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  1. 19 1月, 2019 8 次提交
  3. 18 1月, 2019 1 次提交
    • D
      net: introduce SO_BINDTOIFINDEX sockopt · f5dd3d0c
      由 David Herrmann 提交于 
      This introduces a new generic SOL_SOCKET-level socket option called
SO_BINDTOIFINDEX. It behaves similar to SO_BINDTODEVICE, but takes a
network interface index as argument, rather than the network interface
name.

User-space often refers to network-interfaces via their index, but has
to temporarily resolve it to a name for a call into SO_BINDTODEVICE.
This might pose problems when the network-device is renamed
asynchronously by other parts of the system. When this happens, the
SO_BINDTODEVICE might either fail, or worse, it might bind to the wrong
device.

In most cases user-space only ever operates on devices which they
either manage themselves, or otherwise have a guarantee that the device
name will not change (e.g., devices that are UP cannot be renamed).
However, particularly in libraries this guarantee is non-obvious and it
would be nice if that race-condition would simply not exist. It would
make it easier for those libraries to operate even in situations where
the device-name might change under the hood.

A real use-case that we recently hit is trying to start the network
stack early in the initrd but make it survive into the real system.
Existing distributions rename network-interfaces during the transition
from initrd into the real system. This, obviously, cannot affect
devices that are up and running (unless you also consider moving them
between network-namespaces). However, the network manager now has to
make sure its management engine for dormant devices will not run in
parallel to these renames. Particularly, when you offload operations
like DHCP into separate processes, these might setup their sockets
early, and thus have to resolve the device-name possibly running into
this race-condition.

By avoiding a call to resolve the device-name, we no longer depend on
the name and can run network setup of dormant devices in parallel to
the transition off the initrd. The SO_BINDTOIFINDEX ioctl plugs this
race.
Reviewed-by: NTom Gundersen <teg@jklm.no>
Signed-off-by: NDavid Herrmann <dh.herrmann@gmail.com>
Acked-by: NWillem de Bruijn <willemb@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      f5dd3d0c
  5. 09 1月, 2019 1 次提交
  7. 08 1月, 2019 1 次提交
  9. 06 1月, 2019 2 次提交
    • E
      fscrypt: add Adiantum support · 8094c3ce
      由 Eric Biggers 提交于 
      Add support for the Adiantum encryption mode to fscrypt.  Adiantum is a
tweakable, length-preserving encryption mode with security provably
reducible to that of XChaCha12 and AES-256, subject to a security bound.
It's also a true wide-block mode, unlike XTS.  See the paper
"Adiantum: length-preserving encryption for entry-level processors"
(https://eprint.iacr.org/2018/720.pdf) for more details.  Also see
commit 059c2a4d ("crypto: adiantum - add Adiantum support").

On sufficiently long messages, Adiantum's bottlenecks are XChaCha12 and
the NH hash function.  These algorithms are fast even on processors
without dedicated crypto instructions.  Adiantum makes it feasible to
enable storage encryption on low-end mobile devices that lack AES
instructions; currently such devices are unencrypted.  On ARM Cortex-A7,
on 4096-byte messages Adiantum encryption is about 4 times faster than
AES-256-XTS encryption; decryption is about 5 times faster.

In fscrypt, Adiantum is suitable for encrypting both file contents and
names.  With filenames, it fixes a known weakness: when two filenames in
a directory share a common prefix of >= 16 bytes, with CTS-CBC their
encrypted filenames share a common prefix too, leaking information.
Adiantum does not have this problem.

Since Adiantum also accepts long tweaks (IVs), it's also safe to use the
master key directly for Adiantum encryption rather than deriving
per-file keys, provided that the per-file nonce is included in the IVs
and the master key isn't used for any other encryption mode.  This
configuration saves memory and improves performance.  A new fscrypt
policy flag is added to allow users to opt-in to this configuration.
Signed-off-by: NEric Biggers <ebiggers@google.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>
      8094c3ce
    • M
      arch: remove stale comments "UAPI Header export list" · d4ce5458
      由 Masahiro Yamada 提交于 
      These comments are leftovers of commit fcc8487d ("uapi: export all
headers under uapi directories").

