[PATCH v14 00/17] arm64/riscv: Add support for crashkernel CMA reservation

[PATCH v14 00/17] arm64/riscv: Add support for crashkernel CMA reservation

[Jinjie Ruan]

The crash memory allocation, and the exclude of crashk_res, crashk_low_res
and crashk_cma memory are almost identical across different architectures,
This patch set handle them in crash core in a general way, which eliminate
a lot of duplication code.

And add support for crashkernel CMA reservation for arm64 and riscv.

Also add support for arm64 crash hotplug.

This patch set is rebased on v7.1-rc1.

Basic second kernel boot test were performed on QEMU platforms for x86,
ARM64 and RISC-V architectures with the following parameters:

	"cma=256M crashkernel=4G crashkernel=64M,cma"

For first kernel, there will be such log:

	# dmesg | grep crash
	[    0.000000] crashkernel low memory reserved: 0xe8000000 - 0xf0000000 (128 MB)
	[    0.000000] crashkernel reserved: 0x000000023e600000 - 0x000000033e600000 (4096 MB)
	[    0.000000] crashkernel CMA reserved: 64 MB in 1 ranges

	# dmesg | grep cma
	[    0.000000] cma: Reserved 256 MiB at 0x00000000f0000000
	[    0.000000] cma: Reserved 64 MiB at 0x0000000100000000

For second kernel, there will be such log:

	[    0.000000] OF: fdt: Looking for usable-memory-range property...
	[    0.000000] OF: fdt: cap_mem_regions[0]: base=0x000000023e600000, size=0x0000000100000000
	[    0.000000] OF: fdt: cap_mem_regions[1]: base=0x00000000e8000000, size=0x0000000008000000
	[    0.000000] OF: fdt: cap_mem_regions[2]: base=0x0000000100000000, size=0x0000000004000000

Changes in v14:
- Fix image->elf_headers memory leak during retry loop for arm64 as Sashiko
  AI code review pointed out.
- Solve the hotplug notifier arch_crash_handle_hotplug_event() AA
  self-deadlock problem as Sashiko AI code review pointed out.
- Fix the TOCTOU issue in prepare_elf_headers() by get_online_mems().
- -ENOMEM -> -EAGAIN as Breno suggested.
- Add support for arm64 crash hotplug.
- Link to v13: https://lore.kernel.org/all/20260511030454.1730881-1-ruanjinjie@huawei.com/

Changes in v13:
- Rebased on v7.1-rc1.
- Update the commit message.
- Add Reviewed-by.
- Link to v12: https://lore.kernel.org/all/20260402072701.628293-1-ruanjinjie@huawei.com/

Changes in v12:
- Remove the unused "nr_mem_ranges" for x86.
- Add "Fix crashk_low_res not exclude bug" test log.
- Provide a separate patch for each architecture for using
  crash_prepare_headers(), which will make the review more convenient.
- Add Reviewed-by and Tested-by.
- Link to v11: https://lore.kernel.org/all/20260328074013.3589544-1-ruanjinjie@huawei.com/

Changes in v11:
- Avoid silently drop crash memory if the crash kernel is built without
  CONFIG_CMA.
- Remove unnecessary "cmem->nr_ranges = 0" for arch_crash_populate_cmem()
  as we use kvzalloc().
- Provide a separate patch for each architecture to fix the existing
  buffer overflow issue.
- Add Acked-bys for arm64.

Changes in v10:
- Fix crashk_low_res not excluded bug in the existing
  RISC-V code.
- Fix an existing memory leak issue in the existing PowerPC code.
- Fix the ordering issue of adding CMA ranges to
  "linux,usable-memory-range".
- Fix an existing concurrency issue. A Concurrent memory hotplug may occur
  between reading memblock and attempting to fill cmem during kexec_load()
  for almost all existing architectures.
- Link to v9: https://lore.kernel.org/all/20260323072745.2481719-1-ruanjinjie@huawei.com/

Changes in v9:
- Collect Reviewed-by and Acked-by, and prepare for Sashiko AI review.
- Link to v8: https://lore.kernel.org/all/20260302035315.3892241-1-ruanjinjie@huawei.com/

Changes in v8:
- Fix the build issues reported by kernel test robot and Sourabh.
- Link to v7: https://lore.kernel.org/all/20260226130437.1867658-1-ruanjinjie@huawei.com/

Changes in v7:
- Correct the inclusion of CMA-reserved ranges for kdump kernel in of/kexec
  for arm64 and riscv.
- Add Acked-by.
- Link to v6: https://lore.kernel.org/all/20260224085342.387996-1-ruanjinjie@huawei.com/

Changes in v6:
- Update the crash core exclude code as Mike suggested.
- Rebased on v7.0-rc1.
- Add acked-by.
- Link to v5: https://lore.kernel.org/all/20260212101001.343158-1-ruanjinjie@huawei.com/

Jinjie Ruan (16):
  riscv: kexec_file: Fix crashk_low_res not exclude bug
  powerpc/crash: Fix possible memory leak in update_crash_elfcorehdr()
  arm64: kexec: Fix image->elf_headers memory leak during retry loop
  x86/kexec: Fix potential buffer overflow in prepare_elf_headers()
  arm64: kexec_file: Fix potential buffer overflow in
    prepare_elf_headers()
  riscv: kexec_file: Fix potential buffer overflow in
    prepare_elf_headers()
  LoongArch: kexec: Fix potential buffer overflow in
    prepare_elf_headers()
  crash: Add crash_prepare_headers() to exclude crash kernel memory
  arm64: kexec_file: Use crash_prepare_headers() helper to simplify code
  x86/kexec: Use crash_prepare_headers() helper to simplify code
  riscv: kexec_file: Use crash_prepare_headers() helper to simplify code
  LoongArch: kexec: Use crash_prepare_headers() helper to simplify code
  crash: Use crash_exclude_core_ranges() on powerpc
  arm64: kexec: Add support for crashkernel CMA reservation
  riscv: kexec: Add support for crashkernel CMA reservation
  arm64/crash: Add crash hotplug support

Sourabh Jain (1):
  powerpc/crash: sort crash memory ranges before preparing elfcorehdr

 .../admin-guide/kernel-parameters.txt         |  16 +--
 arch/arm64/Kconfig                            |   3 +
 arch/arm64/include/asm/kexec.h                |  14 +-
 arch/arm64/kernel/Makefile                    |   1 +
 arch/arm64/kernel/crash.c                     | 125 ++++++++++++++++++
 arch/arm64/kernel/kexec_image.c               |  22 ++-
 arch/arm64/kernel/machine_kexec_file.c        |  78 ++++++-----
 arch/arm64/mm/init.c                          |   5 +-
 arch/loongarch/kernel/machine_kexec_file.c    |  43 +++---
 arch/powerpc/include/asm/kexec_ranges.h       |   1 -
 arch/powerpc/kexec/crash.c                    |   7 +-
 arch/powerpc/kexec/ranges.c                   | 101 +-------------
 arch/riscv/kernel/machine_kexec_file.c        |  42 +++---
 arch/riscv/mm/init.c                          |   5 +-
 arch/x86/kernel/crash.c                       |  92 ++-----------
 drivers/of/fdt.c                              |   9 +-
 drivers/of/kexec.c                            |   9 ++
 include/linux/crash_core.h                    |  11 ++
 include/linux/crash_reserve.h                 |   4 +-
 kernel/crash_core.c                           | 102 +++++++++++++-
 20 files changed, 392 insertions(+), 298 deletions(-)
 create mode 100644 arch/arm64/kernel/crash.c

-- 
2.34.1

[PATCH v14 01/17] riscv: kexec_file: Fix crashk_low_res not exclude bug

[Jinjie Ruan]

As done in commit 944a45abfabc ("arm64: kdump: Reimplement crashkernel=X")
and commit 4831be702b95 ("arm64/kexec: Fix missing extra range for
crashkres_low.") for arm64, while implementing crashkernel=X,[high,low],
riscv should have excluded the "crashk_low_res" reserved ranges from
the crash kernel memory to prevent them from being exported through
/proc/vmcore, and the exclusion would need an extra crash_mem range.

Just simply tested on qemu with crashkernel=4G with kexec in [1] mentioned
in [2]. And the second kernel can be started normally.

