarek <gospo@broadcom.com>
Signed-off-by: Edwin Peer <edwin.peer@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

When the PF is no longer enforcing an assigned MAC address on a VF, the
VF needs to call bnxt_approve_mac() to tell the PF what MAC address it is
now using.  Otherwise it gets out of sync and the PF won't know what
MAC address the VF wants to use.  Ultimately the VF will fail when it
tries to setup the L2 MAC filter for the vnic.
Reviewed-by: Edwin Peer <edwin.peer@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Move it before bnxt_update_vf_mac().  In the next patch, we need to call
bnxt_approve_mac() from bnxt_update_mac() under some conditions.  This
will avoid forward declaration.
Reviewed-by: Edwin Peer <edwin.peer@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

It is perfectly legal for the stack to query and configure VFs via PF
NDOs while the NIC is administratively down.  Remove the unnecessary
check for the PF to be in open state.
Signed-off-by: Edwin Peer <edwin.peer@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Firmware previously only allowed promiscuous mode for VFs associated with
a default VLAN. It is now possible to enable promiscuous mode for a VF
having no VLAN configured provided that it is trusted. In such cases the
VF will see all packets received by the PF, irrespective of destination
MAC or VLAN.

Note, it is necessary to query firmware at the time of bnxt_promisc_ok()
instead of in bnxt_hwrm_func_qcfg() because the trusted status might be
altered by the PF after the VF has been configured. This check must now
also be deferred because the firmware call sleeps.
Signed-off-by: Edwin Peer <edwin.peer@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

In the current code, the driver will not shutdown the link during
IFDOWN if there are still VFs sharing the port.  Newer firmware will
manage the link down decision when the port is shared by VFs, so
we can just call firmware to shutdown the port unconditionally and
let firmware make the final decision.
Reviewed-by: Edwin Peer <edwin.peer@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Copy the phy related feature flags from the firmware call
HWRM_PORT_PHY_QCAPS to this new field.  We can also remove the flags
field in the bnxt_test_info structure.  It's cleaner to have all PHY
related flags in one location, directly copied from the firmware.

To keep the BNXT_PHY_CFG_ABLE() macro logic the same, we need to make
a slight adjustment to check that it is a PF.
Reviewed-by: Edwin Peer <edwin.peer@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Firmware reports link signalling mode for certain speeds. In these
cases, print the signalling modes in kernel log link up messages.
Reviewed-by: Andy Gospodarek <gospo@broadcom.com>
Signed-off-by: Edwin Peer <edwin.peer@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

The default behavior for source MACVLAN is to duplicate packets to
appropriate type source devices, and then do the normal destination MACVLAN
flow. This patch adds an option to skip destination MACVLAN processing if
any matching source MACVLAN device has the option set.

This allows setting up a "catch all" device for source MACVLAN: create one
or more devices with type source nodst, and one device with e.g. type vepa,
and incoming traffic will be received on exactly one device.

v2: netdev wants non-standard line length
Signed-off-by: Jethro Beekman <kernel@jbeekman.nl>
Signed-off-by: David S. Miller <davem@davemloft.net>

Saeed Mahameed says:

====================
mlx5-updates-2021-04-21

devlink external port attribute for SF (Sub-Function) port flavour

This adds the support to instantiate Sub-Functions on external hosts
E.g when Eswitch manager is enabled on the ARM SmarNic SoC CPU, users
are now able to spawn new Sub-Functions on the Host server CPU.

Parav Pandit Says:
==================

This series introduces and uses external attribute for the SF port to
indicate that a SF port belongs to an external controller.

This is needed to generate unique phys_port_name when PF and SF numbers
are overlapping between local and external controllers.
For example two controllers 0 and 1, both of these controller have a SF.
having PF number 0, SF number 77. Here, phys_port_name has duplicate
entry which doesn't have controller number in it.

Hence, add controller number optionally when a SF port is for an
external controller. This extension is similar to existing PF and VF
eswitch ports of the external controller.

