During the setup() stage, HCI device drivers expect the chip to
acknowledge its setup() completion via vendor specific frames.

If userspace opens() such HCI device in HCI_USER_CHANNEL [1] mode,
the vendor specific frames are never tranmitted to the driver, as
they are filtered in hci_rx_work().

Allow HCI devices which operate in HCI_USER_CHANNEL mode to receive
frames if the HCI device is is HCI_INIT state.

[1] https://www.spinics.net/lists/linux-bluetooth/msg37345.html

Fixes: 23500189 ("Bluetooth: Introduce new HCI socket channel for user operation")
Signed-off-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

It appears that some Broadcom controllers (eg BCM20702A0) reject LE Set
Advertising Parameters command if advertising intervals provided are not
within range for undirected and low duty directed advertising.

Workaround this bug by populating min and max intervals with 'valid'
values.

< HCI Command: LE Set Advertising Parameters (0x08|0x0006) plen 15
        Min advertising interval: 0.000 msec (0x0000)
        Max advertising interval: 0.000 msec (0x0000)
        Type: Connectable directed - ADV_DIRECT_IND (high duty cycle) (0x01)
        Own address type: Public (0x00)
        Direct address type: Random (0x01)
        Direct address: E2:F0:7B:9F:DC:F4 (Static)
        Channel map: 37, 38, 39 (0x07)
        Filter policy: Allow Scan Request from Any, Allow Connect Request from Any (0x00)
> HCI Event: Command Complete (0x0e) plen 4
      LE Set Advertising Parameters (0x08|0x0006) ncmd 1
        Status: Invalid HCI Command Parameters (0x12)
Signed-off-by: Szymon Janc <szymon.janc@codecoup.pl>
Tested-by: Sören Beye <linux@hypfer.de>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

All users of this driver have been converted to the serdev based
hci_ll driver. The unused driver can be safely dropped now.
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

It looks like in hci_init4_req() the request is being
initialised from cpu-endian data but the packet is specified
to be little-endian. This causes an warning from sparse due
to __le16 to u16 conversion.

Fix this by using cpu_to_le16() on the two fields in the packet.

net/bluetooth/hci_core.c:845:27: warning: incorrect type in assignment (different base types)
net/bluetooth/hci_core.c:845:27:    expected restricted __le16 [usertype] tx_len
net/bluetooth/hci_core.c:845:27:    got unsigned short [usertype] le_max_tx_len
net/bluetooth/hci_core.c:846:28: warning: incorrect type in assignment (different base types)
net/bluetooth/hci_core.c:846:28:    expected restricted __le16 [usertype] tx_time
net/bluetooth/hci_core.c:846:28:    got unsigned short [usertype] le_max_tx_time
Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

As nice as it would be to update firmware faster, that patch broke
at least two different boards, an OMAP4+WL1285 based Motorola Droid
4, as reported by Sebasian Reichel and the Logic PD i.MX6Q +
WL1837MOD.

This reverts commit a2e02f38.
Signed-off-by: Adam Ford <aford173@gmail.com>
Acked-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Cc: stable@vger.kernel.org
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

For the different hardware support options, it is better to use
IS_ENABLED check. Let the compiler do the needed optimizations.
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>

The btusb_rtl_cmd_timeout() function is used inside of an
ifdef, leading to a warning when this part is hidden
from the compiler:

drivers/bluetooth/btusb.c:530:13: error: unused function 'btusb_rtl_cmd_timeout' [-Werror,-Wunused-function]

Use an IS_ENABLED() check instead so the compiler can see
the code and then discard it silently.

Fixes: d7ef0d1e ("Bluetooth: btusb: Use cmd_timeout to reset Realtek device")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

After FW download there is no print to confirm the current
FW version. Add print to check FW version incase of FW download.
Signed-off-by: Amit K Bag <amit.k.bag@intel.com>
Signed-off-by: Yoni Shavit <yshavit@chromium.org>
Signed-off-by: Chethan Tumkur Narayan <chethan.tumkur.narayan@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

It does not need the '-' for PTR_ERR(skb) because PTR_ERR(skb) will
return the negative value during errors.
Signed-off-by: Max Chou <max.chou@realtek.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

'skb_pad()' a few lines above already initializes the "padded" byte to 0.
So there is no need to do it twice.

