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 679EB3D16EB for ; Mon, 16 Mar 2026 17:13:33 +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=1773681213; cv=none; b=ZmC+yQE4FUiCJSId8DBFrBappcC4HzOsgx3+5kzB6sK19/fJKLTCx49L/p2NobR5m1vEv6kexJnLoHiPAbMGoB/Dt833hsoGzwKoRnHMIM6t7bFhpEGn7R2J0HGRWc29QOiTnrggicOfePZOal6r951J+8kzaDcs4RueTynzOBw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773681213; c=relaxed/simple; bh=ZRE+TfloXdZ1if6rmtD97C6SqL87kqd+K3WPmC9aFfg=; h=Date:Message-ID:From:To:Cc:Subject:References:MIME-Version: Content-Type; b=YiTqEQncdt3h4Pu+TK0J8CcQxDyvNSyqOUlccoQgP3fSAz1rHaV0VvOUS7UzUAtH9GBBnpX5Pz7YfrxgI9HcMnh706/D6ssTnht+ee1XphcGFqy6IJ1+5Zy0mMtIwRYQcNNDl/XQ7LDmkIkK9qt7+icWeezISdf+foR+LnIVXTM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=gPw6CwVr; 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="gPw6CwVr" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 58091C19421; Mon, 16 Mar 2026 17:13:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773681213; bh=ZRE+TfloXdZ1if6rmtD97C6SqL87kqd+K3WPmC9aFfg=; h=Date:From:To:Cc:Subject:References:From; b=gPw6CwVr7zo1Z0OKI4OoXzr/S2SENmsWAb3HT91qxnuv0RoGE429pv6YQdM5s7jpp HKGbbHfDqNR6RG2D26iVe1s53oHKn6/a+CuQ9OlNQNR+Iiq77y8z/S8z9kTJsBIFsC SSbD8OxS8XLPSf9TMyQAYgRpX7NAIO3jdqs/Jm9jGHrq4CRgFL+WR7kOdoaoI0zaKl b3lxGDty8bHqpgQvBOA8TyDzfRUGtbKvvvuW/GXXLJqbfmz9cOkiWjXvEoVwsDIsDM ghec47dmJAOq+mXQreNd6p8gVLNRZYNqSTfzwS/83sGmRc88F+0+ocnqHTWoIkOyTj cVpNRExN5xe1A== Date: Mon, 16 Mar 2026 18:13:29 +0100 Message-ID: <20260316164951.413709497@kernel.org> User-Agent: quilt/0.68 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" Subject: [patch 7/8] x86/vdso: Prepare for robust futex unlock support References: <20260316162316.356674433@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 instruction window so it can clear the pointer when the task is interrupted within that race window. Add the 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(). Signed-off-by: Thomas Gleixner --- arch/x86/entry/vdso/vma.c | 20 ++++++++++++++++++++ arch/x86/include/asm/vdso.h | 3 +++ arch/x86/tools/vdso2c.c | 17 ++++++++++------- 3 files changed, 33 insertions(+), 7 deletions(-) --- a/arch/x86/entry/vdso/vma.c +++ b/arch/x86/entry/vdso/vma.c @@ -73,6 +73,23 @@ 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; + + current->mm->futex.unlock_cs_start_ip = + vdso + image->sym___vdso_futex_robust_try_unlock_cs_start; + current->mm->futex.unlock_cs_success_ip = + vdso + image->sym___vdso_futex_robust_try_unlock_cs_success; + current->mm->futex.unlock_cs_end_ip = + vdso + image->sym___vdso_futex_robust_try_unlock_cs_end; +} +#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 +97,7 @@ 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 +207,8 @@ 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 +25,9 @@ struct vdso_image { long sym_int80_landing_pad; long sym_vdso32_sigreturn_landing_pad; long sym_vdso32_rt_sigreturn_landing_pad; + long sym___vdso_futex_robust_try_unlock_cs_start; + long sym___vdso_futex_robust_try_unlock_cs_success; + long sym___vdso_futex_robust_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 +75,16 @@ 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}, + {"__vdso_futex_robust_try_unlock_cs_start", true}, + {"__vdso_futex_robust_try_unlock_cs_success", true}, + {"__vdso_futex_robust_try_unlock_cs_end", true}, }; __attribute__((format(printf, 1, 2))) __attribute__((noreturn))