	# dmesg | grep crash
	[    0.000000] crashkernel low memory reserved: 0xf8000000 - 0x100000000 (128 MB)
	[    0.000000] crashkernel reserved: 0x000000017fe00000 - 0x000000027fe00000 (4096 MB)

Cc: Guo Ren <guoren@kernel.org>
Cc: Baoquan He <bhe@redhat.com>
[1]: https://github.com/chenjh005/kexec-tools/tree/build-test-riscv-v2
[2]: https://lore.kernel.org/all/20230726175000.2536220-1-chenjiahao16@huawei.com/
Fixes: 5882e5acf18d ("riscv: kdump: Implement crashkernel=X,[high,low]")
Reviewed-by: Guo Ren <guoren@kernel.org>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 arch/riscv/kernel/machine_kexec_file.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/arch/riscv/kernel/machine_kexec_file.c b/arch/riscv/kernel/machine_kexec_file.c
index 54e2d9552e93..3f7766057cac 100644
--- a/arch/riscv/kernel/machine_kexec_file.c
+++ b/arch/riscv/kernel/machine_kexec_file.c
@@ -61,7 +61,7 @@ static int prepare_elf_headers(void **addr, unsigned long *sz)
 	unsigned int nr_ranges;
 	int ret;
 
-	nr_ranges = 1; /* For exclusion of crashkernel region */
+	nr_ranges = 2; /* For exclusion of crashkernel region */
 	walk_system_ram_res(0, -1, &nr_ranges, get_nr_ram_ranges_callback);
 
 	cmem = kmalloc_flex(*cmem, ranges, nr_ranges);
@@ -76,8 +76,16 @@ static int prepare_elf_headers(void **addr, unsigned long *sz)
 
 	/* Exclude crashkernel region */
 	ret = crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end);
-	if (!ret)
-		ret = crash_prepare_elf64_headers(cmem, true, addr, sz);
+	if (ret)
+		goto out;
+
+	if (crashk_low_res.end) {
+		ret = crash_exclude_mem_range(cmem, crashk_low_res.start, crashk_low_res.end);
+		if (ret)
+			goto out;
+	}
+
+	ret = crash_prepare_elf64_headers(cmem, true, addr, sz);
 
 out:
 	kfree(cmem);
-- 
2.34.1

[PATCH v14 02/17] powerpc/crash: Fix possible memory leak in update_crash_elfcorehdr()

[Jinjie Ruan]

In get_crash_memory_ranges(), if crash_exclude_mem_range() failed
after realloc_mem_ranges() has successfully allocated the cmem
memory, it just returns an error but leaves cmem pointing to
the allocated memory, nor is it freed in the caller
update_crash_elfcorehdr(), which cause a memory leak, goto out
to free the cmem.

Cc: Sourabh Jain <sourabhjain@linux.ibm.com>
Cc: Hari Bathini <hbathini@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Fixes: 849599b702ef ("powerpc/crash: add crash memory hotplug support")
Reviewed-by: Sourabh Jain <sourabhjain@linux.ibm.com>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 arch/powerpc/kexec/crash.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/kexec/crash.c b/arch/powerpc/kexec/crash.c
index e6539f213b3d..a520f851c3a6 100644
--- a/arch/powerpc/kexec/crash.c
+++ b/arch/powerpc/kexec/crash.c
@@ -502,7 +502,7 @@ static void update_crash_elfcorehdr(struct kimage *image, struct memory_notify *
 	ret = get_crash_memory_ranges(&cmem);
 	if (ret) {
 		pr_err("Failed to get crash mem range\n");
-		return;
+		goto out;
 	}
 
 	/*
-- 
2.34.1

[PATCH v14 03/17] powerpc/crash: sort crash memory ranges before preparing elfcorehdr

[Jinjie Ruan]

From: Sourabh Jain <sourabhjain@linux.ibm.com>

During a memory hot-remove event, the elfcorehdr is rebuilt to exclude
the removed memory. While updating the crash memory ranges for this
operation, the crash memory ranges array can become unsorted. This
happens because remove_mem_range() may split a memory range into two
parts and append the higher-address part as a separate range at the end
of the array.

So far, no issues have been observed due to the unsorted crash memory
ranges. However, this could lead to problems once crash memory range
removal is handled by generic code, as introduced in the upcoming
patches in this series.

Currently, powerpc uses a platform-specific function,
remove_mem_range(), to exclude hot-removed memory from the crash memory
ranges. This function performs the same task as the generic
crash_exclude_mem_range() in crash_core.c. The generic helper also
ensures that the crash memory ranges remain sorted. So remove the
redundant powerpc-specific implementation and instead call
crash_exclude_mem_range_guarded() (which internally calls
crash_exclude_mem_range()) to exclude the hot-removed memory ranges.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Baoquan he <bhe@redhat.com>
Cc: Jinjie Ruan <ruanjinjie@huawei.com>
Cc: Hari Bathini <hbathini@linux.ibm.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Mahesh Salgaonkar <mahesh@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Cc: Shivang Upadhyay <shivangu@linux.ibm.com>
Cc: linux-kernel@vger.kernel.org
Acked-by: Baoquan He <bhe@redhat.com>
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 arch/powerpc/include/asm/kexec_ranges.h |  4 +-
 arch/powerpc/kexec/crash.c              |  5 +-
 arch/powerpc/kexec/ranges.c             | 87 +------------------------
 3 files changed, 7 insertions(+), 89 deletions(-)

diff --git a/arch/powerpc/include/asm/kexec_ranges.h b/arch/powerpc/include/asm/kexec_ranges.h
index 14055896cbcb..ad95e3792d10 100644
--- a/arch/powerpc/include/asm/kexec_ranges.h
+++ b/arch/powerpc/include/asm/kexec_ranges.h
@@ -7,7 +7,9 @@
 void sort_memory_ranges(struct crash_mem *mrngs, bool merge);
 struct crash_mem *realloc_mem_ranges(struct crash_mem **mem_ranges);
 int add_mem_range(struct crash_mem **mem_ranges, u64 base, u64 size);
-int remove_mem_range(struct crash_mem **mem_ranges, u64 base, u64 size);
+int crash_exclude_mem_range_guarded(struct crash_mem **mem_ranges,
+				    unsigned long long mstart,
+				    unsigned long long mend);
 int get_exclude_memory_ranges(struct crash_mem **mem_ranges);
 int get_reserved_memory_ranges(struct crash_mem **mem_ranges);
 int get_crash_memory_ranges(struct crash_mem **mem_ranges);
diff --git a/arch/powerpc/kexec/crash.c b/arch/powerpc/kexec/crash.c
index a520f851c3a6..d634db67becc 100644
--- a/arch/powerpc/kexec/crash.c
+++ b/arch/powerpc/kexec/crash.c
@@ -493,7 +493,7 @@ static void update_crash_elfcorehdr(struct kimage *image, struct memory_notify *
 	struct crash_mem *cmem = NULL;
 	struct kexec_segment *ksegment;
 	void *ptr, *mem, *elfbuf = NULL;
-	unsigned long elfsz, memsz, base_addr, size;
+	unsigned long elfsz, memsz, base_addr, size, end;
 
 	ksegment = &image->segment[image->elfcorehdr_index];
 	mem = (void *) ksegment->mem;
@@ -512,7 +512,8 @@ static void update_crash_elfcorehdr(struct kimage *image, struct memory_notify *
 	if (image->hp_action == KEXEC_CRASH_HP_REMOVE_MEMORY) {
 		base_addr = PFN_PHYS(mn->start_pfn);
 		size = mn->nr_pages * PAGE_SIZE;
-		ret = remove_mem_range(&cmem, base_addr, size);
+		end = base_addr + size - 1;
+		ret = crash_exclude_mem_range_guarded(&cmem, base_addr, end);
 		if (ret) {
 			pr_err("Failed to remove hot-unplugged memory from crash memory ranges\n");
 			goto out;
diff --git a/arch/powerpc/kexec/ranges.c b/arch/powerpc/kexec/ranges.c
index 867135560e5c..6c58bcc3e130 100644
--- a/arch/powerpc/kexec/ranges.c
+++ b/arch/powerpc/kexec/ranges.c
@@ -553,7 +553,7 @@ int get_usable_memory_ranges(struct crash_mem **mem_ranges)
 #endif /* CONFIG_KEXEC_FILE */
 
 #ifdef CONFIG_CRASH_DUMP
-static int crash_exclude_mem_range_guarded(struct crash_mem **mem_ranges,
+int crash_exclude_mem_range_guarded(struct crash_mem **mem_ranges,
 					   unsigned long long mstart,
 					   unsigned long long mend)
 {
@@ -641,89 +641,4 @@ int get_crash_memory_ranges(struct crash_mem **mem_ranges)
 		pr_err("Failed to setup crash memory ranges\n");
 	return ret;
 }
-
-/**
- * remove_mem_range - Removes the given memory range from the range list.
- * @mem_ranges:    Range list to remove the memory range to.
- * @base:          Base address of the range to remove.
- * @size:          Size of the memory range to remove.
- *
- * (Re)allocates memory, if needed.
- *
- * Returns 0 on success, negative errno on error.
- */
-int remove_mem_range(struct crash_mem **mem_ranges, u64 base, u64 size)
-{
-	u64 end;
-	int ret = 0;
-	unsigned int i;
-	u64 mstart, mend;
-	struct crash_mem *mem_rngs = *mem_ranges;
-
-	if (!size)
-		return 0;
-
-	/*
-	 * Memory range are stored as start and end address, use
-	 * the same format to do remove operation.
-	 */
-	end = base + size - 1;
-
-	for (i = 0; i < mem_rngs->nr_ranges; i++) {
-		mstart = mem_rngs->ranges[i].start;
-		mend = mem_rngs->ranges[i].end;
-
-		/*
-		 * Memory range to remove is not part of this range entry
-		 * in the memory range list
-		 */
-		if (!(base >= mstart && end <= mend))
-			continue;
-
-		/*
-		 * Memory range to remove is equivalent to this entry in the
-		 * memory range list. Remove the range entry from the list.
-		 */
-		if (base == mstart && end == mend) {
-			for (; i < mem_rngs->nr_ranges - 1; i++) {
-				mem_rngs->ranges[i].start = mem_rngs->ranges[i+1].start;
-				mem_rngs->ranges[i].end = mem_rngs->ranges[i+1].end;
-			}
-			mem_rngs->nr_ranges--;
-			goto out;
-		}
-		/*
-		 * Start address of the memory range to remove and the
-		 * current memory range entry in the list is same. Just
-		 * move the start address of the current memory range
-		 * entry in the list to end + 1.
-		 */
-		else if (base == mstart) {
-			mem_rngs->ranges[i].start = end + 1;
-			goto out;
-		}
-		/*
-		 * End address of the memory range to remove and the
-		 * current memory range entry in the list is same.
-		 * Just move the end address of the current memory
-		 * range entry in the list to base - 1.
-		 */
-		else if (end == mend)  {
-			mem_rngs->ranges[i].end = base - 1;
-			goto out;
-		}
-		/*
-		 * Memory range to remove is not at the edge of current
-		 * memory range entry. Split the current memory entry into
-		 * two half.
-		 */
-		else {
-			size = mem_rngs->ranges[i].end - end + 1;
-			mem_rngs->ranges[i].end = base - 1;
-			ret = add_mem_range(mem_ranges, end + 1, size);
-		}
-	}
-out:
-	return ret;
-}
 #endif /* CONFIG_CRASH_DUMP */
-- 
2.34.1

[PATCH v14 04/17] arm64: kexec: Fix image->elf_headers memory leak during retry loop

[Jinjie Ruan]

Sashiko AI code review pointed out a potential memory leak of
image->elf_headers when load_other_segments() fails on error paths.

