This series is dependent upon "refactor Kconfig to consolidate
KEXEC and CRASH options".
https://lore.kernel.org/lkml/[email protected]/
Once the kdump service is loaded, if changes to CPUs or memory occur,
either by hot un/plug or off/onlining, the crash elfcorehdr must also
be updated.
The elfcorehdr describes to kdump the CPUs and memory in the system,
and any inaccuracies can result in a vmcore with missing CPU context
or memory regions.
The current solution utilizes udev to initiate an unload-then-reload
of the kdump image (eg. kernel, initrd, boot_params, purgatory and
elfcorehdr) by the userspace kexec utility. In the original post I
outlined the significant performance problems related to offloading
this activity to userspace.
This patchset introduces a generic crash handler that registers with
the CPU and memory notifiers. Upon CPU or memory changes, from either
hot un/plug or off/onlining, this generic handler is invoked and
performs important housekeeping, for example obtaining the appropriate
lock, and then invokes an architecture specific handler to do the
appropriate elfcorehdr update.
Note the description in patch 'crash: change crash_prepare_elf64_headers()
to for_each_possible_cpu()' and 'x86/crash: optimize CPU changes' that
enables further optimizations related to CPU plug/unplug/online/offline
performance of elfcorehdr updates.
In the case of x86_64, the arch specific handler generates a new
elfcorehdr, and overwrites the old one in memory; thus no involvement
with userspace needed.
To realize the benefits/test this patchset, one must make a couple
of minor changes to userspace:
- Prevent udev from updating kdump crash kernel on hot un/plug changes.
Add the following as the first lines to the RHEL udev rule file
/usr/lib/udev/rules.d/98-kexec.rules:
# The kernel updates the crash elfcorehdr for CPU and memory changes
SUBSYSTEM=="cpu", ATTRS{crash_hotplug}=="1", GOTO="kdump_reload_end"
SUBSYSTEM=="memory", ATTRS{crash_hotplug}=="1", GOTO="kdump_reload_end"
With this changeset applied, the two rules evaluate to false for
CPU and memory change events and thus skip the userspace
unload-then-reload of kdump.
- Change to the kexec_file_load for loading the kdump kernel:
Eg. on RHEL: in /usr/bin/kdumpctl, change to:
standard_kexec_args="-p -d -s"
which adds the -s to select kexec_file_load() syscall.
This kernel patchset also supports kexec_load() with a modified kexec
userspace utility. A working changeset to the kexec userspace utility
is posted to the kexec-tools mailing list here:
http://lists.infradead.org/pipermail/kexec/2023-May/027049.html
To use the kexec-tools patch, apply, build and install kexec-tools,
then change the kdumpctl's standard_kexec_args to replace the -s with
--hotplug. The removal of -s reverts to the kexec_load syscall and
the addition of --hotplug invokes the changes put forth in the
kexec-tools patch.
Regards,
eric
---
v23: 12jun2023
- Rebased onto 6.4.0-rc6
- Refactored Kconfig, per Thomas. See series:
https://lore.kernel.org/lkml/[email protected]/
- Reworked commit messages to conform to style, per Thomas.
- Applied Baoquan He Acked-by to kexec_load() patch.
- Applied Hari Bathini Acked-by for the series.
- No code changes.
v22: 3may2023
https://lore.kernel.org/lkml/[email protected]/
- Rebased onto 6.3.0
- Improved support for kexec_load(), per Hari Bathini. See
"crash: hotplug support for kexec_load()" which is the only
change to this series.
- Applied Baoquan He's Acked-by for all other patches.
v21: 4apr2023
https://lkml.org/lkml/2023/4/4/1136
https://lore.kernel.org/lkml/[email protected]/
- Rebased onto 6.3.0-rc5
- Additional simplification of indentation in crash_handle_hotplug_event(),
per Baoquan.
v20: 17mar2023
https://lkml.org/lkml/2023/3/17/1169
https://lore.kernel.org/lkml/[email protected]/
- Rebased onto 6.3.0-rc2
- Defaulting CRASH_HOTPLUG for x86 to Y, per Sourabh.
- Explicitly initializing image->hp_action, per Baoquan.
- Simplified kexec_trylock() in crash_handle_hotplug_event(),
per Baoquan.
- Applied Sourabh's Reviewed-by to the series.
v19: 6mar2023
https://lkml.org/lkml/2023/3/6/1358
https://lore.kernel.org/lkml/[email protected]/
- Rebased onto 6.2.0
- Did away with offlinecpu, per Thomas Gleixner.