All what is needed is to increase the len of the skb. So 'skb_put(..., 1)'
is enough here.
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

Fixes gcc '-Wunused-but-set-variable' warning:

net/bluetooth/smp.c: In function 'smp_irk_matches':
net/bluetooth/smp.c:505:18: warning: variable 'smp' set but not used [-Wunused-but-set-variable]

net/bluetooth/smp.c: In function 'smp_generate_rpa':
net/bluetooth/smp.c:526:18: warning: variable 'smp' set but not used [-Wunused-but-set-variable]

It is not used since commit 28a220aa ("bluetooth: switch
to AES library")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

Make sure that we completely quiesce the network device, including its
DMA to avoid having it continue to receive packets while there is no
software alive to service those.
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Acked-by: Doug Berger <opendmb@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Use more linkmode_* helpers rather than open-coding the bitmap
operations.
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

Added TDC test cases for Ethernet LAYERED_OP operations:
- set single source Ethernet MAC
- set single destination Ethernet MAC
- set single invalid destination Ethernet MAC
- set Ethernet type
- invert source/destination/type fields
- add operation on Ethernet type field
Signed-off-by: Roman Mashak <mrv@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Instead of having a hard failure and stopping the driver's probe
routine, generate a random Ethernet MAC address to keep going.
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Acked-by: Doug Berger <opendmb@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

After commit eeb84aa0 ("net_sched: sch_fq: do not assume EDT
packets are ordered"), all skbs get a non zero time_to_send
in flow_queue_add()

This means @time_next_packet variable in fq_dequeue()
can no longer be zero.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Commit 323ebb61 ("net: use listified RX for handling GRO_NORMAL
skbs") made use of listified skb processing for the users of
napi_gro_frags().
The same technique can be used in a way more common napi_gro_receive()
to speed up non-merged (GRO_NORMAL) skbs for a wide range of drivers
including gro_cells and mac80211 users.
This slightly changes the return value in cases where skb is being
dropped by the core stack, but it seems to have no impact on related
drivers' functionality.
gro_normal_batch is left untouched as it's very individual for every
single system configuration and might be tuned in manual order to
achieve an optimal performance.
Signed-off-by: Alexander Lobakin <alobakin@dlink.ru>
Acked-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Current code assumes PAGE_SIZE (the guest page size) is equal
to the page size used to communicate with Hyper-V (which is
always 4K). While this assumption is true on x86, it may not
be true for Hyper-V on other architectures. For example,
Linux on ARM64 may have PAGE_SIZE of 16K or 64K. A new symbol,
HV_HYP_PAGE_SIZE, has been previously introduced to use when
the Hyper-V page size is intended instead of the guest page size.

Make this code work on non-x86 architectures by using the new
HV_HYP_PAGE_SIZE symbol instead of PAGE_SIZE, where appropriate.
Also replace the now redundant PAGE_SIZE_4K with HV_HYP_PAGE_SIZE.
The change has no effect on x86, but lays the groundwork to run
on ARM64 and others.
Signed-off-by: Himadri Pandya <himadrispandya@gmail.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Jiri Pirko says:

====================
mlxsw: Add support for 400Gbps (50Gbps per lane) link modes

Add 400Gbps bits to ethtool and introduce support in mlxsw. These modes
are supported by the Spectrum-2 switch ASIC.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

Extend speed support with 400Gbps
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Add support for 400Gbps speed, link modes of 50Gbps per lane
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Use my kernel.org address for all entries in MAINTAINERS.
Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Vladimir Oltean says:

====================
Scatter/gather SPI for SJA1105 DSA

This is a small series that reduces the stack memory usage for the
sja1105 driver.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

This reworks the SPI transfer implementation to make use of more of the
SPI core features. The main benefit is to avoid the memcpy in
sja1105_xfer_buf().

The memcpy was only needed because the function was transferring a
single buffer at a time. So it needed to copy the caller-provided buffer
at buf + 4, to store the SPI message header in the "headroom" area.

But the SPI core supports scatter-gather messages, comprised of multiple
transfers. We can actually use those to break apart every SPI message
into 2 transfers: one for the header and one for the actual payload.

To keep the behavior the same regarding the chip select signal, it is
necessary to tell the SPI core to de-assert the chip select after each
chunk. This was not needed before, because each spi_message contained
only 1 single transfer.

The meaning of the per-transfer cs_change=1 is:

- If the transfer is the last one of the message, keep CS asserted
- Otherwise, deassert CS

We need to deassert CS in the "otherwise" case, which was implicit
before.