Prior to that commit, exported headers must be explicitly added to
header-y. Now, all headers under the uapi/ directories are exported.
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>
      d4ce5458
  11. 05 1月, 2019 6 次提交
  13. 01 1月, 2019 1 次提交
  15. 30 12月, 2018 2 次提交
    • D
      csky: define syscall_get_arch() · d770b256
      由 Dmitry V. Levin 提交于 
      syscall_get_arch() is required to be implemented on all architectures
in order to extend the generic ptrace API with PTRACE_GET_SYSCALL_INFO
request.

Cc: Guo Ren <guoren@kernel.org>
Cc: Paul Moore <paul@paul-moore.com>
Cc: Eric Paris <eparis@redhat.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Elvira Khabirova <lineprinter@altlinux.org>
Cc: Eugene Syromyatnikov <esyr@redhat.com>
Cc: linux-audit@redhat.com
Signed-off-by: NDmitry V. Levin <ldv@altlinux.org>
Signed-off-by: NGuo Ren <guoren@kernel.org>

 arch/csky/include/asm/syscall.h | 7 +++++++
 include/uapi/linux/audit.h      | 1 +
 2 files changed, 8 insertions(+)
      d770b256
    • D
      elf-em.h: add EM_CSKY · 077b930a
      由 Dmitry V. Levin 提交于 
      The uapi/linux/audit.h header is going to use EM_CSKY in order
to define AUDIT_ARCH_CSKY which is needed to implement
syscall_get_arch() which in turn is required to extend
the generic ptrace API with PTRACE_GET_SYSCALL_INFO request.

The value for EM_CSKY has been taken from arch/csky/include/asm/elf.h
and confirmed by binutils:include/elf/common.h

Cc: Guo Ren <guoren@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Elvira Khabirova <lineprinter@altlinux.org>
Cc: Eugene Syromyatnikov <esyr@redhat.com>
Signed-off-by: NDmitry V. Levin <ldv@altlinux.org>
Signed-off-by: NGuo Ren <guoren@kernel.org>
      077b930a
  17. 21 12月, 2018 5 次提交
    • A
      vfio_pci: Add NVIDIA GV100GL [Tesla V100 SXM2] subdriver · 7f928917
      由 Alexey Kardashevskiy 提交于 
      POWER9 Witherspoon machines come with 4 or 6 V100 GPUs which are not
pluggable PCIe devices but still have PCIe links which are used
for config space and MMIO. In addition to that the GPUs have 6 NVLinks
which are connected to other GPUs and the POWER9 CPU. POWER9 chips
have a special unit on a die called an NPU which is an NVLink2 host bus
adapter with p2p connections to 2 to 3 GPUs, 3 or 2 NVLinks to each.
These systems also support ATS (address translation services) which is
a part of the NVLink2 protocol. Such GPUs also share on-board RAM
(16GB or 32GB) to the system via the same NVLink2 so a CPU has
cache-coherent access to a GPU RAM.

This exports GPU RAM to the userspace as a new VFIO device region. This
preregisters the new memory as device memory as it might be used for DMA.
This inserts pfns from the fault handler as the GPU memory is not onlined
until the vendor driver is loaded and trained the NVLinks so doing this
earlier causes low level errors which we fence in the firmware so
it does not hurt the host system but still better be avoided; for the same
reason this does not map GPU RAM into the host kernel (usual thing for
emulated access otherwise).

This exports an ATSD (Address Translation Shootdown) register of NPU which
allows TLB invalidations inside GPU for an operating system. The register
conveniently occupies a single 64k page. It is also presented to
the userspace as a new VFIO device region. One NPU has 8 ATSD registers,
each of them can be used for TLB invalidation in a GPU linked to this NPU.
This allocates one ATSD register per an NVLink bridge allowing passing
up to 6 registers. Due to the host firmware bug (just recently fixed),
only 1 ATSD register per NPU was actually advertised to the host system
so this passes that alone register via the first NVLink bridge device in
the group which is still enough as QEMU collects them all back and
presents to the guest via vPHB to mimic the emulated NPU PHB on the host.

