Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <68003017-5111-176a-de34-5d576b6e3488@meta.com>
Date:   Fri, 9 Jun 2023 20:51:52 -0700
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0)
 Gecko/20100101 Thunderbird/102.12.0
Subject: Re: [PATCH bpf-next v4 0/3] bpf, x86: allow function arguments up to
 12 for TRACING
Content-Language: en-US
To:     menglong8.dong@gmail.com, andrii.nakryiko@gmail.com,
        alan.maguire@oracle.com
Cc:     ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org,
        martin.lau@linux.dev, song@kernel.org, yhs@fb.com,
        john.fastabend@gmail.com, kpsingh@kernel.org, sdf@google.com,
        haoluo@google.com, jolsa@kernel.org, bpf@vger.kernel.org,
        linux-kernel@vger.kernel.org, Menglong Dong <imagedong@tencent.com>
References: <20230609095653.1406173-1-imagedong@tencent.com>
From:   Yonghong Song <yhs@meta.com>
In-Reply-To: <20230609095653.1406173-1-imagedong@tencent.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?Vm1lZk9VclJZTitSSmF6U29GUEV0Ym5QOWZORjJkQ2RGbmEyM2tleUhkbktY?=
 =?utf-8?B?SjhPYkQwYTg0aWIyNmxMYmRrdkYzRVM1enBsakxXdzFKbHNuVFFHK1N4eEg4?=
 =?utf-8?B?QmNBeUNPaTNVanAzRDdkbkxhSUlmb2VzQ3crRWZQbHdQUGVrbUt1aG9iUTRR?=
 =?utf-8?B?Z0t0SUh5UUwwU3ZvRjArNUxRZlMwL21DbmFkMVJnN05pSFNMK3V1TDNrSEJn?=
 =?utf-8?B?cTEvc1lhNlBNUWhaWWZCRVpKRjJxRTFkdVpsY2hoN0hSaFV1cWVKUHRSNFpQ?=
 =?utf-8?B?dHRpWGVDMEl1S3hET0VvTFh1T2VBWTBuT2hZemRaR2xGTXQyTEVyV1dFZ1Ax?=
 =?utf-8?B?V2NEV3VuYXB4OWpnTzZPQ3JiV0cwMnB1K2R0REtzNDQ3ZExiRldQMDgvQ2VT?=
 =?utf-8?B?VlJoU2xrdjBpMlMwY2RlcUdtMEVjNEZ5L25yQmJUbythajl5SStSTnF6d0Iz?=
 =?utf-8?B?QllyVHNYUFRrekROS0tyeTNCZHllTEkrT0dqcnJtMzJvakMrN2VCMWY4SG9h?=
 =?utf-8?B?Y0R0NHBFL3g0OXFxZmpNSE1DeGtyVXFTckN4RUZVanBUKzV1OU1SVVE5Um9F?=
 =?utf-8?B?bitCa3praVdadjlXejROanFGT1crL3dvSmltMXR3aDFVYkNzRG83alBrdnRQ?=
 =?utf-8?B?NEkxUThDWWs2U1pReHpvamdRS1M3MEZLUDRSb01rZElDczVTVnhXMlZ1b24w?=
 =?utf-8?B?bS9LYStqK1R1S0dUd1dzUjNTYjVkaUdpQVlPTkRzMEM5Yk5Cc0xmUzMyK1o2?=
 =?utf-8?B?RjRDUkNsN3gvNTVzMXZwOWdVQW4wWENmV1NCYnhyNFBFSUJxU1NJV0hQM3V4?=
 =?utf-8?B?VG1jQkp3QVI3RjZtNFpWWEdBOFpjMUZaYkdSTG9VOXBlTXBzN0wyem1lcU5H?=
 =?utf-8?B?aWZVSHFvcHlpNGdsR3FidnYrQzBqZzF0Nmc4d1lpamE3dHUvNGk5SlpEbzN3?=
 =?utf-8?B?TnV2TEhwQ21FQ1ZCenBleDFHekxUaENsNlJBTmtTS3dtRHNaRUpVUnNMTjJ2?=
 =?utf-8?B?bnNrUjdpRGZUSmdnblo3ek9OQmVSc3p0MlJEZzJjemR5U0VwVzVnU2drUTI4?=
 =?utf-8?B?aXBiRzdRT3FmVktDWmhLUmF6Ny9jR3lFd1l1YzBsc2RlYjJDZUdOOCtHdFpE?=
 =?utf-8?B?bDZGblVvckZwODEyMnVoYitBeUhnaWY2WDI2bWErMHgwcWhuSEkxRXhEd1VD?=
 =?utf-8?B?STRWQzdFZ1VrVU40cmpkLzJBV1FhOGkxNG96bWlRSFl6QXV4N0dCcHgrRTl2?=
