From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 8403E34E74D; Sat, 26 Sep 2026 10:55:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790420151; cv=none; b=iiFs8KyoRX7NuGgOXK4wHU+4IuQi7nL7VP7wu0m678Q2J7W6Bu157xaORJX/69E0x/+Ckd80EIc5riBaFQ1VZF+mp+VhH0IJk0oea1Oloc3DYnliHn7m0ANkubU7frMNHazomtxpb+lfWH2JfKk5QqMb75IuWMwcdBdTv3Qgwz4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790420151; c=relaxed/simple; bh=yNDUdvk15wiQndcnyxC8neLqoZ2aSDfTLymCaeg9aI4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ShcG1Betpp2dE65IU/QbriFwpiam/Q92yoX6B7Uz/BfuUqIQM7gKEsfDgpsJjv5SMY11a8d0BvGWpF/VxVLiHf3YHYDdc4+5sox7WP8ZGxAipEHY8E6SdJTE+DSOvD57Ww6KA8FrQOIRqtL0SksDVHH7WuDgMowqsQMMJhfC72g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=IHBSTyxM; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="IHBSTyxM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4FF751F000FF; Sat, 26 Sep 2026 10:55:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790420149; bh=M3v70KpW/UEgjbC3QoaHE8/Wwn5JI4Q7Nay7Ujw/kRM=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=IHBSTyxMLUw3GVcRSy3mO/ECQ4hJ1yBZZ2Fg+yVS1RarSpt8dFI4iFDIo95Lwa9PP cfvHzKodI/lFDD0B3BiP+pmPS6/+dMiXZ2aYTlQwawo1uA30hTSbG1OzGWKCm4ceR/ 1izip1d0LM1TP3PdLeyH/9HabEnFS8hE2+FPHy1cSMnD8uz2cVae8sQwCx9X7neF2a h/mYvHClf0b2Gc5QDjffkFvIyKKai+xRudGhuP9ff+JJWIqFsSYpef0O2k7Z5UotR5 45FLjP0GWzu1GyLnWI1k8axuM4LPHOIjh+CUhWiw4yNmf82WYJU9QnBsbdZoxRdUfP 6jdo8KZfLDGTQ== Message-ID: <9d1c338b-368f-4ea2-a12e-c28d49adff5e@kernel.org> Date: Sat, 26 Sep 2026 12:55:34 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] random: vDSO: Avoid call to memset() when zeroing reserved in __cvdso_getrandom_data() To: "Jason A. Donenfeld" , Nick Desaulniers Cc: Nathan Chancellor , Andy Lutomirski , Thomas Gleixner , Theodore Ts'o , Vincenzo Frascino , Bill Wendling , Justin Stitt , Catalin Marinas , Will Deacon , Mark Rutland , Huacai Chen , WANG Xuerui , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , x86@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, loongarch@lists.linux.dev, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, llvm@lists.linux.dev References: <20260925-vdso-getrandom-avoid-memset-llvm-24-v2-1-ce640f872393@kernel.org> Content-Language: fr-FR From: "Christophe Leroy (CS GROUP)" In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Hi Jason, Le 26/09/2026 à 12:02, Jason A. Donenfeld a écrit : > On Fri, Sep 25, 2026 at 03:00:46PM -0700, Nick Desaulniers wrote: >> On Fri, Sep 25, 2026 at 2:56 PM Nick Desaulniers >> wrote: >>> >>> On Fri, Sep 25, 2026 at 2:53 PM Nick Desaulniers >>> wrote: >>>> >>>> On Fri, Sep 25, 2026 at 2:46 PM Nathan Chancellor wrote: >>>>> >>>>> After a recent change in LLVM [1], builds with the random vDSO >>>>> implementation, such as PowerPC and RISC-V, fail when checking the vDSO: >>>>> >>>>> arch/powerpc/kernel/vdso/vdso32.so.dbg: dynamic relocations are not supported >>>>> arch/riscv/kernel/vdso/vdso.so.dbg: dynamic relocations are not supported >>>>> >>>>> memset() is now generated when zeroing params->reserved for some builds >>>>> because LLVM has an optimization (now run in more instances) that can >>>>> recognize at compile time when it is assigning a static value to a >>>>> contiguous area of memory and turn that into a call to memset(). Both >>>>> clang and GCC assume memset() is always available [2]. >>>>> >>>>> clang provides a builtin, __builtin_memset_inline [3][4], that can be >>>>> used to ensure an external function call is not generated when zeroing >>>>> this memory. Use it when it is available. >>>>> >>>>> While GCC has no issues with the current code, it has generated memset() >>>>> before, as seen in commit b7bad082e113 ("random: vDSO: avoid call to out >>>>> of line memset()"). GCC 14 provides '-finline-stringops=memset' [5][6] >>>>> with a similar guarantee to the clang builtin, so use it and >>>>> __builtin_memset() when available. >>>>> >>>>> If no option is available, provide a simple memset_inline() like the one >>>>> from lib/string.c to avoid adding an ugly ifdef. >>>>> >>>>> Link: https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fllvm%2Fllvm-project%2Fcommit%2F90cebef1411617fc3eedd359bdf00cb44b1c2439&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7C4df96063ffd94e6204df08df1bb54e3d%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C639260137659627802%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=ku4l8Ol5OJ2qi%2BcSblspxxUKOA6rNpiUO3ZvGSoAb1s%3D&reserved=0 [1] >>>>> Link: https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgcc.gnu.org%2Fonlinedocs%2Fgcc-16.2.0%2Fgcc%2FStandards.html%23index-ffreestanding&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7C4df96063ffd94e6204df08df1bb54e3d%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C639260137659651194%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=jQa1eTDLk3cPNTa3GEBwVEohHh67ukShaRHMZvA%2FHDg%3D&reserved=0 [2] >>>>> Link: https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fllvm%2Fllvm-project%2Fcommit%2F38637ee477541370a90b37f149069d8e5c0c2efd&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7C4df96063ffd94e6204df08df1bb54e3d%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C639260137659668579%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=zY7Kr9ZZNNZR%2FVsnwYRlubPRpbMaKe9QtMD2snd8ZvA%3D&reserved=0 [3] >>>>> Link: https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fclang.llvm.org%2Fdocs%2FLanguageExtensions.html%23guaranteed-inlined-memset&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7C4df96063ffd94e6204df08df1bb54e3d%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C639260137659678360%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=vUU2fhCVcUWsbQD3IsRaUzSO8KVSpxwSpgr9San4aq0%3D&reserved=0 [4] >>>>> Link: https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgcc.gnu.org%2Fgit%2F%3Fp%3Dgcc.git%3Ba%3Dcommit%3Bh%3D1ff6d9f7428b0668cd8ab0b3e3ab94f1d733124d&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7C4df96063ffd94e6204df08df1bb54e3d%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C639260137659687815%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=qHRqxAO252imwH1W93yHlp6jdcFGkFOr2Y2hXbG2MLU%3D&reserved=0 [5] >>>>> Link: https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgcc.gnu.org%2Fonlinedocs%2Fgcc%2FOptimize-Options.html%23index-finline-stringops&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7C4df96063ffd94e6204df08df1bb54e3d%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C639260137659698298%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=0ecc%2BXd6o3nozh3N71aq%2F98Xam%2Fdol7GUHmC637Iv7I%3D&reserved=0 [6] >>>>> Suggested-by: "Jason A. Donenfeld" >>>>> Suggested-by: Nick Desaulniers >>>>> Signed-off-by: Nathan Chancellor >>>>> --- >>>>> Changes in v2: >>>>> - Switch approach entirely (Jason, Nick) >>>>> - clang: use __builtin_memset_inline() to avoid external call >>>>> - GCC 14+: use __builtin_memset + -finline-stringops=memset (hence the >>>>> massive CC list increase) >>>>> - GCC < 14: no issues currently but avoid ifdef with simple memset >>>>> implementation >>>>> - Link to v1: https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatch.msgid.link%2F20260916-vdso-getrandom-avoid-memset-llvm-24-v1-1-80a92f2e225a%40kernel.org&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7C4df96063ffd94e6204df08df1bb54e3d%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C639260137659712983%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=%2Ftq3tUHqDmbXesqB69w6umXAuaTsfzOIhk54Jy76cwo%3D&reserved=0 >>>>> --- >>>>> arch/arm64/kernel/vdso/Makefile | 2 +- >>>>> arch/loongarch/vdso/Makefile | 1 + >>>>> arch/powerpc/kernel/vdso/Makefile | 1 + >>>>> arch/riscv/kernel/vdso/Makefile | 1 + >>>>> arch/s390/kernel/vdso/Makefile | 1 + >>>>> arch/x86/entry/vdso/vdso64/Makefile | 2 +- >>>>> init/Kconfig | 7 +++++++ >>>>> lib/vdso/getrandom.c | 19 +++++++++++++++++-- >>>>> 8 files changed, 30 insertions(+), 4 deletions(-) >>>>> >>>>> diff --git a/arch/arm64/kernel/vdso/Makefile b/arch/arm64/kernel/vdso/Makefile >>>>> index 7dec05dd33b7..f6619e1cb2ce 100644 >>>>> --- a/arch/arm64/kernel/vdso/Makefile >>>>> +++ b/arch/arm64/kernel/vdso/Makefile >>>>> @@ -41,7 +41,7 @@ CC_FLAGS_REMOVE_VDSO := $(CC_FLAGS_FTRACE) -Os $(CC_FLAGS_SCS) \ >>>>> $(CC_FLAGS_LTO) $(CC_FLAGS_CFI) \ >>>>> -Wmissing-prototypes -Wmissing-declarations >>>>> >>>>> -CC_FLAGS_ADD_VDSO := -O2 -mcmodel=tiny -fasynchronous-unwind-tables >>>>> +CC_FLAGS_ADD_VDSO := -O2 -mcmodel=tiny -fasynchronous-unwind-tables $(CONFIG_CC_OPT_INLINE_MEMSET) >>>>> >>>>> CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_REMOVE_VDSO) >>>>> CFLAGS_REMOVE_vgetrandom.o = $(CC_FLAGS_REMOVE_VDSO) >>>>> diff --git a/arch/loongarch/vdso/Makefile b/arch/loongarch/vdso/Makefile >>>>> index 9c9181bb4071..0b84892d084b 100644 >>>>> --- a/arch/loongarch/vdso/Makefile >>>>> +++ b/arch/loongarch/vdso/Makefile >>>>> @@ -16,6 +16,7 @@ ccflags-vdso := \ >>>>> $(filter -m64,$(KBUILD_CFLAGS)) \ >>>>> $(filter -march=%,$(KBUILD_CFLAGS)) \ >>>>> $(filter -m%-float,$(KBUILD_CFLAGS)) \ >>>>> + $(CONFIG_CC_OPT_INLINE_MEMSET) \ >>>>> $(CLANG_FLAGS) \ >>>>> -D__VDSO__ >>>>> >>>>> diff --git a/arch/powerpc/kernel/vdso/Makefile b/arch/powerpc/kernel/vdso/Makefile >>>>> index 368759f81708..0d1a49529885 100644 >>>>> --- a/arch/powerpc/kernel/vdso/Makefile >>>>> +++ b/arch/powerpc/kernel/vdso/Makefile >>>>> @@ -43,6 +43,7 @@ ccflags-y := -fno-common -fno-builtin -DBUILD_VDSO >>>>> ccflags-y += $(DISABLE_LATENT_ENTROPY_PLUGIN) >>>>> ccflags-y += $(call cc-option, -fno-stack-protector) >>>>> ccflags-y += -DDISABLE_BRANCH_PROFILING >>>>> +ccflags-y += $(CONFIG_CC_OPT_INLINE_MEMSET) >>>>> ccflags-y += -ffreestanding -fasynchronous-unwind-tables >>>>> ccflags-remove-y := $(CC_FLAGS_FTRACE) >>>>> ldflags-y := -Wl,--hash-style=both -nostdlib -shared -z noexecstack $(CLANG_FLAGS) >>>>> diff --git a/arch/riscv/kernel/vdso/Makefile b/arch/riscv/kernel/vdso/Makefile >>>>> index 8dbf2532a573..c023046a3fd7 100644 >>>>> --- a/arch/riscv/kernel/vdso/Makefile >>>>> +++ b/arch/riscv/kernel/vdso/Makefile >>>>> @@ -36,6 +36,7 @@ endif >>>>> ccflags-y := -fno-stack-protector >>>>> ccflags-y += -DDISABLE_BRANCH_PROFILING >>>>> ccflags-y += -fno-builtin >>>>> +ccflags-y += $(CONFIG_CC_OPT_INLINE_MEMSET) >>>>> ccflags-y += $(KBUILD_BASE_ISA)$(CFI_MARCH) >>>>> ccflags-y += $(CFI_FULL) >>>>> asflags-y += $(KBUILD_BASE_ISA)$(CFI_MARCH) >>>>> diff --git a/arch/s390/kernel/vdso/Makefile b/arch/s390/kernel/vdso/Makefile >>>>> index 35c834b895ec..54bcf2984ca1 100644 >>>>> --- a/arch/s390/kernel/vdso/Makefile >>>>> +++ b/arch/s390/kernel/vdso/Makefile >>>>> @@ -29,6 +29,7 @@ KBUILD_CFLAGS_VDSO := $(filter-out -munaligned-symbols,$(KBUILD_CFLAGS_VDSO)) >>>>> KBUILD_CFLAGS_VDSO := $(filter-out -fno-asynchronous-unwind-tables,$(KBUILD_CFLAGS_VDSO)) >>>>> KBUILD_CFLAGS_VDSO += -fPIC -fno-common -fno-builtin -fasynchronous-unwind-tables >>>>> KBUILD_CFLAGS_VDSO += -fno-stack-protector $(DISABLE_KSTACK_ERASE) >>>>> +KBUILD_CFLAGS_VDSO += $(CONFIG_CC_OPT_INLINE_MEMSET) >>>>> ldflags-y := -shared -soname=linux-vdso.so.1 \ >>>>> --hash-style=both --build-id=sha1 \ >>>>> $(call ld-option, --eh-frame-hdr) -T >>>>> diff --git a/arch/x86/entry/vdso/vdso64/Makefile b/arch/x86/entry/vdso/vdso64/Makefile >>>>> index 7c0790065b5e..c2353a065279 100644 >>>>> --- a/arch/x86/entry/vdso/vdso64/Makefile >>>>> +++ b/arch/x86/entry/vdso/vdso64/Makefile >>>>> @@ -14,7 +14,7 @@ vobjs-$(CONFIG_X86_SGX) += vsgx.o >>>>> vobjs-$(CONFIG_FUTEX_ROBUST_UNLOCK) += vfutex.o >>>>> >>>>> # Compilation flags >>>>> -flags-y := -DBUILD_VDSO64 -m64 -mcmodel=small >>>>> +flags-y := -DBUILD_VDSO64 -m64 -mcmodel=small $(CONFIG_CC_OPT_INLINE_MEMSET) >>>>> >>>>> # The location of this include matters! >>>>> include $(src)/../common/Makefile.include >>>>> diff --git a/init/Kconfig b/init/Kconfig >>>>> index 8583d9f06c52..ff3f8475dd2f 100644 >>>>> --- a/init/Kconfig >>>>> +++ b/init/Kconfig >>>>> @@ -173,6 +173,13 @@ config CC_HAS_ALLOC_TOKEN >>>>> config CC_HAS_MULTIDIMENSIONAL_NONSTRING >>>>> def_bool $(success,echo 'char tag[][4] __attribute__((__nonstring__)) = { };' | $(CC) $(CLANG_FLAGS) -x c - -c -o /dev/null -Werror) >>>>> >>>>> +config CC_HAS_OPT_INLINE_MEMSET >>>>> + def_bool $(cc-option,-finline-stringops=memset) >>>>> + >>>>> +config CC_OPT_INLINE_MEMSET >>>>> + string >>>>> + default "-finline-stringops=memset" if