When a SF is for external controller an example view of external SF
port and config sequence:

On eswitch system:
$ devlink dev eswitch set pci/0033:01:00.0 mode switchdev

$ devlink port show
pci/0033:01:00.0/196607: type eth netdev enP51p1s0f0np0 flavour physical port 0 splittable false
pci/0033:01:00.0/131072: type eth netdev eth0 flavour pcipf controller 1 pfnum 0 external true splittable false
  function:
    hw_addr 00:00:00:00:00:00

$ devlink port add pci/0033:01:00.0 flavour pcisf pfnum 0 sfnum 77 controller 1
pci/0033:01:00.0/163840: type eth netdev eth1 flavour pcisf controller 1 pfnum 0 sfnum 77 splittable false
  function:
    hw_addr 00:00:00:00:00:00 state inactive opstate detached

phys_port_name construction:
$ cat /sys/class/net/eth1/phys_port_name
c1pf0sf77

Patch summary:
First 3 patches prepares the eswitch to handle vports in more generic
way using xarray to lookup vport from its unique vport number.
Patch-1 returns maximum eswitch ports only when eswitch is enabled
Patch-2 prepares eswitch to return eswitch max ports from a struct
Patch-3 uses xarray for vport and representor lookup
Patch-4 considers SF for an additioanl range of SF vports
Patch-5 relies on SF hw table to check SF support
Patch-6 extends SF devlink port attribute for external flag
Patch-7 stores the per controller SF allocation attributes
Patch-8 uses SF function id for filtering events
Patch-9 uses helper for allocation and free
Patch-10 splits hw table into per controller table and generic one
Patch-11 extends sf table for additional range

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

====================
Signed-off-by: David S. Miller <davem@davemloft.net>

This adds device tree probing to the IXP4xx ethernet
driver.

Add a platform data bool to tell us whether to
register an MDIO bus for the device or not, as well
as the corresponding NPE.

We need to drop the memory region request as part of
this since the OF core will request the memory for the
device.

Cc: Zoltan HERPAI <wigyori@uid0.hu>
Cc: Raylynn Knight <rayknight@me.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

This driver was using a really dated way of obtaining the
phy by printing a string and using it with phy_connect().
Switch to using more reasonable modern interfaces.
Suggested-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

This adds device tree bindings for the IXP4xx ethernet
controller with optional MDIO bridge.

Cc: Zoltan HERPAI <wigyori@uid0.hu>
Cc: Raylynn Knight <rayknight@me.com>
Cc: devicetree@vger.kernel.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

Remove DELL_TB_RX_AGG_BUG and LENOVO_MACPASSTHRU flags of rtl8152_flags.
They are only set when initializing and wouldn't be change. It is enough
to record them with variables.
Signed-off-by: Hayes Wang <hayeswang@realtek.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Currently the netvsc/VF binding logic only checks the PCI serial number.

The Microsoft Azure Network Adapter (MANA) supports multiple net_device
interfaces (each such interface is called a "vPort", and has its unique
MAC address) which are backed by the same VF PCI device, so the binding
logic should check both the MAC address and the PCI serial number.

The change should not break any other existing VF drivers, because
Hyper-V NIC SR-IOV implementation requires the netvsc network
interface and the VF network interface have the same MAC address.
Co-developed-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Co-developed-by: Shachar Raindel <shacharr@microsoft.com>
Signed-off-by: Shachar Raindel <shacharr@microsoft.com>
Acked-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Variable result is being assigned a value from a calculation
however the variable is never read, so this redundant variable
can be removed.

Cleans up the following clang-analyzer warning:

drivers/net/ethernet/chelsio/inline_crypto/ch_ktls/chcr_ktls.c:1488:2:
warning: Value stored to 'pos' is never read
[clang-analyzer-deadcode.DeadStores].

drivers/net/ethernet/chelsio/inline_crypto/ch_ktls/chcr_ktls.c:876:3:
warning: Value stored to 'pos' is never read
[clang-analyzer-deadcode.DeadStores].

drivers/net/ethernet/chelsio/inline_crypto/ch_ktls/chcr_ktls.c:36:3:
warning: Value stored to 'start' is never read
[clang-analyzer-deadcode.DeadStores].
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Alexei Starovoitov says:

====================
pull-request: bpf-next 2021-04-23

The following pull-request contains BPF updates for your *net-next* tree.