Avoiding the memcpy creates yet another opportunity. The device can't
process more than 256 bytes of SPI payload at a time, so the
sja1105_xfer_long_buf() function used to exist, to split the larger
caller buffer into chunks.

But these chunks couldn't be used as scatter/gather buffers for
spi_message until now, because of that memcpy (we would have needed more
memory for each chunk). So we can now remove the sja1105_xfer_long_buf()
function and have a single implementation for long and short buffers.

Another benefit is lower usage of stack memory. Previously we had to
store 2 SPI buffers for each chunk. Due to the elimination of the
memcpy, we can now send pointers to the actual chunks from the
caller-supplied buffer to the SPI core.

Since the patch merges two functions into a rewritten implementation,
the function prototype was also changed, mainly for cosmetic consistency
with the structures used within it.
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

This is a cosmetic patch that reduces some boilerplate in the SPI
interaction of the driver.
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

The variable reg is being assigned a value that is never read
and is being re-assigned in the following for-loop. The
assignment is redundant and hence can be removed.

Addresses-Coverity: ("Unused value")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Vladimir Oltean says:

====================
PTP driver refactoring for SJA1105 DSA

This series creates a better separation between the driver core and the
PTP portion. Therefore, users who are not interested in PTP can get a
simpler and smaller driver by compiling it out.

This is in preparation for further patches: SPI transfer timestamping,
synchronizing the hardware clock (as opposed to keeping it
free-running), PPS input/output, etc.
====================
Acked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

The PTP command register contains enable bits for:
- Putting the 64-bit PTPCLKVAL register in add/subtract or write mode
- Taking timestamps off of the corrected vs free-running clock
- Starting/stopping the TTEthernet scheduling
- Starting/stopping PPS output
- Resetting the switch

When a command needs to be issued (e.g. "change the PTPCLKVAL from write
mode to add/subtract mode"), one cannot simply write to the command
register setting the PTPCLKADD bit to 1, because that would zeroize the
other settings. One also cannot do a read-modify-write (that would be
too easy for this hardware) because not all bits of the command register
are readable over SPI.

So this leaves us with the only option of keeping the value of the PTP
command register in the driver, and operating on that.

Actually there are 2 types of PTP operations now:
- Operations that modify the cached PTP command. These operate on
  ptp_data->cmd as a pointer.
- Operations that apply all previously cached PTP settings, but don't
  otherwise cache what they did themselves. The sja1105_ptp_reset
  function is such an example. It copies the ptp_data->cmd on stack
  before modifying and writing it to SPI.

This practically means that struct sja1105_ptp_cmd is no longer an
implementation detail, since it needs to be stored in full into struct
sja1105_ptp_data, and hence in struct sja1105_private. So the (*ptp_cmd)
function prototype can change and take struct sja1105_ptp_cmd as second
argument now.
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

This is a non-functional change with 2 goals (both for the case when
CONFIG_NET_DSA_SJA1105_PTP is not enabled):

- Reduce the size of the sja1105_private structure.
- Make the PTP code more self-contained.

Leaving priv->ptp_data.lock to be initialized in sja1105_main.c is not a
leftover: it will be used in a future patch "net: dsa: sja1105: Restore
PTP time after switch reset".
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

The new rule (as already started for sja1105_tas.h) is for functions of
optional driver components (ones which may be disabled via Kconfig - PTP
and TAS) to take struct dsa_switch *ds instead of struct sja1105_private
*priv as first argument.

This is so that forward-declarations of struct sja1105_private can be
avoided.

So make sja1105_ptp.h the second user of this rule.
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

We need priv->ptp_caps to hold a structure and not just a pointer,
because we use container_of in the various PTP callbacks.

Therefore, the sja1105_ptp_caps structure declared in the global memory
of the driver serves no further purpose after copying it into
priv->ptp_caps.

So just populate priv->ptp_caps with the needed operations and remove
sja1105_ptp_caps.
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Alexei Starovoitov says:

====================
pull-request: bpf-next 2019-10-14

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

12 days of development and
85 files changed, 1889 insertions(+), 1020 deletions(-)

The main changes are:

1) auto-generation of bpf_helper_defs.h, from Andrii.

2) split of bpf_helpers.h into bpf_{helpers, helper_defs, endian, tracing}.h
   and move into libbpf, from Andrii.

