From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 0E7E23D7D69 for ; Tue, 23 Jun 2026 15:25:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=13.77.154.182 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782228306; cv=none; b=HYItvdX/27gBYykT6QW8sazHKeeHffjhaiKTYsBeBnM7Wv90jFYfomlkeWVsLtXf/M4uW6BmoCFtnFfR3r6SmFV2aOWXdqD7kzMBjveL1AE4zy3QgT7tASnR7QmsmCo4oiCjzRJalKhXOo3EkEsxXmPftKp1CIaw4m9pFCxFA7k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782228306; c=relaxed/simple; bh=hyCYxjq5MIZ6SQvWAFFdiIuTML8j8H+H2rebe9ZeVpU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=eU0ZgU85nZn0G9/YNHT+7V5OsaO+fAxLHoFhK7uZN7M4MQ52XHAW7L1r5KNItgSetB9rz0UIsTf29fu4/ICcnpdWkLl0e39HD5bKUqecXLVAaIecbylGcJYtXb1P4Lvq7vxHhtLnnxO00Ebp5b40PKBbpoZjBMX464Bp2wHVYS4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.microsoft.com; spf=pass smtp.mailfrom=linux.microsoft.com; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b=i9noF5Y8; arc=none smtp.client-ip=13.77.154.182 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.microsoft.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.microsoft.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b="i9noF5Y8" Received: by linux.microsoft.com (Postfix, from userid 1216) id 226CA20B716A; Tue, 23 Jun 2026 08:25:01 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 226CA20B716A DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1782228301; bh=HE8j8Fah9ai+uNDQxXRz/3TUz8+8oh0eUmOY579kL5Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=i9noF5Y8Kfr3oHufctNQnqc+q+SFabyvGbuFSynT0j+ekyV7hbGTkWVER6CExps3X sDEyInVN/Cu1OzRwJTeGlRuArc6rkF020Qa8F723Cc2SJ9laDZSAtFmOVfYS3prRfC 9dfZaqXyRxVU/xq+X104s0K2cnJ1ZTWxgfEGe0yY= From: Hamza Mahfooz To: x86@kernel.org Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Andy Lutomirski , Peter Zijlstra , Ard Biesheuvel , Nathan Chancellor , linux-kernel@vger.kernel.org, Hamza Mahfooz , Jared White Subject: [PATCH v2 2/2] x86/mm/64: free the gap between BSS_MAIN and BSS_DECRYPTED Date: Tue, 23 Jun 2026 11:24:30 -0400 Message-ID: <20260623152430.1473481-2-hamzamahfooz@linux.microsoft.com> X-Mailer: git-send-email 2.43.7 In-Reply-To: <20260623152430.1473481-1-hamzamahfooz@linux.microsoft.com> References: <20260623152430.1473481-1-hamzamahfooz@linux.microsoft.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit This region is unused after mark_rodata_ro() and takes up, up to 2 MiB of memory. So, free it in mark_rodata_ro(). Co-developed-by: Jared White Signed-off-by: Jared White Signed-off-by: Hamza Mahfooz --- arch/x86/include/asm/sections.h | 1 + arch/x86/kernel/vmlinux.lds.S | 2 ++ arch/x86/mm/init_64.c | 4 ++++ 3 files changed, 7 insertions(+) diff --git a/arch/x86/include/asm/sections.h b/arch/x86/include/asm/sections.h index 30e8ee7006f9..1d6589bc0f68 100644 --- a/arch/x86/include/asm/sections.h +++ b/arch/x86/include/asm/sections.h @@ -8,6 +8,7 @@ extern char __relocate_kernel_start[], __relocate_kernel_end[]; extern char __brk_base[], __brk_limit[]; extern char __end_rodata_aligned[]; +extern char __start_bss_decrypted_gap[]; #if defined(CONFIG_X86_64) extern char __end_rodata_hpage_align[]; diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S index 53519fa7c772..de9901bda7d0 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -94,6 +94,8 @@ const_cpu_current_top_of_stack = cpu_current_top_of_stack; * decrypted to avoid exposing more than we wish. */ #define BSS_DECRYPTED \ + . = ALIGN(PAGE_SIZE); \ + __start_bss_decrypted_gap = .; \ . = ALIGN(PMD_SIZE); \ __start_bss_decrypted = .; \ __pi___start_bss_decrypted = .; \ diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c index df2261fa4f98..3d90bd593637 100644 --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -1396,6 +1396,8 @@ void mark_rodata_ro(void) unsigned long end = (unsigned long)__end_rodata_hpage_align; unsigned long text_end = PFN_ALIGN(_etext); unsigned long rodata_end = PFN_ALIGN(__end_rodata); + unsigned long bss_decrypted_gap_start = PFN_ALIGN(__start_bss_decrypted_gap); + unsigned long bss_decrypted_gap_stop = PFN_ALIGN(__start_bss_decrypted); unsigned long all_end; printk(KERN_INFO "Write protecting the kernel read-only data: %luk\n", @@ -1433,6 +1435,8 @@ void mark_rodata_ro(void) (void *)text_end, (void *)rodata_start); free_kernel_image_pages("unused kernel image (rodata/data gap)", (void *)rodata_end, (void *)_sdata); + free_kernel_image_pages("unused kernel image (bss_decrypted gap)", + (void *)bss_decrypted_gap_start, (void *)bss_decrypted_gap_stop); } /* -- 2.54.0