Commit Graph

16 Commits

Author SHA1 Message Date
Greg Kroah-Hartman
b16bfd6279 Revert "Revert "bpf: Fix fexit trampoline.""
This reverts commit bc751d322e as the
kabi can be updated at this point in time.

Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: Ic38de1d64f2f581383836fe5036b9202a472554a
2021-04-09 21:09:04 -07:00
Greg Kroah-Hartman
bc751d322e Revert "bpf: Fix fexit trampoline."
This reverts commit e21d2b9235

It breaks the abi but we can bring it back later on when the KABI update
happens in a few days.

Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I7a5861c037be3e35973893d8c91eda9133bf8595
2021-04-09 09:38:25 +02:00
Greg Kroah-Hartman
e92949726c Merge 5.10.28 into android12-5.10
Changes in 5.10.28
	arm64: mm: correct the inside linear map range during hotplug check
	bpf: Fix fexit trampoline.
	virtiofs: Fail dax mount if device does not support it
	ext4: shrink race window in ext4_should_retry_alloc()
	ext4: fix bh ref count on error paths
	fs: nfsd: fix kconfig dependency warning for NFSD_V4
	rpc: fix NULL dereference on kmalloc failure
	iomap: Fix negative assignment to unsigned sis->pages in iomap_swapfile_activate
	ASoC: rt1015: fix i2c communication error
	ASoC: rt5640: Fix dac- and adc- vol-tlv values being off by a factor of 10
	ASoC: rt5651: Fix dac- and adc- vol-tlv values being off by a factor of 10
	ASoC: sgtl5000: set DAP_AVC_CTRL register to correct default value on probe
	ASoC: es8316: Simplify adc_pga_gain_tlv table
	ASoC: soc-core: Prevent warning if no DMI table is present
	ASoC: cs42l42: Fix Bitclock polarity inversion
	ASoC: cs42l42: Fix channel width support
	ASoC: cs42l42: Fix mixer volume control
	ASoC: cs42l42: Always wait at least 3ms after reset
	NFSD: fix error handling in NFSv4.0 callbacks
	kernel: freezer should treat PF_IO_WORKER like PF_KTHREAD for freezing
	vhost: Fix vhost_vq_reset()
	io_uring: fix ->flags races by linked timeouts
	scsi: st: Fix a use after free in st_open()
	scsi: qla2xxx: Fix broken #endif placement
	staging: comedi: cb_pcidas: fix request_irq() warn
	staging: comedi: cb_pcidas64: fix request_irq() warn
	ASoC: rt5659: Update MCLK rate in set_sysclk()
	ASoC: rt711: add snd_soc_component remove callback
	thermal/core: Add NULL pointer check before using cooling device stats
	locking/ww_mutex: Simplify use_ww_ctx & ww_ctx handling
	locking/ww_mutex: Fix acquire/release imbalance in ww_acquire_init()/ww_acquire_fini()
	nvmet-tcp: fix kmap leak when data digest in use
	io_uring: imply MSG_NOSIGNAL for send[msg]()/recv[msg]() calls
	static_call: Align static_call_is_init() patching condition
	ext4: do not iput inode under running transaction in ext4_rename()
	io_uring: call req_set_fail_links() on short send[msg]()/recv[msg]() with MSG_WAITALL
	net: mvpp2: fix interrupt mask/unmask skip condition
	flow_dissector: fix TTL and TOS dissection on IPv4 fragments
	can: dev: move driver related infrastructure into separate subdir
	net: introduce CAN specific pointer in the struct net_device
	can: tcan4x5x: fix max register value
	brcmfmac: clear EAP/association status bits on linkdown events
	ath11k: add ieee80211_unregister_hw to avoid kernel crash caused by NULL pointer
	rtw88: coex: 8821c: correct antenna switch function
	netdevsim: dev: Initialize FIB module after debugfs
	iwlwifi: pcie: don't disable interrupts for reg_lock
	ath10k: hold RCU lock when calling ieee80211_find_sta_by_ifaddr()
	net: ethernet: aquantia: Handle error cleanup of start on open
	appletalk: Fix skb allocation size in loopback case
