From patchwork Wed Jun 12 03:27:17 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dmitry Safonov via B4 Relay X-Patchwork-Id: 13694407 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 498041DFF0; Wed, 12 Jun 2024 03:29:02 +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=1718162942; cv=none; b=XvT/MI32Vsji8y/oNowHxltHzljyG5dvQh7ldnFRInlKw6QTPNLNFa+COsr9A/inlLjfYDqv6eByqwI3kzgs1JmXDrYgwmDtkipKYbDOgvsRB0bnihqqT00rvodgkeQF0i+l2OzwET2ACAx0DqsA5w7maemtb9nQHWmL/SHAois= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718162942; c=relaxed/simple; bh=dzytYAPA2vntPxLFoQACxn5mDGtGCdAdzSX3DYn4Sy0=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:To:Cc; b=QPC8fTD6kj5Hz9We0N1huk7sWeuyNhc9DaAxLHeewxgXJNl8cP8FbqsmK4ofn8jIzUk3ODZIGKHDHIYIrY74cCn6L5OmZoQngX6xBqnWmhwqBCyfsH0v6cDn/FhAOa0llwoevCntiOjUFahv9GVWrqqWOgCLJ/NYITyfYmxRa88= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=TfZ3uEfp; 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="TfZ3uEfp" Received: by smtp.kernel.org (Postfix) with ESMTPS id D1EEDC32786; Wed, 12 Jun 2024 03:29:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1718162941; bh=dzytYAPA2vntPxLFoQACxn5mDGtGCdAdzSX3DYn4Sy0=; h=From:Date:Subject:To:Cc:Reply-To:From; b=TfZ3uEfp1sH8DRTaiFN3apxLEzXcEDhJjfHsGkQ5VlIoPBxuj6Ms+6iQZtJaPoY0s gQXyoPncqufuYUTX1IFiR2iQkpGIfre2JTpQL60NhLzwIiyFPLjMik0A9FcpIr7VFC 18qIsLPh2I3TAPFZgcMt1IWHqEyhP54YvGsoks8zRvMYfIlRE4YzS/Ly7/W4i4FFXV 6L6+VfT6odL7ELpbA5J4Je2/q0gjrvBSfa77grZyVdeiCgw1/gd8vFDhz3y7kgWH60 lKLiYEddd8VfYyg10u9eZ7/uPGxQXT5MNWY6/6MYL1cwyy+Kpfbs3JncZBM9masQ5R atq8xh9UXLY7w== Received: from aws-us-west-2-korg-lkml-1.web.codeaurora.org (localhost.localdomain [127.0.0.1]) by smtp.lore.kernel.org (Postfix) with ESMTP id C45E6C27C53; Wed, 12 Jun 2024 03:29:01 +0000 (UTC) From: Dmitry Safonov via B4 Relay Date: Wed, 12 Jun 2024 04:27:17 +0100 Subject: [PATCH RFC v2] kbuild/x86: Use $(KBUILD_AFLAGS) in Kbuild's version of $(as-instr) Precedence: bulk X-Mailing-List: linux-kbuild@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20240612-as-instr-opt-wrussq-v2-1-bd950f7eead7@gmail.com> X-B4-Tracking: v=1; b=H4sIAJUVaWYC/22OzQrCMBCEX0X27EqTBjWeBMEH8Co9bOO2Ddgfs 7Uqpe9uWjx6nGG+mRlBOHgWOKxGCDx48W0ThV6vwFXUlIz+FjXoRJvEqARJ0DfSB2y7Hl/hKfJ As2eX7jjd6sRAJLvAhX8vrVe4nE+QRTMnYcwDNa6aC2uSnsOcrrz0bfgsFwa1ML819XdtUKjQ2 lyRImsLmx7Lmvx949oasmmavuAli9LUAAAA To: Borislav Petkov , Dave Hansen , Ingo Molnar , "H. Peter Anvin" , Masahiro Yamada , Thomas Gleixner , x86@kernel.org Cc: linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org, Dmitry Safonov <0x7f454c46@gmail.com> X-Mailer: b4 0.12.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1718162850; l=6387; i=0x7f454c46@gmail.com; s=20240410; h=from:subject:message-id; bh=mE/MtJBn2tZ2pMC+jU16KAPPWHc/zIAQ99jOTODDD5E=; b=+ml6hQMsHqv7+mqb7hjrBh5lDWB7+8/2dGtaJhoUzvYoMQcYXrueH858HPd3C/nuBRFU8VOueaEV n5HA69KaAboO5X0CfNO40u34XTuavXrpBuLRgEQvfP5TjJX+IPce X-Developer-Key: i=0x7f454c46@gmail.com; a=ed25519; pk=cFSWovqtkx0HrT5O9jFCEC/Cef4DY8a2FPeqP4THeZQ= X-Endpoint-Received: by B4 Relay for 0x7f454c46@gmail.com/20240410 