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

Add selftest validating various aspects of statically linking BTF-defined map
definitions. Legacy map definitions do not support extern resolution between
object files. Some of the aspects validated:
  - correct resolution of extern maps against concrete map definitions;
  - extern maps can currently only specify map type and key/value size and/or
    type information;
  - weak concrete map definitions are resolved properly.

Static map definitions are not yet supported by libbpf, so they are not
explicitly tested, though manual testing showes that BPF linker handles them
properly.
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/20210423181348.1801389-18-andrii@kernel.org

Add selftest validating various aspects of statically linking global
variables:
  - correct resolution of extern variables across .bss, .data, and .rodata
    sections;
  - correct handling of weak definitions;
  - correct de-duplication of repeating special externs (.kconfig, .ksyms).
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/20210423181348.1801389-17-andrii@kernel.org

Add selftest validating various aspects of statically linking functions:
  - no conflicts and correct resolution for name-conflicting static funcs;
  - correct resolution of extern functions;
  - correct handling of weak functions, both resolution itself and libbpf's
    handling of unused weak function that "lost" (it leaves gaps in code with
    no ELF symbols);
  - correct handling of hidden visibility to turn global function into
    "static" for the purpose of BPF verification.
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/20210423181348.1801389-16-andrii@kernel.org

Skip generating individual BPF skeletons for files that are supposed to be
linked together to form the final BPF object file. Very often such files are
"incomplete" BPF object files, which will fail libbpf bpf_object__open() step,
if used individually, thus failing BPF skeleton generation. This is by design,
so skip individual BPF skeletons and only validate them as part of their
linked final BPF object file and skeleton.
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/20210423181348.1801389-15-andrii@kernel.org

While -Og is designed to work well with debugger, it's still inferior to -O0
in terms of debuggability experience. It will cause some variables to still be
inlined, it will also prevent single-stepping some statements and otherwise
interfere with debugging experience. So switch to -O0 which turns off any
optimization and provides the best debugging experience.
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/20210423181348.1801389-14-andrii@kernel.org

Add extra logic to handle map externs (only BTF-defined maps are supported for
linking). Re-use the map parsing logic used during bpf_object__open(). Map
externs are currently restricted to always match complete map definition. So
all the specified attributes will be compared (down to pining, map_flags,
numa_node, etc). In the future this restriction might be relaxed with no
backwards compatibility issues. If any attribute is mismatched between extern
and actual map definition, linker will report an error, pointing out which one
mismatches.

The original intent was to allow for extern to specify attributes that matters
(to user) to enforce. E.g., if you specify just key information and omit
value, then any value fits. Similarly, it should have been possible to enforce
map_flags, pinning, and any other possible map attribute. Unfortunately, that
means that multiple externs can be only partially overlapping with each other,
which means linker would need to combine their type definitions to end up with
the most restrictive and fullest map definition. This requires an extra amount
of BTF manipulation which at this time was deemed unnecessary and would
require further extending generic BTF writer APIs. So that is left for future
follow ups, if there will be demand for that. But the idea seems intresting
and useful, so I want to document it here.

Weak definitions are also supported, but are pretty strict as well, just
like externs: all weak map definitions have to match exactly. In the follow up
patches this most probably will be relaxed, with __weak map definitions being
able to differ between each other (with non-weak definition always winning, of
course).
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/20210423181348.1801389-13-andrii@kernel.org

Add BPF static linker logic to resolve extern variables and functions across
multiple linked together BPF object files.

For that, linker maintains a separate list of struct glob_sym structures,
which keeps track of few pieces of metadata (is it extern or resolved global,
is it a weak symbol, which ELF section it belongs to, etc) and ties together
BTF type info and ELF symbol information and keeps them in sync.

With adding support for extern variables/funcs, it's now possible for some
sections to contain both extern and non-extern definitions. This means that
some sections may start out as ephemeral (if only externs are present and thus
there is not corresponding ELF section), but will be "upgraded" to actual ELF
section as symbols are resolved or new non-extern definitions are appended.

Additional care is taken to not duplicate extern entries in sections like
.kconfig and .ksyms.

Given libbpf requires BTF type to always be present for .kconfig/.ksym
externs, linker extends this requirement to all the externs, even those that
are supposed to be resolved during static linking and which won't be visible
to libbpf. With BTF information always present, static linker will check not
just ELF symbol matches, but entire BTF type signature match as well. That
logic is stricter that BPF CO-RE checks. It probably should be re-used by
.ksym resolution logic in libbpf as well, but that's left for follow up
patches.

To make it unnecessary to rewrite ELF symbols and minimize BTF type
rewriting/removal, ELF symbols that correspond to externs initially will be
updated in place once they are resolved. Similarly for BTF type info, VAR/FUNC
and var_secinfo's (sec_vars in struct bpf_linker) are staying stable, but
types they point to might get replaced when extern is resolved. This might
leave some left-over types (even though we try to minimize this for common
cases of having extern funcs with not argument names vs concrete function with
names properly specified). That can be addresses later with a generic BTF
garbage collection. That's left for a follow up as well.

Given BTF type appending phase is separate from ELF symbol
appending/resolution, special struct glob_sym->underlying_btf_id variable is
used to communicate resolution and rewrite decisions. 0 means
underlying_btf_id needs to be appended (it's not yet in final linker->btf), <0
values are used for temporary storage of source BTF type ID (not yet
rewritten), so -glob_sym->underlying_btf_id is BTF type id in obj-btf. But by
the end of linker_append_btf() phase, that underlying_btf_id will be remapped
and will always be > 0. This is the uglies part of the whole process, but
keeps the other parts much simpler due to stability of sec_var and VAR/FUNC
types, as well as ELF symbol, so please keep that in mind while reviewing.

BTF-defined maps require some extra custom logic and is addressed separate in
the next patch, so that to keep this one smaller and easier to review.
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/20210423181348.1801389-12-andrii@kernel.org

It should never fail, but if it does, it's better to know about this rather
than end up with nonsensical type IDs.
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/20210423181348.1801389-11-andrii@kernel.org

Add logic to validate extern symbols, plus some other minor extra checks, like
ELF symbol #0 validation, general symbol visibility and binding validations.
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/20210423181348.1801389-10-andrii@kernel.org