	net: ipa: remove two unused register definitions
	net: ipa: fix register write command validation
	net: wan/lmc: unregister device when no matching device is found
	net: 9p: advance iov on empty read
	bpf: Remove MTU check in __bpf_skb_max_len
	ACPI: tables: x86: Reserve memory occupied by ACPI tables
	ACPI: processor: Fix CPU0 wakeup in acpi_idle_play_dead()
	ALSA: usb-audio: Apply sample rate quirk to Logitech Connect
	ALSA: hda: Re-add dropped snd_poewr_change_state() calls
	ALSA: hda: Add missing sanity checks in PM prepare/complete callbacks
	ALSA: hda/realtek: fix a determine_headset_type issue for a Dell AIO
	ALSA: hda/realtek: call alc_update_headset_mode() in hp_automute_hook
	ALSA: hda/realtek: fix mute/micmute LEDs for HP 640 G8
	xtensa: fix uaccess-related livelock in do_page_fault
	xtensa: move coprocessor_flush to the .text section
	KVM: SVM: load control fields from VMCB12 before checking them
	KVM: SVM: ensure that EFER.SVME is set when running nested guest or on nested vmexit
	PM: runtime: Fix race getting/putting suppliers at probe
	PM: runtime: Fix ordering in pm_runtime_get_suppliers()
	tracing: Fix stack trace event size
	s390/vdso: copy tod_steering_delta value to vdso_data page
	s390/vdso: fix tod_steering_delta type
	mm: fix race by making init_zero_pfn() early_initcall
	drm/amdkfd: dqm fence memory corruption
	drm/amdgpu: fix offset calculation in amdgpu_vm_bo_clear_mappings()
	drm/amdgpu: check alignment on CPU page for bo map
	reiserfs: update reiserfs_xattrs_initialized() condition
	drm/imx: fix memory leak when fails to init
	drm/tegra: dc: Restore coupling of display controllers
	drm/tegra: sor: Grab runtime PM reference across reset
	vfio/nvlink: Add missing SPAPR_TCE_IOMMU depends
	pinctrl: rockchip: fix restore error in resume
	extcon: Add stubs for extcon_register_notifier_all() functions
	extcon: Fix error handling in extcon_dev_register
	firmware: stratix10-svc: reset COMMAND_RECONFIG_FLAG_PARTIAL to 0
	usb: dwc3: pci: Enable dis_uX_susphy_quirk for Intel Merrifield
	video: hyperv_fb: Fix a double free in hvfb_probe
	firewire: nosy: Fix a use-after-free bug in nosy_ioctl()
	usbip: vhci_hcd fix shift out-of-bounds in vhci_hub_control()
	USB: quirks: ignore remote wake-up on Fibocom L850-GL LTE modem
	usb: musb: Fix suspend with devices connected for a64
	usb: xhci-mtk: fix broken streams issue on 0.96 xHCI
	cdc-acm: fix BREAK rx code path adding necessary calls
	USB: cdc-acm: untangle a circular dependency between callback and softint
	USB: cdc-acm: downgrade message to debug
	USB: cdc-acm: fix double free on probe failure
	USB: cdc-acm: fix use-after-free after probe failure
	usb: gadget: udc: amd5536udc_pci fix null-ptr-dereference
	usb: dwc2: Fix HPRT0.PrtSusp bit setting for HiKey 960 board.
	usb: dwc2: Prevent core suspend when port connection flag is 0
	usb: dwc3: qcom: skip interconnect init for ACPI probe
	usb: dwc3: gadget: Clear DEP flags after stop transfers in ep disable
	soc: qcom-geni-se: Cleanup the code to remove proxy votes
	staging: rtl8192e: Fix incorrect source in memcpy()
	staging: rtl8192e: Change state information from u16 to u8
	driver core: clear deferred probe reason on probe retry
	drivers: video: fbcon: fix NULL dereference in fbcon_cursor()
	riscv: evaluate put_user() arg before enabling user access
	Revert "kernel: freezer should treat PF_IO_WORKER like PF_KTHREAD for freezing"
	bpf: Use NOP_ATOMIC5 instead of emit_nops(&prog, 5) for BPF_TRAMP_F_CALL_ORIG
	Linux 5.10.28

Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: Ifdbbeda8de3ee22a7aa3f5d3b10becf0aba1a124
2021-04-09 09:29:17 +02:00
Alexei Starovoitov
e21d2b9235 bpf: Fix fexit trampoline.
[ Upstream commit e21aa341785c679dd409c8cb71f864c00fe6c463 ]

The fexit/fmod_ret programs can be attached to kernel functions that can sleep.
The synchronize_rcu_tasks() will not wait for such tasks to complete.
In such case the trampoline image will be freed and when the task
wakes up the return IP will point to freed memory causing the crash.
Solve this by adding percpu_ref_get/put for the duration of trampoline
and separate trampoline vs its image life times.
The "half page" optimization has to be removed, since
first_half->second_half->first_half transition cannot be guaranteed to
complete in deterministic time. Every trampoline update becomes a new image.
The image with fmod_ret or fexit progs will be freed via percpu_ref_kill and
call_rcu_tasks. Together they will wait for the original function and
trampoline asm to complete. The trampoline is patched from nop to jmp to skip
fexit progs. They are freed independently from the trampoline. The image with
fentry progs only will be freed via call_rcu_tasks_trace+call_rcu_tasks which
will wait for both sleepable and non-sleepable progs to complete.

Fixes: fec56f5890 ("bpf: Introduce BPF trampoline")
Reported-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Paul E. McKenney <paulmck@kernel.org>  # for RCU
Link: https://lore.kernel.org/bpf/20210316210007.38949-1-alexei.starovoitov@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-04-07 15:00:03 +02:00
Kuan-Ying Lee
2ff446fc4d ANDROID: bpf: Add vendor hook
Add vendor hook for bpf, so we can get memory type and
use it to do memory type check for architecture
dependent page table setting.

Bug: 181639260

Signed-off-by: Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com>
Change-Id: Icac325a040fb88c7f6b04b2409029b623bd8515f
2021-03-15 15:38:19 +00:00
Jiri Olsa
6298399bfc bpf: Move btf_resolve_size into __btf_resolve_size
Moving btf_resolve_size into __btf_resolve_size and
keeping btf_resolve_size public with just first 3
arguments, because the rest of the arguments are not
used by outside callers.

Following changes are adding more arguments, which
are not useful to outside callers. They will be added
to the __btf_resolve_size function.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200825192124.710397-4-jolsa@kernel.org
2020-08-25 15:37:41 -07:00
Andrey Ignatov
2872e9ac33 bpf: Set map_btf_{name, id} for all map types
Set map_btf_name and map_btf_id for all map types so that map fields can
be accessed by bpf programs.

Signed-off-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/a825f808f22af52b018dbe82f1c7d29dab5fc978.1592600985.git.rdna@fb.com
2020-06-22 22:22:58 +02:00
Alexei Starovoitov
2c78ee898d bpf: Implement CAP_BPF
Implement permissions as stated in uapi/linux/capability.h
In order to do that the verifier allow_ptr_leaks flag is split
into four flags and they are set as:
  env->allow_ptr_leaks = bpf_allow_ptr_leaks();
  env->bypass_spec_v1 = bpf_bypass_spec_v1();
  env->bypass_spec_v4 = bpf_bypass_spec_v4();
  env->bpf_capable = bpf_capable();

The first three currently equivalent to perfmon_capable(), since leaking kernel
pointers and reading kernel memory via side channel attacks is roughly
equivalent to reading kernel memory with cap_perfmon.

'bpf_capable' enables bounded loops, precision tracking, bpf to bpf calls and
other verifier features. 'allow_ptr_leaks' enable ptr leaks, ptr conversions,
subtraction of pointers. 'bypass_spec_v1' disables speculative analysis in the
verifier, run time mitigations in bpf array, and enables indirect variable
access in bpf programs. 'bypass_spec_v4' disables emission of sanitation code
by the verifier.

