Messages in this thread | | | Subject | Re: [RFC PATCH 1/3] x86/xen: add basic KASAN support for PV kernel | From | Jürgen Groß <> | Date | Wed, 18 Dec 2019 10:24:38 +0100 |
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On 17.12.19 15:08, Sergey Dyasli wrote: > This enables to use Outline instrumentation for Xen PV kernels. > > KASAN_INLINE and KASAN_VMALLOC options currently lead to boot crashes > and hence disabled. > > Rough edges in the patch are marked with XXX. > > Signed-off-by: Sergey Dyasli <sergey.dyasli@citrix.com> > --- > arch/x86/mm/init.c | 14 ++++++++++++++ > arch/x86/mm/kasan_init_64.c | 28 ++++++++++++++++++++++++++++ > arch/x86/xen/Makefile | 7 +++++++ > arch/x86/xen/enlighten_pv.c | 3 +++ > arch/x86/xen/mmu_pv.c | 13 +++++++++++-- > arch/x86/xen/multicalls.c | 10 ++++++++++ > drivers/xen/Makefile | 2 ++ > kernel/Makefile | 2 ++ > lib/Kconfig.kasan | 3 ++- > 9 files changed, 79 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c > index e7bb483557c9..0c98a45eec6c 100644 > --- a/arch/x86/mm/init.c > +++ b/arch/x86/mm/init.c > @@ -8,6 +8,8 @@ > #include <linux/kmemleak.h> > #include <linux/sched/task.h> > > +#include <xen/xen.h> > + > #include <asm/set_memory.h> > #include <asm/e820/api.h> > #include <asm/init.h> > @@ -835,6 +837,18 @@ void free_kernel_image_pages(const char *what, void *begin, void *end) > unsigned long end_ul = (unsigned long)end; > unsigned long len_pages = (end_ul - begin_ul) >> PAGE_SHIFT; > > + /* > + * XXX: skip this for now. Otherwise it leads to: > + * > + * (XEN) mm.c:2713:d157v0 Bad type (saw 8c00000000000001 != exp e000000000000000) for mfn 36f40 (pfn 02f40) > + * (XEN) mm.c:1043:d157v0 Could not get page type PGT_writable_page > + * (XEN) mm.c:1096:d157v0 Error getting mfn 36f40 (pfn 02f40) from L1 entry 8010000036f40067 for l1e_owner d157, pg_owner d157 > + * > + * and further #PF error: [PROT] [WRITE] in the kernel. > + */ > + if (xen_pv_domain() && IS_ENABLED(CONFIG_KASAN)) > + return; > +
I guess this is related to freeing some kasan page tables without unpinning them?
> free_init_pages(what, begin_ul, end_ul); > > /* > diff --git a/arch/x86/mm/kasan_init_64.c b/arch/x86/mm/kasan_init_64.c > index cf5bc37c90ac..caee2022f8b0 100644 > --- a/arch/x86/mm/kasan_init_64.c > +++ b/arch/x86/mm/kasan_init_64.c > @@ -13,6 +13,8 @@ > #include <linux/sched/task.h> > #include <linux/vmalloc.h> > > +#include <xen/xen.h> > + > #include <asm/e820/types.h> > #include <asm/pgalloc.h> > #include <asm/tlbflush.h> > @@ -20,6 +22,9 @@ > #include <asm/pgtable.h> > #include <asm/cpu_entry_area.h> > > +#include <xen/interface/xen.h> > +#include <asm/xen/hypervisor.h> > + > extern struct range pfn_mapped[E820_MAX_ENTRIES]; > > static p4d_t tmp_p4d_table[MAX_PTRS_PER_P4D] __initdata __aligned(PAGE_SIZE); > @@ -305,6 +310,12 @@ static struct notifier_block kasan_die_notifier = { > }; > #endif > > +#ifdef CONFIG_XEN > +/* XXX: this should go to some header */ > +void __init set_page_prot(void *addr, pgprot_t prot); > +void __init pin_pagetable_pfn(unsigned cmd, unsigned long pfn); > +#endif > +
Instead of exporting those, why don't you ...
> void __init kasan_early_init(void) > { > int i; > @@ -332,6 +343,16 @@ void __init kasan_early_init(void) > for (i = 0; pgtable_l5_enabled() && i < PTRS_PER_P4D; i++) > kasan_early_shadow_p4d[i] = __p4d(p4d_val); > > + if (xen_pv_domain()) { > + /* PV page tables must have PAGE_KERNEL_RO */ > + set_page_prot(kasan_early_shadow_pud, PAGE_KERNEL_RO); > + set_page_prot(kasan_early_shadow_pmd, PAGE_KERNEL_RO); > + set_page_prot(kasan_early_shadow_pte, PAGE_KERNEL_RO);
add a function doing that to mmu_pv.c (e.g. xen_pv_kasan_early_init())?