In order to provide the userspace with the information about GPU-to-NVLink
connections, this exports an additional capability called "tgt"
(which is an abbreviated host system bus address). The "tgt" property
tells the GPU its own system address and allows the guest driver to
conglomerate the routing information so each GPU knows how to get directly
to the other GPUs.

For ATS to work, the nest MMU (an NVIDIA block in a P9 CPU) needs to
know LPID (a logical partition ID or a KVM guest hardware ID in other
words) and PID (a memory context ID of a userspace process, not to be
confused with a linux pid). This assigns a GPU to LPID in the NPU and
this is why this adds a listener for KVM on an IOMMU group. A PID comes
via NVLink from a GPU and NPU uses a PID wildcard to pass it through.

This requires coherent memory and ATSD to be available on the host as
the GPU vendor only supports configurations with both features enabled
and other configurations are known not to work. Because of this and
because of the ways the features are advertised to the host system
(which is a device tree with very platform specific properties),
this requires enabled POWERNV platform.

The V100 GPUs do not advertise any of these capabilities via the config
space and there are more than just one device ID so this relies on
the platform to tell whether these GPUs have special abilities such as
NVLinks.
Signed-off-by: NAlexey Kardashevskiy <aik@ozlabs.ru>
Acked-by: NAlex Williamson <alex.williamson@redhat.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>
      7f928917
    • M
      IB/core: Move query port to ioctl · 641d1207
      由 Michael Guralnik 提交于 
      Add a method for query port under the uverbs global methods.  Current
ib_port_attr struct is passed as a single attribute and port_cap_flags2 is
added as a new attribute to the function.
Signed-off-by: NMichael Guralnik <michaelgur@mellanox.com>
Signed-off-by: NLeon Romanovsky <leonro@mellanox.com>
Signed-off-by: NJason Gunthorpe <jgg@mellanox.com>
      641d1207
    • M
      RDMA/nldev: Expose port_cap_flags2 · 4fa2813d
      由 Michael Guralnik 提交于 
      port_cap_flags2 represents IBTA PortInfo:CapabilityMask2.

The field safely extends the RDMA_NLDEV_ATTR_CAP_FLAGS operand as it was
exported as 64 bit to allow this kind of extension.
Signed-off-by: NMichael Guralnik <michaelgur@mellanox.com>
Signed-off-by: NLeon Romanovsky <leonro@mellanox.com>
Signed-off-by: NJason Gunthorpe <jgg@mellanox.com>
      4fa2813d
    • R
      fbdev: make FB_BACKLIGHT a tristate · b4a1ed0c
      由 Rob Clark 提交于 
      BACKLIGHT_CLASS_DEVICE is already tristate, but a dependency
FB_BACKLIGHT prevents it from being built as a module.  There
doesn't seem to be any particularly good reason for this, so
switch FB_BACKLIGHT over to tristate.
Signed-off-by: NRob Clark <robdclark@gmail.com>
Tested-by: NArnd Bergmann <arnd@arndb.de>
Cc: Simon Horman <horms+renesas@verge.net.au>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Ulf Magnusson <ulfalizer@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Hans de Goede <j.w.r.degoede@gmail.com>
Signed-off-by: NBartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
      b4a1ed0c
    • D
      vfs: Suppress MS_* flag defs within the kernel unless explicitly enabled · e262e32d
      由 David Howells 提交于 
      Only the mount namespace code that implements mount(2) should be using the
MS_* flags.  Suppress them inside the kernel unless uapi/linux/mount.h is
included.
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
Reviewed-by: NDavid Howells <dhowells@redhat.com>
      e262e32d
  19. 20 12月, 2018 3 次提交
  21. 19 12月, 2018 7 次提交
    • C
      binder: implement binderfs · 3ad20fe3
      由 Christian Brauner 提交于 
      As discussed at Linux Plumbers Conference 2018 in Vancouver [1] this is the
implementation of binderfs.

