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 0795A1A2643 for ; Wed, 9 Jul 2025 20:17:22 +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=1752092245; cv=none; b=MQjF4FYrcyGkrNGLqCXCyJL7F4KdajUiOsTL1nUC8YILvH2yl0dosNo4m3uDHXRYod+dZ5TRh03cHYftERk5xesNyNBBJy/5ND/RPHx8WI0tmszyZ76izpL4EF2GdmrgPQNcwxAPk93Cpe5GzUVGhvIqeygsF/wIJnNb/Gjv+ps= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752092245; c=relaxed/simple; bh=9cdKlVIq07K+LOmAuPiShw1Re+uLRRRQ5SU2/0La+4s=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References; b=iRLH/M4ksnBUziEw3vtzBHcoNt72ZE4u+mfGdNEsPj5JWreSvCZ3TdmRYGL3MU6MFa6Zi0q0YpyniN36G1jt1yAECoXYHS0A7ez4PdOzcFap6rEhNL0+dFFb9gipUqLgVIuq38jvErvA8gabW2+sGC+NEQ+OiUtkZKRM5rxT5aQ= 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=UNwEzBWR; 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="UNwEzBWR" Received: by linux.microsoft.com (Postfix, from userid 1216) id A4EC82112209; Wed, 9 Jul 2025 13:17:22 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com A4EC82112209 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1752092242; bh=loxMhYAhkVerxLNLpPv4l1YtrAuDnz920Ay7okkZJfg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=UNwEzBWRkTp0XcMYWHoligIW2jAYXrWjPLNpuzkYADKw8NFfUlc7K0vOkNFNcr10a vT9IUUx8i+FPbm/pJkBgUBVdPasEru21sOvPo/kT6qr+2FlizdlCy6odDUH6ZGbYfT 2HHdmvCSb6leOTnuZV+555MZqUAF/654Ly+60U8M= From: Hamza Mahfooz To: linux-kernel@vger.kernel.org Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Andy Lutomirski , Peter Zijlstra , David Woodhouse , Guenter Roeck , Hamza Mahfooz , Jared White Subject: [PATCH 2/2] x86/mm/64: free the gap between BSS_MAIN and BSS_DECRYPTED Date: Wed, 9 Jul 2025 13:16:59 -0700 Message-Id: <1752092219-16248-2-git-send-email-hamzamahfooz@linux.microsoft.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1752092219-16248-1-git-send-email-hamzamahfooz@linux.microsoft.com> References: <1752092219-16248-1-git-send-email-hamzamahfooz@linux.microsoft.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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 522297cebe7c..f74a7a0d7a01 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -82,6 +82,8 @@ 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 fdb6cab524f0..ff7ff5c12eb4 100644 --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -1385,6 +1385,8 @@ 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", @@ -1422,6 +1424,8 @@ 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); } /* -- 2.49.0