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With latest llvm19, I hit the following selftest failures with
$ ./test_progs -j
libbpf: prog 'on_event': BPF program load failed: Permission denied
libbpf: prog 'on_event': -- BEGIN PROG LOAD LOG --
combined stack size of 4 calls is 544. Too large
verification time 1344153 usec
stack depth 24+440+0+32
processed 51008 insns (limit 1000000) max_states_per_insn 19 total_states 1467 peak_states 303 mark_read 146
-- END PROG LOAD LOG --
libbpf: prog 'on_event': failed to load: -13
libbpf: failed to load object 'strobemeta_subprogs.bpf.o'
scale_test:FAIL:expect_success unexpected error: -13 (errno 13)
#498 verif_scale_strobemeta_subprogs:FAIL
The verifier complains too big of the combined stack size (544 bytes) which
exceeds the maximum stack limit 512. This is a regression from llvm19 ([1]).
In the above error log, the original stack depth is 24+440+0+32.
To satisfy interpreter's need, in verifier the stack depth is adjusted to
32+448+32+32=544 which exceeds 512, hence the error. The same adjusted
stack size is also used for jit case.
But the jitted codes could use smaller stack size.
$ egrep -r stack_depth | grep round_up
arm64/net/bpf_jit_comp.c: ctx->stack_size = round_up(prog->aux->stack_depth, 16);
loongarch/net/bpf_jit.c: bpf_stack_adjust = round_up(ctx->prog->aux->stack_depth, 16);
powerpc/net/bpf_jit_comp.c: cgctx.stack_size = round_up(fp->aux->stack_depth, 16);
riscv/net/bpf_jit_comp32.c: round_up(ctx->prog->aux->stack_depth, STACK_ALIGN);
riscv/net/bpf_jit_comp64.c: bpf_stack_adjust = round_up(ctx->prog->aux->stack_depth, 16);
s390/net/bpf_jit_comp.c: u32 stack_depth = round_up(fp->aux->stack_depth, 8);
sparc/net/bpf_jit_comp_64.c: stack_needed += round_up(stack_depth, 16);
x86/net/bpf_jit_comp.c: EMIT3_off32(0x48, 0x81, 0xEC, round_up(stack_depth, 8));
x86/net/bpf_jit_comp.c: int tcc_off = -4 - round_up(stack_depth, 8);
x86/net/bpf_jit_comp.c: round_up(stack_depth, 8));
x86/net/bpf_jit_comp.c: int tcc_off = -4 - round_up(stack_depth, 8);
x86/net/bpf_jit_comp.c: EMIT3_off32(0x48, 0x81, 0xC4, round_up(stack_depth, 8));
In the above, STACK_ALIGN in riscv/net/bpf_jit_comp32.c is defined as 16.
So stack is aligned in either 8 or 16, x86/s390 having 8-byte stack alignment and
the rest having 16-byte alignment.
This patch calculates total stack depth based on 16-byte alignment if jit is requested.
For the above failing case, the new stack size will be 32+448+0+32=512 and no verification
failure. llvm19 regression will be discussed separately in llvm upstream.
The verifier change caused three test failures as these tests compared messages
with stack size. More specifically,
- test_global_funcs/global_func1: fail with interpreter mode and success with jit mode.
Adjusted stack sizes so both jit and interpreter modes will fail.
- async_stack_depth/{pseudo_call_check, async_call_root_check}: since jit and interpreter
will calculate different stack sizes, the failure msg is adjusted to omit those
specific stack size numbers.
[1] https://lore.kernel.org/bpf/32bde0f0-1881-46c9-931a-673be566c61d@linux.dev/
Suggested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20240214232951.4113094-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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