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Subject[PATCH][v6] PM / hibernate: Print the possible panic reason when resuming with inconsistent e820 map
Date
On some platforms, there is occasional panic triggered when trying to
resume from hibernation, a typical panic looks like:

"BUG: unable to handle kernel paging request at ffff880085894000
IP: [<ffffffff810c5dc2>] load_image_lzo+0x8c2/0xe70"

This is because e820 map has been changed by BIOS before/after
hibernation, and one of the page frames from first kernel
is right located in second kernel's unmapped region, so panic
comes out when accessing unmapped kernel address.

In order to tell the user why this happeneded, and for scalability,
we introduce a framework(a new file named hibernation_e820.c) to
compare the e820 maps before/after hibernation. If these two
e820 maps are not compatible with each other, we will print
warning about the first corrupt e820 entry's information
(there might be more than one broken e820 entries) once the
system goes into panic, for example:

BUG: unable to handle kernel paging request at ffff8800a9688000
IP: [<ffffffff810c5dc2>] load_image_lzo+0x8c2/0xe70
PM: Hibernation Caution! Oops might be due to inconsistent e820 table.
PM: mem [0xa963b000-0xa963d000][ACPI Table] is an invalid old e820 region.
PM: Inconsistent with current [mem 0xa963b000-0xa963e000][ACPI Table].
PM: Please update your BIOS, or do not use hibernation on this machine.

The following kind of e820 entries will be regarded as invalid ones:
1.E820_RAM: old region is not a subset of any current region.
2.E820_ACPI: old region is not strictly the same as any current
region(example above).

Signed-off-by: Chen Yu <yu.c.chen@intel.com>
---
v6:
- Fix some compiling errors reported by 0day/LKP, adjust
Kconfig/variable namings.
v5:
- Rewrite this patch to just warn user of the broken BIOS
when panic.
v4:
- Add __attribute__ ((unused)) for swsusp_page_is_valid,
to eliminate the warnning of:
'swsusp_page_is_valid' defined but not used
on non-x86 platforms.

v3:
- Adjust the logic to exclude the end_pfn boundary in pfn_mapped
when invoking mark_valid_pages, because the end_pfn is not
a mapped page frame, we should not regard it as a valid page.

Move the sanity check of valid pages to a early stage in resuming
process(moved to mark_unsafe_pages), in this way, we can avoid
unnecessarily accessing these invalid pages in later stage(yes,
move to the original position Joey once introduced in:
Commit 84c91b7ae07c ("PM / hibernate: avoid unsafe pages in e820
reserved regions")

With v3 patch applied, I did 30 cycles on my problematic platform,
no panic triggered anymore(50% reproducible before patched, by
plugging/unplugging memory peripheral during hibernation), and it
just warns of invalid pages.

v2:
- According to Ingo's suggestion, rewrite this patch.

New version just checks each page frame according to pfn_mapped array.
So that we do not need to touch existing code related to
E820_RESERVED_KERN. And this method can naturely guarantee
that the system before/after hibernation do not need to be of
the same memory size on x86_64.
---
arch/x86/Kconfig | 1 +
arch/x86/power/Makefile | 2 +-
arch/x86/power/hibernate_e820.c | 243 ++++++++++++++++++++++++++++++++++++++++
include/linux/suspend.h | 19 ++++
kernel/power/Kconfig | 4 +
kernel/power/power.h | 8 ++
kernel/power/snapshot.c | 8 ++
7 files changed, 284 insertions(+), 1 deletion(-)
create mode 100644 arch/x86/power/hibernate_e820.c

