From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-183.mta0.migadu.com (out-183.mta0.migadu.com [91.218.175.183]) (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 2BEED1369B4 for ; Sun, 19 Oct 2025 02:03:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.183 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760839437; cv=none; b=XAC5YwIeJYfevzu5/+aDchLrYXWn2aj66l20+gNY7a6WViFRad0F/IUWv2dmUKRDV9BMnp/jpSNbsao/1sUlEepDiI6zM05laPPxSnypTGc1lSv4AF3gYt3lYq8ylFC9vzPIX16KdF65JDqfgvqT02DgmKSN7OUhm+2/TT4qDus= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760839437; c=relaxed/simple; bh=DnvOKalVAVTmP151v/ZOmkEW3cLfcyqfzYbgYMRFUtA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=aEvW6Atq/czY1fedKeKbPu+81mjpRR/bnYiRS5nuy1rh+6A+FC4y1RKUYKC4x73DzCPkt1tfxkb+iMGAuw/faJd5NCW/aLaunhll0q5qWFfPNhw85qvMSzDXfJtJ1SfIImbKm6X6+2gtmLmI/ZIFWXx9Bpv2HF7SV8ji+qkJFlw= 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=MSZ/LYOY; arc=none smtp.client-ip=91.218.175.183 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="MSZ/LYOY" 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=1760839422; 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=wZyruvAclY3XxcYUgR0c6gPD3I5WTfaEJbImoUXKt9o=; b=MSZ/LYOYqKz/xl0FKiuovLN+VhzedBMrN8knRkbEugO2Nq4D2r6rWq0ofe+lAvhLCUnWCj 47GCtPelO7PehfBd7dDS3i5+C5yC64hyicB6GQVWJPVSesHi5NYp3L6ImUvz8q9s9sMhcV TeM6rxCe7UhUIQT4OepNoO64XC7vIAs= From: Menglong Dong To: ast@kernel.org, jolsa@kernel.org, Menglong Dong Cc: daniel@iogearbox.net, john.fastabend@gmail.com, andrii@kernel.org, martin.lau@linux.dev, eddyz87@gmail.com, song@kernel.org, yonghong.song@linux.dev, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, mattbobrowski@google.com, rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, leon.hwang@linux.dev, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Subject: Re: [PATCH RFC bpf-next 3/5] bpf,x86: add tracing session supporting for x86_64 Date: Sun, 19 Oct 2025 10:03:31 +0800 Message-ID: <12764740.O9o76ZdvQC@7950hx> In-Reply-To: <20251018142124.783206-4-dongml2@chinatelecom.cn> References: <20251018142124.783206-1-dongml2@chinatelecom.cn> <20251018142124.783206-4-dongml2@chinatelecom.cn> Precedence: bulk X-Mailing-List: linux-kernel@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 2025/10/18 22:21, Menglong Dong wrote: > Add BPF_TRACE_SESSION supporting to x86_64. invoke_bpf_session_entry and > invoke_bpf_session_exit is introduced for this purpose. > > In invoke_bpf_session_entry(), we will check if the return value of the > fentry is 0, and clear the corresponding flag if not. And in > invoke_bpf_session_exit(), we will check if the corresponding flag is > set. If not set, the fexit will be skipped. > > Signed-off-by: Menglong Dong > Co-developed-by: Leon Hwang > Signed-off-by: Leon Hwang > --- > arch/x86/net/bpf_jit_comp.c | 115 +++++++++++++++++++++++++++++++++++- > 1 file changed, 114 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c > index d4c93d9e73e4..0586b96ed529 100644 > --- a/arch/x86/net/bpf_jit_comp.c > +++ b/arch/x86/net/bpf_jit_comp.c > @@ -3108,6 +3108,97 @@ static int invoke_bpf_mod_ret(const struct btf_func_model *m, u8 **pprog, > return 0; > } > > +static int invoke_bpf_session_entry(const struct btf_func_model *m, u8 **pprog, > + struct bpf_tramp_links *tl, int stack_size, > + int run_ctx_off, int session_off, > + void *image, void *rw_image) > +{ > + u64 session_flags; > + u8 *prog = *pprog; > + u8 *jmp_insn; > + int i; > + > + /* clear the session flags: > + * > + * xor rax, rax > + * mov QWORD PTR [rbp - session_off], rax > + */ > + EMIT3(0x48, 0x31, 0xC0); > + emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -session_off); > + > + for (i = 0; i < tl->nr_links; i++) { > + if (invoke_bpf_prog(m, &prog, tl->links[i], stack_size, run_ctx_off, true, > + image, rw_image)) > + return -EINVAL; > + > + /* fentry prog stored return value into [rbp - 8]. Emit: > + * if (*(u64 *)(rbp - 8) != 0) > + * *(u64 *)(rbp - session_off) |= (1 << (i + 1)); > + */ > + /* cmp QWORD PTR [rbp - 0x8], 0x0 */ > + EMIT4(0x48, 0x83, 0x7d, 0xf8); EMIT1(0x00); > + /* emit 2 