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Andrii Nakryiko b416d88580
UPSTREAM: bpf: allow precision tracking for programs with subprogs
[ Upstream commit be2ef8161572ec1973124ebc50f56dafc2925e07 ]

Stop forcing precise=true for SCALAR registers when BPF program has any
subprograms. Current restriction means that any BPF program, as soon as
it uses subprograms, will end up not getting any of the precision
tracking benefits in reduction of number of verified states.

This patch keeps the fallback mark_all_scalars_precise() behavior if
precise marking has to cross function frames. E.g., if subprogram
requires R1 (first input arg) to be marked precise, ideally we'd need to
backtrack to the parent function and keep marking R1 and its
dependencies as precise. But right now we give up and force all the
SCALARs in any of the current and parent states to be forced to
precise=true. We can lift that restriction in the future.

But this patch fixes two issues identified when trying to enable
precision tracking for subprogs.

First, prevent "escaping" from top-most state in a global subprog. While
with entry-level BPF program we never end up requesting precision for
R1-R5 registers, because R2-R5 are not initialized (and so not readable
in correct BPF program), and R1 is PTR_TO_CTX, not SCALAR, and so is
implicitly precise. With global subprogs, though, it's different, as
global subprog a) can have up to 5 SCALAR input arguments, which might
get marked as precise=true and b) it is validated in isolation from its
main entry BPF program. b) means that we can end up exhausting parent
state chain and still not mark all registers in reg_mask as precise,
which would lead to verifier bug warning.

To handle that, we need to consider two cases. First, if the very first
state is not immediately "checkpointed" (i.e., stored in state lookup
hashtable), it will get correct first_insn_idx and last_insn_idx
instruction set during state checkpointing. As such, this case is
already handled and __mark_chain_precision() already handles that by
just doing nothing when we reach to the very first parent state.
st->parent will be NULL and we'll just stop. Perhaps some extra check
for reg_mask and stack_mask is due here, but this patch doesn't address
that issue.

More problematic second case is when global function's initial state is
immediately checkpointed before we manage to process the very first
instruction. This is happening because when there is a call to global
subprog from the main program the very first subprog's instruction is
marked as pruning point, so before we manage to process first
instruction we have to check and checkpoint state. This patch adds
a special handling for such "empty" state, which is identified by having
st->last_insn_idx set to -1. In such case, we check that we are indeed
validating global subprog, and with some sanity checking we mark input
args as precise if requested.

Note that we also initialize state->first_insn_idx with correct start
insn_idx offset. For main program zero is correct value, but for any
subprog it's quite confusing to not have first_insn_idx set. This
doesn't have any functional impact, but helps with debugging and state
printing. We also explicitly initialize state->last_insns_idx instead of
relying on is_state_visited() to do this with env->prev_insns_idx, which
will be -1 on the very first instruction. This concludes necessary
changes to handle specifically global subprog's precision tracking.

Second identified problem was missed handling of BPF helper functions
that call into subprogs (e.g., bpf_loop and few others). From precision
tracking and backtracking logic's standpoint those are effectively calls
into subprogs and should be called as BPF_PSEUDO_CALL calls.

This patch takes the least intrusive way and just checks against a short
list of current BPF helpers that do call subprogs, encapsulated in
is_callback_calling_function() function. But to prevent accidentally
forgetting to add new BPF helpers to this "list", we also do a sanity
check in __check_func_call, which has to be called for each such special
BPF helper, to validate that BPF helper is indeed recognized as
callback-calling one. This should catch any missed checks in the future.
Adding some special flags to be added in function proto definitions
seemed like an overkill in this case.

With the above changes, it's possible to remove forceful setting of
reg->precise to true in __mark_reg_unknown, which turns on precision
tracking both inside subprogs and entry progs that have subprogs. No
warnings or errors were detected across all the selftests, but also when
validating with veristat against internal Meta BPF objects and Cilium
objects. Further, in some BPF programs there are noticeable reduction in
number of states and instructions validated due to more effective
precision tracking, especially benefiting syncookie test.