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 96d058a..9f72144 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -30,6 +30,7 @@ config X86
select ARCH_HAS_PMEM_API if X86_64
select ARCH_HAS_MMIO_FLUSH
select ARCH_HAS_SG_CHAIN
+ select ARCH_HAS_RESUME_IMAGE_CHECKER if HIBERNATION
select ARCH_HAVE_NMI_SAFE_CMPXCHG
select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
select ARCH_MIGHT_HAVE_PC_PARPORT
diff --git a/arch/x86/power/Makefile b/arch/x86/power/Makefile
index a6a198c..8877cfb 100644
--- a/arch/x86/power/Makefile
+++ b/arch/x86/power/Makefile
@@ -4,4 +4,4 @@ nostackp := $(call cc-option, -fno-stack-protector)
CFLAGS_cpu.o := $(nostackp)

obj-$(CONFIG_PM_SLEEP) += cpu.o
-obj-$(CONFIG_HIBERNATION) += hibernate_$(BITS).o hibernate_asm_$(BITS).o
+obj-$(CONFIG_HIBERNATION) += hibernate_$(BITS).o hibernate_asm_$(BITS).o hibernate_e820.o
diff --git a/arch/x86/power/hibernate_e820.c b/arch/x86/power/hibernate_e820.c
new file mode 100644
index 0000000..f51a892
--- /dev/null
+++ b/arch/x86/power/hibernate_e820.c
@@ -0,0 +1,243 @@
+/*
+ * Hibernation e820 consistence checking for x86.
+ *
+ * Copyright (C) 2015, Intel Corporation
+ * Authors: Chen Yu <yu.c.chen@intel.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/suspend.h>
+#include <linux/kdebug.h>
+
+/*
+ * The following code is to check whether the old e820 map
+ * (system before hibernation) is compatible with current
+ * e820 map(system for resuming).
+ * We check two types of regions: E820_RAM and E820_ACPI,
+ * and to make sure the two kinds of regions will satisfy:
+ * 1. E820_RAM: each old region is a subset of the current ones.
+ * 2. E820_ACPI: each old region is strictly the same as the current ones.
+ *
+ * We save the old e820 map inside the swsusp_info page,
+ * then pass it to the second system for resuming, by the
+ * following format:
+ *
+ *
+ * +--------+---------+------+------+------+
+ * | swsusp |e820entry|entry0|entry1|entry2|
+ * | info | number | | | |
+ * +--------+---------+------+------+------+
+ * ^ ^
+ * | |
+ * +--------------struct swsusp_info(PAGE_SIZE)-------------+
+ */
+
+/*
+ * Record the first pair of conflicted new/old
+ * e820 entries if there's any.
+ */
+static u32 bad_old_type;
+static u64 bad_old_start, bad_old_end;
+
+static u32 bad_new_type;
+static u64 bad_new_start, bad_new_end;
+
+/**
+ * arch_image_info_save - save specified e820 data to
+ * the hibernation image header
+ * @dst: address to save the data to.
+ * @src: source data need to be saved,
+ * if NULL then save current system's e820 map.
+ * @limit_len: max len in bytes to write.
+ */
+int arch_image_info_save(char *dst, const char *src, unsigned int limit_len)
+{
+ unsigned int nr_e820_map;
+ unsigned int size_to_copy;
+ struct e820map *e820_map;
+
+ /*
+ * The final copied structure is illustrated below:
+ * [number_of_e820entry][e820entry0)[e820entry1)...
+ */
+ if (src) {
+ nr_e820_map = *(unsigned int *)src;
+ e820_map = (struct e820map *)(src + sizeof(unsigned int));
+ } else {
+ nr_e820_map = e820_saved.nr_map;
+ e820_map = &e820_saved;
+ }
+
+ size_to_copy = nr_e820_map * sizeof(struct e820entry);
+
+ if ((size_to_copy + sizeof(unsigned int)) > limit_len) {
+ pr_warn("PM: Hibernation can not save extra info due to too many e820 entries\n");
+ return -ENOMEM;
+ }
+ *(unsigned int *)dst = nr_e820_map;
+ dst += sizeof(unsigned int);
+ memcpy(dst, (void *)&e820_map->map[0], size_to_copy);
+ return 0;
+}
+
+/**
+ * arch_image_info_check - check the relationship between
+ * new and old e820 map, to make sure that, the E820_RAM
+ * in old e820, is a subset of the new e820 map, and the
+ * E820_ACPI regions in old e820 map, are strictly the
+ * same as new e820 map. If it is, return true, otherwise return false.
+ *
+ * @new: New e820 map address, usually it is the
+ * current system's e820_saved.
+ * @old: Old e820 map address, it is usually the
+ * e820 map before hibernation.
+ */
+bool arch_image_info_check(const char *new, const char *old)
+{
+ struct e820map *e820_old, *e820_new;