 =?utf-8?B?L1hvSWt1ZkszRitCaXo2RUZPRnFOd29iL3VuK0srMGFNdGdmZUdkS1pVdXRV?=
 =?utf-8?B?d21EQXdudFBQeHJ4YVpLUkpaWlVqaDJjOHBwTTdDVlNtMXZvSUtKZ052R0xw?=
 =?utf-8?B?WHVkeCtDZWVnZEhEVytkMFQ2V2dnMXVOTFZwaWVTTkh5Ri9aUSthaGNoMHla?=
 =?utf-8?B?c01wdDZvdmhNdVlMNk5GTXRLZFhOZlBMQUZ6NCtnZVJGblFJZ2NEQ08xalR2?=
 =?utf-8?B?TXJRaGo4Rm8wMlU2NDZZNzBJRW9pY3lKU0RoVXBVbnBqdG1pUFF6RW9uRlBO?=
 =?utf-8?B?Z3k3dWE4MzJ6V2dlVFdkcEZpNVdGczJzMzZwWk9EcTB5NUJkR1pzeUlGcHpj?=
 =?utf-8?B?UVZFV1h1cjYyRnRTNVNCNzljMlFEenFZcGhlKzJpNVF4QkF3SGFKNHV4Z2Vl?=
 =?utf-8?B?bWpKSXZGUmppK2VTeHNUOHJSMVZUWHBzNURYeHVubUo1L2RSU0Q5dWxaNXVx?=
 =?utf-8?B?VEQwdnMrWXFqNk1sT0x0RitiM240QzFvU3pUM0JBMHBJZDkvZVI4NnNxMUI4?=
 =?utf-8?B?N09FbldJcmpWUGFPVThiUnczczVHcVMxanNRNkFJNFRsN3l5UzhVQmM2WWNp?=
 =?utf-8?B?MXp5UmY0VnlOTWtROEpva3BIcjVvdEpucGw4TXkwcXZydGx1a0RLTlY1RjVy?=
 =?utf-8?B?K1ppYmw1Y1BDWUVlSy9CUHU1aUZubHBXTTRsRXI4VkFxbUJLY2dpeUI2Rk1I?=
 =?utf-8?B?cGo4alp0a1dXYXpSYVZLYXhLbHZLSmlHZlJZZWh0b2dtWEY0U1RFQUJ5NGZL?=
 =?utf-8?B?SVRxYXA0R2VPRjNqNFdsOEU4NWFwbVU4Si9LL1FsSktkUHdzdHQzNVAwdWRO?=
 =?utf-8?B?ZGxLdmRQNkxQUmhyY1ZTSjJwOFlvL2RDSGRzSTZtMHhzYTZzTVcvSFk0NmUr?=
 =?utf-8?B?NVE9PQ==?=
X-OriginatorOrg: meta.com
X-MS-Exchange-CrossTenant-Network-Message-Id: b0706b47-7142-4ff4-54f0-08db696608bf
X-MS-Exchange-CrossTenant-AuthSource: SN6PR1501MB2064.namprd15.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 10 Jun 2023 03:51:55.8858
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: RMkNfNalimqcADHOTGXdYLlC3DutxDH6E5tM0Rl5q40GA+5kTuUMnEY8k7A2H7tU
X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH0PR15MB4527
X-Proofpoint-ORIG-GUID: -aWrUyf0Y7sztTxzSh4KgacOCZe3eCLF
X-Proofpoint-GUID: -aWrUyf0Y7sztTxzSh4KgacOCZe3eCLF
X-Proofpoint-Virus-Version: vendor=baseguard
 engine=ICAP:2.0.254,Aquarius:18.0.957,Hydra:6.0.573,FMLib:17.11.176.26
 definitions=2023-06-10_01,2023-06-09_01,2023-05-22_02
X-Spam-Status: No, score=-2.9 required=5.0 tests=BAYES_00,DKIM_SIGNED,
        DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,NICE_REPLY_A,RCVD_IN_DNSWL_LOW,
        RCVD_IN_MSPIKE_H3,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_PASS,
        T_SCC_BODY_TEXT_LINE,URIBL_BLOCKED autolearn=ham autolearn_force=no
        version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
        lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org


On 6/9/23 2:56 AM, menglong8.dong@gmail.com wrote:
> From: Menglong Dong <imagedong@tencent.com>
> 
> For now, the BPF program of type BPF_PROG_TYPE_TRACING can only be used
