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Re: [Xen-devel] [RFC PATCH 1/3] x86/xen: add basic KASAN support for PV kernel
- To: Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxx, kasan-dev@xxxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx
- From: Jürgen Groß <jgross@xxxxxxxx>
- Date: Wed, 18 Dec 2019 10:24:38 +0100
- Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>, Alexander Potapenko <glider@xxxxxxxxxx>, Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>, Dmitry Vyukov <dvyukov@xxxxxxxxxx>
- Delivery-date: Wed, 18 Dec 2019 09:24:47 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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@xxxxxxxxxx>
---
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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