- Changed to CPUHP_BP_PREPARE_DYN instead of CPUHP_AP_ONLINE_DYN.
- Did away with elfcorehdr_index_valid, per Sourabh.
- Convert to for_each_possible_cpu() in crash_prepare_elf64_headers()
per Sourabh.
- Small optimization for x86 cpu changes.
v18: 31jan2023
https://lkml.org/lkml/2023/1/31/1356
https://lore.kernel.org/lkml/[email protected]/
- Rebased onto 6.2.0-rc6
- Renamed struct kimage member hotplug_event to hp_action, and
re-enumerated the KEXEC_CRASH_HP_x items, adding _NONE at 0.
- Moved to cpuhp state CPUHP_BP_PREPARE_DYN instead of
CPUHP_AP_ONLINE_DYN in order to minimize window of time CPU
is not reflected in elfcorehdr.
- Reworked some of the comments and commit messages to offer
more of the why, than what, per Thomas Gleixner.
v17: 18jan2023
https://lkml.org/lkml/2023/1/18/1420
https://lore.kernel.org/lkml/[email protected]/
- Rebased onto 6.2.0-rc4
- Moved a bit of code around so that kexec_load()-only builds
work, per Sourabh.
- Corrected computation of number of memory region Phdrs needed
when x86 memory hotplug is not enabled, per Baoquan.
v16: 5jan2023
https://lkml.org/lkml/2023/1/5/673
https://lore.kernel.org/lkml/[email protected]/
- Rebased onto 6.2.0-rc2
- Corrected error identified by Baoquan.
v15: 9dec2022
https://lkml.org/lkml/2022/12/9/520
https://lore.kernel.org/lkml/[email protected]/
- Rebased onto 6.1.0-rc8
- Replaced arch_un/map_crash_pages() with direct use of
kun/map_local_pages(), per Boris.
- Some x86 changes, per Boris.
v14: 16nov2022
https://lkml.org/lkml/2022/11/16/1645
https://lore.kernel.org/lkml/[email protected]/
- Rebased onto 6.1.0-rc5
- Introduced CRASH_HOTPLUG Kconfig item to better fine tune
compilation of feature components, per Boris.
- Removed hp_action parameter to arch_crash_handle_hotplug_event()
as it is unused.
v13: 31oct2022
https://lkml.org/lkml/2022/10/31/854
https://lore.kernel.org/lkml/[email protected]/
- Rebased onto 6.1.0-rc3, which means converting to use the new
kexec_trylock() away from mutex_lock(kexec_mutex).
- Moved arch_un/map_crash_pages() into kexec.h and default
implementation using k/unmap_local_pages().
- Changed more #ifdef's into IS_ENABLED()
- Changed CRASH_MAX_MEMORY_RANGES to 8192 from 32768, and it moved
into x86 crash.c as #define rather Kconfig item, per Boris.
- Check number of Phdrs against PN_XNUM, max possible.
v12: 9sep2022
https://lkml.org/lkml/2022/9/9/1358
https://lore.kernel.org/lkml/[email protected]/
- Rebased onto 6.0-rc4
- Addressed some minor formatting items, per Baoquan
v11: 26aug2022
https://lkml.org/lkml/2022/8/26/963
https://lore.kernel.org/lkml/[email protected]/
- Rebased onto 6.0-rc2
- Redid the rework of __weak to use asm/kexec.h, per Baoquan
- Reworked some comments and minor items, per Baoquan
v10: 21jul2022
https://lkml.org/lkml/2022/7/21/1007
https://lore.kernel.org/lkml/[email protected]/
- Rebased to 5.19.0-rc7
- Per Sourabh, corrected build issue with arch_un/map_crash_pages()
for architectures not supporting this feature.
- Per David Hildebrand, removed the WARN_ONCE() altogether.
- Per David Hansen, converted to use of kmap_local_page().
- Per Baoquan He, replaced use of __weak with the kexec technique.
v9: 13jun2022
https://lkml.org/lkml/2022/6/13/3382
https://lore.kernel.org/lkml/[email protected]/
- Rebased to 5.18.0
- Per Sourabh, moved crash_prepare_elf64_headers() into common
crash_core.c to avoid compile issues with kexec_load only path.
- Per David Hildebrand, replaced mutex_trylock() with mutex_lock().
