From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-176.mta1.migadu.com (out-176.mta1.migadu.com [95.215.58.176]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 14E19225402 for ; Wed, 7 Jan 2026 06:59:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.176 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767769193; cv=none; b=RW+ivmSmZdLdL3QTUKpnVwls1zLlZDh9BrBO32QvkIAU+UPDDIo1HNih0nvyzEy1wiJDE/IjgX/Tt7jaEgKtLZaywdKAB6YLSGCtMNPBGWTcc10Yc3a3mM0RKvpkN9uKyEqBhZIJhZUXLtsDiVCtZPOhRdSBUSQzHiro7J2mHxM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767769193; c=relaxed/simple; bh=haXUM8NiZ+OKjrpNIs/REj7ESu9ButIA4SUKcQMQlDQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=beWTy1z+JHE23yVOMUeCef0uL31k9A7WaXK4dhEo2joVSZ+Oxrv78u3qo2W1hjdLd11OUFbI546VhnVxVQrOOLtKotW8FgaN1dMgHQkcU71GLa3NbB85OtSqgzFAtofQBBba20CxY8slbdXrZ2V6xOmw1/HL8AnIEtivRfD3YQo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=qy4B+2QW; arc=none smtp.client-ip=95.215.58.176 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="qy4B+2QW" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1767769179; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=6/UUn689YoV4jOLODHTjr2eRQnXX+WILjGReLI+8SkE=; b=qy4B+2QWFvLMG+PY8oDqF4linJkP+zxFmWwrTdI/9UVote+4XCqTVC7ogcZepF2ilYC2f2 ZK1j6scDsoxx12vxwyuLQmiqgL1VZ36UpzyJ6t7s8kWZjVLvDSWczsSmWHkaMz2ubQ4h4y 0fq2cs4nNVQvErd3P/Xh1ljlyW8ToXM= From: Menglong Dong To: ast@kernel.org, andrii@kernel.org, Menglong Dong Cc: daniel@iogearbox.net, martin.lau@linux.dev, eddyz87@gmail.com, song@kernel.org, yonghong.song@linux.dev, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org, davem@davemloft.net, dsahern@kernel.org, tglx@linutronix.de, mingo@redhat.com, jiang.biao@linux.dev, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, bpf@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH bpf-next v7 00/11] bpf: fsession support Date: Wed, 07 Jan 2026 14:59:23 +0800 Message-ID: <2815019.mvXUDI8C0e@7940hx> In-Reply-To: <20260107064352.291069-1-dongml2@chinatelecom.cn> References: <20260107064352.291069-1-dongml2@chinatelecom.cn> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="utf-8" X-Migadu-Flow: FLOW_OUT On 2026/1/7 14:43 Menglong Dong write: > Hi, all. > > No changes in this version, just a rebase to deal with conflicts. Ah, this message is not correct. Pls see the change log part for the changes of this version, which is: Changes since v6: * change the prototype of bpf_session_cookie() and bpf_session_is_return(), and reuse them instead of introduce new kfunc for fsession. > > overall > ------- > Sometimes, we need to hook both the entry and exit of a function with > TRACING. Therefore, we need define a FENTRY and a FEXIT for the target > function, which is not convenient. > > Therefore, we add a tracing session support for TRACING. Generally > speaking, it's similar to kprobe session, which can hook both the entry > and exit of a function with a single BPF program. > > We allow the usage of bpf_get_func_ret() to get the return value in the > fentry of the tracing session, as it will always get "0", which is safe > enough and is OK. > > Session cookie is also supported with the kfunc bpf_session_cookie(). > In order to limit the stack usage, we limit the maximum number of cookies > to 4. > > kfunc design > ------------ > In order to keep consistency with existing kfunc, we don't introduce new > kfunc for fsession. Instead, we reuse the existing kfunc > bpf_session_cookie() and bpf_session_is_return(). > > The prototype of bpf_session_cookie() and bpf_session_is_return() don't > satisfy our needs, so we change their prototype by adding the argument > "void *ctx" to them. > > We introduce the function bpf_fsession_is_return() and > bpf_fsession_cookie(), and change the calling to bpf_session_cookie() and > bpf_session_is_return() to