From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 21E83FED2F1 for ; Thu, 12 Mar 2026 08:55:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=6m3iVjAJ3GnbX16/A8yr0Uv8IZ6KsZjKuUcZqEbIVJA=; b=osxdG4RspToC4RWUKaNG3F1q50 Js5Wp23aWlHKPKymv9eaNaAhDSSP/32rXBrDl38OiuemGm0n4KoJ1VF3d+ouqtxsaFDyW3fMktaHm ZzBJcqaLY9EdTdA21mpEsP5JGvdU2/oysj/Dwt+BctbT+1UXMlnP160fIB54uuvTA4di85yL/wH1a ZmFbZhxWzh6TgnAvKlIe07I78v6BOO9d1Wm26Ek0XgrZKYfUqXmhOrYmzOrcq8I1yxeD7DIYQaLvb p9A8ArL2usxXL27DZjh0mZ9QRMebCelmSbtHf5oUdMgI16u0rsYBbeG0Mx0SF1d68LBCciT1DtKNJ Sab8wcRA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1w0bpD-0000000DfYl-2vTq; Thu, 12 Mar 2026 08:55:23 +0000 Received: from mail-wm1-x32a.google.com ([2a00:1450:4864:20::32a]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1w0bpA-0000000DfXn-3OLg for linux-arm-kernel@lists.infradead.org; Thu, 12 Mar 2026 08:55:22 +0000 Received: by mail-wm1-x32a.google.com with SMTP id 5b1f17b1804b1-4852f73d0a3so6798545e9.3 for ; Thu, 12 Mar 2026 01:55:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1773305719; x=1773910519; darn=lists.infradead.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=6m3iVjAJ3GnbX16/A8yr0Uv8IZ6KsZjKuUcZqEbIVJA=; b=Sb/eZap21jrg6FHEcy602lJ2VhXtllFeJkz24xx2fn0OvQgi3yrFQZ8fHGHfgqd9x2 YzqVzb8Vnxl5XY5cw4oSAITY0c2K2E2mO+IFy8J74Nl9FHH6IEgLoKeJi1v8GAo2GQq6 r1kUeNITwPkAmoMXfUwNxzQSzx9SZXwU6OfWFCEIlmOMPHoZBEF/k2PNFyXgsEFaAlYj Yfadrjdm6nIZVdwd5Y23+RyBT8YxzP7vPVgxEZD0RRsEkH/5cU5BoQBMWqlLNB31d6ou dwG0GVzW0GB5ThcbKt5RQWTe0CfARlgOOSnQR6QmolfjZrwF+JNuOEUiEu81pf1GyG1+ c44w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1773305719; x=1773910519; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=6m3iVjAJ3GnbX16/A8yr0Uv8IZ6KsZjKuUcZqEbIVJA=; b=ubuTGOXXTI9/VQna4lCK5G3vURVzyGkeiS7GOgS40ofRzQ+RyCLpJksx8oUHTVWR6o TQeIBlr2xg8gdtKSo6EdPysVZjhuSvuuW2I75exNtjbTU83b/WkNrua7/foNa62+RYNp FUvuO68BnkKppGX6L3SfmwegJfixbEP0rAF9aZJZsFY+mjZj4OLXb+eSXCFr7ps3yFr1 IqggSWMASKqQxmVQgpAJY8/2yaJgd8NzbXmzvNQuCq7X41zEP1A2H3v/6moFfkFkpQk5 i8YfzmpGDNpwacunsTZ7o1CaTUrmFVGf2fH/9pOuB88utjtGBEBnP38AdXZJ44l3RNY4 2M5Q== X-Forwarded-Encrypted: i=1; AJvYcCWGlurjQfewpKmW4wU+OEQKRdTw0EID+cxGyjkEcjhDjfZefo6h7Vp30+O2ZnThzn2pe7xB6jTIMeb3ZqMa08qy@lists.infradead.org X-Gm-Message-State: AOJu0YwjwBeo+Gbx2uP/D66wd51nx7dmdF1Lhqj9dYjTk4a+my3ptluY AHyVYpvlQZmNfm/XYqI+wIt3AzLT+6DoBVUH0cnP8u2P4Ma8s5Jm2tVMi71JfI2d5A== X-Gm-Gg: ATEYQzwr6RQ2avAbtgZNf4iulaPReXVbsi9QyH4spSmDIuF20m87kDVFbUwp0v/2Lmc rrUJdkiqIF7LOOLEk+5uC3FPQvIYKDj/Ao1S6hkP77Ax/79REEC/6pWQn99kfKx1n+85SPoyLlq 4KCNOTsV+35c9wAr3vYTEYH1F7Eu5UhwQPAvdEzQoYygWUEo2NOE6K9jwQ0x49invpJ5qcEmJNu 0Bnqi3I1643+XUukYIrjLOZk4J0Axzued09EepCk3txtoACAg42ZeoK2Wjh4BPLqbLSLs3YvKpB 5sOfe2MKZf2JaiGHdxGXpjfQt821Bb7mtmxPGbGqKcAajp/kxy+k9UX9rRXQQzAwJsCKfNZM6Kz e66nDeT6bypp/S94HI169X4i5VFGJlFssgXg5y+H5bU0ZCP3tq4JFjD9OiqvpaNR4lY7LQmibTP 4U5hdDcUYV1R2gxPq09yuvgta/TVLmgOD1D6qPSvOziBFMl/8Ykb7Gthsp56x0d76/m0s= X-Received: by 2002:a05:600c:4455:b0:485:3e6c:aa84 with SMTP id 5b1f17b1804b1-4854b13b3cbmr83483945e9.33.1773305718060; Thu, 12 Mar 2026 01:55:18 -0700 (PDT) Received: from google.com (198.115.140.34.bc.googleusercontent.com. [34.140.115.198]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4854b47145dsm110869815e9.0.2026.03.12.01.55.