Commit d2b6dc61 authored May 08, 2017 by Andy Lutomirski Committed by Ingo Molnar May 09, 2017

x86/boot/32: Fix UP boot on Quark and possibly other platforms



This partially reverts commit:

  23b2a4dd ("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@siemens.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Garnier <thgarnie@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 861ce4a3

arch/x86/kernel/setup.c

+15 −0

Original line number	Diff line number	Diff line
		@@ -1225,6 +1225,21 @@ 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();

arch/x86/kernel/setup_percpu.c

+5 −5

Original line number	Diff line number	Diff line
		@@ -291,11 +291,11 @@ 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,

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