them in verifier for fsession. > > architecture > ------------ > The fsession stuff is arch related, so the -EOPNOTSUPP will be returned if > it is not supported yet by the arch. In this series, we only support > x86_64. And later, other arch will be implemented. > > Changes since v6: > * change the prototype of bpf_session_cookie() and bpf_session_is_return(), > and reuse them instead of introduce new kfunc for fsession. > > Changes since v5: > * No changes in this version, just a rebase to deal with conflicts. > > Changes since v4: > * use fsession terminology consistently in all patches > * 1st patch: > - use more explicit way in __bpf_trampoline_link_prog() > * 4th patch: > - remove "cookie_cnt" in struct bpf_trampoline > * 6th patch: > - rename nr_regs to func_md > - define cookie_off in a new line > * 7th patch: > - remove the handling of BPF_TRACE_SESSION in legacy fallback path for > BPF_RAW_TRACEPOINT_OPEN > > Changes since v3: > * instead of adding a new hlist to progs_hlist in trampoline, add the bpf > program to both the fentry hlist and the fexit hlist. > * introduce the 2nd patch to reuse the nr_args field in the stack to > store all the information we need(except the session cookies). > * limit the maximum number of cookies to 4. > * remove the logic to skip fexit if the fentry return non-zero. > > Changes since v2: > * squeeze some patches: > - the 2 patches for the kfunc bpf_tracing_is_exit() and > bpf_fsession_cookie() are merged into the second patch. > - the testcases for fsession are also squeezed. > > * fix the CI error by move the testcase for bpf_get_func_ip to > fsession_test.c > > Changes since v1: > * session cookie support. > In this version, session cookie is implemented, and the kfunc > bpf_fsession_cookie() is added. > > * restructure the layout of the stack. > In this version, the session stuff that stored in the stack is changed, > and we locate them after the return value to not break > bpf_get_func_ip(). > > * testcase enhancement. > Some nits in the testcase that suggested by Jiri is fixed. Meanwhile, > the testcase for get_func_ip and session cookie is added too. > > Menglong Dong (11): > bpf: add fsession support > bpf: use last 8-bits for the nr_args in trampoline > bpf: change prototype of bpf_session_{cookie,is_return} > bpf: support fsession for bpf_session_is_return > bpf: support fsession for bpf_session_cookie > bpf,x86: introduce emit_st_r0_imm64() for trampoline > bpf,x86: add fsession support for x86_64 > libbpf: add fsession support > selftests/bpf: add testcases for fsession > selftests/bpf: add testcases for fsession cookie > selftests/bpf: test fsession mixed with fentry and fexit > > arch/x86/net/bpf_jit_comp.c | 48 ++++- > include/linux/bpf.h | 40 ++++ > include/uapi/linux/bpf.h | 1 + > kernel/bpf/btf.c | 2 + > kernel/bpf/syscall.c | 18 +- > kernel/bpf/trampoline.c | 53 ++++- > kernel/bpf/verifier.c | 79 +++++-- > kernel/trace/bpf_trace.c | 50 +++-- > net/bpf/test_run.c | 1 + > net/core/bpf_sk_storage.c | 1 + > tools/bpf/bpftool/common.c | 1 + > tools/include/uapi/linux/bpf.h | 1 + > tools/lib/bpf/bpf.c | 1 + > tools/lib/bpf/libbpf.c | 3 + > tools/testing/selftests/bpf/bpf_kfuncs.h | 4 +- > .../selftests/bpf/prog_tests/fsession_test.c | 115 ++++++++++ > .../bpf/prog_tests/tracing_failure.c | 2 +- > .../selftests/bpf/progs/fsession_test.c | 198 ++++++++++++++++++ > .../bpf/progs/kprobe_multi_session_cookie.c | 12 +- > .../bpf/progs/uprobe_multi_session.c | 4 +- > .../bpf/progs/uprobe_multi_session_cookie.c | 12 +- > .../progs/uprobe_multi_session_recursive.c | 8 +- > 22 files changed, 583 insertions(+), 71 deletions(-) > create mode 100644 tools/testing/selftests/bpf/prog_tests/fsession_test.c > create mode 100644 tools/testing/selftests/bpf/progs/fsession_test.c > > -- > 2.52.0 > > >