with auth_id=152 X-Original-From: Dmitry Safonov <0x7f454c46@gmail.com> Reply-To: 0x7f454c46@gmail.com From: Dmitry Safonov <0x7f454c46@gmail.com> At Arista some products use compatible 32-bit userspace running on x86. As a part of disto build for ia32 it also compiles the 64-bit kernel. While the toolchain for the kernel build is yet the same, with 64-bit gcc: > / @Bru-na-Boinne% file /usr/bin/gcc-11 > /usr/bin/gcc-11: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, BuildID[sha1]=6571ad50d8f12eece053f1bac7a95a2c767f32c9, for GNU/Linux 3.2.0, stripped It seems that gcc is being smart and detects that it's running in a 32-bit container (personality flag? 32-bit mmap base? something else inherited post-exec? haven't yet figured it out) and by default tries to build 32-bit binaries. That results in a failing toolchain check: > / @Bru-na-Boinne% printf "%b\n" "wrussq %rax, (%rbx)" | /usr/bin/gcc-11 -Wa,--fatal-warnings -c -x assembler-with-cpp -o /dev/null - > : Assembler messages: > :1: Error: `wrussq' is only supported in 64-bit mode Which passes when -m64 is directly specify for the build check: > / @Bru-na-Boinne% printf "%b\n" "wrussq %rax, (%rbx)" | /usr/bin/gcc-11 -m64 -Wa,--fatal-warnings -c -x assembler-with-cpp -o /dev/null - > / @Bru-na-Boinne% echo $? > 0 As a result, kbuild produces different value for CONFIG_AS_WRUSS for native 64-bit containers and ia32 containers with 64-bit gcc, which produces different kernels with enabled/disabled CONFIG_X86_USER_SHADOW_STACK. arch/x86/Makefile already properly defines KBUILD_AFLAGS += -m64, which is luckly already available at the point of toolchain check in arch/x86/Kconfig.assembler By hacking around Kbuild variable the following way: > --- a/scripts/Kconfig.include > +++ b/scripts/Kconfig.include > @@ -13,7 +13,8 @@ left_paren := ( > > # $(if-success,,,) > # Return if exits with 0, otherwise. > -if-success = $(shell,{ $(1); } >/dev/null 2>&1 && echo "$(2)" || echo "$(3)") > +if-success = $(shell,echo '$(1)' 1>&2;{ $(1); } >/dev/null 2>&1 && echo "$(2)" || echo "$(3)") I got the following output for the toolchain check, before: > linux @Bru-na-Boinne% make ARCH=x86_64 oldconfig V=1 2>&1 | grep wrus > printf "%b\n" "wrussq %rax,(%rbx)" | gcc -c -x assembler-with-cpp -o /dev/null - and after: > linux @Bru-na-Boinne% make ARCH=x86_64 oldconfig V=1 2>&1 | grep wrus > printf "%b\n" "wrussq %rax,(%rbx)" | gcc -D__ASSEMBLY__ -fno-PIE -m64 -c -x assembler-with-cpp -o /dev/null - Which seems appropriate to me. This also reflects the existing definition in scripts/Makefile.compiler for $(as-instr) that already has $(KBUILD_AFLAGS). In order to eliminate a possible circular dependency of Kconfig => arch/.../Makefile => Kconfig => ... which exist i.e. in arm64/Makefile for KASAN_SHADOW_SCALE_SHIFT that depends on CONFIG_KASAH_SW_TAGS and CONFIG_KASAN_GENERIC kconfigs, ignore KBUILD_AFLAGS difference in auto.conf.cmd as it is expected that the variable will differ between fist and later Makefile passes. Use that in Kconfig toolchain checks. Signed-off-by: Dmitry Safonov <0x7f454c46@gmail.com> --- Changes in v2: - I made a mistake in version 1 by not testing it on a clean tree. Which passed on an existing "dirty" tree, but went into build busy-loop over a fresh clean kernel tree. With a little debug, I found out that the reason was subdir-asflags-y in scripts/. They are "empty", but they update KBUILD_AFLAGS with an extra trailing space. Ugh. That resulted in include/config/auto.conf.cmd being unhappy and triggering rebuild after rebuild. - Then I've added a patch to scripts/kconfig/preprocess.c that removes any extra head or tail spaces from the environment variables. - That was a working patch set on x86_64, but that broke arm64 by creating a circular dependency on KASAN_SHADOW_SCALE_SHIFT. - In the end, I decided to just ignore KBUILD_AFLAGS in auto.conf.cmd for RFC v2. Probably, I could just add $(as-instr-config,...) function to Kconfig that would take -m64 just for AS_WRUSS, but that seems like fixing one specific place, rather than more generic fix. Unsure, sending this as RFC, please advise/vote on the best approach. - Link to v1: https://lore.kernel.org/r/20240411-as-instr-opt-wrussq-v1-1-99b1a1a99f93@gmail.com --- scripts/Kconfig.include | 2 +- scripts/kconfig/preprocess.c | 14 +++++++++++++- 2 files changed, 14 insertions(+), 2 deletions(-) --- base-commit: 83a7eefedc9b56fe7bfeff13b6c7356688ffa670 change-id: 20240410-as-instr-opt-wrussq-48ec37e36204 Best regards, diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include index 3ee8ecfb8c04..d8574c1faf2d 100644 --- a/scripts/Kconfig.include +++ b/scripts/Kconfig.include @@ -33,7 +33,7 @@ ld-option = $(success,$(LD) -v $(1)) # $(as-instr,) # Return y if the assembler supports , n otherwise -as-instr = $(success,printf "%b\n" "$(1)" | $(CC) $(CLANG_FLAGS) -Wa$(comma)--fatal-warnings -c -x assembler-with-cpp -o /dev/null -) +as-instr = $(success,printf "%b\n" "$(1)" | $(CC) $(CLANG_FLAGS) $(KBUILD_AFLAGS) -Wa$(comma)--fatal-warnings -c -x assembler-with-cpp -o /dev/null -) # check if $(CC) and $(LD) exist $(error-if,$(failure,command -v $(CC)),C compiler '$(CC)' not found) diff --git a/scripts/kconfig/preprocess.c b/scripts/kconfig/preprocess.c index f0a4a218c4a5..cf7389f13f00 100644 --- a/scripts/kconfig/preprocess.c +++ b/scripts/kconfig/preprocess.c @@ -61,6 +61,17 @@ static void env_del(struct env *e) free(e); } +static bool env_ignore(const char *name) +{ + /* + * Break the circular dependency Kconfig => arch/.../Makefile => Kconfig + * On the first Makefile pass only AFLAGS that do not depend on + * CONFIG_* set will be defined. Those are used by Kconfig for + * toolchain checks. + */ + return !strcmp(name, "KBUILD_AFLAGS"); +} + /* The returned pointer must be freed when done */ static char *env_expand(const char *name) { @@ -83,7 +94,8 @@ static char *env_expand(const char *name) * We need to remember all referenced environment variables. * They will be written out to include/config/auto.conf.cmd */ - env_add(name, value); + if (!env_ignore(name)) + env_add(name, value); return xstrdup(value); }