- Changed the __weak arch_crash_handle_hotplug_event() to utilize
WARN_ONCE() instead of WARN(). Fix some formatting issues.
- Per Sourabh, introduced sysfs attribute crash_hotplug for memory
and CPUs; for use by userspace (udev) to determine if the kernel
performs crash hot un/plug support.
- Per Sourabh, moved the code detecting the elfcorehdr segment from
arch/x86 into crash_core:handle_hotplug_event() so both kexec_load
and kexec_file_load can benefit.
- Updated userspace kexec-tools kexec utility to reflect change to
using CRASH_MAX_MEMORY_RANGES and get_nr_cpus().
- Updated the new proposed udev rules to reflect using the sysfs
attributes crash_hotplug.
v8: 5may2022
https://lkml.org/lkml/2022/5/5/1133
https://lore.kernel.org/lkml/[email protected]/
- Per Borislav Petkov, eliminated CONFIG_CRASH_HOTPLUG in favor
of CONFIG_HOTPLUG_CPU || CONFIG_MEMORY_HOTPLUG, ie a new define
is not needed. Also use of IS_ENABLED() rather than #ifdef's.
Renamed crash_hotplug_handler() to handle_hotplug_event().
And other corrections.
- Per Baoquan, minimized the parameters to the arch_crash_
handle_hotplug_event() to hp_action and cpu.
- Introduce KEXEC_CRASH_HP_INVALID_CPU definition, per Baoquan.
- Per Sourabh Jain, renamed and repurposed CRASH_HOTPLUG_ELFCOREHDR_SZ
to CONFIG_CRASH_MAX_MEMORY_RANGES, mirroring kexec-tools change
by David Hildebrand. Folded this patch into the x86
kexec_file_load support patch.
v7: 13apr2022
https://lkml.org/lkml/2022/4/13/850
https://lore.kernel.org/lkml/[email protected]/
- Resolved parameter usage to crash_hotplug_handler(), per Baoquan.
v6: 1apr2022
https://lkml.org/lkml/2022/4/1/1203
https://lore.kernel.org/lkml/[email protected]/
- Reword commit messages and some comment cleanup per Baoquan.
- Changed elf_index to elfcorehdr_index for clarity.
- Minor code changes per Baoquan.
v5: 3mar2022
https://lkml.org/lkml/2022/3/3/674
https://lore.kernel.org/lkml/[email protected]/
- Reworded description of CRASH_HOTPLUG_ELFCOREHDR_SZ, per
David Hildenbrand.
- Refactored slightly a few patches per Baoquan recommendation.
v4: 9feb2022
https://lkml.org/lkml/2022/2/9/1406
https://lore.kernel.org/lkml/[email protected]/
- Refactored patches per Baoquan suggestsions.
- A few corrections, per Baoquan.
v3: 10jan2022
https://lkml.org/lkml/2022/1/10/1212
https://lore.kernel.org/lkml/[email protected]/
- Rebasing per Baoquan He request.
- Changed memory notifier per David Hildenbrand.
- Providing example kexec userspace change in cover letter.
RFC v2: 7dec2021
https://lkml.org/lkml/2021/12/7/1088
https://lore.kernel.org/lkml/[email protected]/
- Acting upon Baoquan He suggestion of removing elfcorehdr from
the purgatory list of segments, removed purgatory code from
patchset, and it is signficiantly simpler now.
RFC v1: 18nov2021
https://lkml.org/lkml/2021/11/18/845
https://lore.kernel.org/lkml/[email protected]/
- working patchset demonstrating kernel handling of hotplug
updates to x86 elfcorehdr for kexec_file_load
RFC: 14dec2020
https://lkml.org/lkml/2020/12/14/532
https://lore.kernel.org/lkml/[email protected]/
- proposed concept of allowing kernel to handle hotplug update
of elfcorehdr
---
Eric DeVolder (8):
crash: move a few code bits to setup support of crash hotplug
crash: add generic infrastructure for crash hotplug support
kexec: exclude elfcorehdr from the segment digest
crash: memory and CPU hotplug sysfs attributes
x86/crash: add x86 crash hotplug support
crash: hotplug support for kexec_load()
crash: change crash_prepare_elf64_headers() to for_each_possible_cpu()
x86/crash: optimize CPU changes
.../admin-guide/mm/memory-hotplug.rst | 8 +
Documentation/core-api/cpu_hotplug.rst | 18 +
arch/x86/Kconfig | 3 +
arch/x86/include/asm/kexec.h | 18 +
arch/x86/kernel/crash.c | 140 ++++++-
drivers/base/cpu.c | 14 +
drivers/base/memory.c | 13 +
include/linux/crash_core.h | 9 +
include/linux/kexec.h | 63 +++-
include/uapi/linux/kexec.h | 1 +
kernel/Kconfig.kexec | 31 ++
kernel/crash_core.c | 355 ++++++++++++++++++
kernel/kexec.c | 5 +
kernel/kexec_core.c | 6 +
kernel/kexec_file.c | 187 +--------
kernel/ksysfs.c | 15 +
16 files changed, 681 insertions(+), 205 deletions(-)
--
2.31.1
The hotplug support for kexec_load() requires changes to the
userspace kexec-tools and a little extra help from the kernel.