In the arm64 kexec_file file-load path, kexec_image.c runs a retry loop
calling kexec_add_buffer() to find a suitable location for the kernel
segment. On each iteration, load_other_segments() is invoked to allocate
and populate alternative segments such as initrd, DTB, and ELF headers.

However, if a placement or allocation failure occurs later in
load_other_segments() (e.g., when adding initrd or dtb), the execution
jumps to the out_err label. While this path restores image->nr_segments
via orig_segments, it returns an error back to the caller without freeing
the previously allocated image->elf_headers vmalloc buffer.

As a result, the retry loop in image_load() unconditionally allocates
new ELF headers on the next iteration and overwrites image->elf_headers,
permanently leaking the memory blocks allocated in previous iterations.

To fix this, decouple the ELF header allocation from the target-seeking
retry loop. Since the contents and size of ELF headers only depend on
the host memory layout and do not change with the kernel's physical
placement, move prepare_elf_headers() completely outside and prior to
the while retry loop in image_load().

Concurrently, remove the prepare_elf_headers() call from inside
load_other_segments() and have it directly reuse the single, pre-allocated
image->elf_headers. Also, ensure that image->nr_segments is explicitly
rolled back to kernel_segment_number on retry failures to safely discard
stale segment tracking state.

This optimization eliminates redundant memory allocation/deallocation
overhead during kexec placement retries and eradicates the Use-After-Free
and memory leak risk.

Fixes: 108aa503657e ("arm64: kexec_file: try more regions if loading segments fails")
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 arch/arm64/include/asm/kexec.h         |  3 ++-
 arch/arm64/kernel/kexec_image.c        | 22 ++++++++++++++++++++--
 arch/arm64/kernel/machine_kexec_file.c | 16 +++-------------
 3 files changed, 25 insertions(+), 16 deletions(-)

diff --git a/arch/arm64/include/asm/kexec.h b/arch/arm64/include/asm/kexec.h
index 892e5bebda95..cc2f36b1b0d4 100644
--- a/arch/arm64/include/asm/kexec.h
+++ b/arch/arm64/include/asm/kexec.h
@@ -127,7 +127,8 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image);
 extern int load_other_segments(struct kimage *image,
 		unsigned long kernel_load_addr, unsigned long kernel_size,
 		char *initrd, unsigned long initrd_len,
-		char *cmdline);
+		char *cmdline, void *headers, unsigned long headers_size);
+extern int prepare_elf_headers(void **addr, unsigned long *sz);
 #endif
 
 #endif /* __ASSEMBLER__ */
diff --git a/arch/arm64/kernel/kexec_image.c b/arch/arm64/kernel/kexec_image.c
index b70f4df15a1a..79efeaeb71e9 100644
--- a/arch/arm64/kernel/kexec_image.c
+++ b/arch/arm64/kernel/kexec_image.c
@@ -44,6 +44,11 @@ static void *image_load(struct kimage *image,
 	struct kexec_buf kbuf = {};
 	unsigned long text_offset, kernel_segment_number;
 	struct kexec_segment *kernel_segment;
+#ifdef CONFIG_CRASH_DUMP
+	/* load elf core header */
+	unsigned long headers_sz;
+	void *headers;
+#endif
 	int ret;
 
 	/*
@@ -89,6 +94,18 @@ static void *image_load(struct kimage *image,
 
 	kernel_segment_number = image->nr_segments;
 
+#ifdef CONFIG_CRASH_DUMP
+	if (image->type == KEXEC_TYPE_CRASH) {
+		ret = prepare_elf_headers(&headers, &headers_sz);
+		if (ret) {
+			pr_err("Preparing elf core header failed\n");
+			return ERR_PTR(ret);
+		}
+		image->elf_headers = headers;
+		image->elf_headers_sz = headers_sz;
+	}
+#endif
+
 	/*
 	 * The location of the kernel segment may make it impossible to satisfy
 	 * the other segment requirements, so we try repeatedly to find a
@@ -99,7 +116,8 @@ static void *image_load(struct kimage *image,
 		kernel_segment = &image->segment[kernel_segment_number];
 		ret = load_other_segments(image, kernel_segment->mem,
 					  kernel_segment->memsz, initrd,
-					  initrd_len, cmdline);
+					  initrd_len, cmdline,
+					  headers, headers_sz);
 		if (!ret)
 			break;
 
@@ -107,7 +125,7 @@ static void *image_load(struct kimage *image,
 		 * We couldn't find space for the other segments; erase the
 		 * kernel segment and try the next available hole.
 		 */
-		image->nr_segments -= 1;
+		image->nr_segments = kernel_segment_number;
 		kbuf.buf_min = kernel_segment->mem + kernel_segment->memsz;
 		kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
 	}
diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c
index e31fabed378a..daf81a873bbd 100644
--- a/arch/arm64/kernel/machine_kexec_file.c
+++ b/arch/arm64/kernel/machine_kexec_file.c
@@ -40,7 +40,7 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image)
 }
 
 #ifdef CONFIG_CRASH_DUMP
-static int prepare_elf_headers(void **addr, unsigned long *sz)
+int prepare_elf_headers(void **addr, unsigned long *sz)
 {
 	struct crash_mem *cmem;
 	unsigned int nr_ranges;
@@ -92,7 +92,8 @@ int load_other_segments(struct kimage *image,
 			unsigned long kernel_load_addr,
 			unsigned long kernel_size,
 			char *initrd, unsigned long initrd_len,
-			char *cmdline)
+			char *cmdline, void *headers,
+			unsigned long headers_sz)
 {
 	struct kexec_buf kbuf = {};
 	void *dtb = NULL;
@@ -105,16 +106,7 @@ int load_other_segments(struct kimage *image,
 	kbuf.buf_min = kernel_load_addr + kernel_size;
 
 #ifdef CONFIG_CRASH_DUMP
-	/* load elf core header */
-	void *headers;
-	unsigned long headers_sz;
 	if (image->type == KEXEC_TYPE_CRASH) {
-		ret = prepare_elf_headers(&headers, &headers_sz);
-		if (ret) {
-			pr_err("Preparing elf core header failed\n");
-			goto out_err;
-		}
-
 		kbuf.buffer = headers;
 		kbuf.bufsz = headers_sz;
 		kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
@@ -128,9 +120,7 @@ int load_other_segments(struct kimage *image,
 			vfree(headers);
 			goto out_err;
 		}
-		image->elf_headers = headers;
 		image->elf_load_addr = kbuf.mem;
-		image->elf_headers_sz = headers_sz;
 
 		kexec_dprintk("Loaded elf core header at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
 			      image->elf_load_addr, kbuf.bufsz, kbuf.memsz);
-- 
2.34.1

[PATCH v14 05/17] x86/kexec: Fix potential buffer overflow in prepare_elf_headers()

[Jinjie Ruan]

Sashiko AI code review pointed out a there is a TOCTOU (Time-of-Check to
Time-of-Use) race condition in prepare_elf_headers() between the initial
pass that counts System RAM ranges and the second pass that populates them.
If a memory hotplug event occurs between these two steps, the number of
memory regions may increase, causing an out-of-bounds write to
the cmem->ranges[] array.

Directly introducing get_online_mems() inside prepare_elf_headers() would
trigger an immediate recursive read-after-write deadlock when invoked by
the runtime hotplug notification path (which already holds the hotplug
write lock).

To eliminate the TOCTOU window safely without deadlock risks, move the
get_online_mems() read lock to the top-level architecture image loaders.
Since these top-level loaders are strictly executed on the initial system
call path and are never re-entered by the runtime hotplug notifier, this
approach physically isolates the locking contexts. The system memory ranges
are forced to be statically frozen during the entire layout generation,
eradicating the buffer overflow vulnerability.