$ ./veristat -C -e file,prog,insns,states ~/baseline-results.csv ~/subprog-precise-results.csv  | grep -v '+0'
File                                      Program                     Total insns (A)  Total insns (B)  Total insns (DIFF)  Total states (A)  Total states (B)  Total states (DIFF)
----------------------------------------  --------------------------  ---------------  ---------------  ------------------  ----------------  ----------------  -------------------
pyperf600_bpf_loop.bpf.linked1.o          on_event                               3966             3678       -288 (-7.26%)               306               276         -30 (-9.80%)
pyperf_global.bpf.linked1.o               on_event                               7563             7530        -33 (-0.44%)               520               517          -3 (-0.58%)
pyperf_subprogs.bpf.linked1.o             on_event                              36358            36934       +576 (+1.58%)              2499              2531         +32 (+1.28%)
setget_sockopt.bpf.linked1.o              skops_sockopt                          3965             4038        +73 (+1.84%)               343               347          +4 (+1.17%)
test_cls_redirect_subprogs.bpf.linked1.o  cls_redirect                          64965            64901        -64 (-0.10%)              4619              4612          -7 (-0.15%)
test_misc_tcp_hdr_options.bpf.linked1.o   misc_estab                             1491             1307      -184 (-12.34%)               110               100         -10 (-9.09%)
test_pkt_access.bpf.linked1.o             test_pkt_access                         354              349         -5 (-1.41%)                25                24          -1 (-4.00%)
test_sock_fields.bpf.linked1.o            egress_read_sock_fields                 435              375       -60 (-13.79%)                22                20          -2 (-9.09%)
test_sysctl_loop2.bpf.linked1.o           sysctl_tcp_mem                         1508             1501         -7 (-0.46%)                29                28          -1 (-3.45%)
test_tc_dtime.bpf.linked1.o               egress_fwdns_prio100                    468              435        -33 (-7.05%)                45                41          -4 (-8.89%)
test_tc_dtime.bpf.linked1.o               ingress_fwdns_prio100                   398              408        +10 (+2.51%)                42                39          -3 (-7.14%)
test_tc_dtime.bpf.linked1.o               ingress_fwdns_prio101                  1096              842      -254 (-23.18%)                97                73        -24 (-24.74%)
test_tcp_hdr_options.bpf.linked1.o        estab                                  2758             2408      -350 (-12.69%)               208               181        -27 (-12.98%)
test_urandom_usdt.bpf.linked1.o           urand_read_with_sema                    466              448        -18 (-3.86%)                31                28          -3 (-9.68%)
test_urandom_usdt.bpf.linked1.o           urand_read_without_sema                 466              448        -18 (-3.86%)                31                28          -3 (-9.68%)
test_urandom_usdt.bpf.linked1.o           urandlib_read_with_sema                 466              448        -18 (-3.86%)                31                28          -3 (-9.68%)
test_urandom_usdt.bpf.linked1.o           urandlib_read_without_sema              466              448        -18 (-3.86%)                31                28          -3 (-9.68%)
test_xdp_noinline.bpf.linked1.o           balancer_ingress_v6                    4302             4294         -8 (-0.19%)               257               256          -1 (-0.39%)
xdp_synproxy_kern.bpf.linked1.o           syncookie_tc                         583722           405757   -177965 (-30.49%)             35846             25735     -10111 (-28.21%)
xdp_synproxy_kern.bpf.linked1.o           syncookie_xdp                        609123           479055   -130068 (-21.35%)             35452             29145      -6307 (-17.79%)
----------------------------------------  --------------------------  ---------------  ---------------  ------------------  ----------------  ----------------  -------------------