Given a kdump capture kernel loaded via kexec_load(), and a
subsequent hotplug event, the crash hotplug handler finds the
elfcorehdr and rewrites it to reflect the hotplug change.
That is the desired outcome, however, at kernel panic time,
the purgatory integrity check fails (because the elfcorehdr
changed), and the capture kernel does not boot and no vmcore
is generated.
Therefore, the userspace kexec-tools/kexec must indicate to the
kernel that the elfcorehdr can be modified (because the kexec
excluded the elfcorehdr from the digest, and sized the elfcorehdr
memory buffer appropriately).
To facilitate hotplug support with kexec_load():
- a new kexec flag KEXEC_UPATE_ELFCOREHDR indicates that it is
safe for the kernel to modify the kexec_load()'d elfcorehdr
- the /sys/kernel/crash_elfcorehdr_size node communicates the
preferred size of the elfcorehdr memory buffer
- The sysfs crash_hotplug nodes (ie.
/sys/devices/system/[cpu|memory]/crash_hotplug) dynamically
take into account kexec_file_load() vs kexec_load() and
KEXEC_UPDATE_ELFCOREHDR.
This is critical so that the udev rule processing of crash_hotplug
is all that is needed to determine if the userspace unload-then-load
of the kdump image is to be skipped, or not. The proposed udev
rule change looks like:
# The kernel updates the crash elfcorehdr for CPU and memory changes
SUBSYSTEM=="cpu", ATTRS{crash_hotplug}=="1", GOTO="kdump_reload_end"
SUBSYSTEM=="memory", ATTRS{crash_hotplug}=="1", GOTO="kdump_reload_end"
The table below indicates the behavior of kexec_load()'d kdump image
updates (with the new udev crash_hotplug rule in place):
Kernel |Kexec
-------+-----+----
Old |Old |New
| a | a
-------+-----+----
New | a | b
-------+-----+----
where kexec 'old' and 'new' delineate kexec-tools has the needed
modifications for the crash hotplug feature, and kernel 'old' and
'new' delineate the kernel supports this crash hotplug feature.
Behavior 'a' indicates the unload-then-reload of the entire kdump
image. For the kexec 'old' column, the unload-then-reload occurs
due to the missing flag KEXEC_UPDATE_ELFCOREHDR. An 'old' kernel
(with 'new' kexec) does not present the crash_hotplug sysfs node,
which leads to the unload-then-reload of the kdump image.
Behavior 'b' indicates the desired optimized behavior of the kernel
directly modifying the elfcorehdr and avoiding the unload-then-reload
of the kdump image.
If the udev rule is not updated with crash_hotplug node check, then
no matter any combination of kernel or kexec is new or old, the
kdump image continues to be unload-then-reload on hotplug changes.
To fully support crash hotplug feature, there needs to be a rollout
of kernel, kexec-tools and udev rule changes. However, the order of
the rollout of these pieces does not matter; kexec_load()'d kdump
images still function for hotplug as-is.
