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 X-Spam-Level: X-Spam-Status: No, score=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E010FC43381 for ; Mon, 18 Mar 2019 16:38:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A644C21473 for ; Mon, 18 Mar 2019 16:38:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="B6ydHxaz" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727518AbfCRQiU (ORCPT ); Mon, 18 Mar 2019 12:38:20 -0400 Received: from mail-pg1-f196.google.com ([209.85.215.196]:33864 "EHLO mail-pg1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726910AbfCRQiT (ORCPT ); Mon, 18 Mar 2019 12:38:19 -0400 Received: by mail-pg1-f196.google.com with SMTP id v12so11800693pgq.1 for ; Mon, 18 Mar 2019 09:38:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=sRUrL3chxqebXkM+sBPvfyP4wLwfp+u5Gaca9ioMO9I=; b=B6ydHxaz5oEYv0h8+JdrJVggAOaZ66YVaw9o0gRJcpv2RHWxQlUk453g1YzgKluDRc qohmme8UKwPQpHH8MB6Qz4qTi2s6wHUnvMtW1F/025pwhs4LsEy9xati8dLpzH5DQCHL TTrFkcZMQBqZY/4UeoewLYBVYj11rQOKf9/z0= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=sRUrL3chxqebXkM+sBPvfyP4wLwfp+u5Gaca9ioMO9I=; b=tOTaZgVyY6HxFLJsyijBshZSPC4wGs/g4rCSccKbXWcYzc/A5HPXX+COZIevlZMD8c zejZCpHQLCIR/gqmKO0/x3xzGAA2NoxrhOLokKBpaJ/3WNfkE8OwvaOfw1KuOglD8ig0 TEM0dSzXT2pEOzY4Q8XqyFq54SwcJEsYGBMKxeg8wpgmP1BUqDDcG3j//PCkG+QWP1yU K1Tf2YxKjwvtp8vooVxskRMuCAiGVik9cFdY0Y2RrPeiIN5L1a1B0+lDUHg1R0+eFUG4 qjVb+Gzh7I6k+LEzbsyms4doOqlLDZu9xxxlxewheSQz6GT957ATjngpTLgQjijW3WZG 2fTQ== X-Gm-Message-State: APjAAAUk6Y99H5O+5QFJhzy1ktTdkzxDrwmDvy/OAwZs0YskeHKdkhOP sUoIQVjhw4hQ4PLVE6nHMptHGA== X-Google-Smtp-Source: APXvYqzgDbJYkvnETHI+KINxyWQoiaJZN+I9GqHXgS/gxwK50OlvkE16xbXZPg5xi7zBrBQLiCSlEQ== X-Received: by 2002:a65:620e:: with SMTP id d14mr10160332pgv.28.1552927097637; Mon, 18 Mar 2019 09:38:17 -0700 (PDT) Received: from localhost ([2620:15c:202:1:75a:3f6e:21d:9374]) by smtp.gmail.com with ESMTPSA id r86sm17553831pfa.82.2019.03.18.09.38.16 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 18 Mar 2019 09:38:16 -0700 (PDT) Date: Mon, 18 Mar 2019 09:38:16 -0700 From: Matthias Kaehlcke To: hpa@zytor.com Cc: Nick Desaulniers , Andy Lutomirski , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, LKML , Manoj Gupta , Tiancong Wang , Stephen Hines , clang-built-linux@googlegroups.com, Miguel Ojeda Subject: Re: [PATCH] lib: Add shared copy of __lshrti3 from libgcc Message-ID: <20190318163816.GG112750@google.com> References: <18F0D032-4FC4-4194-A2F4-B7ED68C2C5F2@zytor.com> <20190315234701.GF112750@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 15, 2019 at 04:53:40PM -0700, hpa@zytor.com wrote: > On March 15, 2019 4:47:01 PM PDT, Matthias Kaehlcke wrote: > >On Fri, Mar 15, 2019 at 03:12:08PM -0700, hpa@zytor.com wrote: > >> On March 15, 2019 3:06:37 PM