+ int i, j, nr_e820_old, nr_e820_new;
+
+ e820_old = (struct e820map *)old;
+ nr_e820_old = *(unsigned int *)e820_old;
+
+ if (new)
+ e820_new = (struct e820map *)new;
+ else
+ e820_new = &e820_saved;
+
+ nr_e820_new = e820_new->nr_map;
+
+ if ((nr_e820_old == 0) || (nr_e820_new == 0) ||
+ (nr_e820_old > E820_X_MAX) || (nr_e820_new > E820_X_MAX))
+ return false;
+
+ for (i = 0; i < nr_e820_old; i++) {
+ u64 old_start, old_end;
+ struct e820entry *ei_old;
+ bool valid_old_entry = false;
+
+ ei_old = &e820_old->map[i];
+
+ /*
+ * Only check RAM memory and ACPI table regions,
+ * and we follow this policy:
+ * 1.The old e820 RAM region must be new RAM's subset.
+ * 2.The old e820 ACPI table region must be the same
+ * as the new one.
+ */
+ if (ei_old->type != E820_RAM && ei_old->type != E820_ACPI)
+ continue;
+
+ old_start = ei_old->addr;
+ old_end = ei_old->addr + ei_old->size;
+
+ for (j = 0; j < nr_e820_new; j++) {
+ u64 new_start, new_end;
+ struct e820entry *ei_new;
+
+ if (valid_old_entry)
+ break;
+
+ ei_new = &e820_new->map[i];
+ new_start = ei_new->addr;
+ new_end = ei_new->addr + ei_new->size;
+
+ /*
+ * Check the relationship between these two regions.
+ */
+ if (old_start >= new_start && old_start < new_end) {
+ /* Must be of the same type. */
+ if ((ei_old->type != ei_new->type) ||
+ /* E820_RAM must be the subset */
+ ((ei_old->type == E820_RAM) &&
+ (old_end > new_end)) ||
+ /* E820_ACPI must remain unchanged. */
+ ((ei_old->type == E820_ACPI) &&
+ (old_start != new_start ||
+ old_end != new_end))) {
+ bad_old_start = old_start;
+ bad_old_end = old_end;
+ bad_old_type = ei_old->type;
+ bad_new_start = new_start;
+ bad_new_end = new_end;
+ bad_new_type = ei_new->type;
+
+ return false;
+ }
+ /* OK, this one is a valid e820 region. */
+ valid_old_entry = true;
+ }
+ }
+ /* If we did not find any overlapping between this old e820
+ * region and the new regions, return invalid.
+ */
+ if (!valid_old_entry) {
+ bad_old_start = old_start;
+ bad_old_end = old_end;
+ return false;
+ }
+ }
+ /* All the old e820 entries are valid */
+ return true;
+}
+
+static void e820_dump_map(struct e820map *e820_dump)
+{
+ int i;
+
+ for (i = 0; i < e820_dump->nr_map; i++) {
+ printk(KERN_ERR "[mem %#018Lx-%#018Lx] [%d]\n",
+ (unsigned long long) e820_dump->map[i].addr,
+ (unsigned long long)
+ (e820_dump->map[i].addr + e820_dump->map[i].size - 1),
+ e820_dump->map[i].type);
+ }
+}
+
+/*
+ * This hook is invoked when kernel dies, and will print the broken e820 map
+ * if it is caused by BIOS memory bug.
+ */
+static int arch_hibernation_die_check(struct notifier_block *nb,
+ unsigned long action,
+ void *data)
+{
+ if (!bad_old_start || !bad_old_end)
+ return 0;
+
+ pr_err("PM: Hibernation Caution! Oops might be due to inconsistent e820 table.\n");
+ pr_err("PM: [mem %#010llx-%#010llx][%s] is an invalid old e820 region.\n",
+ bad_old_start, bad_old_end - 1,
+ (bad_old_type == E820_RAM) ? "RAM" : "ACPI Table");
+ if (bad_new_start && bad_new_end)
+ pr_err("PM: Inconsistent with current [mem %#010llx-%#010llx][%s]\n",
+ bad_new_start, bad_new_end - 1,
+ (bad_new_type == E820_RAM) ? "RAM" : "ACPI Table");
+ pr_err("PM: Please update your BIOS, or do not use hibernation on this machine.\n");
+ pr_err("PM: Current system's e820 table:\n");
+ e820_dump_map(&e820_saved);
+ /* Avoid nested die print*/
+ bad_old_start = bad_old_end = 0;
+
+ return 0;
+}
+
+static struct notifier_block hibernation_notifier = {
+ .notifier_call = arch_hibernation_die_check,
+};
+
+static int __init arch_init_hibernation(void)
+{
+ int retval;
+
+ retval = register_die_notifier(&hibernation_notifier);
+ if (retval)
+ return retval;
+
+ return 0;
+}
+
+late_initcall(arch_init_hibernation);
diff --git a/include/linux/suspend.h b/include/linux/suspend.h
index 5efe743..5946b5c 100644
--- a/include/linux/suspend.h
+++ b/include/linux/suspend.h
@@ -361,6 +361,25 @@ static inline bool system_entering_hibernation(void) { return false; }
static inline bool hibernation_available(void) { return false; }
#endif /* CONFIG_HIBERNATION */