nops that will be replaced with JE insn */ > + jmp_insn = prog; > + emit_nops(&prog, 2); > + > + session_flags = (1ULL << (i + 1)); > + /* mov rax, $session_flags */ > + emit_mov_imm64(&prog, BPF_REG_0, session_flags >> 32, (u32) session_flags); > + /* or QWORD PTR [rbp - session_off], rax */ > + EMIT2(0x48, 0x09); > + emit_insn_suffix(&prog, BPF_REG_FP, BPF_REG_0, -session_off); > + > + jmp_insn[0] = X86_JE; > + jmp_insn[1] = prog - jmp_insn - 2; > + } > + > + *pprog = prog; > + return 0; > +} > + > +static int invoke_bpf_session_exit(const struct btf_func_model *m, u8 **pprog, > + struct bpf_tramp_links *tl, int stack_size, > + int run_ctx_off, int session_off, > + void *image, void *rw_image) > +{ > + u64 session_flags; > + u8 *prog = *pprog; > + u8 *jmp_insn; > + int i; > + > + /* set the bpf_trace_is_exit flag to the session flags */ > + /* mov rax, 1 */ > + emit_mov_imm32(&prog, false, BPF_REG_0, 1); > + /* or QWORD PTR [rbp - session_off], rax */ > + EMIT2(0x48, 0x09); > + emit_insn_suffix(&prog, BPF_REG_FP, BPF_REG_0, -session_off); > + > + for (i = 0; i < tl->nr_links; i++) { > + /* check if (1 << (i+1)) is set in the session flags, and > + * skip the execution of the fexit program if it is. > + */ > + session_flags = 1ULL << (i + 1); > + /* mov rax, $session_flags */ > + emit_mov_imm64(&prog, BPF_REG_1, session_flags >> 32, (u32) session_flags); > + /* test QWORD PTR [rbp - session_off], rax */ > + EMIT2(0x48, 0x85); > + emit_insn_suffix(&prog, BPF_REG_FP, BPF_REG_1, -session_off); > + /* emit 2 nops that will be replaced with JE insn */ > + jmp_insn = prog; > + emit_nops(&prog, 2); > + > + if (invoke_bpf_prog(m, &prog, tl->links[i], stack_size, run_ctx_off, false, > + image, rw_image)) > + return -EINVAL; > + > + jmp_insn[0] = X86_JNE; > + jmp_insn[1] = prog - jmp_insn - 2; > + } > + > + *pprog = prog; > + return 0; > +} > + > /* mov rax, qword ptr [rbp - rounded_stack_depth - 8] */ > #define LOAD_TRAMP_TAIL_CALL_CNT_PTR(stack) \ > __LOAD_TCC_PTR(-round_up(stack, 8) - 8) > @@ -3179,8 +3270,10 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *rw_im > void *func_addr) > { > int i, ret, nr_regs = m->nr_args, stack_size = 0; > - int regs_off, nregs_off, ip_off, run_ctx_off, arg_stack_off, rbx_off; > + int regs_off, nregs_off, session_off, ip_off, run_ctx_off, > + arg_stack_off, rbx_off; > struct bpf_tramp_links *fentry = &tlinks[BPF_TRAMP_FENTRY]; > + struct bpf_tramp_links *session = &tlinks[BPF_TRAMP_SESSION]; > struct bpf_tramp_links *fexit = &tlinks[BPF_TRAMP_FEXIT]; > struct bpf_tramp_links *fmod_ret = &tlinks[BPF_TRAMP_MODIFY_RETURN]; > void *orig_call = func_addr; > @@ -3222,6 +3315,8 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *rw_im > * > * RBP - nregs_off [ regs count ] always > * > + * RBP - session_off [ session flags ] tracing session > + * > * RBP - ip_off [ traced function ] BPF_TRAMP_F_IP_ARG flag > * > * RBP - rbx_off [ rbx value ] always > @@ -3246,6 +3341,8 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *rw_im > /* regs count */ > stack_size += 8; > nregs_off = stack_size; > + stack_size += 8; > + session_off = stack_size; Oops, this break bpf_get_func_ip(), which will get the ip with ctx[-2]. I'll introduce a "bpf_get_func_ip_proto_tracing_session" to fix it. > > if (flags & BPF_TRAMP_F_IP_ARG) > stack_size += 8; /* room for IP address argument */ > @@ -3345,6 +3442,13 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *rw_im > return -EINVAL; > } > > + if (session->nr_links) { > + if (invoke_bpf_session_entry(m, &prog, session, regs_off, > + run_ctx_off, session_off, > + image, rw_image)) > + return -EINVAL; > + } > + > if (fmod_ret->nr_links) { > branches = kcalloc(fmod_ret->nr_links, sizeof(u8 *), > GFP_KERNEL); > @@ -3409,6 +3513,15 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *rw_im > } > } > > + if (session->nr_links) { > + if (invoke_bpf_session_exit(m, &prog, session, regs_off, > + run_ctx_off, session_off, > + image, rw_image)) { > + ret = -EINVAL; > + goto cleanup; > + } > + } > + > if (flags & BPF_TRAMP_F_RESTORE_REGS) > restore_regs(m, &prog, regs_off); > >