/* Abstract */
binderfs is a backwards-compatible filesystem for Android's binder ipc
mechanism. Each ipc namespace will mount a new binderfs instance. Mounting
binderfs multiple times at different locations in the same ipc namespace
will not cause a new super block to be allocated and hence it will be the
same filesystem instance.
Each new binderfs mount will have its own set of binder devices only
visible in the ipc namespace it has been mounted in. All devices in a new
binderfs mount will follow the scheme binder%d and numbering will always
start at 0.

/* Backwards compatibility */
Devices requested in the Kconfig via CONFIG_ANDROID_BINDER_DEVICES for the
initial ipc namespace will work as before. They will be registered via
misc_register() and appear in the devtmpfs mount. Specifically, the
standard devices binder, hwbinder, and vndbinder will all appear in their
standard locations in /dev. Mounting or unmounting the binderfs mount in
the initial ipc namespace will have no effect on these devices, i.e. they
will neither show up in the binderfs mount nor will they disappear when the
binderfs mount is gone.

/* binder-control */
Each new binderfs instance comes with a binder-control device. No other
devices will be present at first. The binder-control device can be used to
dynamically allocate binder devices. All requests operate on the binderfs
mount the binder-control device resides in.
Assuming a new instance of binderfs has been mounted at /dev/binderfs
via mount -t binderfs binderfs /dev/binderfs. Then a request to create a
new binder device can be made as illustrated in [2].
Binderfs devices can simply be removed via unlink().

/* Implementation details */
- dynamic major number allocation:
  When binderfs is registered as a new filesystem it will dynamically
  allocate a new major number. The allocated major number will be returned
  in struct binderfs_device when a new binder device is allocated.
- global minor number tracking:
  Minor are tracked in a global idr struct that is capped at
  BINDERFS_MAX_MINOR. The minor number tracker is protected by a global
  mutex. This is the only point of contention between binderfs mounts.
- struct binderfs_info:
  Each binderfs super block has its own struct binderfs_info that tracks
  specific details about a binderfs instance:
  - ipc namespace
  - dentry of the binder-control device
  - root uid and root gid of the user namespace the binderfs instance
    was mounted in
- mountable by user namespace root:
  binderfs can be mounted by user namespace root in a non-initial user
  namespace. The devices will be owned by user namespace root.
- binderfs binder devices without misc infrastructure:
  New binder devices associated with a binderfs mount do not use the
  full misc_register() infrastructure.
  The misc_register() infrastructure can only create new devices in the
  host's devtmpfs mount. binderfs does however only make devices appear
  under its own mountpoint and thus allocates new character device nodes
  from the inode of the root dentry of the super block. This will have
  the side-effect that binderfs specific device nodes do not appear in
  sysfs. This behavior is similar to devpts allocated pts devices and
  has no effect on the functionality of the ipc mechanism itself.

[1]: https://goo.gl/JL2tfX
[2]: program to allocate a new binderfs binder device:

     #define _GNU_SOURCE
     #include <errno.h>
     #include <fcntl.h>
     #include <stdio.h>
     #include <stdlib.h>
     #include <string.h>
     #include <sys/ioctl.h>
     #include <sys/stat.h>
     #include <sys/types.h>
     #include <unistd.h>
     #include <linux/android/binder_ctl.h>

     int main(int argc, char *argv[])
     {
             int fd, ret, saved_errno;
             size_t len;
             struct binderfs_device device = { 0 };

             if (argc < 2)
                     exit(EXIT_FAILURE);

             len = strlen(argv[1]);
             if (len > BINDERFS_MAX_NAME)
                     exit(EXIT_FAILURE);

             memcpy(device.name, argv[1], len);

             fd = open("/dev/binderfs/binder-control", O_RDONLY | O_CLOEXEC);
             if (fd < 0) {
                     printf("%s - Failed to open binder-control device\n",
                            strerror(errno));
                     exit(EXIT_FAILURE);
             }

