selftests/bpf: Test bpf_kptr_xchg stashing of bpf_rb_root

There was some confusion amongst Meta sched_ext folks regarding whether
stashing bpf_rb_root - the tree itself, rather than a single node - was
supported. This patch adds a small test which demonstrates this
functionality: a local kptr with rb_root is created, a node is created
and added to the tree, then the tree is kptr_xchg'd into a mapval.

Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/bpf/20231204211722.571346-1-davemarchevsky@fb.com

selftests/bpf: Test bpf_refcount_acquire of node obtained via direct ld

This patch demonstrates that verifier changes earlier in this series
result in bpf_refcount_acquire(mapval->stashed_kptr) passing
verification. The added test additionally validates that stashing a kptr
in mapval and - in a separate BPF program - refcount_acquiring the kptr
without unstashing works as expected at runtime.

Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Link: https://lore.kernel.org/r/20231107085639.3016113-7-davemarchevsky@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

selftests/bpf: Add a local kptr test with no special fields

Add a local kptr test with no special fields in the struct. Without the
previous patch, the following warning will hit:

[ 44.683877] WARNING: CPU: 3 PID: 485 at kernel/bpf/syscall.c:660 bpf_obj_free_fields+0x220/0x240
[ 44.684640] Modules linked in: bpf_testmod(OE)
[ 44.685044] CPU: 3 PID: 485 Comm: kworker/u8:5 Tainted: G OE 6.5.0-rc5-01703-g260d855e9b90 #248
[ 44.685827] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
[ 44.686693] Workqueue: events_unbound bpf_map_free_deferred
[ 44.687297] RIP: 0010:bpf_obj_free_fields+0x220/0x240
[ 44.687775] Code: e8 55 17 1f 00 49 8b 74 24 08 4c 89 ef e8 e8 14 05 00 e8 a3 da e2 ff e9 55 fe ff ff 0f 0b e9 4e fe ff
ff 0f 0b e9 47 fe ff ff <0f> 0b e8 d9 d9 e2 ff 31 f6 eb d5 48 83 c4 10 5b 41 5c e
[ 44.689353] RSP: 0018:ffff888106467cb8 EFLAGS: 00010246
[ 44.689806] RAX: 0000000000000000 RBX: ffff888112b3a200 RCX: 0000000000000001
[ 44.690433] RDX: 0000000000000000 RSI: dffffc0000000000 RDI: ffff8881128ad988
[ 44.691094] RBP: 0000000000000002 R08: ffffffff81370bd0 R09: 1ffff110216231a5
[ 44.691643] R10: dffffc0000000000 R11: ffffed10216231a6 R12: ffff88810d68a488
[ 44.692245] R13: ffff88810767c288 R14: ffff88810d68a400 R15: ffff88810d68a418
[ 44.692829] FS: 0000000000000000(0000) GS:ffff8881f7580000(0000) knlGS:0000000000000000
[ 44.693484] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 44.693964] CR2: 000055c7f2afce28 CR3: 000000010fee4002 CR4: 0000000000370ee0
[ 44.694513] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 44.695102] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 44.695747] Call Trace:
[ 44.696001] <TASK>
[ 44.696183] ? __warn+0xfe/0x270
[ 44.696447] ? bpf_obj_free_fields+0x220/0x240
[ 44.696817] ? report_bug+0x220/0x2d0
[ 44.697180] ? handle_bug+0x3d/0x70
[ 44.697507] ? exc_invalid_op+0x1a/0x50
[ 44.697887] ? asm_exc_invalid_op+0x1a/0x20
[ 44.698282] ? btf_find_struct_meta+0xd0/0xd0
[ 44.698634] ? bpf_obj_free_fields+0x220/0x240
[ 44.699027] ? bpf_obj_free_fields+0x1e2/0x240
[ 44.699414] array_map_free+0x1a3/0x260
[ 44.699763] bpf_map_free_deferred+0x7b/0xe0
[ 44.700154] process_one_work+0x46d/0x750
[ 44.700523] worker_thread+0x49e/0x900
[ 44.700892] ? pr_cont_work+0x270/0x270
[ 44.701224] kthread+0x1ae/0x1d0
[ 44.701516] ? kthread_blkcg+0x50/0x50
[ 44.701860] ret_from_fork+0x34/0x50
[ 44.702178] ? kthread_blkcg+0x50/0x50
[ 44.702508] ret_from_fork_asm+0x11/0x20
[ 44.702880] </TASK>

With the previous patch, there is no warnings.

Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20230824063422.203097-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

selftests/bpf: Add a failure test for bpf_kptr_xchg() with local kptr

For a bpf_kptr_xchg() with local kptr, if the map value kptr type and
allocated local obj type does not match, with the previous patch,
the below verifier error message will be logged:
R2 is of type <allocated local obj type> but <map value kptr type> is expected

Without the previous patch, the test will have unexpected success.

Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20230822050058.2887354-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

selftests/bpf: Add local kptr stashing test

Add a new selftest, local_kptr_stash, which uses bpf_kptr_xchg to stash
a bpf_obj_new-allocated object in a map. Test the following scenarios:

* Stash two rb_nodes in an arraymap, don't unstash them, rely on map
free to destruct them
* Stash two rb_nodes in an arraymap, unstash the second one in a
separate program, rely on map free to destruct first

Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Link: https://lore.kernel.org/r/20230310230743.2320707-4-davemarchevsky@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>