Change-Id: I90399ff14e41c200639ac487a801496be99fd8cd
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20221104163649.121784-4-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Stable-dep-of: ecdf985d7615 ("bpf: track immediate values written to stack by BPF_ST instruction")
Signed-off-by: Pu Lehui <pulehui@huawei.com>
Tested-by: Luiz Capitulino <luizcap@amazon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2026-01-14 18:13:07 -08:00
android Merge tag 'LA.UM.9.14.r1-26500-LAHAINA.QSSI16.0' of https://git.codelinaro.org/clo/la/kernel/msm-5.4 into android13-5.4-lahaina 2025-11-08 16:13:44 +02:00
arch UPSTREAM: bpf: Handle return value of BPF_PROG_TYPE_STRUCT_OPS prog 2026-01-14 18:12:57 -08:00
block Merge tag 'ASB-2025-12-01_11-5.4' of https://android.googlesource.com/kernel/common into android13-5.4-lahaina 2025-12-04 19:21:35 +02:00
certs
crypto BACKPORT: crypto: lib/sha1 - rename "sha" to "sha1" 2025-12-23 13:36:17 -08:00
Documentation BACKPORT: bpf: Restrict bpf_trace_printk()'s %s usage and add %pks, %pus specifier 2026-01-14 18:12:53 -08:00
drivers UPSTREAM: module: Fix up module_notifier return values 2026-01-14 18:12:53 -08:00
fs UPSTREAM: sysctl: Convert to iter interfaces 2026-01-14 18:12:28 -08:00
include UPSTREAM: list: Add hlist_unhashed_lockless() 2026-01-14 18:13:06 -08:00
init UPSTREAM: bpf: Restrict bpf_probe_read{, str}() only to archs where they work 2026-01-14 18:12:54 -08:00
ipc BACKPORT: sysctl: pass kernel pointers to ->proc_handler 2025-12-23 13:36:15 -08:00
kernel UPSTREAM: bpf: allow precision tracking for programs with subprogs 2026-01-14 18:13:07 -08:00
lib BACKPORT: bpf: Restrict bpf_trace_printk()'s %s usage and add %pks, %pus specifier 2026-01-14 18:12:53 -08:00
LICENSES
mm UPSTREAM: maccess: rename strncpy_from_unsafe_strict to strncpy_from_kernel_nofault 2026-01-14 18:12:55 -08:00
net BACKPORT: ANDROID: fix ABI by undoing atomic64_t -> u64 type conversion 2026-01-14 18:13:05 -08:00
samples UPSTREAM: devmap: Adjust tracepoint for map-less queue flush 2025-12-23 13:35:54 -08:00
scripts UPSTREAM: bpf: Fix bpf_redirect_neigh helper api to support supplying nexthop 2026-01-14 18:12:45 -08:00
security UPSTREAM: bpf: Implement bpf_local_storage for inodes 2026-01-14 18:12:21 -08:00
sound BACKPORT: mm: remove the pgprot argument to __vmalloc 2026-01-14 17:48:09 -08:00
techpack Merge tag 'LA.UM.9.14.r1-26000-LAHAINA.QSSI15.0' of https://git.codelinaro.org/clo/la/platform/vendor/opensource/display-drivers into android13-5.4-lahaina 2025-04-12 09:35:58 +00:00
tools UPSTREAM: bpf: track immediate values written to stack by BPF_ST instruction 2026-01-14 18:13:06 -08:00
usr FROMLIST: kbuild: Add environment variables for userprogs flags 2025-09-28 10:00:32 +02:00
virt KVM: arm64: Ignore PMCNTENSET_EL0 while checking for overflow status 2024-12-19 18:05:04 +01:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore Merge android11-5.4.289(4c8fb32) into msm-5.4 2025-03-26 11:56:22 +05:30
.mailmap
Android.mk
Androidbp
build.config.aarch64
build.config.allmodconfig
build.config.allmodconfig.aarch64
build.config.allmodconfig.arm
build.config.allmodconfig.x86_64
build.config.arm
build.config.common
build.config.db845c
build.config.gki
build.config.gki-debug.aarch64
build.config.gki-debug.x86_64
build.config.gki.aarch64 ANDROID: GKI: add Trimble symbol list 2025-01-16 06:41:15 -08:00
build.config.gki.x86_64
build.config.gki_kasan
build.config.gki_kasan.aarch64
build.config.gki_kasan.x86_64
build.config.gki_kprobes
build.config.gki_kprobes.aarch64
build.config.gki_kprobes.x86_64
build.config.hikey960
build.config.msm.common
build.config.msm.gki
build.config.msm.lahaina
build.config.x86_64
build.targets
COPYING
CREDITS
gen_headers_arm.bp
gen_headers_arm64.bp
gen_headers_arm64_auto.bp
gen_headers_arm_auto.bp
Kbuild
Kconfig
kernel_headers.py
LICENSE
MAINTAINERS BACKPORT: bpf: Introduce BPF_PROG_TYPE_LSM 2025-12-23 13:36:09 -08:00
Makefile BACKPORT: bpf: Resolve BTF IDs in vmlinux image 2026-01-14 18:12:02 -08:00
modules.list.msm.lahaina
OWNERS
README
README.md

How do I submit patches to Android Common Kernels

  1. BEST: Make all of your changes to upstream Linux. If appropriate, backport to the stable releases. These patches will be merged automatically in the corresponding common kernels. If the patch is already in upstream Linux, post a backport of the patch that conforms to the patch requirements below.

  2. LESS GOOD: Develop your patches out-of-tree (from an upstream Linux point-of-view). Unless these are fixing an Android-specific bug, these are very unlikely to be accepted unless they have been coordinated with kernel-team@android.com. If you want to proceed, post a patch that conforms to the patch requirements below.

Common Kernel patch requirements

  • All patches must conform to the Linux kernel coding standards and pass script/checkpatch.pl
  • Patches shall not break gki_defconfig or allmodconfig builds for arm, arm64, x86, x86_64 architectures (see https://source.android.com/setup/build/building-kernels)
  • If the patch is not merged from an upstream branch, the subject must be tagged with the type of patch: UPSTREAM:, BACKPORT:, FROMGIT:, FROMLIST:, or ANDROID:.
  • All patches must have a Change-Id: tag (see https://gerrit-review.googlesource.com/Documentation/user-changeid.html)
  • If an Android bug has been assigned, there must be a Bug: tag.
  • All patches must have a Signed-off-by: tag by the author and the submitter

Additional requirements are listed below based on patch type

Requirements for backports from mainline Linux: UPSTREAM:, BACKPORT:

  • If the patch is a cherry-pick from Linux mainline with no changes at all
    • tag the patch subject with UPSTREAM:.
    • add upstream commit information with a (cherry-picked from ...) line
    • Example:
      • if the upstream commit message is
        important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>
    - then Joe Smith would upload the patch for the common kernel as
        UPSTREAM: important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>

        Bug: 135791357
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        (cherry-picked from c31e73121f4c1ec41143423ac6ce3ce6dafdcec1)
        Signed-off-by: Joe Smith <joe.smith@foo.org>
  • If the patch requires any changes from the upstream version, tag the patch with BACKPORT: instead of UPSTREAM:.
    • use the same tags as UPSTREAM:
    • add comments about the changes under the (cherry-picked from ...) line
    • Example:
        BACKPORT: important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>

        Bug: 135791357
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        (cherry-picked from c31e73121f4c1ec41143423ac6ce3ce6dafdcec1)
        [ Resolved minor conflict in drivers/foo/bar.c ]
        Signed-off-by: Joe Smith <joe.smith@foo.org>

Requirements for other backports: FROMGIT:, FROMLIST:,

  • If the patch has been merged into an upstream maintainer tree, but has not yet been merged into Linux mainline
    • tag the patch subject with FROMGIT:
    • add info on where the patch came from as (cherry picked from commit <sha1> <repo> <branch>). This must be a stable maintainer branch (not rebased, so don't use linux-next for example).
    • if changes were required, use BACKPORT: FROMGIT:
    • Example:
      • if the commit message in the maintainer tree is
        important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>
    - then Joe Smith would upload the patch for the common kernel as
        FROMGIT: important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>

        Bug: 135791357
        (cherry picked from commit 878a2fd9de10b03d11d2f622250285c7e63deace
         https://git.kernel.org/pub/scm/linux/kernel/git/foo/bar.git test-branch)
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        Signed-off-by: Joe Smith <joe.smith@foo.org>
  • If the patch has been submitted to LKML, but not accepted into any maintainer tree
    • tag the patch subject with FROMLIST:
    • add a Link: tag with a link to the submittal on lore.kernel.org
    • if changes were required, use BACKPORT: FROMLIST:
    • Example:
        FROMLIST: important patch from upstream

        This is the detailed description of the important patch

        Signed-off-by: Fred Jones <fred.jones@foo.org>

        Bug: 135791357
        Link: https://lore.kernel.org/lkml/20190619171517.GA17557@someone.com/
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        Signed-off-by: Joe Smith <joe.smith@foo.org>

Requirements for Android-specific patches: ANDROID:

  • If the patch is fixing a bug to Android-specific code
    • tag the patch subject with ANDROID:
    • add a Fixes: tag that cites the patch with the bug
    • Example:
        ANDROID: fix android-specific bug in foobar.c

        This is the detailed description of the important fix

        Fixes: 1234abcd2468 ("foobar: add cool feature")
        Change-Id: I4caaaa566ea080fa148c5e768bb1a0b6f7201c01
        Signed-off-by: Joe Smith <joe.smith@foo.org>
  • If the patch is a new feature
    • tag the patch subject with ANDROID:
    • add a Bug: tag with the Android bug (required for android-specific features)

Vibrator driver for HHG device

How to merge the driver into kernel source tree

  1. Copy ${this_project}/drivers/hid/hid-aksys.c into ${your_kernel_root}/drivers/hid/

  2. Compare and merge ${this_project}/drivers/hid/hid-ids.h into ${your_kernel_root}/drivers/hid/hid-ids.h : Add the following code before the last line of this file

    	#define USB_VENDER_ID_QUALCOMM  0x0a12
    	#define USB_VENDER_ID_TEMP_HHG_AKSY 0x1234
    	#define USB_PRODUCT_ID_AKSYS_HHG  0x1000
    
  3. Merge ${this_project}/drivers/hid/Kconfig into ${your_kernel_root}/drivers/hid/Kconfig : Add the following code before the last line of this file

    config HID_AKSYS_QRD
    	tristate "AKSys gamepad USB adapter support"
    	depends on HID
    	---help---
    	Support for AKSys gamepad USB adapter
    
    config AKSYS_QRD_FF
    	bool "AKSys gamepad USB adapter force feedback support"
    	depends on HID_AKSYS_QRD
    	select INPUT_FF_MEMLESS
    	---help---
    	Say Y here if you have a AKSys gamepad USB adapter and want to
    	enable force feedback support for it.
    
  4. Merge ${this_project}/drivers/hid/Makefile into ${your_kernel_root}/drivers/hid/Makefile : Add the following code at the end of this file

    obj-$(CONFIG_HID_AKSYS_QRD)	+= hid-aksys.o
    
  5. Modify your kernel's default build configuration file. Add the following two lines:

    CONFIG_HID_AKSYS_QRD=m
    CONFIG_AKSYS_QRD_FF=y