> + > + /* Add mappings to the initial PV page tables */ > + kasan_map_early_shadow((pgd_t *)xen_start_info->pt_base); > + } > + > kasan_map_early_shadow(early_top_pgt); > kasan_map_early_shadow(init_top_pgt); > } > @@ -369,6 +390,13 @@ void __init kasan_init(void) > __pgd(__pa(tmp_p4d_table) | _KERNPG_TABLE)); > } > > + if (xen_pv_domain()) { > + /* PV page tables must be pinned */ > + set_page_prot(early_top_pgt, PAGE_KERNEL_RO); > + pin_pagetable_pfn(MMUEXT_PIN_L4_TABLE, > + PFN_DOWN(__pa_symbol(early_top_pgt)));
and another one like xen_pv_kasan_init() here.
> + } > + > load_cr3(early_top_pgt); > __flush_tlb_all(); > > diff --git a/arch/x86/xen/Makefile b/arch/x86/xen/Makefile > index 084de77a109e..102fad0b0bca 100644 > --- a/arch/x86/xen/Makefile > +++ b/arch/x86/xen/Makefile > @@ -1,3 +1,10 @@ > +KASAN_SANITIZE_enlighten_pv.o := n > +KASAN_SANITIZE_enlighten.o := n > +KASAN_SANITIZE_irq.o := n > +KASAN_SANITIZE_mmu_pv.o := n > +KASAN_SANITIZE_p2m.o := n > +KASAN_SANITIZE_multicalls.o := n > + > # SPDX-License-Identifier: GPL-2.0 > OBJECT_FILES_NON_STANDARD_xen-asm_$(BITS).o := y > > diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c > index ae4a41ca19f6..27de55699f24 100644 > --- a/arch/x86/xen/enlighten_pv.c > +++ b/arch/x86/xen/enlighten_pv.c > @@ -72,6 +72,7 @@ > #include <asm/mwait.h> > #include <asm/pci_x86.h> > #include <asm/cpu.h> > +#include <asm/kasan.h> > > #ifdef CONFIG_ACPI > #include <linux/acpi.h> > @@ -1231,6 +1232,8 @@ asmlinkage __visible void __init xen_start_kernel(void) > /* Get mfn list */ > xen_build_dynamic_phys_to_machine(); > > + kasan_early_init(); > + > /* > * Set up kernel GDT and segment registers, mainly so that > * -fstack-protector code can be executed. > diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c > index c8dbee62ec2a..eaf63f1f26af 100644 > --- a/arch/x86/xen/mmu_pv.c > +++ b/arch/x86/xen/mmu_pv.c > @@ -1079,7 +1079,7 @@ static void xen_exit_mmap(struct mm_struct *mm) > > static void xen_post_allocator_init(void); > > -static void __init pin_pagetable_pfn(unsigned cmd, unsigned long pfn) > +void __init pin_pagetable_pfn(unsigned cmd, unsigned long pfn) > { > struct mmuext_op op; > > @@ -1767,7 +1767,7 @@ static void __init set_page_prot_flags(void *addr, pgprot_t prot, > if (HYPERVISOR_update_va_mapping((unsigned long)addr, pte, flags)) > BUG(); > } > -static void __init set_page_prot(void *addr, pgprot_t prot) > +void __init set_page_prot(void *addr, pgprot_t prot) > { > return set_page_prot_flags(addr, prot, UVMF_NONE); > } > @@ -1943,6 +1943,15 @@ void __init xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn) > if (i && i < pgd_index(__START_KERNEL_map)) > init_top_pgt[i] = ((pgd_t *)xen_start_info->pt_base)[i]; > > +#ifdef CONFIG_KASAN > + /* > + * Copy KASAN mappings > + * ffffec0000000000 - fffffbffffffffff (=44 bits) kasan shadow memory (16TB) > + */ > + for (i = 0xec0 >> 3; i < 0xfc0 >> 3; i++) > + init_top_pgt[i] = ((pgd_t *)xen_start_info->pt_base)[i]; > +#endif > + > /* Make pagetable pieces RO */ > set_page_prot(init_top_pgt, PAGE_KERNEL_RO); > set_page_prot(level3_ident_pgt, PAGE_KERNEL_RO); > diff --git a/arch/x86/xen/multicalls.c b/arch/x86/xen/multicalls.c > index 07054572297f..5e4729efbbe2 100644 > --- a/arch/x86/xen/multicalls.c > +++ b/arch/x86/xen/multicalls.c > @@ -99,6 +99,15 @@ void xen_mc_flush(void) > ret++; > } > > + /* > + * XXX: Kasan produces quite a lot (~2000) of warnings in a form of: > + * > + * (XEN) mm.c:3222:d155v0 mfn 3704b already pinned > + * > + * during kasan_init(). They are benign, but silence them for now. > + * Otherwise, booting takes too long due to printk() spam. > + */ > +#ifndef CONFIG_KASAN
It might be interesting to identify the problematic page tables.
I guess this would require some hacking to avoid the multicalls in order to identify which page table should not be pinned again.
Juergen
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