That means that the networking BPF program loaded with CAP_BPF + CAP_NET_ADMIN
will have speculative checks done by the verifier and other spectre mitigation
applied. Such networking BPF program will not be able to leak kernel pointers
and will not be able to access arbitrary kernel memory.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200513230355.7858-3-alexei.starovoitov@gmail.com
2020-05-15 17:29:41 +02:00
David S. Miller
9fb16955fb Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net
Overlapping header include additions in macsec.c

A bug fix in 'net' overlapping with the removal of 'version'
string in ena_netdev.c

Overlapping test additions in selftests Makefile

Overlapping PCI ID table adjustments in iwlwifi driver.

Signed-off-by: David S. Miller <davem@davemloft.net>
2020-03-25 18:58:11 -07:00
Martin KaFai Lau
8e5290e710 bpf: Return better error value in delete_elem for struct_ops map
The current always succeed behavior in bpf_struct_ops_map_delete_elem()
is not ideal for userspace tool.  It can be improved to return proper
error value.

If it is in TOBEFREE, it means unregistration has been already done
before but it is in progress and waiting for the subsystem to clear
the refcnt to zero, so -EINPROGRESS.

If it is INIT, it means the struct_ops has not been registered yet,
so -ENOENT.

Fixes: 85d33df357 ("bpf: Introduce BPF_MAP_TYPE_STRUCT_OPS")
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200305013447.535326-1-kafai@fb.com
2020-03-05 14:15:48 -08:00
KP Singh
88fd9e5352 bpf: Refactor trampoline update code
As we need to introduce a third type of attachment for trampolines, the
flattened signature of arch_prepare_bpf_trampoline gets even more
complicated.

Refactor the prog and count argument to arch_prepare_bpf_trampoline to
use bpf_tramp_progs to simplify the addition and accounting for new
attachment types.

Signed-off-by: KP Singh <kpsingh@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200304191853.1529-2-kpsingh@chromium.org
2020-03-04 13:41:05 -08:00
Gustavo A. R. Silva
d7f10df862 bpf: Replace zero-length array with flexible-array member
The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:

struct foo {
        int stuff;
        struct boo array[];
};

By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.

Also, notice that, dynamic memory allocations won't be affected by
this change:

"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]

This issue was found with the help of Coccinelle.

[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 7649773293 ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20200227001744.GA3317@embeddedor
2020-02-28 01:21:02 +01:00
Martin KaFai Lau
d3e42bb0a3 bpf: Reuse log from btf_prase_vmlinux() in btf_struct_ops_init()
Instead of using a locally defined "struct bpf_verifier_log log = {}",
btf_struct_ops_init() should reuse the "log" from its calling
function "btf_parse_vmlinux()".  It should also resolve the
frame-size too large compiler warning in some ARCH.

Fixes: 27ae7997a6 ("bpf: Introduce BPF_PROG_TYPE_STRUCT_OPS")
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200127175145.1154438-1-kafai@fb.com
2020-01-29 16:40:54 +01:00
Martin KaFai Lau
3b4130418f bpf: Fix seq_show for BPF_MAP_TYPE_STRUCT_OPS
Instead of using bpf_struct_ops_map_lookup_elem() which is
not implemented, bpf_struct_ops_map_seq_show_elem() should
also use bpf_struct_ops_map_sys_lookup_elem() which does
an inplace update to the value.  The change allocates
a value to pass to bpf_struct_ops_map_sys_lookup_elem().

[root@arch-fb-vm1 bpf]# cat /sys/fs/bpf/dctcp
{{{1}},BPF_STRUCT_OPS_STATE_INUSE,{{00000000df93eebc,00000000df93eebc},0,2, ...

Fixes: 85d33df357 ("bpf: Introduce BPF_MAP_TYPE_STRUCT_OPS")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200114072647.3188298-1-kafai@fb.com
2020-01-14 09:54:31 -08:00
Martin KaFai Lau
85d33df357 bpf: Introduce BPF_MAP_TYPE_STRUCT_OPS
The patch introduces BPF_MAP_TYPE_STRUCT_OPS.  The map value
is a kernel struct with its func ptr implemented in bpf prog.
This new map is the interface to register/unregister/introspect
a bpf implemented kernel struct.

