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 5F54C3CBE89 for ; Tue, 2 Jun 2026 09:10:11 +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=1780391412; cv=none; b=i/wfPN3gRtKeVrOSaCszgp+qkcYRldDW4095QugEQyliHDhj3dkmcbKE8DT4GtEQBuoK4aTKtvGM7pHVJusuZzI0ewLvwCsQA3ijO/0VdPVm63zbMD/lzbMg3yYLFqIDA6AdRTo59PV9Jd00TdXjHZzB1J63yblK/iYU2olXs/4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780391412; c=relaxed/simple; bh=Mhk+WWScUew74y2+evVXh52IuXRVqFziEiPsXbfMK9A=; h=Date:Message-ID:From:To:Cc:Subject:References:MIME-Version: Content-Type; b=Ox++SXvX3hXM5Yl2fABqO5zfp0z+kwA50IuRZMHEiScWGY7CBJltINeSZk2eKXCydLj4qURanyXq8Hi06X3O3jIPfhSi1zfBlcPSg5Da1Iabz4XY6F2T/65YxE3FgcFpLltEf84eRB2X4lvWoA4DMkdF/lM57uzLpCminJZ5IMA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=nGC+T+l+; 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="nGC+T+l+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 614A11F00893; Tue, 2 Jun 2026 09:10:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1780391411; bh=vQp2Q0BevHGNtawvhJyJ+I6GpIpJmTtCboxuT3qByWs=; h=Date:From:To:Cc:Subject:References; b=nGC+T+l+0dw0W0eLtctLe1RlAISAAlTp7E6zcrMsDvXK2TnJQ+HrkKbzUbHi21xFM zJau/2Z6fOg6OCf/aexuIHngNHzlfaEK20f+ciY8Dw0+tbOYZPQdodt8+ud3ncDflt VWV6/czWPu51u/ZlhHYOHvZ1KhltkFiip4xkDn5q+oaP+vspXcS5O2zgBQh9eZvZN0 6aZBtguhP1883iBu+hshZ1IAR9k+x3QxhCKHZqhoJGoNchOVihPMxpl/cR9chhfsdy eXSIi5mnvgLbplv0a0Bies8o9EYUjuPlrvDwo6Mo3WiTu4dQElYziU59GNIiOXwLnN wUcGI5kcRGmXA== Date: Tue, 02 Jun 2026 11:10:08 +0200 Message-ID: <20260602090535.828312645@kernel.org> User-Agent: quilt/0.69 From: Thomas Gleixner To: LKML Cc: Mathieu Desnoyers , =?UTF-8?q?Andr=C3=A9=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?= , Mark Brown , Richard Weinberger Subject: [patch V5 12/16] x86/vdso: Prepare for robust futex unlock support References: <20260602084648.462672743@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 Reviewed-by: AndrĂ© Almeida --- 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 | 16 ++++++++++------ 3 files changed, 43 insertions(+), 6 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, + vdso + 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, + vdso + 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; } @@ -185,6 +212,8 @@ 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 @@ -24,6 +24,10 @@ 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 @@ -75,12 +75,16 @@ struct vdso_sym { }; struct vdso_sym required_syms[] = { - {"__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}, + {"__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))