             ret = ioctl(fd, BINDER_CTL_ADD, &device);
             saved_errno = errno;
             close(fd);
             errno = saved_errno;
             if (ret < 0) {
                     printf("%s - Failed to allocate new binder device\n",
                            strerror(errno));
                     exit(EXIT_FAILURE);
             }

             printf("Allocated new binder device with major %d, minor %d, and "
                    "name %s\n", device.major, device.minor,
                    device.name);

             exit(EXIT_SUCCESS);
     }

Cc: Martijn Coenen <maco@android.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NChristian Brauner <christian.brauner@ubuntu.com>
Acked-by: NTodd Kjos <tkjos@google.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      3ad20fe3
    • D
      net: Use __kernel_clockid_t in uapi net_stamp.h · e2c4cf7f
      由 Davide Caratti 提交于 
      Herton reports the following error when building a userspace program that
includes net_stamp.h:

 In file included from foo.c:2:
 /usr/include/linux/net_tstamp.h:158:2: error: unknown type name
 ‘clockid_t’
   clockid_t clockid; /* reference clockid */
   ^~~~~~~~~

Fix it by using __kernel_clockid_t in place of clockid_t.

Fixes: 80b14dee ("net: Add a new socket option for a future transmit time.")
Cc: Timothy Redaelli <tredaelli@redhat.com>
Reported-by: NHerton R. Krzesinski <herton@redhat.com>
Signed-off-by: NDavide Caratti <dcaratti@redhat.com>
Tested-by: NPaolo Abeni <pabeni@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      e2c4cf7f
    • J
      bpf: sockmap, metadata support for reporting size of msg · 3bdbd022
      由 John Fastabend 提交于 
      This adds metadata to sk_msg_md for BPF programs to read the sk_msg
size.

When the SK_MSG program is running under an application that is using
sendfile the data is not copied into sk_msg buffers by default. Rather
the BPF program uses sk_msg_pull_data to read the bytes in. This
avoids doing the costly memcopy instructions when they are not in
fact needed. However, if we don't know the size of the sk_msg we
have to guess if needed bytes are available by doing a pull request
which may fail. By including the size of the sk_msg BPF programs can
check the size before issuing sk_msg_pull_data requests.

Additionally, the same applies for sendmsg calls when the application
provides multiple iovs. Here the BPF program needs to pull in data
to update data pointers but its not clear where the data ends without
a size parameter. In many cases "guessing" is not easy to do
and results in multiple calls to pull and without bounded loops
everything gets fairly tricky.

Clean this up by including a u32 size field. Note, all writes into
sk_msg_md are rejected already from sk_msg_is_valid_access so nothing
additional is needed there.
Signed-off-by: NJohn Fastabend <john.fastabend@gmail.com>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>
      3bdbd022
    • M
      IB/uverbs: Add support to advise_mr · ad8a4496
      由 Moni Shoua 提交于 
      Add new ioctl method for the MR object - ADVISE_MR.

This command can be used by users to give an advice or directions to the
kernel about an address range that belongs to memory regions.

A new ib_device callback, advise_mr(), is introduced here to suupport the
new command. This command takes the following arguments:

- pd:		The protection domain to which all memory regions belong
- advice: 	The type of the advice
	  	* IB_UVERBS_ADVISE_MR_ADVICE_PREFETCH - Pre-fetch a range of
		an on-demand paging MR
	  	* IB_UVERBS_ADVISE_MR_ADVICE_PREFETCH_WRITE - Pre-fetch a range
		of an on-demand paging MR with write intention
- flags:	The properties of the advice
		* IB_UVERBS_ADVISE_MR_FLAG_FLUSH - Operation must end before
		return to the caller
- sg_list:	The list of memory ranges
- num_sge:	The number of memory ranges in the list
- attrs:	More attributes to be parsed by the provider
Signed-off-by: NMoni Shoua <monis@mellanox.com>
Reviewed-by: NGuy Levi <guyle@mellanox.com>
Signed-off-by: NLeon Romanovsky <leonro@mellanox.com>
Signed-off-by: NJason Gunthorpe <jgg@mellanox.com>
      ad8a4496
    • P
      RDMA/uverbs: Add an ioctl method to destroy an object · bbc13cda
      由 Parav Pandit 提交于 
      Add an ioctl method to destroy the PD, MR, MW, AH, flow, RWQ indirection
table and XRCD objects by handle which doesn't require any output response
during destruction.
Signed-off-by: NParav Pandit <parav@mellanox.com>
Signed-off-by: NLeon Romanovsky <leonro@mellanox.com>
Signed-off-by: NJason Gunthorpe <jgg@mellanox.com>
      bbc13cda
    • J
      RDMA/uverbs: Add a method to introspect handles in a context · 149d3845
      由 Jason Gunthorpe 提交于 
      Introduce a helper function gather_objects_handle() to copy object handles
under a spin lock.

