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Add several ./test_progs tests:
- arena_atomics/load_acquire
- arena_atomics/store_release
- verifier_load_acquire/*
- verifier_store_release/*
- verifier_precision/bpf_load_acquire
- verifier_precision/bpf_store_release
The last two tests are added to check if backtrack_insn() handles the
new instructions correctly.
Additionally, the last test also makes sure that the verifier
"remembers" the value (in src_reg) we store-release into e.g. a stack
slot. For example, if we take a look at the test program:
#0: r1 = 8;
/* store_release((u64 *)(r10 - 8), r1); */
#1: .8byte %[store_release];
#2: r1 = *(u64 *)(r10 - 8);
#3: r2 = r10;
#4: r2 += r1;
#5: r0 = 0;
#6: exit;
At #1, if the verifier doesn't remember that we wrote 8 to the stack,
then later at #4 we would be adding an unbounded scalar value to the
stack pointer, which would cause the program to be rejected:
VERIFIER LOG:
=============
...
math between fp pointer and register with unbounded min value is not allowed
For easier CI integration, instead of using built-ins like
__atomic_{load,store}_n() which depend on the new
__BPF_FEATURE_LOAD_ACQ_STORE_REL pre-defined macro, manually craft
load-acquire/store-release instructions using __imm_insn(), as suggested
by Eduard.
All new tests depend on:
(1) Clang major version >= 18, and
(2) ENABLE_ATOMICS_TESTS is defined (currently implies -mcpu=v3 or
v4), and
(3) JIT supports load-acquire/store-release (currently arm64 and
x86-64)
In .../progs/arena_atomics.c:
/* 8-byte-aligned */
__u8 __arena_global load_acquire8_value = 0x12;
/* 1-byte hole */
__u16 __arena_global load_acquire16_value = 0x1234;
That 1-byte hole in the .addr_space.1 ELF section caused clang-17 to
crash:
fatal error: error in backend: unable to write nop sequence of 1 bytes
To work around such llvm-17 CI job failures, conditionally define
__arena_global variables as 64-bit if __clang_major__ < 18, to make sure
.addr_space.1 has no holes. Ideally we should avoid compiling this file
using clang-17 at all (arena tests depend on
__BPF_FEATURE_ADDR_SPACE_CAST, and are skipped for llvm-17 anyway), but
that is a separate topic.
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Peilin Ye <yepeilin@google.com>
Link: https://lore.kernel.org/r/1b46c6feaf0f1b6984d9ec80e500cc7383e9da1a.1741049567.git.yepeilin@google.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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llvm change [1] made a change such that __sync_fetch_and_{and,or,xor}()
will generate atomic_fetch_*() insns even if the return value is not used.
This is a deliberate choice to make sure barrier semantics are preserved
from source code to asm insn.
But the change in [1] caused arena_atomics selftest failure.
test_arena_atomics:PASS:arena atomics skeleton open 0 nsec
libbpf: prog 'and': BPF program load failed: Permission denied
libbpf: prog 'and': -- BEGIN PROG LOAD LOG --
arg#0 reference type('UNKNOWN ') size cannot be determined: -22
0: R1=ctx() R10=fp0
; if (pid != (bpf_get_current_pid_tgid() >> 32)) @ arena_atomics.c:87
0: (18) r1 = 0xffffc90000064000 ; R1_w=map_value(map=arena_at.bss,ks=4,vs=4)
2: (61) r6 = *(u32 *)(r1 +0) ; R1_w=map_value(map=arena_at.bss,ks=4,vs=4) R6_w=scalar(smin=0,smax=umax=0xffffffff,v
ar_off=(0x0; 0xffffffff))
3: (85) call bpf_get_current_pid_tgid#14 ; R0_w=scalar()
4: (77) r0 >>= 32 ; R0_w=scalar(smin=0,smax=umax=0xffffffff,var_off=(0x0; 0xffffffff))
5: (5d) if r0 != r6 goto pc+11 ; R0_w=scalar(smin=0,smax=umax=0xffffffff,var_off=(0x0; 0xffffffff)) R6_w=scalar(smin=0,smax=umax=0xffffffff,var_off=(0x0; 0x)
; __sync_fetch_and_and(&and64_value, 0x011ull << 32); @ arena_atomics.c:91
6: (18) r1 = 0x100000000060 ; R1_w=scalar()
8: (bf) r1 = addr_space_cast(r1, 0, 1) ; R1_w=arena
9: (18) r2 = 0x1100000000 ; R2_w=0x1100000000
11: (db) r2 = atomic64_fetch_and((u64 *)(r1 +0), r2)
BPF_ATOMIC stores into R1 arena is not allowed
processed 9 insns (limit 1000000) max_states_per_insn 0 total_states 0 peak_states 0 mark_read 0
-- END PROG LOAD LOG --
libbpf: prog 'and': failed to load: -13
libbpf: failed to load object 'arena_atomics'
libbpf: failed to load BPF skeleton 'arena_atomics': -13
test_arena_atomics:FAIL:arena atomics skeleton load unexpected error: -13 (errno 13)
#3 arena_atomics:FAIL
The reason of the failure is due to [2] where atomic{64,}_fetch_{and,or,xor}() are not
allowed by arena addresses.
Version 2 of the patch fixed the issue by using inline asm ([3]). But further discussion
suggested to find a way from source to generate locked insn which is more user
friendly. So in not-merged llvm patch ([4]), if relax memory ordering is used and
the return value is not used, locked insn could be generated.
So with llvm patch [4] to compile the bpf selftest, the following code
__c11_atomic_fetch_and(&and64_value, 0x011ull << 32, memory_order_relaxed);
is able to generate locked insn, hence fixing the selftest failure.
[1] https://github.com/llvm/llvm-project/pull/106494
[2] d503a04f8bc0 ("bpf: Add support for certain atomics in bpf_arena to x86 JIT")
[3] https://lore.kernel.org/bpf/20240803025928.4184433-1-yonghong.song@linux.dev/
[4] https://github.com/llvm/llvm-project/pull/107343
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20240909223431.1666305-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Check that __sync_*() functions don't cause kernel panics when handling
freed arena pages.
x86_64 does not support some arena atomics yet, and aarch64 may or may
not support them, based on the availability of LSE atomics at run time.
Do not enable this test for these architectures for simplicity.
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20240701234304.14336-12-iii@linux.ibm.com
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While clang uses __attribute__((address_space(1))) both for defining
arena pointers and arena globals, GCC requires different syntax for
both. While __arena covers the first use case, introduce __arena_global
to cover the second one.
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20240701234304.14336-11-iii@linux.ibm.com
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Add selftests for atomic instructions in bpf_arena.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20240405231134.17274-2-alexei.starovoitov@gmail.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
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