We've added 69 non-merge commits during the last 22 day(s) which contain
a total of 69 files changed, 3141 insertions(+), 866 deletions(-).

The main changes are:

1) Add BPF static linker support for extern resolution of global, from Andrii.

2) Refine retval for bpf_get_task_stack helper, from Dave.

3) Add a bpf_snprintf helper, from Florent.

4) A bunch of miscellaneous improvements from many developers.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

Extended the SF table to cover additioanl SF id range of external
controller.

A user optionallly provides the external controller number when user
wants to create SF on the external controller.

An example on eswitch system:
$ devlink dev eswitch set pci/0033:01:00.0 mode switchdev

$ devlink port show
pci/0033:01:00.0/196607: type eth netdev enP51p1s0f0np0 flavour physical port 0 splittable false
pci/0033:01:00.0/131072: type eth netdev eth0 flavour pcipf controller 1 pfnum 0 external true splittable false
  function:
    hw_addr 00:00:00:00:00:00

$ devlink port add pci/0033:01:00.0 flavour pcisf pfnum 0 sfnum 77 controller 1
pci/0033:01:00.0/163840: type eth netdev eth1 flavour pcisf controller 1 pfnum 0 sfnum 77 external true splittable false
  function:
    hw_addr 00:00:00:00:00:00 state inactive opstate detached
Signed-off-by: Parav Pandit <parav@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

Device has SF ids in two different contiguous ranges. One for the local
controller and second for the external controller's PF.

Each such range has its own maximum number of functions and base id.
To allocate SF from either of the range, prepare code to split into
range specific fields into its own structure.
Signed-off-by: Parav Pandit <parav@nvidia.com>
Reviewed-by: Vu Pham <vuhuong@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

Use helper routines for SF id and SF table allocation and free
so that subsequent patch can reuse it for multiple SF function
id range.
Signed-off-by: Parav Pandit <parav@nvidia.com>
Reviewed-by: Vu Pham <vuhuong@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

Vhca events on eswitch manager are received for all the functions on the
NIC, including for SFs of external host PF controllers.

While SF device handler is only interested in SF devices events related
to its own PF.
Hence, validate if the function belongs to self or not.
Signed-off-by: Parav Pandit <parav@nvidia.com>
Reviewed-by: Vu Pham <vuhuong@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

SF ids in the device are in two different contiguous ranges. One for
the local controller and second for the external host controller.

Prepare code to handle multiple start function id by storing it in the
table.
Signed-off-by: Parav Pandit <parav@nvidia.com>
Reviewed-by: Vu Pham <vuhuong@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

Extended SF port attributes to have optional external flag similar to
PCI PF and VF port attributes.

External atttibute is required to generate unique phys_port_name when PF number
and SF number are overlapping between two controllers similar to SR-IOV
VFs.

When a SF is for external controller an example view of external SF
port and config sequence.

On eswitch system:
$ devlink dev eswitch set pci/0033:01:00.0 mode switchdev

$ devlink port show
pci/0033:01:00.0/196607: type eth netdev enP51p1s0f0np0 flavour physical port 0 splittable false
pci/0033:01:00.0/131072: type eth netdev eth0 flavour pcipf controller 1 pfnum 0 external true splittable false
  function:
    hw_addr 00:00:00:00:00:00

$ devlink port add pci/0033:01:00.0 flavour pcisf pfnum 0 sfnum 77 controller 1
pci/0033:01:00.0/163840: type eth netdev eth1 flavour pcisf controller 1 pfnum 0 sfnum 77 splittable false
  function:
    hw_addr 00:00:00:00:00:00 state inactive opstate detached

phys_port_name construction:
$ cat /sys/class/net/eth1/phys_port_name
c1pf0sf77
Signed-off-by: Parav Pandit <parav@nvidia.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Reviewed-by: Vu Pham <vuhuong@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

Supporting SF allocation is currently checked at two places:
(a) SF devlink port allocator and
(b) SF HW table handler.

Both layers are using HCA CAP to identify it using helper routine
mlx5_sf_supported() and mlx5_sf_max_functions().

