linux-kernel - [tip: x86/mm] x86/realmode: Add comment for Global bit usage in trampoline

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Mon, 06 Dec 2021 21:57:46 -0000
From:   "tip-bot2 for Joerg Roedel" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Joerg Roedel <jroedel@...e.de>, Borislav Petkov <bp@...e.de>,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: x86/mm] x86/realmode: Add comment for Global bit usage in
 trampoline_pgd

The following commit has been merged into the x86/mm branch of tip:

Commit-ID:     9de4999050b5f2e847c84372c6a1aa1fe32bb269
Gitweb:        https://git.kernel.org/tip/9de4999050b5f2e847c84372c6a1aa1fe32bb269
Author:        Joerg Roedel <jroedel@...e.de>
AuthorDate:    Thu, 02 Dec 2021 16:32:23 +01:00
Committer:     Borislav Petkov <bp@...e.de>
CommitterDate: Sat, 04 Dec 2021 13:50:08 +01:00

x86/realmode: Add comment for Global bit usage in trampoline_pgd

Document the fact that using the trampoline_pgd will result in the
creation of global TLB entries in the user range of the address
space.

Signed-off-by: Joerg Roedel <jroedel@...e.de>
Signed-off-by: Borislav Petkov <bp@...e.de>
Link: https://lkml.kernel.org/r/20211202153226.22946-2-joro@8bytes.org
---
 arch/x86/mm/init.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index 1895986..4ba024d 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -714,6 +714,11 @@ static void __init memory_map_bottom_up(unsigned long map_start,
 static void __init init_trampoline(void)
 {
 #ifdef CONFIG_X86_64
+	/*
+	 * The code below will alias kernel page-tables in the user-range of the
+	 * address space, including the Global bit. So global TLB entries will
+	 * be created when using the trampoline page-table.
+	 */
 	if (!kaslr_memory_enabled())
 		trampoline_pgd_entry = init_top_pgt[pgd_index(__PAGE_OFFSET)];
 	else