4.9-stable review patch. If anyone has any objections, please let me know.
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From: Andy Lutomirski luto@kernel.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@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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.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,