Expose these objects handles via the uverbs ioctl interface.
Signed-off-by: NJason Gunthorpe <jgg@mellanox.com>
Signed-off-by: NParav Pandit <parav@mellanox.com>
Signed-off-by: NLeon Romanovsky <leonro@mellanox.com>
      149d3845
    • J
      RDMA/uverbs: Implement an ioctl that can call write and write_ex handlers · 4785860e
      由 Jason Gunthorpe 提交于 
      Now that the handlers do not process their own udata we can make a
sensible ioctl that wrappers them. The ioctl follows the same format as
the write_ex() and has the user explicitly specify the core and driver
in/out opaque structures and a command number.

This works for all forms of write commands.
Signed-off-by: NJason Gunthorpe <jgg@mellanox.com>
Signed-off-by: NLeon Romanovsky <leonro@mellanox.com>
Signed-off-by: NDoug Ledford <dledford@redhat.com>
      4785860e
  23. 18 12月, 2018 3 次提交
    • S
      nl80211: Add support to notify radar event info received from STA · 30c63115
      由 Sriram R 提交于 
      Currently radar detection and corresponding channel switch is handled
at the AP device. STA ignores these detected radar events since the
radar signal can be seen mostly by the AP as well. But in scenarios where
a radar signal is seen only at STA, notifying this event to the AP which
can trigger a channel switch can be useful.
Stations can report such radar events autonomously through Spectrum
management (Measurement Report) action frame to its AP. The userspace on
processing the report can notify the kernel with the use of the added
NL80211_CMD_NOTIFY_RADAR to indicate the detected event and inturn adding
the reported channel to NOL.
Signed-off-by: NSriram R <srirrama@codeaurora.org>
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>
      30c63115
    • J
      cfg80211: clarify LCI/civic location documentation · 30db641e
      由 Johannes Berg 提交于 
      The older code and current userspace assumed that this data
is the content of the Measurement Report element, starting
with the Measurement Token. Clarify this in the documentation.
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>
      30db641e
    • Y
      bpf: btf: fix struct/union/fwd types with kind_flag · 9d5f9f70
      由 Yonghong Song 提交于 
      This patch fixed two issues with BTF. One is related to
struct/union bitfield encoding and the other is related to
forward type.

Issue #1 and solution:

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

Current btf encoding of bitfield follows what pahole generates.
For each bitfield, pahole will duplicate the type chain and
put the bitfield size at the final int or enum type.
Since the BTF enum type cannot encode bit size,
pahole workarounds the issue by generating
an int type whenever the enum bit size is not 32.

For example,
  -bash-4.4$ cat t.c
  typedef int ___int;
  enum A { A1, A2, A3 };
  struct t {
    int a[5];
    ___int b:4;
    volatile enum A c:4;
  } g;
  -bash-4.4$ gcc -c -O2 -g t.c
The current kernel supports the following BTF encoding:
  $ pahole -JV t.o
  [1] TYPEDEF ___int type_id=2
  [2] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED
  [3] ENUM A size=4 vlen=3
        A1 val=0
        A2 val=1
        A3 val=2
  [4] STRUCT t size=24 vlen=3
        a type_id=5 bits_offset=0
        b type_id=9 bits_offset=160
        c type_id=11 bits_offset=164
  [5] ARRAY (anon) type_id=2 index_type_id=2 nr_elems=5
  [6] INT sizetype size=8 bit_offset=0 nr_bits=64 encoding=(none)
  [7] VOLATILE (anon) type_id=3
  [8] INT int size=1 bit_offset=0 nr_bits=4 encoding=(none)
  [9] TYPEDEF ___int type_id=8
  [10] INT (anon) size=1 bit_offset=0 nr_bits=4 encoding=SIGNED
  [11] VOLATILE (anon) type_id=10

