From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-189.mta0.migadu.com (out-189.mta0.migadu.com [91.218.175.189]) (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 BD2A613AD1C for ; Fri, 27 Sep 2024 15:24:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.189 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727450664; cv=none; b=Uu/ng0N7tFKBot9tYcrM6pZtWn1sAAHPLuE1aiO/uBdwFBlVevxGY00STyg+l5N3tXXe4iQ0BTD5ZsK/VHajmYeLAfKb+X1t/J/Nidy95zMIHiHLoNZJr1kIG3xcprK0ugOxCHuCcaPJFavFLl1YZciF2HloNPd97HJ4uSkYW2I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727450664; c=relaxed/simple; bh=ZkweLvyag97akDboOxMZOkNg64bbiHQY6aByshyepaA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=b8IlGGLAdc6Pu3OEB06l44R/YWzocBYkx0Kd9351KiiVMJGTGik0tlaF+VGTxSUf/W+04gNtcrfiWF6OXKDx9EgrMMuUfzFi/ok0VBTkIIQvgFfphMhdMmJtS7zLXJf6EWrHEB+dFvTGNJdyM548vmfxBmiXaPc6ajDjI6GiaSU= 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=e/NU6Onw; arc=none smtp.client-ip=91.218.175.189 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="e/NU6Onw" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1727450660; 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=0GN1WCbWnVujnXCJ+8hJO2y/H0/A20AHKmN4AIhZJ4Q=; b=e/NU6Onw1Q2VCjP298F5P3PnfX07NhK1+CkpD+j1NgmgrUR5jva4/7TwIqCA8z+yIUXx8M ZTIrczRx8JHNDC8X+tkC6MhJKQO695RyO9GrUEnskaDUHQq3cjkrmzTEdNef+7FumFUiB5 oTASnL4BHKpUUpEVWIMExPV3QJLMGVE= Date: Fri, 27 Sep 2024 08:24:12 -0700 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH bpf-next v3 4/5] bpf, x86: Add jit support for private stack To: Leon Hwang , bpf@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , kernel-team@fb.com, Martin KaFai Lau References: <20240926234506.1769256-1-yonghong.song@linux.dev> <20240926234526.1770736-1-yonghong.song@linux.dev> <44ddec9e-cc74-4686-9228-52e4db301e8a@gmail.com> Content-Language: en-GB X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Yonghong Song In-Reply-To: <44ddec9e-cc74-4686-9228-52e4db301e8a@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 9/26/24 9:58 PM, Leon Hwang wrote: > Hi Yonghong, > > A brief review about the usage of this_cpu_off on non-SMP systems. > > On 27/9/24 07:45, Yonghong Song wrote: >> Add jit support for private stack. For a particular subtree, e.g., >> subtree_root <== stack depth 120 >> subprog1 <== stack depth 80 >> subprog2 <== stack depth 40 >> subprog3 <== stack depth 160 >> >> Let us say that private_stack_ptr is the memory address allocated for >> private stack. The frame pointer for each above is calculated like below: >> subtree_root <== subtree_root_fp = private_stack_ptr + 120 >> subprog1 <== subtree_subprog1_fp = subtree_root_fp + 80 >> subprog2 <== subtree_subprog2_fp = subtree_subprog1_fp + 40 >> subprog3 <== subtree_subprog1_fp = subtree_root_fp + 160 >> >> For any function call to helper/kfunc, push/pop prog frame pointer >> is needed in order to preserve frame pointer value. >> >> To deal with exception handling, push/pop frame pointer is also used >> surrounding call to subsequent subprog. For example, >> subtree_root >> subprog1 >> ... >> insn: call bpf_throw >> ... >> >> After jit, we will have >> subtree_root >> insn: push r9 >> subprog1 >> ... >> insn: push r9 >> insn: call bpf_throw >> insn: pop r9 >> ... >> insn: pop r9 >> >> exception_handler >> pop r9 >> ... >> where r9 represents the fp for each subprog. >> >> Signed-off-by: Yonghong Song >> --- >> arch/x86/net/bpf_jit_comp.c | 87 ++++++++++++++++++++++++++++++++++--- >> 1 file changed, 81 insertions(+), 6 deletions(-) >> >> diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c >> index 06b080b61aa5..c264822c926b 100644 >> --- a/arch/x86/net/bpf_jit_comp.c >> +++ b/arch/x86/net/bpf_jit_comp.c >> @@ -325,6 +325,22 @@ struct jit_context { >> /* Number of bytes that will be skipped on tailcall */ >> #define X86_TAIL_CALL_OFFSET (12 + ENDBR_INSN_SIZE) >> >> +static void push_r9(u8 **pprog) >> +{ >> + u8 *prog = *pprog; >> + >> + EMIT2(0x41, 0x51); /* push r9 */ >> + *pprog = prog; >> +} >> + >> +static void pop_r9(u8 **pprog) >> +{ >> + u8 *prog = *pprog; >> + >> + EMIT2(0x41, 0x59); /* pop r9 */ >> + *pprog = prog; >> +} >> + >> static void push_r12(u8 **pprog) >> { >> u8 *prog = *pprog; >> @@ -491,7 +507,7 @@ static void emit_prologue_tail_call(u8 **pprog, bool is_subprog) >> */ >> static void emit_prologue(u8 **pprog, u32 stack_depth, bool ebpf_from_cbpf, >> bool tail_call_reachable, bool is_subprog, >> - bool is_exception_cb) >> + bool is_exception_cb, enum bpf_pstack_state pstack) >> { >> u8 *prog = *pprog; >> >> @@ -518,6 +534,8 @@ static void emit_prologue(u8 **pprog, u32 stack_depth, bool ebpf_from_cbpf, >> * first restore those callee-saved regs from stack, before >> * reusing the stack frame. >> */ >> + if (pstack) >> + pop_r9(&prog); >> pop_callee_regs(&prog, all_callee_regs_used); >> pop_r12(&prog); >> /* Reset the stack frame. */ >> @@ -1404,6 +1422,22 @@ static void emit_shiftx(u8 **pprog, u32 dst_reg, u8 src_reg, bool is64, u8 op) >> *pprog = prog; >> } >> >> +static void emit_private_frame_ptr(u8 **pprog, void *private_frame_ptr) >> +{ >> + u8 *prog = *pprog; >> + >> + /* movabs r9, private_frame_ptr */ >> + emit_mov_imm64(&prog, X86_REG_R9, (long) private_frame_ptr >> 32, >> + (u32) (long) private_frame_ptr); >> + >> + /* add , gs:[] */ >> + EMIT2(0x65, 0x4c); >> + EMIT3(0x03, 0x0c, 0x25); >> + EMIT((u32)(unsigned long)&this_cpu_off, 4); > It should check CONFIG_SMP here like this commit: > 1e9e0b85255e ("bpf: handle CONFIG_SMP=n configuration in x86 BPF JIT"). > > So, it seems better to reuse the code snippet of the commit. Thanks for pointing this out. I will make the change after waiting some other reviews. > > Thanks, > Leon >