Instead, rely on the HW table handler to check if SF is supported
or not.
Signed-off-by: Parav Pandit <parav@nvidia.com>
Reviewed-by: Vu Pham <vuhuong@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

Query SF vports count and base id of host PF from the firmware.

Account these ports in the total port calculation whenever it is non
zero.
Signed-off-by: Parav Pandit <parav@nvidia.com>
Reviewed-by: Roi Dayan <roid@nvidia.com>
Reviewed-by: Vu Pham <vuhuong@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

Currently vport number to vport and its representor are mapped using an
array and an index.

Vport numbers of different types of functions are not contiguous. Adding
new such discontiguous range using index and number mapping is increasingly
complex and hard to maintain.

Hence, maintain an xarray of vport and rep whose lookup is done based on
the vport number.
Each VF and SF entry is marked with a xarray mark to identify the function
type. Additionally PF and VF needs special handling for legacy inline
mode. They are additionally marked as host function using additional
HOST_FN mark.
Signed-off-by: Parav Pandit <parav@nvidia.com>
Reviewed-by: Roi Dayan <roid@nvidia.com>
Reviewed-by: Vu Pham <vuhuong@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

Total vports are already stored during eswitch initialization. Instead
of calculating everytime, read directly from eswitch.

Additionally, host PF's SF vport information is available using
QUERY_HCA_CAP command. It is not available through HCA_CAP of the
eswitch manager PF.
Hence, this patch prepares the return total eswitch vport count from the
existing eswitch struct.

This further helps to keep eswitch port counting macros and logic within
eswitch.
Signed-off-by: Parav Pandit <parav@nvidia.com>
Reviewed-by: Roi Dayan <roid@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

mlx5_eswitch_get_total_vports() doesn't honor MLX5_ESWICH Kconfig flag.

When MLX5_ESWITCH is disabled, FS layer continues to initialize eswitch
specific ACL namespaces.
Instead, start honoring MLX5_ESWITCH flag and perform vport specific
initialization only when vport count is non zero.
Signed-off-by: Parav Pandit <parav@nvidia.com>
Reviewed-by: Roi Dayan <roid@nvidia.com>
Reviewed-by: Vu Pham <vuhuong@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

pahole starts to use libbpf definitions and APIs since v1.13 after the
commit 21507cd3e97b ("pahole: add libbpf as submodule under lib/bpf").
It works well with the git repository because the libbpf submodule will
use "git submodule update --init --recursive" to update.

Unfortunately, the default github release source code does not contain
libbpf submodule source code and this will cause build issues, the tarball
from https://git.kernel.org/pub/scm/devel/pahole/pahole.git/ is same with
github, you can get the source tarball with corresponding libbpf submodule
codes from

https://fedorapeople.org/~acme/dwarves

This change documents the above issues to give more information so that
we can get the tarball from the right place, early discussion is here:

https://lore.kernel.org/bpf/2de4aad5-fa9e-1c39-3c92-9bb9229d0966@loongson.cn/Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Link: https://lore.kernel.org/bpf/1619141010-12521-1-git-send-email-yangtiezhu@loongson.cn

Added .config_intr and .handle_interrupt callbacks.

Link event interrupt will trigger an interrupt every time when the link
goes up or down.
Signed-off-by: Radu Pirea (NXP OSS) <radu-nicolae.pirea@oss.nxp.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

There is a spelling mistake in a printk message. Fix it.
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

We found that with the latest mainline kernel (5.12.0-051200rc8) on
some KVM instances / bare-metal systems, the following tests will take
longer than the kselftest framework default timeout (45 seconds) to
run and thus got terminated with TIMEOUT error:
* xfrm_policy.sh - took about 2m20s
* pmtu.sh - took about 3m5s
* udpgso_bench.sh - took about 60s

Bump the timeout setting to 5 minutes to allow them have a chance to
finish.

https://bugs.launchpad.net/bugs/1856010Signed-off-by: Po-Hsu Lin <po-hsu.lin@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Mat Martineau says:

====================
mptcp: Compatibility with common msg flags

These patches from the MPTCP tree handle some of the msg flags that are
typically used with TCP, to make it easier to adapt userspace programs
for use with MPTCP.