Cc: Thomas Gleixner <tglx@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: stable@vger.kernel.org
Fixes: 8d5f894a3108 ("x86: kexec_file: lift CRASH_MAX_RANGES limit on crash_mem buffer")
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 arch/x86/kernel/crash.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index cd796818d94d..f319308b06ee 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -25,6 +25,7 @@
 #include <linux/slab.h>
 #include <linux/vmalloc.h>
 #include <linux/memblock.h>
+#include <linux/memory_hotplug.h>
 
 #include <asm/bootparam.h>
 #include <asm/processor.h>
@@ -226,6 +227,9 @@ static int prepare_elf64_ram_headers_callback(struct resource *res, void *arg)
 {
 	struct crash_mem *cmem = arg;
 
+	if (WARN_ON_ONCE(cmem->nr_ranges >= cmem->max_nr_ranges))
+		return -EAGAIN;
+
 	cmem->ranges[cmem->nr_ranges].start = res->start;
 	cmem->ranges[cmem->nr_ranges].end = res->end;
 	cmem->nr_ranges++;
@@ -419,10 +423,14 @@ int crash_load_segments(struct kimage *image)
 				  .buf_max = ULONG_MAX, .top_down = false };
 
 	/* Prepare elf headers and add a segment */
+	get_online_mems();
 	ret = prepare_elf_headers(&kbuf.buffer, &kbuf.bufsz, &pnum);
-	if (ret)
+	if (ret) {
+		put_online_mems();
 		return ret;
+	}
 
+	put_online_mems();
 	image->elf_headers	= kbuf.buffer;
 	image->elf_headers_sz	= kbuf.bufsz;
 	kbuf.memsz		= kbuf.bufsz;
-- 
2.34.1

[PATCH v14 06/17] arm64: kexec_file: Fix potential buffer overflow in prepare_elf_headers()

[Jinjie Ruan]

Sashiko AI code review pointed out there is a TOCTOU (Time-of-Check to
Time-of-Use) race condition in prepare_elf_headers() between the initial
pass that counts System RAM ranges and the second pass that populates them.
If a memory hotplug event occurs between these two steps, the number of
memory regions may increase, causing an out-of-bounds write to
the cmem->ranges[] array.

Directly introducing get_online_mems() inside prepare_elf_headers() would
trigger an immediate recursive read-after-write deadlock when invoked by
the runtime hotplug notification path (which already holds the hotplug
write lock).

To eliminate the TOCTOU window safely without deadlock risks, move the
get_online_mems() read lock to the top-level architecture image loaders.
Since these top-level loaders are strictly executed on the initial system
call path and are never re-entered by the runtime hotplug notifier, this
approach physically isolates the locking contexts. The system memory ranges
are forced to be statically frozen during the entire layout generation,
eradicating the buffer overflow vulnerability.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Breno Leitao <leitao@debian.org>
Cc: stable@vger.kernel.org
Fixes: 3751e728cef2 ("arm64: kexec_file: add crash dump support")
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 arch/arm64/kernel/kexec_image.c        | 4 ++++
 arch/arm64/kernel/machine_kexec_file.c | 5 +++++
 2 files changed, 9 insertions(+)

diff --git a/arch/arm64/kernel/kexec_image.c b/arch/arm64/kernel/kexec_image.c
index 79efeaeb71e9..884e446f08e3 100644
--- a/arch/arm64/kernel/kexec_image.c
+++ b/arch/arm64/kernel/kexec_image.c
@@ -12,6 +12,7 @@
 #include <linux/errno.h>
 #include <linux/kernel.h>
 #include <linux/kexec.h>
+#include <linux/memory_hotplug.h>
 #include <linux/pe.h>
 #include <linux/string.h>
 #include <asm/byteorder.h>
@@ -96,11 +97,14 @@ static void *image_load(struct kimage *image,
 
 #ifdef CONFIG_CRASH_DUMP
 	if (image->type == KEXEC_TYPE_CRASH) {
+		get_online_mems();
 		ret = prepare_elf_headers(&headers, &headers_sz);
 		if (ret) {
 			pr_err("Preparing elf core header failed\n");
+			put_online_mems();
 			return ERR_PTR(ret);
 		}
+		put_online_mems();
 		image->elf_headers = headers;
 		image->elf_headers_sz = headers_sz;
 	}
diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c
index daf81a873bbd..c0ace89ded92 100644
--- a/arch/arm64/kernel/machine_kexec_file.c
+++ b/arch/arm64/kernel/machine_kexec_file.c
@@ -59,6 +59,11 @@ int prepare_elf_headers(void **addr, unsigned long *sz)
 	cmem->max_nr_ranges = nr_ranges;
 	cmem->nr_ranges = 0;
 	for_each_mem_range(i, &start, &end) {
+		if (WARN_ON_ONCE(cmem->nr_ranges >= cmem->max_nr_ranges)) {
+			ret = -EAGAIN;
+			goto out;
+		}
+
 		cmem->ranges[cmem->nr_ranges].start = start;
 		cmem->ranges[cmem->nr_ranges].end = end - 1;
 		cmem->nr_ranges++;
-- 
2.34.1

[PATCH v14 07/17] riscv: kexec_file: Fix potential buffer overflow in prepare_elf_headers()

[Jinjie Ruan]

Sashiko AI code review pointed out there is a TOCTOU (Time-of-Check to
Time-of-Use) race condition in prepare_elf_headers() between the initial
pass that counts System RAM ranges and the second pass that populates them.
If a memory hotplug event occurs between these two steps, the number of
memory regions may increase, causing an out-of-bounds write to
the cmem->ranges[] array.

Directly introducing get_online_mems() inside prepare_elf_headers() would
trigger an immediate recursive read-after-write deadlock when invoked by
the runtime hotplug notification path (which already holds the hotplug
write lock).

To eliminate the TOCTOU window safely without deadlock risks, move the
get_online_mems() read lock to the top-level architecture image loaders.
Since these top-level loaders are strictly executed on the initial system
call path and are never re-entered by the runtime hotplug notifier, this
approach physically isolates the locking contexts. The system memory ranges
are forced to be statically frozen during the entire layout generation,
eradicating the buffer overflow vulnerability.

Cc: Paul Walmsley <pjw@kernel.org>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: songshuaishuai@tinylab.org
Cc: bjorn@rivosinc.com
Cc: leitao@debian.org
Fixes: 8acea455fafa ("RISC-V: Support for kexec_file on panic")
Reviewed-by: Guo Ren <guoren@kernel.org>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 arch/riscv/kernel/machine_kexec_file.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/riscv/kernel/machine_kexec_file.c b/arch/riscv/kernel/machine_kexec_file.c
index 3f7766057cac..a88362dfbd89 100644
--- a/arch/riscv/kernel/machine_kexec_file.c
+++ b/arch/riscv/kernel/machine_kexec_file.c
@@ -8,6 +8,7 @@
  */
 #include <linux/kexec.h>
 #include <linux/elf.h>
+#include <linux/memory_hotplug.h>
 #include <linux/slab.h>
 #include <linux/of.h>
 #include <linux/libfdt.h>
@@ -48,6 +49,9 @@ static int prepare_elf64_ram_headers_callback(struct resource *res, void *arg)
 {
 	struct crash_mem *cmem = arg;
 
+	if (WARN_ON_ONCE(cmem->nr_ranges >= cmem->max_nr_ranges))
+		return -EAGAIN;
+
 	cmem->ranges[cmem->nr_ranges].start = res->start;
 	cmem->ranges[cmem->nr_ranges].end = res->end;
 	cmem->nr_ranges++;
@@ -281,12 +285,15 @@ int load_extra_segments(struct kimage *image, unsigned long kernel_start,
 	if (image->type == KEXEC_TYPE_CRASH) {
 		void *headers;
 		unsigned long headers_sz;
+		get_online_mems();
 		ret = prepare_elf_headers(&headers, &headers_sz);
 		if (ret) {
+			put_online_mems();
 			pr_err("Preparing elf core header failed\n");
 			goto out;
 		}
 
+		put_online_mems();
 		kbuf.buffer = headers;
 		kbuf.bufsz = headers_sz;
 		kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
-- 
2.34.1

[PATCH v14 08/17] LoongArch: kexec: Fix potential buffer overflow in prepare_elf_headers()

[Jinjie Ruan]

Sashiko AI code review pointed out there is a TOCTOU (Time-of-Check to
Time-of-Use) race condition in prepare_elf_headers() between the initial
pass that counts System RAM ranges and the second pass that populates them.
If a memory hotplug event occurs between these two steps, the number of
memory regions may increase, causing an out-of-bounds write to
the cmem->ranges[] array.

Directly introducing get_online_mems() inside prepare_elf_headers() would
trigger an immediate recursive read-after-write deadlock when invoked by
the runtime hotplug notification path (which already holds the hotplug
write lock).

To eliminate the TOCTOU window safely without deadlock risks, move the
get_online_mems() read lock to the top-level architecture image loaders.
Since these top-level loaders are strictly executed on the initial system
call path and are never re-entered by the runtime hotplug notifier, this
approach physically isolates the locking contexts. The system memory ranges
are forced to be statically frozen during the entire layout generation,
eradicating the buffer overflow vulnerability.