Two issues are in the above:
  . by changing enum type to int, we lost the original
    type information and this will not be ideal later
    when we try to convert BTF to a header file.
  . the type duplication for bitfields will cause
    BTF bloat. Duplicated types cannot be deduplicated
    later if the bitfield size is different.

To fix this issue, this patch implemented a compatible
change for BTF struct type encoding:
  . the bit 31 of struct_type->info, previously reserved,
    now is used to indicate whether bitfield_size is
    encoded in btf_member or not.
  . if bit 31 of struct_type->info is set,
    btf_member->offset will encode like:
      bit 0 - 23: bit offset
      bit 24 - 31: bitfield size
    if bit 31 is not set, the old behavior is preserved:
      bit 0 - 31: bit offset

So if the struct contains a bit field, the maximum bit offset
will be reduced to (2^24 - 1) instead of MAX_UINT. The maximum
bitfield size will be 256 which is enough for today as maximum
bitfield in compiler can be 128 where int128 type is supported.

This kernel patch intends to support the new BTF encoding:
  $ pahole -JV t.o
  [1] TYPEDEF ___int type_id=2
  [2] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED
  [3] ENUM A size=4 vlen=3
        A1 val=0
        A2 val=1
        A3 val=2
  [4] STRUCT t kind_flag=1 size=24 vlen=3
        a type_id=5 bitfield_size=0 bits_offset=0
        b type_id=1 bitfield_size=4 bits_offset=160
        c type_id=7 bitfield_size=4 bits_offset=164
  [5] ARRAY (anon) type_id=2 index_type_id=2 nr_elems=5
  [6] INT sizetype size=8 bit_offset=0 nr_bits=64 encoding=(none)
  [7] VOLATILE (anon) type_id=3

Issue #2 and solution:
======================

Current forward type in BTF does not specify whether the original
type is struct or union. This will not work for type pretty print
and BTF-to-header-file conversion as struct/union must be specified.
  $ cat tt.c
  struct t;
  union u;
  int foo(struct t *t, union u *u) { return 0; }
  $ gcc -c -g -O2 tt.c
  $ pahole -JV tt.o
  [1] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED
  [2] FWD t type_id=0
  [3] PTR (anon) type_id=2
  [4] FWD u type_id=0
  [5] PTR (anon) type_id=4

To fix this issue, similar to issue #1, type->info bit 31
is used. If the bit is set, it is union type. Otherwise, it is
a struct type.

  $ pahole -JV tt.o
  [1] INT int size=4 bit_offset=0 nr_bits=32 encoding=SIGNED
  [2] FWD t kind_flag=0 type_id=0
  [3] PTR (anon) kind_flag=0 type_id=2
  [4] FWD u kind_flag=1 type_id=0
  [5] PTR (anon) kind_flag=0 type_id=4

Pahole/LLVM change:
===================

The new kind_flag functionality has been implemented in pahole
and llvm:
  https://github.com/yonghong-song/pahole/tree/bitfield
  https://github.com/yonghong-song/llvm/tree/bitfield

Note that pahole hasn't implemented func/func_proto kind
and .BTF.ext. So to print function signature with bpftool,
the llvm compiler should be used.

Fixes: 69b693f0 ("bpf: btf: Introduce BPF Type Format (BTF)")
Acked-by: NMartin KaFai Lau <kafai@fb.com>
Signed-off-by: NMartin KaFai Lau <kafai@fb.com>
Signed-off-by: NYonghong Song <yhs@fb.com>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>
      9d5f9f70