Patches 1, 2, and 4 add support for MSG_ERRQUEUE (no-op for now),
MSG_TRUNC, and MSG_PEEK on the receive side.

Patch 3 ignores unsupported msg flags for send and receive.

Patch 5 adds a selftest for MSG_PEEK.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

Extend mptcp_connect tool with MSG_PEEK support and add a test case in
mptcp_connect.sh that checks the data received from/after recv() with
MSG_PEEK.
Acked-by: Paolo Abeni <pabeni@redhat.com>
Co-developed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Yonglong Li <liyonglong@chinatelecom.cn>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

This patch adds support for MSG_PEEK flag. Packets are not removed
from the receive_queue if MSG_PEEK set in recv() system call.
Acked-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Yonglong Li <liyonglong@chinatelecom.cn>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Currently mptcp_sendmsg() fails with EOPNOTSUPP if the
user-space provides some unsupported flag. That is unexpected
and may foul existing applications migrated to MPTCP, which
expect a different behavior.

Change the mentioned function to silently ignore the unsupported
flags except MSG_FASTOPEN. This is the only flags currently not
supported by MPTCP with user-space visible side-effects.

Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/162Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

The mentioned flag is currently silenlty ignored. This
change implements the TCP-like behaviour, dropping the
pending data up to the specified length.
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Sigend-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

mptcp_recvmsg() currently silently ignores MSG_ERRQUEUE, returning
input data instead of error cmsg.

This change provides a dummy implementation for MSG_ERRQUEUE - always
returns no data. That is consistent with the current lack of a suitable
IP_RECVERR setsockopt() support.
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Andrii Nakryiko says:

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

Add BPF static linker support for extern resolution of global variables,
functions, and BTF-defined maps.

This patch set consists of 4 parts:
  - few patches are extending bpftool to simplify working with BTF dump;
  - libbpf object loading logic is extended to support __hidden functions and
    overriden (unused) __weak functions; also BTF-defined map parsing logic is
    refactored to be re-used by linker;
  - the crux of the patch set is BPF static linker logic extension to perform
    extern resolution for three categories: global variables, BPF
    sub-programs, BTF-defined maps;
  - a set of selftests that validate that all the combinations of
    extern/weak/__hidden are working as expected.

See respective patches for more details.

One aspect hasn't been addressed yet and is going to be resolved in the next
patch set, but is worth mentioning. With BPF static linking of multiple .o
files, dealing with static everything becomes more problematic for BPF
skeleton and in general for any by name look up APIs. This is due to static
entities are allowed to have non-unique name. Historically this was never
a problem due to BPF programs were always confined to a single C file. That
changes now and needs to be addressed. The thinking so far is for BPF static
linker to prepend filename to each static variable and static map (which is
currently not supported by libbpf, btw), so that they can be unambiguously
resolved by (mostly) unique name. Mostly, because even filenames can be
duplicated, but that should be rare and easy to address by wiser choice of
filenames by users. Fortunately, static BPF subprograms don't suffer from this
issues, as they are not independent entities and are neither exposed in BPF
skeleton, nor is lookup-able by any of libbpf APIs (and there is little reason
to do that anyways).

This and few other things will be the topic of the next set of patches.

Some tests rely on Clang fix ([0]), so need latest Clang built from main.

  [0] https://reviews.llvm.org/D100362

v2->v3:
  - allow only STV_DEFAULT and STV_HIDDEN ELF symbol visibility (Yonghong);
  - update selftests' README for required Clang 13 fix dependency (Alexei);
  - comments, typos, slight code changes (Yonghong, Alexei);

v1->v2:
  - make map externs support full attribute list, adjust linked_maps selftest
    to demonstrate that typedef works now (though no shared header file was
    added to simplicity sake) (Alexei);
  - remove commented out parts from selftests and fix few minor code style
    issues;
  - special __weak map definition semantics not yet implemented and will be
    addressed in a follow up.
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Document which fixes are required to generate correct static linking
selftests.
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/20210423181348.1801389-19-andrii@kernel.org