Cc: Youling Tang <tangyouling@kylinos.cn>
Cc: Huacai Chen <chenhuacai@loongson.cn>
Cc: WANG Xuerui <kernel@xen0n.name>
Cc: stable@vger.kernel.org
Fixes: 1bcca8620a91 ("LoongArch: Add crash dump support for kexec_file")
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 arch/loongarch/kernel/machine_kexec_file.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/loongarch/kernel/machine_kexec_file.c b/arch/loongarch/kernel/machine_kexec_file.c
index 5584b798ba46..2a1a6124f043 100644
--- a/arch/loongarch/kernel/machine_kexec_file.c
+++ b/arch/loongarch/kernel/machine_kexec_file.c
@@ -14,6 +14,7 @@
 #include <linux/kernel.h>
 #include <linux/kexec.h>
 #include <linux/memblock.h>
+#include <linux/memory_hotplug.h>
 #include <linux/slab.h>
 #include <linux/string.h>
 #include <linux/types.h>
@@ -75,6 +76,11 @@ static int prepare_elf_headers(void **addr, unsigned long *sz)
 	cmem->max_nr_ranges = nr_ranges;
 	cmem->nr_ranges = 0;
 	for_each_mem_range(i, &start, &end) {
+		if (WARN_ON_ONCE(cmem->nr_ranges >= cmem->max_nr_ranges)) {
+			ret = -EAGAIN;
+			goto out;
+		}
+
 		cmem->ranges[cmem->nr_ranges].start = start;
 		cmem->ranges[cmem->nr_ranges].end = end - 1;
 		cmem->nr_ranges++;
@@ -163,12 +169,15 @@ int load_other_segments(struct kimage *image,
 		void *headers;
 		unsigned long headers_sz;
 
+		get_online_mems();
 		ret = prepare_elf_headers(&headers, &headers_sz);
 		if (ret < 0) {
+			put_online_mems();
 			pr_err("Preparing elf core header failed\n");
 			goto out_err;
 		}
 
+		put_online_mems();
 		kbuf.buffer = headers;
 		kbuf.bufsz = headers_sz;
 		kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
-- 
2.34.1

[PATCH v14 09/17] crash: Add crash_prepare_headers() to exclude crash kernel memory

[Jinjie Ruan]

The crash memory alloc, and the exclude of crashk_res, crashk_low_res
and crashk_cma memory are almost identical across different architectures,
handling them in the crash core would eliminate a lot of duplication, so
add crash_prepare_headers() helper to handle them in the common code.

To achieve the above goal, three architecture-specific functions are
introduced:

- arch_get_system_nr_ranges(). Pre-counts the max number of memory ranges.

- arch_crash_populate_cmem(). Collects the memory ranges and fills them
  into cmem.

- arch_crash_exclude_ranges(). Architecture's additional crash memory
  ranges exclusion, defaulting to empty.

Reviewed-by: Sourabh Jain <sourabhjain@linux.ibm.com>
Acked-by: Baoquan He <bhe@redhat.com>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 include/linux/crash_core.h |  7 +++
 kernel/crash_core.c        | 95 ++++++++++++++++++++++++++++++++++++--
 2 files changed, 99 insertions(+), 3 deletions(-)

diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
index c1dee3f971a9..d69c4c7c1f5e 100644
--- a/include/linux/crash_core.h
+++ b/include/linux/crash_core.h
@@ -59,6 +59,10 @@ extern int crash_exclude_mem_range(struct crash_mem *mem,
 				   unsigned long long mend);
 extern int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map,
 				       void **addr, unsigned long *sz);
+extern int crash_prepare_headers(int need_kernel_map, void **addr,
+				 unsigned long *sz, unsigned long *nr_mem_ranges);
+extern int crash_prepare_headers_locked(int need_kernel_map, void **addr,
+					unsigned long *sz, unsigned long *nr_mem_ranges);
 
 struct kimage;
 struct kexec_segment;
@@ -76,6 +80,9 @@ int kexec_should_crash(struct task_struct *p);
 int kexec_crash_loaded(void);
 void crash_save_cpu(struct pt_regs *regs, int cpu);
 extern int kimage_crash_copy_vmcoreinfo(struct kimage *image);
+extern unsigned int arch_get_system_nr_ranges(void);
+extern int arch_crash_populate_cmem(struct crash_mem *cmem);
+extern int arch_crash_exclude_ranges(struct crash_mem *cmem);
 
 #else /* !CONFIG_CRASH_DUMP*/
 struct pt_regs;
diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index 4f21fc3b108b..e84f3b63e79d 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -13,6 +13,7 @@
 #include <linux/sizes.h>
 #include <linux/kexec.h>
 #include <linux/memory.h>
+#include <linux/memory_hotplug.h>
 #include <linux/mm.h>
 #include <linux/cpuhotplug.h>
 #include <linux/memblock.h>
@@ -168,9 +169,6 @@ static inline resource_size_t crash_resource_size(const struct resource *res)
 	return !res->end ? 0 : resource_size(res);
 }
 
-
-
-
 int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map,
 			  void **addr, unsigned long *sz)
 {
@@ -272,6 +270,97 @@ int crash_prepare_elf64_headers(struct crash_mem *mem, int need_kernel_map,
 	return 0;
 }
 
+static struct crash_mem *alloc_cmem(unsigned int nr_ranges)
+{
+	struct crash_mem *cmem;
+
+	cmem = kvzalloc_flex(*cmem, ranges, nr_ranges);
+	if (!cmem)
+		return NULL;
+
+	cmem->max_nr_ranges = nr_ranges;
+	return cmem;
+}
+
+unsigned int __weak arch_get_system_nr_ranges(void) { return 0; }
+int __weak arch_crash_populate_cmem(struct crash_mem *cmem) { return -1; }
+int __weak arch_crash_exclude_ranges(struct crash_mem *cmem) { return 0; }
+
+static int crash_exclude_core_ranges(struct crash_mem *cmem)
+{
+	int ret, i;
+
+	/* Exclude crashkernel region */
+	ret = crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end);
+	if (ret)
+		return ret;
+
+	if (crashk_low_res.end) {
+		ret = crash_exclude_mem_range(cmem, crashk_low_res.start, crashk_low_res.end);
+		if (ret)
+			return ret;
+	}
+
+	for (i = 0; i < crashk_cma_cnt; ++i) {
+		ret = crash_exclude_mem_range(cmem, crashk_cma_ranges[i].start,
+					      crashk_cma_ranges[i].end);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+int crash_prepare_headers(int need_kernel_map, void **addr, unsigned long *sz,
+			  unsigned long *nr_mem_ranges)
+{
+	unsigned int max_nr_ranges;
+	struct crash_mem *cmem;
+	int ret;
+
+	max_nr_ranges = arch_get_system_nr_ranges();
+	if (!max_nr_ranges)
+		return -ENOMEM;
+
+	cmem = alloc_cmem(max_nr_ranges);
+	if (!cmem)
+		return -ENOMEM;
+
+	ret = arch_crash_populate_cmem(cmem);
+	if (ret)
+		goto out;
+
+	ret = crash_exclude_core_ranges(cmem);
+	if (ret)
+		goto out;
+
+	ret = arch_crash_exclude_ranges(cmem);
+	if (ret)
+		goto out;
+
+	/* Return the computed number of memory ranges, for hotplug usage */
+	if (nr_mem_ranges)
+		*nr_mem_ranges = cmem->nr_ranges;
+
+	ret = crash_prepare_elf64_headers(cmem, need_kernel_map, addr, sz);
+
+out:
+	kvfree(cmem);
+	return ret;
+}
+
+int crash_prepare_headers_locked(int need_kernel_map, void **addr, unsigned long *sz,
+				 unsigned long *nr_mem_ranges)
+{
+	int ret;
+
+	get_online_mems();
+	ret = crash_prepare_headers(need_kernel_map, addr, sz, nr_mem_ranges);
+	put_online_mems();
+
+	return ret;
+}
+
 /**
  * crash_exclude_mem_range - exclude a mem range for existing ranges
  * @mem: mem->range contains an array of ranges sorted in ascending order
-- 
2.34.1

[PATCH v14 10/17] arm64: kexec_file: Use crash_prepare_headers() helper to simplify code

[Jinjie Ruan]

Use the newly introduced crash_prepare_headers() function to replace
the existing prepare_elf_headers(), allocate cmem and exclude crash
kernel memory in the crash core, which reduce code duplication.

Only the following two architecture functions need to be implemented:
- arch_get_system_nr_ranges(). Use for_each_mem_range() to traverse
  and pre-count the max number of memory ranges.

- arch_crash_populate_cmem(). Use for_each_mem_range to traverse
  and collect the memory ranges and fills them into cmem.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Sourabh Jain <sourabhjain@linux.ibm.com>
Acked-by: Baoquan He <bhe@redhat.com>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 arch/arm64/kernel/kexec_image.c        |  6 +---
 arch/arm64/kernel/machine_kexec_file.c | 44 ++++++++------------------
 2 files changed, 14 insertions(+), 36 deletions(-)

diff --git a/arch/arm64/kernel/kexec_image.c b/arch/arm64/kernel/kexec_image.c
index 884e446f08e3..770a4c7bf573 100644
--- a/arch/arm64/kernel/kexec_image.c
+++ b/arch/arm64/kernel/kexec_image.c
@@ -12,7 +12,6 @@
 #include <linux/errno.h>
 #include <linux/kernel.h>
 #include <linux/kexec.h>
-#include <linux/memory_hotplug.h>
 #include <linux/pe.h>
 #include <linux/string.h>
 #include <asm/byteorder.h>
@@ -97,14 +96,11 @@ static void *image_load(struct kimage *image,
 
 #ifdef CONFIG_CRASH_DUMP
 	if (image->type == KEXEC_TYPE_CRASH) {
-		get_online_mems();
-		ret = prepare_elf_headers(&headers, &headers_sz);
+		ret = crash_prepare_headers_locked(true, &headers, &headers_sz, NULL);
 		if (ret) {
 			pr_err("Preparing elf core header failed\n");
-			put_online_mems();
 			return ERR_PTR(ret);
 		}
-		put_online_mems();
 		image->elf_headers = headers;
 		image->elf_headers_sz = headers_sz;
 	}
diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c
index c0ace89ded92..66fbfbaec1c6 100644
--- a/arch/arm64/kernel/machine_kexec_file.c
+++ b/arch/arm64/kernel/machine_kexec_file.c
@@ -40,51 +40,33 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image)
 }
 