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 12 Mar 2026 01:55:17 -0700 (PDT) Date: Thu, 12 Mar 2026 08:55:14 +0000 From: Vincent Donnefort To: Nathan Chancellor Cc: rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, linux-trace-kernel@vger.kernel.org, maz@kernel.org, oliver.upton@linux.dev, joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, jstultz@google.com, qperret@google.com, will@kernel.org, aneesh.kumar@kernel.org, kernel-team@android.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v14 18/30] tracing: Check for undefined symbols in simple_ring_buffer Message-ID: References: <20260309162516.2623589-1-vdonnefort@google.com> <20260309162516.2623589-19-vdonnefort@google.com> <20260311221816.GA316631@ax162> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260311221816.GA316631@ax162> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260312_015521_463954_634EBF48 X-CRM114-Status: GOOD ( 30.05 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Mar 11, 2026 at 03:18:16PM -0700, Nathan Chancellor wrote: > Hi Vincent, > > On Mon, Mar 09, 2026 at 04:25:04PM +0000, Vincent Donnefort wrote: > > The simple_ring_buffer implementation must remain simple enough to be > > used by the pKVM hypervisor. Prevent the object build if unresolved > > symbols are found. > > > > Reviewed-by: Steven Rostedt (Google) > > Signed-off-by: Vincent Donnefort > > > > diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile > > index d106beca8d7f..3182e1bc1cf7 100644 > > --- a/kernel/trace/Makefile > > +++ b/kernel/trace/Makefile > > @@ -132,4 +132,20 @@ obj-$(CONFIG_TRACE_REMOTE) += trace_remote.o > > obj-$(CONFIG_SIMPLE_RING_BUFFER) += simple_ring_buffer.o > > obj-$(CONFIG_TRACE_REMOTE_TEST) += remote_test.o > > > > +# > > +# simple_ring_buffer is used by the pKVM hypervisor which does not have access > > +# to all kernel symbols. Fail the build if forbidden symbols are found. > > +# > > +UNDEFINED_ALLOWLIST := memset alt_cb_patch_nops __x86 __ubsan __asan __kasan __gcov __aeabi_unwind > > +UNDEFINED_ALLOWLIST += __stack_chk_fail stackleak_track_stack __ref_stack __sanitizer > > +UNDEFINED_ALLOWLIST := $(addprefix -e , $(UNDEFINED_ALLOWLIST)) > > + > > +quiet_cmd_check_undefined = NM $< > > + cmd_check_undefined = test -z "`$(NM) -u $< | grep -v $(UNDEFINED_ALLOWLIST)`" > > This check triggers when building allmodconfig targeting arm, arm64, > powerpc, and x86_64 (at least, I did not test more at the moment) with > clang. If this is a hard failure, this really needs to print something > out to the developer/user to help them debug off the bat, versus having > to manually dig the $(NM) command out from the .cmd file or V=1. I came > up with > > diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile > index 3182e1bc1cf7..c725b06876bc 100644 > --- a/kernel/trace/Makefile > +++ b/kernel/trace/Makefile > @@ -141,7 +141,13 @@ UNDEFINED_ALLOWLIST += __stack_chk_fail stackleak_track_stack __ref_stack __sani > UNDEFINED_ALLOWLIST := $(addprefix -e , $(UNDEFINED_ALLOWLIST)) > > quiet_cmd_check_undefined = NM $< > - cmd_check_undefined = test -z "`$(NM) -u $< | grep -v $(UNDEFINED_ALLOWLIST)`" > + cmd_check_undefined = \ > + undefsyms=$$($(NM) -u $< | grep -v $(UNDEFINED_ALLOWLIST) || true); \ > + if [ -n "$$undefsyms" ]; then \ > + echo "Unexpected symbols in $<:" >&2; \ > + echo "$$undefsyms" >&2; \ > + false; \ > + fi > > $(obj)/%.o.checked: $(obj)/%.o FORCE > $(call if_changed,check_undefined) > -- > > which prints > > Unexpected symbols in kernel/trace/simple_ring_buffer.o: > U llvm_gcda_emit_arcs > U llvm_gcda_emit_function > U llvm_gcda_end_file > U llvm_gcda_start_file > U llvm_gcda_summary_info > U llvm_gcov_init > > for arm64, which makes sense since these are LLVM specific GCOV symbols, > so they should probably get the same treatment as the other ones: > > diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile > index c725b06876bc..d464e3aa5bdd 100644 > --- a/kernel/trace/Makefile > +++ b/kernel/trace/Makefile > @@ -136,8 +136,8 @@ obj-$(CONFIG_TRACE_REMOTE_TEST) += remote_test.o > # simple_ring_buffer is used by the pKVM hypervisor which does not have access > # to all kernel symbols. Fail the build if forbidden symbols are found. > # > -UNDEFINED_ALLOWLIST := memset alt_cb_patch_nops __x86 __ubsan __asan __kasan __gcov __aeabi_unwind > -UNDEFINED_ALLOWLIST += __stack_chk_fail stackleak_track_stack __ref_stack __sanitizer > +UNDEFINED_ALLOWLIST := memset alt_cb_patch_nops __x86 __ubsan __asan __kasan __gcov llvm_gcda llvm_gcov > +UNDEFINED_ALLOWLIST += __aeabi_unwind __stack_chk_fail stackleak_track_stack __ref_stack __sanitizer > UNDEFINED_ALLOWLIST := $(addprefix -e , $(UNDEFINED_ALLOWLIST)) > > quiet_cmd_check_undefined = NM $< > -- > > For x86_64, I see > > Unexpected symbols in kernel/trace/simple_ring_buffer.o: > U __clear_pages_unrolled > U __memmove > U copy_page > > which comes from the use of KCFI_ADDRESSABLE(), since allmodconfig has > CONFIG_CFI=y. > > For powerpc (with both clang and GCC), I see > > Unexpected symbols in kernel/trace/simple_ring_buffer.o: > U .TOC. > > For arm (with both clang and GCC), I see > > Unexpected symbols in kernel/trace/simple_ring_buffer.o: > U __stack_chk_guard > U warn_slowpath_fmt > > Presumably adding all of those should be fine as well? > > diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile > index d464e3aa5bdd..4f120cb8c79c 100644 > --- a/kernel/trace/Makefile > +++ b/kernel/trace/Makefile > @@ -137,7 +137,8 @@ obj-$(CONFIG_TRACE_REMOTE_TEST) += remote_test.o > # to all kernel symbols. Fail the build if forbidden symbols are found. > # > UNDEFINED_ALLOWLIST := memset alt_cb_patch_nops __x86 __ubsan __asan __kasan __gcov llvm_gcda llvm_gcov > -UNDEFINED_ALLOWLIST += __aeabi_unwind __stack_chk_fail stackleak_track_stack __ref_stack __sanitizer > +UNDEFINED_ALLOWLIST += __aeabi_unwind __stack_chk_fail __stack_chk_guard stackleak_track_stack __ref_stack __sanitizer > +UNDEFINED_ALLOWLIST += \.TOC\. __clear_pages_unrolled __memmove copy_page warn_slowpath_fmt > UNDEFINED_ALLOWLIST := $(addprefix -e , $(UNDEFINED_ALLOWLIST)) > > quiet_cmd_check_undefined = NM $< > -- > > I don't mind sending a series for these, I just wanted to make sure I > was reasoning about everything correctly. Yes this is all fine. If you have something already, please send it. Meanwhile, I'll try something a bit more durable. Thanks, Vincent > > Cheers, > Nathan