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From: Yonghong Song <yhs@fb.com>
To: Johan Almbladh <johan.almbladh@anyfinetworks.com>,
	<ast@kernel.org>, <daniel@iogearbox.net>, <andrii@kernel.org>
Cc: <kafai@fb.com>, <songliubraving@fb.com>,
	<john.fastabend@gmail.com>, <kpsingh@kernel.org>,
	<Tony.Ambardar@gmail.com>, <netdev@vger.kernel.org>,
	<bpf@vger.kernel.org>
Subject: Re: [PATCH 10/14] bpf/tests: Add branch conversion JIT test
Date: Wed, 28 Jul 2021 16:58:50 -0700	[thread overview]
Message-ID: <693d7244-6b92-8690-4b04-e0a066ca4f6f@fb.com> (raw)
In-Reply-To: <20210728170502.351010-11-johan.almbladh@anyfinetworks.com>



On 7/28/21 10:04 AM, Johan Almbladh wrote:
> Some JITs may need to convert a conditional jump instruction to
> to short PC-relative branch and a long unconditional jump, if the
> PC-relative offset exceeds offset field width in the CPU instruction.
> This test triggers such branch conversion on the 32-bit MIPS JIT.
> 
> Signed-off-by: Johan Almbladh <johan.almbladh@anyfinetworks.com>
> ---
>   lib/test_bpf.c | 38 ++++++++++++++++++++++++++++++++++++++
>   1 file changed, 38 insertions(+)
> 
> diff --git a/lib/test_bpf.c b/lib/test_bpf.c
> index 8b94902702ed..55914b6236aa 100644
> --- a/lib/test_bpf.c
> +++ b/lib/test_bpf.c
> @@ -461,6 +461,36 @@ static int bpf_fill_stxdw(struct bpf_test *self)
>   	return __bpf_fill_stxdw(self, BPF_DW);
>   }
>   
> +static int bpf_fill_long_jmp(struct bpf_test *self)
> +{
> +	unsigned int len = BPF_MAXINSNS;
> +	struct bpf_insn *insn;
> +	int i;
> +
> +	insn = kmalloc_array(len, sizeof(*insn), GFP_KERNEL);
> +	if (!insn)
> +		return -ENOMEM;

When insn will be freed?

> +
> +	insn[0] = BPF_ALU64_IMM(BPF_MOV, R0, 1);
> +	insn[1] = BPF_JMP_IMM(BPF_JEQ, R0, 1, len - 2 - 1);
> +
> +	/*
> +	 * Fill with a complex 64-bit operation that expands to a lot of
> +	 * instructions on 32-bit JITs. The large jump offset can then
> +	 * overflow the conditional branch field size, triggering a branch
> +	 * conversion mechanism in some JITs.
> +	 */
> +	for (i = 2; i < len - 1; i++)
> +		insn[i] = BPF_ALU64_IMM(BPF_MUL, R0, (i << 16) + i);
> +
> +	insn[len - 1] = BPF_EXIT_INSN();
> +
> +	self->u.ptr.insns = insn;
> +	self->u.ptr.len = len;
> +
> +	return 0;
> +}
> +
[...]

  reply	other threads:[~2021-07-28 23:59 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-28 17:04 [PATCH 00/14] bpf/tests: Extend the eBPF test suite Johan Almbladh
2021-07-28 17:04 ` [PATCH 01/14] bpf/tests: Add BPF_JMP32 test cases Johan Almbladh
2021-07-28 22:31   ` Yonghong Song
2021-07-29 21:30     ` Johan Almbladh
2021-07-28 17:04 ` [PATCH 02/14] bpf/tests: Add BPF_MOV tests for zero and sign extension Johan Almbladh
2021-07-28 22:36   ` Yonghong Song
2021-07-28 17:04 ` [PATCH 03/14] bpf/tests: Fix typos in test case descriptions Johan Almbladh
2021-07-28 22:43   ` Yonghong Song
2021-07-28 17:04 ` [PATCH 04/14] bpf/tests: Add more tests of ALU32 and ALU64 bitwise operations Johan Almbladh
2021-07-28 22:53   ` Yonghong Song
2021-07-28 17:04 ` [PATCH 05/14] bpf/tests: Add more ALU32 tests for BPF_LSH/RSH/ARSH Johan Almbladh
2021-07-28 22:57   ` Yonghong Song
2021-07-28 17:04 ` [PATCH 06/14] bpf/tests: Add more BPF_LSH/RSH/ARSH tests for ALU64 Johan Almbladh
2021-07-28 23:30   ` Yonghong Song
2021-07-29 12:34     ` Johan Almbladh
2021-07-29 15:39       ` Yonghong Song
2021-07-28 17:04 ` [PATCH 07/14] bpf/tests: Add more ALU64 BPF_MUL tests Johan Almbladh
2021-07-28 23:32   ` Yonghong Song
2021-07-29 21:21     ` Johan Almbladh
2021-07-28 17:04 ` [PATCH 08/14] bpf/tests: Add tests for ALU operations implemented with function calls Johan Almbladh
2021-07-28 23:52   ` Yonghong Song
2021-07-29 21:17     ` Johan Almbladh
2021-07-29 22:54       ` Yonghong Song
2021-07-28 17:04 ` [PATCH 09/14] bpf/tests: Add word-order tests for load/store of double words Johan Almbladh
2021-07-28 23:54   ` Yonghong Song
2021-07-28 17:04 ` [PATCH 10/14] bpf/tests: Add branch conversion JIT test Johan Almbladh
2021-07-28 23:58   ` Yonghong Song [this message]
2021-07-29 12:45     ` Johan Almbladh
2021-07-29 15:46       ` Yonghong Song
2021-07-29  0:55   ` Yonghong Song
2021-07-29 13:24     ` Johan Almbladh
2021-07-29 15:50       ` Yonghong Song
2021-07-28 17:04 ` [PATCH 11/14] bpf/tests: Add test for 32-bit context pointer argument passing Johan Almbladh
2021-07-29  0:09   ` Yonghong Song
2021-07-29 13:29     ` Johan Almbladh
2021-07-29 15:50       ` Yonghong Song
2021-07-28 17:05 ` [PATCH 12/14] bpf/tests: Add tests for atomic operations Johan Almbladh
2021-07-29  0:36   ` Yonghong Song
2021-07-28 17:05 ` [PATCH 13/14] bpf/tests: Add tests for BPF_CMPXCHG Johan Almbladh
2021-07-29  0:45   ` Yonghong Song
2021-07-28 17:05 ` [PATCH 14/14] bpf/tests: Add tail call test suite Johan Almbladh
2021-07-29  2:56   ` Yonghong Song
2021-07-29 20:44     ` Johan Almbladh

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