 #ifdef CONFIG_CRASH_DUMP
-int prepare_elf_headers(void **addr, unsigned long *sz)
+unsigned int arch_get_system_nr_ranges(void)
 {
-	struct crash_mem *cmem;
-	unsigned int nr_ranges;
-	int ret;
-	u64 i;
+	unsigned int nr_ranges = 2; /* for exclusion of crashkernel region */
 	phys_addr_t start, end;
+	u64 i;
 
-	nr_ranges = 2; /* for exclusion of crashkernel region */
 	for_each_mem_range(i, &start, &end)
 		nr_ranges++;
 
-	cmem = kmalloc_flex(*cmem, ranges, nr_ranges);
-	if (!cmem)
-		return -ENOMEM;
+	return nr_ranges;
+}
+
+int arch_crash_populate_cmem(struct crash_mem *cmem)
+{
+	phys_addr_t start, end;
+	u64 i;
 
-	cmem->max_nr_ranges = nr_ranges;
-	cmem->nr_ranges = 0;
 	for_each_mem_range(i, &start, &end) {
-		if (WARN_ON_ONCE(cmem->nr_ranges >= cmem->max_nr_ranges)) {
-			ret = -EAGAIN;
-			goto out;
-		}
+		if (WARN_ON_ONCE(cmem->nr_ranges >= cmem->max_nr_ranges))
+			return -EAGAIN;
 
 		cmem->ranges[cmem->nr_ranges].start = start;
 		cmem->ranges[cmem->nr_ranges].end = end - 1;
 		cmem->nr_ranges++;
 	}
 
-	/* Exclude crashkernel region */
-	ret = crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end);
-	if (ret)
-		goto out;
-
-	if (crashk_low_res.end) {
-		ret = crash_exclude_mem_range(cmem, crashk_low_res.start, crashk_low_res.end);
-		if (ret)
-			goto out;
-	}
-
-	ret = crash_prepare_elf64_headers(cmem, true, addr, sz);
-
-out:
-	kfree(cmem);
-	return ret;
+	return 0;
 }
 #endif
 
-- 
2.34.1

[PATCH v14 11/17] x86/kexec: Use crash_prepare_headers() helper to simplify code

[Jinjie Ruan]

Use the newly introduced crash_prepare_headers() function to replace
the existing prepare_elf_headers(), allocate cmem and exclude crash kernel
memory in the crash core, which reduce code duplication.

Only the following three architecture functions need to be implemented:
- arch_get_system_nr_ranges(). Call get_nr_ram_ranges_callback()
  to pre-count the max number of memory ranges.

- arch_crash_populate_cmem(). Use prepare_elf64_ram_headers_callback()
  to collect the memory ranges and fills them into cmem.

- arch_crash_exclude_ranges(). Exclude the low 1M for x86.

By the way, remove the unused "nr_mem_ranges" in
arch_crash_handle_hotplug_event().

Cc: Thomas Gleixner <tglx@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Sourabh Jain <sourabhjain@linux.ibm.com>
Acked-by: Baoquan He <bhe@redhat.com>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 arch/x86/kernel/crash.c | 96 ++++++-----------------------------------
 1 file changed, 12 insertions(+), 84 deletions(-)

diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index f319308b06ee..26f140dff348 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -25,7 +25,6 @@
 #include <linux/slab.h>
 #include <linux/vmalloc.h>
 #include <linux/memblock.h>
-#include <linux/memory_hotplug.h>
 
 #include <asm/bootparam.h>
 #include <asm/processor.h>
@@ -154,16 +153,8 @@ static int get_nr_ram_ranges_callback(struct resource *res, void *arg)
 	return 0;
 }
 
-/* Gather all the required information to prepare elf headers for ram regions */
-static struct crash_mem *fill_up_crash_elf_data(void)
+unsigned int arch_get_system_nr_ranges(void)
 {
-	unsigned int nr_ranges = 0;
-	struct crash_mem *cmem;
-
-	walk_system_ram_res(0, -1, &nr_ranges, get_nr_ram_ranges_callback);
-	if (!nr_ranges)
-		return NULL;
-
 	/*
 	 * Exclusion of crash region, crashk_low_res and/or crashk_cma_ranges
 	 * may cause range splits. So add extra slots here.
@@ -178,49 +169,16 @@ static struct crash_mem *fill_up_crash_elf_data(void)
 	 * But in order to lest the low 1M could be changed in the future,
 	 * (e.g. [start, 1M]), add a extra slot.
 	 */
-	nr_ranges += 3 + crashk_cma_cnt;
-	cmem = vzalloc(struct_size(cmem, ranges, nr_ranges));
-	if (!cmem)
-		return NULL;
-
-	cmem->max_nr_ranges = nr_ranges;
+	unsigned int nr_ranges = 3 + crashk_cma_cnt;
 
-	return cmem;
+	walk_system_ram_res(0, -1, &nr_ranges, get_nr_ram_ranges_callback);
+	return nr_ranges;
 }
 
-/*
- * Look for any unwanted ranges between mstart, mend and remove them. This
- * might lead to split and split ranges are put in cmem->ranges[] array
- */
-static int elf_header_exclude_ranges(struct crash_mem *cmem)
+int arch_crash_exclude_ranges(struct crash_mem *cmem)
 {
-	int ret = 0;
-	int i;
-
 	/* Exclude the low 1M because it is always reserved */
-	ret = crash_exclude_mem_range(cmem, 0, SZ_1M - 1);
-	if (ret)
-		return ret;
-
-	/* Exclude crashkernel region */
-	ret = crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end);
-	if (ret)
-		return ret;
-
-	if (crashk_low_res.end)
-		ret = crash_exclude_mem_range(cmem, crashk_low_res.start,
-					      crashk_low_res.end);
-	if (ret)
-		return ret;
-
-	for (i = 0; i < crashk_cma_cnt; ++i) {
-		ret = crash_exclude_mem_range(cmem, crashk_cma_ranges[i].start,
-					      crashk_cma_ranges[i].end);
-		if (ret)
-			return ret;
-	}
-
-	return 0;
+	return crash_exclude_mem_range(cmem, 0, SZ_1M - 1);
 }
 
 static int prepare_elf64_ram_headers_callback(struct resource *res, void *arg)
@@ -237,35 +195,9 @@ static int prepare_elf64_ram_headers_callback(struct resource *res, void *arg)
 	return 0;
 }
 
-/* Prepare elf headers. Return addr and size */
-static int prepare_elf_headers(void **addr, unsigned long *sz,
-			       unsigned long *nr_mem_ranges)
+int arch_crash_populate_cmem(struct crash_mem *cmem)
 {
-	struct crash_mem *cmem;
-	int ret;
-
-	cmem = fill_up_crash_elf_data();
-	if (!cmem)
-		return -ENOMEM;
-
-	ret = walk_system_ram_res(0, -1, cmem, prepare_elf64_ram_headers_callback);
-	if (ret)
-		goto out;
-
-	/* Exclude unwanted mem ranges */
-	ret = elf_header_exclude_ranges(cmem);
-	if (ret)
-		goto out;
-
-	/* Return the computed number of memory ranges, for hotplug usage */
-	*nr_mem_ranges = cmem->nr_ranges;
-
-	/* By default prepare 64bit headers */
-	ret = crash_prepare_elf64_headers(cmem, IS_ENABLED(CONFIG_X86_64), addr, sz);
-
-out:
-	vfree(cmem);
-	return ret;
+	return walk_system_ram_res(0, -1, cmem, prepare_elf64_ram_headers_callback);
 }
 #endif
 
@@ -423,14 +355,11 @@ int crash_load_segments(struct kimage *image)
 				  .buf_max = ULONG_MAX, .top_down = false };
 
 	/* Prepare elf headers and add a segment */
-	get_online_mems();
-	ret = prepare_elf_headers(&kbuf.buffer, &kbuf.bufsz, &pnum);
-	if (ret) {
-		put_online_mems();
+	ret = crash_prepare_headers_locked(IS_ENABLED(CONFIG_X86_64), &kbuf.buffer,
+					   &kbuf.bufsz, &pnum);
+	if (ret)
 		return ret;
-	}
 
-	put_online_mems();
 	image->elf_headers	= kbuf.buffer;
 	image->elf_headers_sz	= kbuf.bufsz;
 	kbuf.memsz		= kbuf.bufsz;
@@ -520,7 +449,6 @@ unsigned int arch_crash_get_elfcorehdr_size(void)
 void arch_crash_handle_hotplug_event(struct kimage *image, void *arg)
 {
 	void *elfbuf = NULL, *old_elfcorehdr;
-	unsigned long nr_mem_ranges;
 	unsigned long mem, memsz;
 	unsigned long elfsz = 0;
 
@@ -538,7 +466,7 @@ void arch_crash_handle_hotplug_event(struct kimage *image, void *arg)
 	 * Create the new elfcorehdr reflecting the changes to CPU and/or
 	 * memory resources.
 	 */
-	if (prepare_elf_headers(&elfbuf, &elfsz, &nr_mem_ranges)) {
+	if (crash_prepare_headers(IS_ENABLED(CONFIG_X86_64), &elfbuf, &elfsz, NULL)) {
 		pr_err("unable to create new elfcorehdr");
 		goto out;
 	}
-- 
2.34.1

[PATCH v14 12/17] riscv: kexec_file: Use crash_prepare_headers() helper to simplify code

[Jinjie Ruan]

Use the newly introduced crash_prepare_headers() function to replace
the existing prepare_elf_headers(), allocate cmem and exclude crash kernel
memory in the crash core, which reduce code duplication.

