From patchwork Wed May 22 11:47:54 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Masahiro Yamada X-Patchwork-Id: 13670807 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 458BE13D62E; Wed, 22 May 2024 11:48:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716378489; cv=none; b=HQ4iGklaUGWunRuLC+GJNSSYE8BCVi0kyp+zEA/Eg5e2TlWVl+Gjg0IY8NDYk/PPTGn+lk8L9hAUnrc1/4HiIqeBQolEm9TE7joqsuguugb8bxFvO9rkv94A3RoO0mtUkwjctW1Eki7NxQQ7qjympwY3YoN39I6DmrPP/sVlw3c= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716378489; c=relaxed/simple; bh=DofAHYGydy0MCK/MriRhv/qvO56aW0i8A+dCe++PsSg=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=WxD3caEk5Vai099cM8ERfSkWb512iWdSUrrmz0lYZ7/6Kdsn9hrtKl+f8liM7IkrmtKBOFFTHhp5dOqDarKjbFc+1hcsDXd7MZ66Fis4cqCQjvoFtK8jLStXamf6Gw6wRXUddy54Xurc/3uBVratSQ9CzUg1h3TtWIM0qf684Vc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=FvWpMfA0; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="FvWpMfA0" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6BFAFC4AF07; Wed, 22 May 2024 11:48:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1716378488; bh=DofAHYGydy0MCK/MriRhv/qvO56aW0i8A+dCe++PsSg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=FvWpMfA0ZKDDpmpdNmMsLDfzEjl2O8ngZw7+tWEel9/y9ODVFBsG2VViWRci2eAdy v7/xHnm/URk9ahj6Ir+1ECgkVs1nczWBa5QNnfJAhyvCkdihNFiAMsLCXAwYXIfuWq XyboSgG+ZmmxB0tix3B+0YZmnL1My+kwgp2n+h81l6TLgsz0q232ijAmerCRHaCHNj UnKnpPiAXDPCT+cBrOumghIE3tBUv8pCNG7fgsgY3ZxrrRtykIOU3VMKiGOvVG8mg6 Iyh9gKHSWrR1ApfKFxgESwnj1JzDsP7ltqi/XHU09CVEZV5FbOn0HHTmsrrd6ZeFIT 0fboDRvyJfLcQ== From: Masahiro Yamada To: linux-kbuild@vger.kernel.org Cc: linux-kernel@vger.kernel.org, bpf@vger.kernel.org, Ard Biesheuvel , Masahiro Yamada , Arnd Bergmann , Nathan Chancellor , Nicolas Schier , linux-arch@vger.kernel.org Subject: [PATCH 2/3] kbuild: remove PROVIDE() for kallsyms symbols Date: Wed, 22 May 2024 20:47:54 +0900 Message-Id: <20240522114755.318238-3-masahiroy@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20240522114755.318238-1-masahiroy@kernel.org> References: <20240522114755.318238-1-masahiroy@kernel.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 This reimplements commit 951bcae6c5a0 ("kallsyms: Avoid weak references for kallsyms symbols"). I am not a big fan of PROVIDE() because it always satisfies the linker even in situations that should result in a link error. In other words, it can potentially shift a compile-time error into a run-time error. Duplicating kallsyms_* in vmlinux.lds.h also reduces maintainability. As an alternative solution, this commit prepends one more kallsyms step. KSYMS .tmp_vmlinux.kallsyms0.S # added AS .tmp_vmlinux.kallsyms0.o # added LD .tmp_vmlinux.btf BTF .btf.vmlinux.bin.o LD .tmp_vmlinux.kallsyms1 NM .tmp_vmlinux.kallsyms1.syms KSYMS .tmp_vmlinux.kallsyms1.S AS .tmp_vmlinux.kallsyms1.o LD .tmp_vmlinux.kallsyms2 NM .tmp_vmlinux.kallsyms2.syms KSYMS .tmp_vmlinux.kallsyms2.S AS .tmp_vmlinux.kallsyms2.o LD vmlinux Step 0 takes /dev/null as input, and generates .tmp_vmlinux.kallsyms0.o, which has a valid kallsyms format with the empty symbol list, and can be linked to vmlinux. Since it is really small, the added compile-time cost is negligible. Signed-off-by: Masahiro Yamada Acked-by: Ard Biesheuvel --- include/asm-generic/vmlinux.lds.h | 19 ------------------- kernel/kallsyms_internal.h | 5 ----- scripts/kallsyms.c | 6 ------ scripts/link-vmlinux.sh | 10 ++++++++-- 4 files changed, 8 insertions(+), 32 deletions(-) diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index 5703526d6ebf..62b4cb0462e6 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -451,30 +451,11 @@ #endif #endif -/* - * Some symbol definitions will not exist yet during the first pass of the - * link, but are guaranteed to exist in the final link. Provide preliminary - * definitions that will be superseded in the final link to avoid having to - * rely on weak external linkage, which requires a GOT when used in position - * independent code. - */ -#define PRELIMINARY_SYMBOL_DEFINITIONS \ - PROVIDE(kallsyms_addresses = .); \ - PROVIDE(kallsyms_offsets = .); \ - PROVIDE(kallsyms_names = .); \ - PROVIDE(kallsyms_num_syms = .); \ - PROVIDE(kallsyms_relative_base = .); \ - PROVIDE(kallsyms_token_table = .); \ - PROVIDE(kallsyms_token_index = .); \ - PROVIDE(kallsyms_markers = .); \ - PROVIDE(kallsyms_seqs_of_names = .); - /* * Read only Data */ #define RO_DATA(align) \ . = ALIGN((align)); \ - PRELIMINARY_SYMBOL_DEFINITIONS \ .rodata : AT(ADDR(.rodata) - LOAD_OFFSET) { \ __start_rodata = .; \ *(.rodata) *(.rodata.*) \ diff --git a/kernel/kallsyms_internal.h b/kernel/kallsyms_internal.h index 85480274fc8f..925f2ab22639 100644 --- a/kernel/kallsyms_internal.h +++ b/kernel/kallsyms_internal.h @@ -4,11 +4,6 @@ #include -/* - * These will be re-linked against their real values during the second link - * stage. Preliminary values must be provided in the linker script using the - * PROVIDE() directive so that the first link stage can complete successfully. - */ extern const unsigned long kallsyms_addresses[]; extern const int kallsyms_offsets[]; extern const u8 kallsyms_names[]; diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c index 47978efe4797..fa53b5eef553 100644 --- a/scripts/kallsyms.c +++ b/scripts/kallsyms.c @@ -259,12 +259,6 @@ static void shrink_table(void) } } table_cnt = pos; - - /* When valid symbol is not registered, exit to error */ - if (!table_cnt) { - fprintf(stderr, "No valid symbol.\n"); - exit(1); - } } static void read_map(const char *in) diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh index b16967d33f1c..fe7db9a265ca 100755 --- a/scripts/link-vmlinux.sh +++ b/scripts/link-vmlinux.sh @@ -225,6 +225,11 @@ ${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init init/version-timestamp.o kallsymso= btf_vmlinux_bin_o= +if is_enabled CONFIG_KALLSYMS; then + # kallsyms step 0 + kallsyms /dev/null .tmp_vmlinux.kallsyms0 +fi + if is_enabled CONFIG_DEBUG_INFO_BTF; then if ! gen_btf .tmp_vmlinux.btf .btf.vmlinux.bin.o ; then echo >&2 "Failed to generate BTF for vmlinux" @@ -237,9 +242,10 @@ if is_enabled CONFIG_KALLSYMS; then # kallsyms support # Generate section listing all symbols and add it into vmlinux - # It's a three step process: + # It's a four step process: + # 0) Generate a dummy __kallsyms with empty symbol list. # 1) Link .tmp_vmlinux.kallsyms1 so it has all symbols and sections, - # but __kallsyms is empty. + # with a dummy __kallsyms. # Running kallsyms on that gives us .tmp_kallsyms1.o with # the right size # 2) Link .tmp_vmlinux.kallsyms2 so it now has a __kallsyms section of