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AJvYcCVXxyjP9FDFeB7x+mabz0JhglVv9YIgkXSooBS0LVZcJOq5Dpar6hTF0nEKSOTWVm8hE3eW3mU2F8z/36yJygxnkEs/ X-Gm-Message-State: AOJu0Ywpd0U2xAW7mqQg1YJQ0Bl4xeZY7TMhh4vcU8+jxqmJfJ8O4Mn9 JRvreGBBP3MN6u5LTt2BkyZ7nyts+wpblycWaV3gaaKsAt3EWHqu X-Google-Smtp-Source: AGHT+IG59nRJZt3InlUYqRWZwXfAdO8XrsFzwE9Qfas5szEm7JUaON8aXh7dVEyJjbJ4XEmfvPWleA== X-Received: by 2002:a17:90a:7448:b0:2c8:4250:66a7 with SMTP id 98e67ed59e1d1-2d3e4539f9fmr1597155a91.1.1723773051730; Thu, 15 Aug 2024 18:50:51 -0700 (PDT) Received: from [192.168.0.235] ([38.34.87.7]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-2d3e2e6d16asm541142a91.21.2024.08.15.18.50.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 15 Aug 2024 18:50:51 -0700 (PDT) Message-ID: <2e86ab640b6acbe8e21af826ccfeeac6c055bc69.camel@gmail.com> Subject: Re: [RFC PATCH bpf-next 3/6] selftests/test: test gen_prologue and gen_epilogue From: Eduard Zingerman To: Martin KaFai Lau Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Yonghong Song , Amery Hung , kernel-team@meta.com, bpf@vger.kernel.org Date: Thu, 15 Aug 2024 18:50:46 -0700 In-Reply-To: <92f724366153f2fbd7d9e92b6ba6f82408970dd7.camel@gmail.com> References: <20240813184943.3759630-1-martin.lau@linux.dev> <20240813184943.3759630-4-martin.lau@linux.dev> <0625a342-887c-4c27-a7a7-9f0eadc31b9d@linux.dev> <92f724366153f2fbd7d9e92b6ba6f82408970dd7.camel@gmail.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.52.3 (3.52.3-1.fc40) Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Thu, 2024-08-15 at 17:23 -0700, Eduard Zingerman wrote: [...] > > Re: __retval(), the struct_ops progs is triggered by a SEC("syscall") p= rog.=20 > > Before calling this syscall prog, the st_ops map needs to be attached f= irst. I=20 > > think the attach part is missing also? or there is a way? >=20 > I think libbpf handles the attachment automatically, I'll double check an= d reply. >=20 In theory, the following addition to the example I've sent already should w= ork: struct st_ops_args; int bpf_kfunc_st_ops_test_prologue(struct st_ops_args *args) __ksym; =20 SEC("syscall") __retval(0) int syscall_prologue(void *ctx) { struct st_ops_args args =3D { -42 }; bpf_kfunc_st_ops_test_prologue(&args); return args.a; } However, the initial value of -42 is not changed, e.g. here is the log: $ ./test_progs -vvv -t struct_ops_epilogue/syscall_prologue ... libbpf: loaded kernel BTF from '/sys/kernel/btf/vmlinux' libbpf: extern (func ksym) 'bpf_kfunc_st_ops_test_prologue': resolved t= o bpf_testmod [104486] libbpf: struct_ops init_kern st_ops: type_id:44 kern_type_id:104321 ker= n_vtype_id:104378 libbpf: struct_ops init_kern st_ops: func ptr test_prologue is set to p= rog test_prologue from data(+0) to kern_data(+0) libbpf: struct_ops init_kern st_ops: func ptr test_epilogue is set to p= rog test_epilogue from data(+8) to kern_data(+8) libbpf: map 'st_ops': created successfully, fd=3D5 run_subtest:PASS:unexpected_load_failure 0 nsec VERIFIER LOG: =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D ... =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D do_prog_test_run:PASS:bpf_prog_test_run 0 nsec run_subtest:FAIL:837 Unexpected retval: -42 !=3D 0 #321/3 struct_ops_epilogue/syscall_prologue:FAIL #321 struct_ops_epilogue:FAIL So, something goes awry in bpf_kfunc_st_ops_test_prologue(): __bpf_kfunc int bpf_kfunc_st_ops_test_prologue(struct st_ops_args *args= ) { int ret =3D -1; =20 mutex_lock(&st_ops_mutex); if (st_ops && st_ops->test_prologue) ret =3D st_ops->test_prologue(args); mutex_unlock(&st_ops_mutex); =20 return ret; } Either st_ops is null or st_ops->test_prologue is null. However, the log above shows: libbpf: struct_ops init_kern st_ops: type_id:44 kern_type_id:104321 ker= n_vtype_id:104378 libbpf: struct_ops init_kern st_ops: func ptr test_prologue is set to p= rog test_prologue from data(+0) to kern_data(+0) libbpf: struct_ops init_kern st_ops: func ptr test_epilogue is set to p= rog test_epilogue from data(+8) to kern_data(+8) Here libbpf does autoload for st_ops map and populates it, so st_ops->test_= prologue should not be null. Will have some time tomorrow to debug this (or you can give it a shot if yo= u'd like).