linux-kernel - [PATCH 4.9 211/241] x86/boot/32: Fix UP boot on Quark and possibly other platforms

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Date:   Mon, 19 Mar 2018 19:07:56 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jan Kiszka <jan.kiszka@...mens.com>,
        Andy Lutomirski <luto@...nel.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Borislav Petkov <bp@...en8.de>,
        Brian Gerst <brgerst@...il.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Juergen Gross <jgross@...e.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Garnier <thgarnie@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-efi@...r.kernel.org, Ingo Molnar <mingo@...nel.org>
Subject: [PATCH 4.9 211/241] x86/boot/32: Fix UP boot on Quark and possibly other platforms

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Andy Lutomirski <luto@...nel.org>

commit d2b6dc61a8dd3c429609b993778cb54e75a5c5f0 upstream.

This partially reverts commit:

  23b2a4ddebdd17f ("x86/boot/32: Defer resyncing initial_page_table until per-cpu is set up")

That commit had one definite bug and one potential bug.  The
definite bug is that setup_per_cpu_areas() uses a differnet generic
implementation on UP kernels, so initial_page_table never got
resynced.  This was fine for access to percpu data (it's in the
identity map on UP), but it breaks other users of
initial_page_table.  The potential bug is that helpers like
efi_init() would be called before the tables were synced.

Avoid both problems by just syncing the page tables in setup_arch()
*and* setup_per_cpu_areas().

Reported-by: Jan Kiszka <jan.kiszka@...mens.com>
Signed-off-by: Andy Lutomirski <luto@...nel.org>
Cc: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Juergen Gross <jgross@...e.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Matt Fleming <matt@...eblueprint.co.uk>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Garnier <thgarnie@...gle.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: linux-efi@...r.kernel.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/kernel/setup.c        |   15 +++++++++++++++
 arch/x86/kernel/setup_percpu.c |   10 +++++-----
 2 files changed, 20 insertions(+), 5 deletions(-)

--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -1200,6 +1200,21 @@ void __init setup_arch(char **cmdline_p)
 
 	kasan_init();
 
+#ifdef CONFIG_X86_32
+	/* sync back kernel address range */
+	clone_pgd_range(initial_page_table + KERNEL_PGD_BOUNDARY,
+			swapper_pg_dir     + KERNEL_PGD_BOUNDARY,
+			KERNEL_PGD_PTRS);
+
+	/*
+	 * sync back low identity map too.  It is used for example
+	 * in the 32-bit EFI stub.
+	 */
+	clone_pgd_range(initial_page_table,
+			swapper_pg_dir     + KERNEL_PGD_BOUNDARY,
+			min(KERNEL_PGD_PTRS, KERNEL_PGD_BOUNDARY));
+#endif
+
 	tboot_probe();
 
 	map_vsyscall();
--- a/arch/x86/kernel/setup_percpu.c
+++ b/arch/x86/kernel/setup_percpu.c
@@ -290,11 +290,11 @@ void __init setup_per_cpu_areas(void)
 
 #ifdef CONFIG_X86_32
 	/*
-	 * Sync back kernel address range.  We want to make sure that
-	 * all kernel mappings, including percpu mappings, are available
-	 * in the smpboot asm.  We can't reliably pick up percpu
-	 * mappings using vmalloc_fault(), because exception dispatch
-	 * needs percpu data.
+	 * Sync back kernel address range again.  We already did this in
+	 * setup_arch(), but percpu data also needs to be available in
+	 * the smpboot asm.  We can't reliably pick up percpu mappings
+	 * using vmalloc_fault(), because exception dispatch needs
+	 * percpu data.
 	 */
 	clone_pgd_range(initial_page_table + KERNEL_PGD_BOUNDARY,
 			swapper_pg_dir     + KERNEL_PGD_BOUNDARY,