PDT, Nick Desaulniers > > wrote: > >> >On Fri, Mar 15, 2019 at 1:54 PM Matthias Kaehlcke > >> >wrote: > >> >> > >> >> The compiler may emit calls to __lshrti3 from the compiler runtime > >> >> library, which results in undefined references: > >> >> > >> >> arch/x86/kvm/x86.o: In function `mul_u64_u64_shr': > >> >> include/linux/math64.h:186: undefined reference to `__lshrti3' > >> > > >> >Looks like Clang will emit this at -Oz (but not -O2): > >> >https://godbolt.org/z/w1_2YC > >> > > >> >> > >> >> Add a copy of the __lshrti3 libgcc routine (from gcc v4.9.2). > >> > > >> >Has it changed since? If so why not a newer version of libgcc_s? > >> > > >> >> > >> >> Include the function for x86 builds with clang, which is the > >> >> environment where the above error was observed. > >> >> > >> >> Signed-off-by: Matthias Kaehlcke > >> >> --- > >> >> arch/x86/Kconfig | 1 + > >> >> include/linux/libgcc.h | 16 ++++++++++++++++ > >> >> lib/Kconfig | 3 +++ > >> >> lib/Makefile | 1 + > >> >> lib/lshrti3.c | 31 +++++++++++++++++++++++++++++++ > >> >> 5 files changed, 52 insertions(+) > >> >> create mode 100644 lib/lshrti3.c > >> >> > >> >> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > >> >> index c1f9b3cf437c..a5e0d923845d 100644 > >> >> --- a/arch/x86/Kconfig > >> >> +++ b/arch/x86/Kconfig > >> >> @@ -105,6 +105,7 @@ config X86 > >> >> select GENERIC_IRQ_PROBE > >> >> select GENERIC_IRQ_RESERVATION_MODE > >> >> select GENERIC_IRQ_SHOW > >> >> + select GENERIC_LIB_LSHRTI3 if CC_IS_CLANG > >> >> select GENERIC_PENDING_IRQ if SMP > >> >> select GENERIC_SMP_IDLE_THREAD > >> >> select GENERIC_STRNCPY_FROM_USER > >> >> diff --git a/include/linux/libgcc.h b/include/linux/libgcc.h > >> >> index 32e1e0f4b2d0..a71036471838 100644 > >> >> --- a/include/linux/libgcc.h > >> >> +++ b/include/linux/libgcc.h > >> >> @@ -22,15 +22,26 @@ > >> >> #include > >> >> > >> >> typedef int word_type __attribute__ ((mode (__word__))); > >> >> +typedef int TItype __attribute__ ((mode (TI))); > >> > > >> >Well that's an interesting new compiler attribute. > >> > >>https://stackoverflow.com/questions/4559025/what-does-gcc-attribute-modexx-actually-do > >> >Please use `__mode(TI)` from include/linux/compiler_attributes.h ex. > >> >typedef int TItype __mode(TI); > >> > > >> >> > >> >> #ifdef __BIG_ENDIAN > >> >> struct DWstruct { > >> >> int high, low; > >> >> }; > >> >> + > >> >> +struct DWstruct128 { > >> >> + long long high, low; > >> >> +}; > >> >> + > >> >> #elif defined(__LITTLE_ENDIAN) > >> >> struct DWstruct { > >> >> int low, high; > >> >> }; > >> >> + > >> >> +struct DWstruct128 { > >> >> + long long low, high; > >> >> +}; > >> >> + > >> >> #else > >> >> #error I feel sick. > >> >> #endif > >> >> @@ -40,4 +51,9 @@ typedef union { > >> >> long long