CC_HAS_OPT_INLINE_MEMSET >>>>> + >>>>> config LD_CAN_USE_KEEP_IN_OVERLAY >>>>> # ld.lld prior to 21.0.0 did not support KEEP within an overlay description >>>>> # https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fllvm%2Fllvm-project%2Fpull%2F130661&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7C4df96063ffd94e6204df08df1bb54e3d%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C639260137659727352%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=03eAQvPTDs%2FN28bYiiZAVYcx2JFSkuOM7x2iwFU%2F%2FxA%3D&reserved=0 >>>>> diff --git a/lib/vdso/getrandom.c b/lib/vdso/getrandom.c >>>>> index 2851afa9154f..f5cad5641985 100644 >>>>> --- a/lib/vdso/getrandom.c >>>>> +++ b/lib/vdso/getrandom.c >>>>> @@ -29,6 +29,22 @@ >>>>> } \ >>>>> } while (0) >>>>> >>>>> +#if __has_builtin(__builtin_memset_inline) >>>>> +#define memset_inline(dst, value, size) __builtin_memset_inline(dst, value, size) >>>>> +#elif IS_ENABLED(CONFIG_CC_HAS_OPT_INLINE_MEMSET) >>>>> +#define memset_inline(dst, value, size) __builtin_memset(dst, value, size) >>>>> +#else >>>>> +static inline void *memset_inline(void *dst, int value, size_t size) >>>>> +{ >>>>> + char *d = dst; >>>>> + >>>>> + while (size--) >>>>> + *d++ = value; >>>>> + >>>>> + return d; >>>>> +} >>>>> +#endif >>>> >>>> Does this work? >>>> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgodbolt.org%2Fz%2FTx6EaGMfb&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7C4df96063ffd94e6204df08df1bb54e3d%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C639260137659741160%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=Xv0rle85Js5BH2qNUL4q2Iv2ZwgJhJ4FaTuHYAvvEVo%3D&reserved=0 >>> >>> Hmmm...possibly. >>> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgodbolt.org%2Fz%2Fec9rzd9Yf&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7C4df96063ffd94e6204df08df1bb54e3d%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C639260137659754022%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=bLajY6c3CbYOZMJlBA4bYlVE3bNVc%2Fxe1KYk0rUJgjM%3D&reserved=0 >>> I don't get it... >> >> Just keep it under 2 pages, it will be fine: >> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgodbolt.org%2Fz%2FqqoMqfxev&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7C4df96063ffd94e6204df08df1bb54e3d%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C639260137659763804%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=Bcp1%2B%2Fir05tsPwf08OQkJx4vDkPliaSppam1e%2BTPprk%3D&reserved=0 > > https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgodbolt.org%2Fz%2F9W9f5a7Wx&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7C4df96063ffd94e6204df08df1bb54e3d%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C639260137659773169%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=YPGYXcKrnM4e1Q2nHdshRUaMT36w%2BRkHuIWIgcbpA94%3D&reserved=0 > > Apparently not on RISCV, which is what prompted this patch in the first > place. So I suspect Nathan's v2 here is the way to go. Don't you have -fno-builtin on RISCV like we have on powerpc ? Or is it clang that is missing this option ? Christophe