Suggested-by: Hari Bathini <[email protected]>
Signed-off-by: Eric DeVolder <[email protected]>
Acked-by: Hari Bathini <[email protected]>
Acked-by: Baoquan He <[email protected]>
---
arch/x86/include/asm/kexec.h | 11 +++++++----
arch/x86/kernel/crash.c | 27 +++++++++++++++++++++++++++
include/linux/kexec.h | 14 ++++++++++++--
include/uapi/linux/kexec.h | 1 +
kernel/crash_core.c | 31 +++++++++++++++++++++++++++++++
kernel/kexec.c | 5 +++++
kernel/ksysfs.c | 15 +++++++++++++++
7 files changed, 98 insertions(+), 6 deletions(-)
diff --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kexec.h
index 9143100ea3ea..3be6a98751f0 100644
--- a/arch/x86/include/asm/kexec.h
+++ b/arch/x86/include/asm/kexec.h
@@ -214,14 +214,17 @@ void arch_crash_handle_hotplug_event(struct kimage *image);
#define arch_crash_handle_hotplug_event arch_crash_handle_hotplug_event
#ifdef CONFIG_HOTPLUG_CPU
-static inline int crash_hotplug_cpu_support(void) { return 1; }
-#define crash_hotplug_cpu_support crash_hotplug_cpu_support
+int arch_crash_hotplug_cpu_support(void);
+#define crash_hotplug_cpu_support arch_crash_hotplug_cpu_support
#endif
#ifdef CONFIG_MEMORY_HOTPLUG
-static inline int crash_hotplug_memory_support(void) { return 1; }
-#define crash_hotplug_memory_support crash_hotplug_memory_support
+int arch_crash_hotplug_memory_support(void);
+#define crash_hotplug_memory_support arch_crash_hotplug_memory_support
#endif
+
+unsigned int arch_crash_get_elfcorehdr_size(void);
+#define crash_get_elfcorehdr_size arch_crash_get_elfcorehdr_size
#endif
#endif /* __ASSEMBLY__ */
diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index c70a111c44fa..caf22bcb61af 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -427,6 +427,33 @@ int crash_load_segments(struct kimage *image)
#undef pr_fmt
#define pr_fmt(fmt) "crash hp: " fmt
+/* These functions provide the value for the sysfs crash_hotplug nodes */
+#ifdef CONFIG_HOTPLUG_CPU
+int arch_crash_hotplug_cpu_support(void)
+{
+ return crash_check_update_elfcorehdr();
+}
+#endif
+
+#ifdef CONFIG_MEMORY_HOTPLUG
+int arch_crash_hotplug_memory_support(void)
+{
+ return crash_check_update_elfcorehdr();
+}
+#endif
+
+unsigned int arch_crash_get_elfcorehdr_size(void)
+{
+ unsigned int sz;
+
+ /* kernel_map, VMCOREINFO and maximum CPUs */
+ sz = 2 + CONFIG_NR_CPUS_DEFAULT;
+ if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG))
+ sz += CONFIG_CRASH_MAX_MEMORY_RANGES;
+ sz *= sizeof(Elf64_Phdr);
+ return sz;
+}
+
/**
* arch_crash_handle_hotplug_event() - Handle hotplug elfcorehdr changes
* @image: a pointer to kexec_crash_image
diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index 6a8a724ac638..bb0e614f2a05 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -335,6 +335,10 @@ struct kimage {
unsigned int preserve_context : 1;
/* If set, we are using file mode kexec syscall */
unsigned int file_mode:1;
+#ifdef CONFIG_CRASH_HOTPLUG
+ /* If set, allow changes to elfcorehdr of kexec_load'd image */
+ unsigned int update_elfcorehdr:1;
+#endif
#ifdef ARCH_HAS_KIMAGE_ARCH
struct kimage_arch arch;
@@ -411,9 +415,9 @@ bool kexec_load_permitted(int kexec_image_type);
/* List of defined/legal kexec flags */
#ifndef CONFIG_KEXEC_JUMP
-#define KEXEC_FLAGS KEXEC_ON_CRASH
+#define KEXEC_FLAGS (KEXEC_ON_CRASH | KEXEC_UPDATE_ELFCOREHDR)
#else
-#define KEXEC_FLAGS (KEXEC_ON_CRASH | KEXEC_PRESERVE_CONTEXT)
+#define KEXEC_FLAGS (KEXEC_ON_CRASH | KEXEC_PRESERVE_CONTEXT | KEXEC_UPDATE_ELFCOREHDR)
#endif
/* List of defined/legal kexec file flags */
@@ -501,6 +505,8 @@ static inline void arch_kexec_pre_free_pages(void *vaddr, unsigned int pages) {
static inline void arch_crash_handle_hotplug_event(struct kimage *image) { }
#endif
+int crash_check_update_elfcorehdr(void);
+
#ifndef crash_hotplug_cpu_support
static inline int crash_hotplug_cpu_support(void) { return 0; }
#endif
@@ -509,6 +515,10 @@ static inline int crash_hotplug_cpu_support(void) { return 0; }
static inline int crash_hotplug_memory_support(void) { return 0; }
#endif
+#ifndef crash_get_elfcorehdr_size
+static inline unsigned int crash_get_elfcorehdr_size(void) { return 0; }
+#endif
+
#else /* !CONFIG_KEXEC_CORE */
struct pt_regs;
struct task_struct;
diff --git a/include/uapi/linux/kexec.h b/include/uapi/linux/kexec.h
index 981016e05cfa..01766dd839b0 100644
--- a/include/uapi/linux/kexec.h
+++ b/include/uapi/linux/kexec.h
@@ -12,6 +12,7 @@
/* kexec flags for different usage scenarios */
#define KEXEC_ON_CRASH 0x00000001
#define KEXEC_PRESERVE_CONTEXT 0x00000002
+#define KEXEC_UPDATE_ELFCOREHDR 0x00000004
#define KEXEC_ARCH_MASK 0xffff0000
/*
diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index 53d211c690a1..fa918176d46d 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -704,6 +704,33 @@ subsys_initcall(crash_save_vmcoreinfo_init);
#ifdef CONFIG_CRASH_HOTPLUG
#undef pr_fmt
#define pr_fmt(fmt) "crash hp: " fmt
+
+/*
+ * This routine utilized when the crash_hotplug sysfs node is read.
