From mboxrd@z Thu Jan 1 00:00:00 1970 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 44B03349AF4 for ; Thu, 2 Apr 2026 15:21:59 +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=1775143319; cv=none; b=m8p5jDaIEr0lxuTiAoK6M/q1UbT2x0R+oXM+lFqgVFWLLEQP6lz9VsBEdsSriWXXq2HnYAI+PwkoDuSDRQ8BvvEofxMNVwuQaBh4U7ZfRPW3L4zNyS31d8Zlj/T43WHBOjx6wRULuKI561v/3wuLvFJL3rdgsO7TX3mevFA9MLY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775143319; c=relaxed/simple; bh=qd4RXONyC6MqQgMNTmXCZ7BUoYzdE6R2GAZLq6FbCPQ=; h=Date:Message-ID:From:To:Cc:Subject:References:MIME-Version: Content-Type; b=TEmIgs0QjBT94ZvBDCzkmyROWT7LlLXzef2HeqVEYw+WcFwuRTtV1Cza3vTgQ/72WFYrOEc02tWab4uD+8s090/0fStp8jFeFGzrGdQc/9DadD6ecLkKXalwpnJi26cSGD3idMJ9wTCLGXduj9gzqgBwA/qqBXM8FtZCChvNRvw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=daV5g0d+; 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="daV5g0d+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6D331C19423; Thu, 2 Apr 2026 15:21:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1775143319; bh=qd4RXONyC6MqQgMNTmXCZ7BUoYzdE6R2GAZLq6FbCPQ=; h=Date:From:To:Cc:Subject:References:From; b=daV5g0d+44KjahVfsLR4vZsNbIhK29MnAMbupHD4L4xu0Pjnx3LIkCa8gFYpFVh6z 5wajQRQb6Dz2RsquRakvvoFO+aWwHh9fHg9E2atDPJ33LyJydaa2GDPnp7otYDJjK6 KDSbAAZFcnZXT6jXnapSbsbtAJzeJwbHDOkcDCQ2NpAkMSQi9a63usVwS/krCKmVLF f+RTZq50neJn23VPED+b9vu92PMFX5T2NxdUgNFo1Up5geHo3EMRo0uE2Oec0K/gpO DJEdhLYU4fJ2zn/mQBQNioAc36Ogxbw6KFV6nL0euIpj29quVBxaYCCTWwvr3MqgOK etxvACeHbk85g== Date: Thu, 02 Apr 2026 17:21:55 +0200 Message-ID: <20260402151940.349951884@kernel.org> User-Agent: quilt/0.68 From: Thomas Gleixner To: LKML Cc: Mathieu Desnoyers , =?UTF-8?q?Andr=C3=A8=20Almeida?= , Sebastian Andrzej Siewior , Carlos O'Donell , Peter Zijlstra , Florian Weimer , Rich Felker , Torvald Riegel , Darren Hart , Ingo Molnar , Davidlohr Bueso , Arnd Bergmann , "Liam R . Howlett" , Uros Bizjak , =?UTF-8?q?Thomas=20Wei=C3=9Fschuh?= Subject: [patch V4 11/14] x86/vdso: Prepare for robust futex unlock support References: <20260402151131.876492985@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 There will be a VDSO function to unlock non-contended robust futexes in user space. The unlock sequence is racy vs. clearing the list_pending_op pointer in the task's robust list head. To plug this race the kernel needs to know the critical section window so it can clear the pointer when the task is interrupted within that race window. The window is determined by labels in the inline assembly. Add these symbols to the vdso2c generator and use them in the VDSO VMA code to update the critical section addresses in mm_struct::futex on (re)map(). The symbols are not exported to user space, but available in the debug version of the vDSO. Signed-off-by: Thomas Gleixner --- V3: Rename the symbols once more V2: Rename the symbols --- arch/x86/entry/vdso/vma.c | 29 +++++++++++++++++++++++++++++ arch/x86/include/asm/vdso.h | 4 ++++ arch/x86/tools/vdso2c.c | 18 +++++++++++------- 3 files changed, 44 