3) Track contents of read-only maps as scalars in the verifier, from Andrii.

4) small x86 JIT optimization, from Daniel.

5) cross compilation support, from Ivan.

6) bpf flow_dissector enhancements, from Jakub and Stanislav.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

Merge tag 'mac80211-next-for-net-next-2019-10-11' of git://git.kernel.org/pub/scm/linux/kernel/git/jberg/mac80211-next

Johannes Berg says:

====================
A few more small things, nothing really stands out:
 * minstrel improvements from Felix
 * a TX aggregation simplification
 * some additional capabilities for hwsim
 * minor cleanups & docs updates
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

Commit c10e6cf8 ("net: genetlink: push attrbuf allocation and parsing
to a separate function") moved attribute buffer allocation and attribute
parsing from genl_family_rcv_msg_doit() into a separate function
genl_family_rcv_msg_attrs_parse() which, unlike the previous code, calls
__nlmsg_parse() even if family->maxattr is 0 (i.e. the family does its own
parsing). The parser error is ignored and does not propagate out of
genl_family_rcv_msg_attrs_parse() but an error message ("Unknown attribute
type") is set in extack and if further processing generates no error or
warning, it stays there and is interpreted as a warning by userspace.

Dumpit requests are not affected as genl_family_rcv_msg_dumpit() bypasses
the call of genl_family_rcv_msg_attrs_parse() if family->maxattr is zero.
Move this logic inside genl_family_rcv_msg_attrs_parse() so that we don't
have to handle it in each caller.

v3: put the check inside genl_family_rcv_msg_attrs_parse()
v2: adjust also argument of genl_family_rcv_msg_attrs_free()

Fixes: c10e6cf8 ("net: genetlink: push attrbuf allocation and parsing to a separate function")
Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

tcp_zerocopy_receive() rounds down the zc->length a multiple of
PAGE_SIZE. This results in two issues:
- tcp_zerocopy_receive sets recv_skip_hint to the length of the
  receive queue if the zc->length input is smaller than the
  PAGE_SIZE, even though the data in receive queue could be
  zerocopied.
- tcp_zerocopy_receive would set recv_skip_hint of 0, in cases
  where we have a little bit of data after the perfectly-sized
  packets.

To fix these issues, do not store the rounded down value in
zc->length. Round down the length passed to zap_page_range(),
and return min(inq, zc->length) when the zap_range is 0.
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Andrii Nakryiko says:

====================
Patch #1 enforces libbpf build to have bpf_helper_defs.h ready before test BPF
programs are built.
Patch #2 drops obsolete BTF/pahole detection logic from Makefile.

v1->v2:
- drop CPU and PROBE (Martin).
====================
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Given lots of selftests won't work without recent enough Clang/LLVM that
fully supports BTF, there is no point in maintaining outdated BTF
support detection and fall-back to pahole logic. Just assume we have
everything we need.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20191011220146.3798961-3-andriin@fb.com

Given BPF programs rely on libbpf's bpf_helper_defs.h, which is
auto-generated during libbpf build, libbpf build has to happen before
we attempt progs/*.c build. Enforce it as order-only dependency.

Fixes: 24f25763 ("libbpf: auto-generate list of BPF helper definitions")
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20191011220146.3798961-2-andriin@fb.com

Ivan Khoronzhuk says:

====================
This series contains mainly fixes/improvements for cross-compilation
but not only, tested for arm, arm64, and intended for any arch.
Also verified on native build (not cross compilation) for x86_64
and arm, arm64.

Initial RFC link:
https://lkml.org/lkml/2019/8/29/1665

Prev. version:
https://lkml.org/lkml/2019/10/9/1045

Besides the patches given here, the RFC also contains couple patches
related to llvm clang
  arm: include: asm: swab: mask rev16 instruction for clang
  arm: include: asm: unified: mask .syntax unified for clang
They are necessarily to verify arm 32 build.

Also, couple more fixes were added but are not merged in bpf-next yet,
they can be needed for verification/configuration steps, if not in
your tree the fixes can be taken here:
https://www.spinics.net/lists/netdev/msg601716.html
https://www.spinics.net/lists/netdev/msg601714.html
https://www.spinics.net/lists/linux-kbuild/msg23468.html

Now, to build samples, SAMPLE_BPF should be enabled in config.