+#ifdef CONFIG_ARCH_HAS_RESUME_IMAGE_CHECKER
+extern int arch_image_info_save(char *dst, const char *src,
+ unsigned int limit_len);
+extern bool arch_image_info_check(const char *new, const char *old);
+#else
+static inline bool arch_image_info_check(const char *new,
+ const char *old)
+{
+ return true;
+}
+
+static inline int arch_image_info_save(char *dst,
+ const char *src,
+ unsigned int limit_len)
+{
+ return 0;
+}
+#endif
+
/* Hibernation and suspend events */
#define PM_HIBERNATION_PREPARE 0x0001 /* Going to hibernate */
#define PM_POST_HIBERNATION 0x0002 /* Hibernation finished */
diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
index 02e8dfa..4d8e6d8 100644
--- a/kernel/power/Kconfig
+++ b/kernel/power/Kconfig
@@ -79,6 +79,10 @@ config HIBERNATION
config ARCH_SAVE_PAGE_KEYS
bool

+config ARCH_HAS_RESUME_IMAGE_CHECKER
+ bool
+ depends on HIBERNATION
+
config PM_STD_PARTITION
string "Default resume partition"
depends on HIBERNATION
diff --git a/kernel/power/power.h b/kernel/power/power.h
index caadb56..d279907 100644
--- a/kernel/power/power.h
+++ b/kernel/power/power.h
@@ -14,6 +14,14 @@ struct swsusp_info {
unsigned long size;
} __aligned(PAGE_SIZE);

+/*
+ * Since struct swsusp_info will take one page size,
+ * some platforms save the extra data right after the
+ * last structure element.
+ */
+#define SWSUSP_INFO_ACTUAL_SIZE \
+ (offsetof(struct swsusp_info, size) + sizeof(unsigned long))
+
#ifdef CONFIG_HIBERNATION
/* kernel/power/snapshot.c */
extern void __init hibernate_reserved_size_init(void);
diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
index 5235dd4..394d20d 100644
--- a/kernel/power/snapshot.c
+++ b/kernel/power/snapshot.c
@@ -1970,6 +1970,11 @@ int snapshot_read_next(struct snapshot_handle *handle)
error = init_header((struct swsusp_info *)buffer);
if (error)
return error;
+
+ arch_image_info_save((char *)buffer + SWSUSP_INFO_ACTUAL_SIZE,
+ NULL,
+ PAGE_SIZE-SWSUSP_INFO_ACTUAL_SIZE);
+
handle->buffer = buffer;
memory_bm_position_reset(&orig_bm);
memory_bm_position_reset(&copy_bm);
@@ -2491,6 +2496,9 @@ int snapshot_write_next(struct snapshot_handle *handle)
if (error)
return error;

+ arch_image_info_check(NULL,
+ (char *)buffer + SWSUSP_INFO_ACTUAL_SIZE);
+
error = memory_bm_create(&copy_bm, GFP_ATOMIC, PG_ANY);
if (error)
return error;
--
1.8.4.2


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