ll; > >> >> } DWunion; > >> >> > >> >> +typedef union { > >> >> + struct DWstruct128 s; > >> >> + TItype ll; > >> >> +} DWunion128; > >> >> + > >> >> #endif /* __ASM_LIBGCC_H */ > >> >> diff --git a/lib/Kconfig b/lib/Kconfig > >> >> index a9e56539bd11..369e10259ea6 100644 > >> >> --- a/lib/Kconfig > >> >> +++ b/lib/Kconfig > >> >> @@ -624,6 +624,9 @@ config GENERIC_LIB_ASHRDI3 > >> >> config GENERIC_LIB_LSHRDI3 > >> >> bool > >> >> > >> >> +config GENERIC_LIB_LSHRTI3 > >> >> + bool > >> >> + > >> >> config GENERIC_LIB_MULDI3 > >> >> bool > >> >> > >> >> diff --git a/lib/Makefile b/lib/Makefile > >> >> index 4e066120a0d6..42648411f451 100644 > >> >> --- a/lib/Makefile > >> >> +++ b/lib/Makefile > >> >> @@ -277,6 +277,7 @@ obj-$(CONFIG_PARMAN) += parman.o > >> >> obj-$(CONFIG_GENERIC_LIB_ASHLDI3) += ashldi3.o > >> >> obj-$(CONFIG_GENERIC_LIB_ASHRDI3) += ashrdi3.o > >> >> obj-$(CONFIG_GENERIC_LIB_LSHRDI3) += lshrdi3.o > >> >> +obj-$(CONFIG_GENERIC_LIB_LSHRTI3) += lshrti3.o > >> >> obj-$(CONFIG_GENERIC_LIB_MULDI3) += muldi3.o > >> >> obj-$(CONFIG_GENERIC_LIB_CMPDI2) += cmpdi2.o > >> >> obj-$(CONFIG_GENERIC_LIB_UCMPDI2) += ucmpdi2.o > >> >> diff --git a/lib/lshrti3.c b/lib/lshrti3.c > >> >> new file mode 100644 > >> >> index 000000000000..2d2123bb3030 > >> >> --- /dev/null > >> >> +++ b/lib/lshrti3.c > >> >> @@ -0,0 +1,31 @@ > >> >> +// SPDX-License-Identifier: GPL-2.0 > >> >> + > >> >> +#include > >> >> +#include > >> >> + > >> >> +long long __lshrti3(long long u, word_type b) > >> >> +{ > >> >> + DWunion128 uu, w; > >> >> + word_type bm; > >> >> + > >> >> + if (b == 0) > >> >> + return u; > >> >> + > >> >> + uu.ll = u; > >> >> + bm = 64 - b; > >> >> + > >> >> + if (bm <= 0) { > >> >> + w.s.high = 0; > >> >> + w.s.low = (unsigned long long) uu.s.high >> -bm; > >> >> + } else { > >> >> + const unsigned long long carries = > >> >> + (unsigned long long) uu.s.high << bm; > >> >> + w.s.high = (unsigned long long) uu.s.high >> b; > >> >> + w.s.low = ((unsigned long long) uu.s.low >> b) | > >> >carries; > >> >> + } > >> >> + > >> >> + return w.ll; > >> >> +} > >> >> +#ifndef BUILD_VDSO > >> >> +EXPORT_SYMBOL(__lshrti3); > >> >> +#endif > >> > > >> >I don't think you want this. Maybe that was carried over from > >> >https://lkml.org/lkml/2019/3/15/669 > >> >by accident? The above linkage error mentions arch/x86/kvm/x86.o > >> >which I wouldn't expect to be linked into the VDSO image? > >> > >> Or just "u64"... > > > >Are you referring to TItype? It currenty is a 128-bit value. > > You're right, so "unsigned __int128"... I liked the idea, however __int128 isn't supported by all platforms: include/linux/libgcc.h:57:11: error: __int128 is not supported on this target unsigned __int128 ll; That's from building the 32-bit VDSO for x86.