The change touches not only cross-compilation and can have impact on
other archs and build environments, so might be good idea to verify
it in order to add appropriate changes, some warn options could be
tuned also.

All is tested on x86-64 with clang installed (has to be built containing
targets for arm, arm64..., see llc --version, usually it's present already)

Instructions to test native on x86_64
=================================================
Native build on x86_64 is done in usual way and shouldn't have difference
except HOSTCC is now printed as CC wile building the samples.

Instructions to test cross compilation on arm64
=================================================
gcc version 8.3.0
(GNU Toolchain for the A-profile Architecture 8.3-2019.03 (arm-rel-8.36))

I've used sdk for TI am65x got here:
http://downloads.ti.com/processor-sdk-linux/esd/AM65X/latest/exports/\
ti-processor-sdk-linux-am65xx-evm-06.00.00.07-Linux-x86-Install.bin

make ARCH=arm64 -C tools/ clean
make ARCH=arm64 -C samples/bpf clean
make ARCH=arm64 clean
make ARCH=arm64 defconfig

make ARCH=arm64 headers_install

make ARCH=arm64 INSTALL_HDR_PATH=/../sdk/\
ti-processor-sdk-linux-am65xx-evm-06.00.00.07/linux-devkit/sysroots/\
aarch64-linux/usr headers_install

make samples/bpf/ ARCH=arm64 CROSS_COMPILE="aarch64-linux-gnu-"\
SYSROOT="/../sdk/ti-processor-sdk-linux-am65xx-evm-06.00.00.07/\
linux-devkit/sysroots/aarch64-linux"

Instructions to test cross compilation on arm
=================================================
arm-linux-gnueabihf-gcc (Linaro GCC 7.2-2017.11) 7.2.1 20171011
or
arm-linux-gnueabihf-gcc
(GNU Toolchain for the A-profile Architecture 8.3-2019.03 \
(arm-rel-8.36)) 8.3.0

http://downloads.ti.com/processor-sdk-linux/esd/AM57X/05_03_00_07/exports/\
ti-processor-sdk-linux-am57xx-evm-05.03.00.07-Linux-x86-Install.bin

make ARCH=arm -C tools/ clean
make ARCH=arm -C samples/bpf clean
make ARCH=arm clean
make ARCH=arm omap2plus_defconfig

make ARCH=arm headers_install

make ARCH=arm INSTALL_HDR_PATH=/../sdk/\
ti-processor-sdk-linux-am57xx-evm-05.03.00.07/linux-devkit/sysroots/\
armv7ahf-neon-linux-gnueabi/usr headers_install

make samples/bpf/ ARCH=arm CROSS_COMPILE="arm-linux-gnueabihf-"\
SYSROOT="/../sdk/ti-processor-sdk-linux-am57xx-evm-05.03\
.00.07/linux-devkit/sysroots/armv7ahf-neon-linux-gnueabi"

Based on bpf-next/master

v5..v4:
- any changes, only missed SOBs are added

v4..v3:
- renamed CLANG_EXTRA_CFLAGS on BPF_EXTRA_CFLAGS
- used filter for ARCH_ARM_SELECTOR
- omit "-fomit-frame-pointer" and use same flags for native and "cross"
- used sample/bpf prefixes
- use C instead of C++ compiler for test_libbpf target

v3..v2:
- renamed makefile.progs to makeifle.target, as more appropriate
- left only __LINUX_ARM_ARCH__ for D options for arm
- for host build - left options from KBUILD_HOST for compatibility reasons
- split patch adding c/cxx/ld flags to libbpf by modules
- moved readme change to separate patch
- added patch setting options for cross-compile
- fixed issue with option error for syscall_nrs.S,
  avoiding overlap for ccflags-y.

v2..v1:
- restructured patches order
- split "samples: bpf: Makefile: base progs build on Makefile.progs"
  to make change more readable. It added couple nice extra patches.
- removed redundant patch:
  "samples: bpf: Makefile: remove target for native build"
- added fix:
  "samples: bpf: makefile: fix cookie_uid_helper_example obj build"
- limited -D option filter only for arm
- improved comments
- added couple instructions to verify cross compilation for arm and
  arm64 arches based on TI am57xx and am65xx sdks.
- corrected include a little order
====================
Tested-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Add couple preparation steps: clean and configuration. Also add newly
added sysroot support info to cross-compile section.
Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20191011002808.28206-16-ivan.khoronzhuk@linaro.org