The kernel struct is actually embedded inside another new struct
(or called the "value" struct in the code).  For example,
"struct tcp_congestion_ops" is embbeded in:
struct bpf_struct_ops_tcp_congestion_ops {
	refcount_t refcnt;
	enum bpf_struct_ops_state state;
	struct tcp_congestion_ops data;  /* <-- kernel subsystem struct here */
}
The map value is "struct bpf_struct_ops_tcp_congestion_ops".
The "bpftool map dump" will then be able to show the
state ("inuse"/"tobefree") and the number of subsystem's refcnt (e.g.
number of tcp_sock in the tcp_congestion_ops case).  This "value" struct
is created automatically by a macro.  Having a separate "value" struct
will also make extending "struct bpf_struct_ops_XYZ" easier (e.g. adding
"void (*init)(void)" to "struct bpf_struct_ops_XYZ" to do some
initialization works before registering the struct_ops to the kernel
subsystem).  The libbpf will take care of finding and populating the
"struct bpf_struct_ops_XYZ" from "struct XYZ".

Register a struct_ops to a kernel subsystem:
1. Load all needed BPF_PROG_TYPE_STRUCT_OPS prog(s)
2. Create a BPF_MAP_TYPE_STRUCT_OPS with attr->btf_vmlinux_value_type_id
   set to the btf id "struct bpf_struct_ops_tcp_congestion_ops" of the
   running kernel.
   Instead of reusing the attr->btf_value_type_id,
   btf_vmlinux_value_type_id s added such that attr->btf_fd can still be
   used as the "user" btf which could store other useful sysadmin/debug
   info that may be introduced in the furture,
   e.g. creation-date/compiler-details/map-creator...etc.
3. Create a "struct bpf_struct_ops_tcp_congestion_ops" object as described
   in the running kernel btf.  Populate the value of this object.
   The function ptr should be populated with the prog fds.
4. Call BPF_MAP_UPDATE with the object created in (3) as
   the map value.  The key is always "0".

During BPF_MAP_UPDATE, the code that saves the kernel-func-ptr's
args as an array of u64 is generated.  BPF_MAP_UPDATE also allows
the specific struct_ops to do some final checks in "st_ops->init_member()"
(e.g. ensure all mandatory func ptrs are implemented).
If everything looks good, it will register this kernel struct
to the kernel subsystem.  The map will not allow further update
from this point.

Unregister a struct_ops from the kernel subsystem:
BPF_MAP_DELETE with key "0".

Introspect a struct_ops:
BPF_MAP_LOOKUP_ELEM with key "0".  The map value returned will
have the prog _id_ populated as the func ptr.

The map value state (enum bpf_struct_ops_state) will transit from:
INIT (map created) =>
INUSE (map updated, i.e. reg) =>
TOBEFREE (map value deleted, i.e. unreg)

The kernel subsystem needs to call bpf_struct_ops_get() and
bpf_struct_ops_put() to manage the "refcnt" in the
"struct bpf_struct_ops_XYZ".  This patch uses a separate refcnt
for the purose of tracking the subsystem usage.  Another approach
is to reuse the map->refcnt and then "show" (i.e. during map_lookup)
the subsystem's usage by doing map->refcnt - map->usercnt to filter out
the map-fd/pinned-map usage.  However, that will also tie down the
future semantics of map->refcnt and map->usercnt.

The very first subsystem's refcnt (during reg()) holds one
count to map->refcnt.  When the very last subsystem's refcnt
is gone, it will also release the map->refcnt.  All bpf_prog will be
freed when the map->refcnt reaches 0 (i.e. during map_free()).