> on the kernel functions whose arguments count less than 6. This is not
> friendly at all, as too many functions have arguments count more than 6.
> According to the current kernel version, below is a statistics of the
> function arguments count:
> 
> argument count | function count
> 7              | 704
> 8              | 270
> 9              | 84
> 10             | 47
> 11             | 47
> 12             | 27
> 13             | 22
> 14             | 5
> 15             | 0
> 16             | 1
> 
> Therefore, let's enhance it by increasing the function arguments count
> allowed in arch_prepare_bpf_trampoline(), for now, only x86_64.
> 
> In the 1st patch, we make arch_prepare_bpf_trampoline() support to copy
> function arguments in stack for x86 arch. Therefore, the maximum
> arguments can be up to MAX_BPF_FUNC_ARGS for FENTRY and FEXIT.
> 
> In the 2nd patch, we clean garbage value in upper bytes of the trampoline
> when we store the arguments from regs or on-stack into stack.
> 
> And the 3rd patches are for the testcases of the 1st patch.
> 
> Changes since v3:
> - try make the stack pointer 16-byte aligned. Not sure if I'm right :)
> - introduce clean_garbage() to clean the grabage when argument count is 7
> - use different data type in bpf_testmod_fentry_test{7,12}
> - add testcase for grabage values in ctx
> 
> Changes since v2:
> - keep MAX_BPF_FUNC_ARGS still
> - clean garbage value in upper bytes in the 2nd patch
> - move bpf_fentry_test{7,12} to bpf_testmod.c and rename them to
>    bpf_testmod_fentry_test{7,12} meanwhile in the 3rd patch
> 
> Changes since v1:
> - change the maximun function arguments to 14 from 12
> - add testcases (Jiri Olsa)
> - instead EMIT4 with EMIT3_off32 for "lea" to prevent overflow
> 
> Menglong Dong (3):
>    bpf, x86: allow function arguments up to 12 for TRACING
>    bpf, x86: clean garbage value in the stack of trampoline
>    selftests/bpf: add testcase for FENTRY/FEXIT with 6+ arguments
> 
>   arch/x86/net/bpf_jit_comp.c                   | 145 ++++++++++++++++--
>   .../selftests/bpf/bpf_testmod/bpf_testmod.c   |  19 ++-
>   .../selftests/bpf/prog_tests/fentry_fexit.c   |   4 +-
>   .../selftests/bpf/prog_tests/fentry_test.c    |   2 +
>   .../selftests/bpf/prog_tests/fexit_test.c     |   2 +
>   .../testing/selftests/bpf/progs/fentry_test.c |  33 ++++
>   .../testing/selftests/bpf/progs/fexit_test.c  |  57 +++++++
>   7 files changed, 245 insertions(+), 17 deletions(-)

Also replace rebase on top of bpf-next. Patch 3 cannot be applied.