+ * It reflects the kernel's ability/permission to update the crash
+ * elfcorehdr directly.
+ */
+int crash_check_update_elfcorehdr(void)
+{
+ int rc = 0;
+
+ /* Obtain lock while reading crash information */
+ if (!kexec_trylock()) {
+ pr_info("kexec_trylock() failed, elfcorehdr may be inaccurate\n");
+ return 0;
+ }
+ if (kexec_crash_image) {
+ if (kexec_crash_image->file_mode)
+ rc = 1;
+ else
+ rc = kexec_crash_image->update_elfcorehdr;
+ }
+ /* Release lock now that update complete */
+ kexec_unlock();
+
+ return rc;
+}
+
/*
* To accurately reflect hot un/plug changes of cpu and memory resources
* (including onling and offlining of those resources), the elfcorehdr
@@ -734,6 +761,10 @@ static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu)
image = kexec_crash_image;
+ /* Check that updating elfcorehdr is permitted */
+ if (!(image->file_mode || image->update_elfcorehdr))
+ goto out;
+
if (hp_action == KEXEC_CRASH_HP_ADD_CPU ||
hp_action == KEXEC_CRASH_HP_REMOVE_CPU)
pr_debug("hp_action %u, cpu %u\n", hp_action, cpu);
diff --git a/kernel/kexec.c b/kernel/kexec.c
index 92d301f98776..107f355eac10 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -129,6 +129,11 @@ static int do_kexec_load(unsigned long entry, unsigned long nr_segments,
if (flags & KEXEC_PRESERVE_CONTEXT)
image->preserve_context = 1;
+#ifdef CONFIG_CRASH_HOTPLUG
+ if (flags & KEXEC_UPDATE_ELFCOREHDR)
+ image->update_elfcorehdr = 1;
+#endif
+
ret = machine_kexec_prepare(image);
if (ret)
goto out;
diff --git a/kernel/ksysfs.c b/kernel/ksysfs.c
index aad7a3bfd846..1d4bc493b2f4 100644
--- a/kernel/ksysfs.c
+++ b/kernel/ksysfs.c
@@ -165,6 +165,18 @@ static ssize_t vmcoreinfo_show(struct kobject *kobj,
}
KERNEL_ATTR_RO(vmcoreinfo);
+#ifdef CONFIG_CRASH_HOTPLUG
+static ssize_t crash_elfcorehdr_size_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ unsigned int sz = crash_get_elfcorehdr_size();
+
+ return sysfs_emit(buf, "%u\n", sz);
+}
+KERNEL_ATTR_RO(crash_elfcorehdr_size);
+
+#endif
+
#endif /* CONFIG_CRASH_CORE */
/* whether file capabilities are enabled */
@@ -255,6 +267,9 @@ static struct attribute * kernel_attrs[] = {
#endif
#ifdef CONFIG_CRASH_CORE
&vmcoreinfo_attr.attr,
+#ifdef CONFIG_CRASH_HOTPLUG
+ &crash_elfcorehdr_size_attr.attr,
+#endif
#endif
#ifndef CONFIG_TINY_RCU
&rcu_expedited_attr.attr,
--
2.31.1