insertions(+), 7 deletions(-) --- a/arch/x86/entry/vdso/vma.c +++ b/arch/x86/entry/vdso/vma.c @@ -6,6 +6,7 @@ */ #include #include +#include #include #include #include @@ -73,6 +74,31 @@ static void vdso_fix_landing(const struc regs->ip = new_vma->vm_start + ipoffset; } +#ifdef CONFIG_FUTEX_ROBUST_UNLOCK +static void vdso_futex_robust_unlock_update_ips(void) +{ + const struct vdso_image *image = current->mm->context.vdso_image; + unsigned long vdso = (unsigned long) current->mm->context.vdso; + struct futex_mm_data *fd = ¤t->mm->futex; + unsigned int idx = 0; + + futex_reset_cs_ranges(fd); + +#ifdef CONFIG_X86_64 + futex_set_vdso_cs_range(fd, idx, vdso, image->sym___futex_list64_try_unlock_cs_start, + image->sym___futex_list64_try_unlock_cs_end, false); + idx++; +#endif /* CONFIG_X86_64 */ + +#if defined(CONFIG_X86_32) || defined(CONFIG_COMPAT) + futex_set_vdso_cs_range(fd, idx, vdso, image->sym___futex_list32_try_unlock_cs_start, + image->sym___futex_list32_try_unlock_cs_end, true); +#endif /* CONFIG_X86_32 || CONFIG_COMPAT */ +} +#else +static inline void vdso_futex_robust_unlock_update_ips(void) { } +#endif + static int vdso_mremap(const struct vm_special_mapping *sm, struct vm_area_struct *new_vma) { @@ -80,6 +106,7 @@ static int vdso_mremap(const struct vm_s vdso_fix_landing(image, new_vma); current->mm->context.vdso = (void __user *)new_vma->vm_start; + vdso_futex_robust_unlock_update_ips(); return 0; } @@ -189,6 +216,8 @@ static int map_vdso(const struct vdso_im current->mm->context.vdso = (void __user *)text_start; current->mm->context.vdso_image = image; + vdso_futex_robust_unlock_update_ips(); + up_fail: mmap_write_unlock(mm); return ret; --- a/arch/x86/include/asm/vdso.h +++ b/arch/x86/include/asm/vdso.h @@ -25,6 +25,10 @@ struct vdso_image { long sym_int80_landing_pad; long sym_vdso32_sigreturn_landing_pad; long sym_vdso32_rt_sigreturn_landing_pad; + long sym___futex_list64_try_unlock_cs_start; + long sym___futex_list64_try_unlock_cs_end; + long sym___futex_list32_try_unlock_cs_start; + long sym___futex_list32_try_unlock_cs_end; }; extern const struct vdso_image vdso64_image; --- a/arch/x86/tools/vdso2c.c +++ b/arch/x86/tools/vdso2c.c @@ -75,13 +75,17 @@ struct vdso_sym { }; struct vdso_sym required_syms[] = { - {"VDSO32_NOTE_MASK", true}, - {"__kernel_vsyscall", true}, - {"__kernel_sigreturn", true}, - {"__kernel_rt_sigreturn", true}, - {"int80_landing_pad", true}, - {"vdso32_rt_sigreturn_landing_pad", true}, - {"vdso32_sigreturn_landing_pad", true}, + {"VDSO32_NOTE_MASK", true}, + {"__kernel_vsyscall", true}, + {"__kernel_sigreturn", true}, + {"__kernel_rt_sigreturn", true}, + {"int80_landing_pad", true}, + {"vdso32_rt_sigreturn_landing_pad", true}, + {"vdso32_sigreturn_landing_pad", true}, + {"__futex_list64_try_unlock_cs_start", true}, + {"__futex_list64_try_unlock_cs_end", true}, + {"__futex_list32_try_unlock_cs_start", true}, + {"__futex_list32_try_unlock_cs_end", true}, }; __attribute__((format(printf, 1, 2))) __attribute__((noreturn))