Only the following two architecture functions need to be implemented:
- arch_get_system_nr_ranges(). Call get_nr_ram_ranges_callback()
  to pre-counts the max number of memory ranges.

- arch_crash_populate_cmem(). Use prepare_elf64_ram_headers_callback()
  to collects the memory ranges and fills them into cmem.

Cc: Paul Walmsley <pjw@kernel.org>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: Guo Ren <guoren@kernel.org>
Reviewed-by: Sourabh Jain <sourabhjain@linux.ibm.com>
Acked-by: Baoquan He <bhe@redhat.com>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 arch/riscv/kernel/machine_kexec_file.c | 51 ++++++--------------------
 1 file changed, 12 insertions(+), 39 deletions(-)

diff --git a/arch/riscv/kernel/machine_kexec_file.c b/arch/riscv/kernel/machine_kexec_file.c
index a88362dfbd89..d2bb61a8b6b6 100644
--- a/arch/riscv/kernel/machine_kexec_file.c
+++ b/arch/riscv/kernel/machine_kexec_file.c
@@ -8,7 +8,6 @@
  */
 #include <linux/kexec.h>
 #include <linux/elf.h>
-#include <linux/memory_hotplug.h>
 #include <linux/slab.h>
 #include <linux/of.h>
 #include <linux/libfdt.h>
@@ -45,6 +44,15 @@ static int get_nr_ram_ranges_callback(struct resource *res, void *arg)
 	return 0;
 }
 
+unsigned int arch_get_system_nr_ranges(void)
+{
+	unsigned int nr_ranges = 2; /* For exclusion of crashkernel region */
+
+	walk_system_ram_res(0, -1, &nr_ranges, get_nr_ram_ranges_callback);
+
+	return nr_ranges;
+}
+
 static int prepare_elf64_ram_headers_callback(struct resource *res, void *arg)
 {
 	struct crash_mem *cmem = arg;
@@ -59,41 +67,9 @@ static int prepare_elf64_ram_headers_callback(struct resource *res, void *arg)
 	return 0;
 }
 
-static int prepare_elf_headers(void **addr, unsigned long *sz)
+int arch_crash_populate_cmem(struct crash_mem *cmem)
 {
-	struct crash_mem *cmem;
-	unsigned int nr_ranges;
-	int ret;
-
-	nr_ranges = 2; /* For exclusion of crashkernel region */
-	walk_system_ram_res(0, -1, &nr_ranges, get_nr_ram_ranges_callback);
-
-	cmem = kmalloc_flex(*cmem, ranges, nr_ranges);
-	if (!cmem)
-		return -ENOMEM;
-
-	cmem->max_nr_ranges = nr_ranges;
-	cmem->nr_ranges = 0;
-	ret = walk_system_ram_res(0, -1, cmem, prepare_elf64_ram_headers_callback);
-	if (ret)
-		goto out;
-
-	/* Exclude crashkernel region */
-	ret = crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end);
-	if (ret)
-		goto out;
-
-	if (crashk_low_res.end) {
-		ret = crash_exclude_mem_range(cmem, crashk_low_res.start, crashk_low_res.end);
-		if (ret)
-			goto out;
-	}
-
-	ret = crash_prepare_elf64_headers(cmem, true, addr, sz);
-
-out:
-	kfree(cmem);
-	return ret;
+	return walk_system_ram_res(0, -1, cmem, prepare_elf64_ram_headers_callback);
 }
 
 static char *setup_kdump_cmdline(struct kimage *image, char *cmdline,
@@ -285,15 +261,12 @@ int load_extra_segments(struct kimage *image, unsigned long kernel_start,
 	if (image->type == KEXEC_TYPE_CRASH) {
 		void *headers;
 		unsigned long headers_sz;
-		get_online_mems();
-		ret = prepare_elf_headers(&headers, &headers_sz);
+		ret = crash_prepare_headers_locked(true, &headers, &headers_sz, NULL);
 		if (ret) {
-			put_online_mems();
 			pr_err("Preparing elf core header failed\n");
 			goto out;
 		}
 
-		put_online_mems();
 		kbuf.buffer = headers;
 		kbuf.bufsz = headers_sz;
 		kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
-- 
2.34.1

[PATCH v14 13/17] LoongArch: kexec: Use crash_prepare_headers() helper to simplify code

[Jinjie Ruan]

Use the newly introduced crash_prepare_headers() function to replace
the existing prepare_elf_headers(), allocate cmem and exclude crash kernel
memory in the crash core, which reduce code duplication.

Only the following two architecture functions need to be implemented:
- arch_get_system_nr_ranges(). Use for_each_mem_range to traverse
  and pre-count the max number of memory ranges.

- arch_crash_populate_cmem(). Use for_each_mem_range to traverse
  and collect the memory ranges and fills them into cmem.

Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: WANG Xuerui <kernel@xen0n.name>
Cc: Youling Tang <tangyouling@kylinos.cn>
Cc: Baoquan He <bhe@redhat.com>
Reviewed-by: Sourabh Jain <sourabhjain@linux.ibm.com>
Acked-by: Baoquan He <bhe@redhat.com>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 arch/loongarch/kernel/machine_kexec_file.c | 50 ++++++----------------
 1 file changed, 14 insertions(+), 36 deletions(-)

diff --git a/arch/loongarch/kernel/machine_kexec_file.c b/arch/loongarch/kernel/machine_kexec_file.c
index 2a1a6124f043..a845fbe8883d 100644
--- a/arch/loongarch/kernel/machine_kexec_file.c
+++ b/arch/loongarch/kernel/machine_kexec_file.c
@@ -14,7 +14,6 @@
 #include <linux/kernel.h>
 #include <linux/kexec.h>
 #include <linux/memblock.h>
-#include <linux/memory_hotplug.h>
 #include <linux/slab.h>
 #include <linux/string.h>
 #include <linux/types.h>
@@ -57,51 +56,33 @@ static void cmdline_add_initrd(struct kimage *image, unsigned long *cmdline_tmpl
 }
 
 #ifdef CONFIG_CRASH_DUMP
-
-static int prepare_elf_headers(void **addr, unsigned long *sz)
+unsigned int arch_get_system_nr_ranges(void)
 {
-	int ret, nr_ranges;
-	uint64_t i;
+	int nr_ranges = 2; /* for exclusion of crashkernel region */
 	phys_addr_t start, end;
-	struct crash_mem *cmem;
+	uint64_t i;
 
-	nr_ranges = 2; /* for exclusion of crashkernel region */
 	for_each_mem_range(i, &start, &end)
 		nr_ranges++;
 
-	cmem = kmalloc_flex(*cmem, ranges, nr_ranges);
-	if (!cmem)
-		return -ENOMEM;
+	return nr_ranges;
+}
+
+int arch_crash_populate_cmem(struct crash_mem *cmem)
+{
+	phys_addr_t start, end;
+	uint64_t i;
 
-	cmem->max_nr_ranges = nr_ranges;
-	cmem->nr_ranges = 0;
 	for_each_mem_range(i, &start, &end) {
-		if (WARN_ON_ONCE(cmem->nr_ranges >= cmem->max_nr_ranges)) {
-			ret = -EAGAIN;
-			goto out;
-		}
+		if (WARN_ON_ONCE(cmem->nr_ranges >= cmem->max_nr_ranges))
+			return -EAGAIN;
 
 		cmem->ranges[cmem->nr_ranges].start = start;
 		cmem->ranges[cmem->nr_ranges].end = end - 1;
 		cmem->nr_ranges++;
 	}
 
-	/* Exclude crashkernel region */
-	ret = crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end);
-	if (ret < 0)
-		goto out;
-
-	if (crashk_low_res.end) {
-		ret = crash_exclude_mem_range(cmem, crashk_low_res.start, crashk_low_res.end);
-		if (ret < 0)
-			goto out;
-	}
-
-	ret = crash_prepare_elf64_headers(cmem, true, addr, sz);
-
-out:
-	kfree(cmem);
-	return ret;
+	return 0;
 }
 
 /*
@@ -169,15 +150,12 @@ int load_other_segments(struct kimage *image,
 		void *headers;
 		unsigned long headers_sz;
 
-		get_online_mems();
-		ret = prepare_elf_headers(&headers, &headers_sz);
+		ret = crash_prepare_headers_locked(true, &headers, &headers_sz, NULL);
 		if (ret < 0) {
-			put_online_mems();
 			pr_err("Preparing elf core header failed\n");
 			goto out_err;
 		}
 
-		put_online_mems();
 		kbuf.buffer = headers;
 		kbuf.bufsz = headers_sz;
 		kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
-- 
2.34.1

[PATCH v14 14/17] crash: Use crash_exclude_core_ranges() on powerpc

[Jinjie Ruan]

The crash memory exclude of crashk_res and crashk_cma memory on powerpc
are almost identical to the generic crash_exclude_core_ranges().