Here is how the bpftool map command will look like:
[root@arch-fb-vm1 bpf]# bpftool map show
6: struct_ops  name dctcp  flags 0x0
	key 4B  value 256B  max_entries 1  memlock 4096B
	btf_id 6
[root@arch-fb-vm1 bpf]# bpftool map dump id 6
[{
        "value": {
            "refcnt": {
                "refs": {
                    "counter": 1
                }
            },
            "state": 1,
            "data": {
                "list": {
                    "next": 0,
                    "prev": 0
                },
                "key": 0,
                "flags": 2,
                "init": 24,
                "release": 0,
                "ssthresh": 25,
                "cong_avoid": 30,
                "set_state": 27,
                "cwnd_event": 28,
                "in_ack_event": 26,
                "undo_cwnd": 29,
                "pkts_acked": 0,
                "min_tso_segs": 0,
                "sndbuf_expand": 0,
                "cong_control": 0,
                "get_info": 0,
                "name": [98,112,102,95,100,99,116,99,112,0,0,0,0,0,0,0
                ],
                "owner": 0
            }
        }
    }
]

Misc Notes:
* bpf_struct_ops_map_sys_lookup_elem() is added for syscall lookup.
  It does an inplace update on "*value" instead returning a pointer
  to syscall.c.  Otherwise, it needs a separate copy of "zero" value
  for the BPF_STRUCT_OPS_STATE_INIT to avoid races.

* The bpf_struct_ops_map_delete_elem() is also called without
  preempt_disable() from map_delete_elem().  It is because
  the "->unreg()" may requires sleepable context, e.g.
  the "tcp_unregister_congestion_control()".

* "const" is added to some of the existing "struct btf_func_model *"
  function arg to avoid a compiler warning caused by this patch.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200109003505.3855919-1-kafai@fb.com
2020-01-09 08:46:18 -08:00
Martin KaFai Lau
27ae7997a6 bpf: Introduce BPF_PROG_TYPE_STRUCT_OPS
This patch allows the kernel's struct ops (i.e. func ptr) to be
implemented in BPF.  The first use case in this series is the
"struct tcp_congestion_ops" which will be introduced in a
latter patch.

This patch introduces a new prog type BPF_PROG_TYPE_STRUCT_OPS.
The BPF_PROG_TYPE_STRUCT_OPS prog is verified against a particular
func ptr of a kernel struct.  The attr->attach_btf_id is the btf id
of a kernel struct.  The attr->expected_attach_type is the member
"index" of that kernel struct.  The first member of a struct starts
with member index 0.  That will avoid ambiguity when a kernel struct
has multiple func ptrs with the same func signature.

For example, a BPF_PROG_TYPE_STRUCT_OPS prog is written
to implement the "init" func ptr of the "struct tcp_congestion_ops".
The attr->attach_btf_id is the btf id of the "struct tcp_congestion_ops"
of the _running_ kernel.  The attr->expected_attach_type is 3.

The ctx of BPF_PROG_TYPE_STRUCT_OPS is an array of u64 args saved
by arch_prepare_bpf_trampoline that will be done in the next
patch when introducing BPF_MAP_TYPE_STRUCT_OPS.

"struct bpf_struct_ops" is introduced as a common interface for the kernel
struct that supports BPF_PROG_TYPE_STRUCT_OPS prog.  The supporting kernel
struct will need to implement an instance of the "struct bpf_struct_ops".

The supporting kernel struct also needs to implement a bpf_verifier_ops.
During BPF_PROG_LOAD, bpf_struct_ops_find() will find the right
bpf_verifier_ops by searching the attr->attach_btf_id.

A new "btf_struct_access" is also added to the bpf_verifier_ops such
that the supporting kernel struct can optionally provide its own specific
check on accessing the func arg (e.g. provide limited write access).

After btf_vmlinux is parsed, the new bpf_struct_ops_init() is called
to initialize some values (e.g. the btf id of the supporting kernel
struct) and it can only be done once the btf_vmlinux is available.

The R0 checks at BPF_EXIT is excluded for the BPF_PROG_TYPE_STRUCT_OPS prog
if the return type of the prog->aux->attach_func_proto is "void".

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200109003503.3855825-1-kafai@fb.com
2020-01-09 08:46:18 -08:00