By introducing the architecture-specific arch_crash_exclude_mem_range()
function with a default implementation of crash_exclude_mem_range(),
and using crash_exclude_mem_range_guarded as powerpc's separate
implementation, the generic crash_exclude_core_ranges() helper function
can be reused.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Hari Bathini <hbathini@linux.ibm.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Mahesh Salgaonkar <mahesh@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Cc: Shivang Upadhyay <shivangu@linux.ibm.com>
Acked-by: Baoquan He <bhe@redhat.com>
Reviewed-by: Sourabh Jain <sourabhjain@linux.ibm.com>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 arch/powerpc/include/asm/kexec_ranges.h |  3 ---
 arch/powerpc/kexec/crash.c              |  2 +-
 arch/powerpc/kexec/ranges.c             | 16 ++++------------
 include/linux/crash_core.h              |  4 ++++
 kernel/crash_core.c                     | 19 +++++++++++++------
 5 files changed, 22 insertions(+), 22 deletions(-)

diff --git a/arch/powerpc/include/asm/kexec_ranges.h b/arch/powerpc/include/asm/kexec_ranges.h
index ad95e3792d10..8489e844b447 100644
--- a/arch/powerpc/include/asm/kexec_ranges.h
+++ b/arch/powerpc/include/asm/kexec_ranges.h
@@ -7,9 +7,6 @@
 void sort_memory_ranges(struct crash_mem *mrngs, bool merge);
 struct crash_mem *realloc_mem_ranges(struct crash_mem **mem_ranges);
 int add_mem_range(struct crash_mem **mem_ranges, u64 base, u64 size);
-int crash_exclude_mem_range_guarded(struct crash_mem **mem_ranges,
-				    unsigned long long mstart,
-				    unsigned long long mend);
 int get_exclude_memory_ranges(struct crash_mem **mem_ranges);
 int get_reserved_memory_ranges(struct crash_mem **mem_ranges);
 int get_crash_memory_ranges(struct crash_mem **mem_ranges);
diff --git a/arch/powerpc/kexec/crash.c b/arch/powerpc/kexec/crash.c
index d634db67becc..775895f31037 100644
--- a/arch/powerpc/kexec/crash.c
+++ b/arch/powerpc/kexec/crash.c
@@ -513,7 +513,7 @@ static void update_crash_elfcorehdr(struct kimage *image, struct memory_notify *
 		base_addr = PFN_PHYS(mn->start_pfn);
 		size = mn->nr_pages * PAGE_SIZE;
 		end = base_addr + size - 1;
-		ret = crash_exclude_mem_range_guarded(&cmem, base_addr, end);
+		ret = arch_crash_exclude_mem_range(&cmem, base_addr, end);
 		if (ret) {
 			pr_err("Failed to remove hot-unplugged memory from crash memory ranges\n");
 			goto out;
diff --git a/arch/powerpc/kexec/ranges.c b/arch/powerpc/kexec/ranges.c
index 6c58bcc3e130..e5fea23b191b 100644
--- a/arch/powerpc/kexec/ranges.c
+++ b/arch/powerpc/kexec/ranges.c
@@ -553,9 +553,9 @@ int get_usable_memory_ranges(struct crash_mem **mem_ranges)
 #endif /* CONFIG_KEXEC_FILE */
 
 #ifdef CONFIG_CRASH_DUMP
-int crash_exclude_mem_range_guarded(struct crash_mem **mem_ranges,
-					   unsigned long long mstart,
-					   unsigned long long mend)
+int arch_crash_exclude_mem_range(struct crash_mem **mem_ranges,
+				 unsigned long long mstart,
+				 unsigned long long mend)
 {
 	struct crash_mem *tmem = *mem_ranges;
 
@@ -604,18 +604,10 @@ int get_crash_memory_ranges(struct crash_mem **mem_ranges)
 			sort_memory_ranges(*mem_ranges, true);
 	}
 
-	/* Exclude crashkernel region */
-	ret = crash_exclude_mem_range_guarded(mem_ranges, crashk_res.start, crashk_res.end);
+	ret = crash_exclude_core_ranges(mem_ranges);
 	if (ret)
 		goto out;
 
-	for (i = 0; i < crashk_cma_cnt; ++i) {
-		ret = crash_exclude_mem_range_guarded(mem_ranges, crashk_cma_ranges[i].start,
-					      crashk_cma_ranges[i].end);
-		if (ret)
-			goto out;
-	}
-
 	/*
 	 * FIXME: For now, stay in parity with kexec-tools but if RTAS/OPAL
 	 *        regions are exported to save their context at the time of
diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
index d69c4c7c1f5e..0f4ea7ffd066 100644
--- a/include/linux/crash_core.h
+++ b/include/linux/crash_core.h
@@ -63,6 +63,7 @@ extern int crash_prepare_headers(int need_kernel_map, void **addr,
 				 unsigned long *sz, unsigned long *nr_mem_ranges);
 extern int crash_prepare_headers_locked(int need_kernel_map, void **addr,
 					unsigned long *sz, unsigned long *nr_mem_ranges);
+extern int crash_exclude_core_ranges(struct crash_mem **cmem);
 
 struct kimage;
 struct kexec_segment;
@@ -83,6 +84,9 @@ extern int kimage_crash_copy_vmcoreinfo(struct kimage *image);
 extern unsigned int arch_get_system_nr_ranges(void);
 extern int arch_crash_populate_cmem(struct crash_mem *cmem);
 extern int arch_crash_exclude_ranges(struct crash_mem *cmem);
+extern int arch_crash_exclude_mem_range(struct crash_mem **mem,
+					unsigned long long mstart,
+					unsigned long long mend);
 
 #else /* !CONFIG_CRASH_DUMP*/
 struct pt_regs;
diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index e84f3b63e79d..33e945da6776 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -286,24 +286,31 @@ unsigned int __weak arch_get_system_nr_ranges(void) { return 0; }
 int __weak arch_crash_populate_cmem(struct crash_mem *cmem) { return -1; }
 int __weak arch_crash_exclude_ranges(struct crash_mem *cmem) { return 0; }
 
-static int crash_exclude_core_ranges(struct crash_mem *cmem)
+int __weak arch_crash_exclude_mem_range(struct crash_mem **mem,
+					unsigned long long mstart,
+					unsigned long long mend)
+{
+	return crash_exclude_mem_range(*mem, mstart, mend);
+}
+
+int crash_exclude_core_ranges(struct crash_mem **cmem)
 {
 	int ret, i;
 
 	/* Exclude crashkernel region */
-	ret = crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end);
+	ret = arch_crash_exclude_mem_range(cmem, crashk_res.start, crashk_res.end);
 	if (ret)
 		return ret;
 
 	if (crashk_low_res.end) {
-		ret = crash_exclude_mem_range(cmem, crashk_low_res.start, crashk_low_res.end);
+		ret = arch_crash_exclude_mem_range(cmem, crashk_low_res.start, crashk_low_res.end);
 		if (ret)
 			return ret;
 	}
 
 	for (i = 0; i < crashk_cma_cnt; ++i) {
-		ret = crash_exclude_mem_range(cmem, crashk_cma_ranges[i].start,
-					      crashk_cma_ranges[i].end);
+		ret = arch_crash_exclude_mem_range(cmem, crashk_cma_ranges[i].start,
+						   crashk_cma_ranges[i].end);
 		if (ret)
 			return ret;
 	}
@@ -330,7 +337,7 @@ int crash_prepare_headers(int need_kernel_map, void **addr, unsigned long *sz,
 	if (ret)
 		goto out;
 
-	ret = crash_exclude_core_ranges(cmem);
+	ret = crash_exclude_core_ranges(&cmem);
 	if (ret)
 		goto out;
 
-- 
2.34.1

[PATCH v14 15/17] arm64: kexec: Add support for crashkernel CMA reservation

[Jinjie Ruan]

Commit 35c18f2933c5 ("Add a new optional ",cma" suffix to the
crashkernel= command line option") and commit ab475510e042 ("kdump:
implement reserve_crashkernel_cma") added CMA support for kdump
crashkernel reservation.

Crash kernel memory reservation wastes production resources if too
large, risks kdump failure if too small, and faces allocation difficulties
on fragmented systems due to contiguous block constraints. The new
CMA-based crashkernel reservation scheme splits the "large fixed
reservation" into a "small fixed region + large CMA dynamic region": the
CMA memory is available to userspace during normal operation to avoid
waste, and is reclaimed for kdump upon crash—saving memory while
improving reliability.

So extend crashkernel CMA reservation support to arm64. The following
changes are made to enable CMA reservation:

- Parse and obtain the CMA reservation size along with other crashkernel
  parameters.
- Call reserve_crashkernel_cma() to allocate the CMA region for kdump.
- Include the CMA-reserved ranges for kdump kernel to use.
- Exclude the CMA-reserved ranges from the crash kernel memory to
  prevent them from being exported through /proc/vmcore, which is already
  done in the crash core.

Update kernel-parameters.txt to document CMA support for crashkernel on
arm64 architecture.

Tested-by: Breno Leitao <leitao@debian.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Acked-by: Baoquan He <bhe@redhat.com>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
v7:
- Correct the inclusion of CMA-reserved ranges for kdump
  kernel in of/kexec.
v3:
- Add Acked-by.
v2:
- Free cmem in prepare_elf_headers()
- Add the mtivation.
---
 Documentation/admin-guide/kernel-parameters.txt | 2 +-
 arch/arm64/kernel/machine_kexec_file.c          | 2 +-
 arch/arm64/mm/init.c                            | 5 +++--
 drivers/of/fdt.c                                | 9 +++++----
 drivers/of/kexec.c                              | 9 +++++++++
 include/linux/crash_reserve.h                   | 4 +++-
 6 files changed, 22 insertions(+), 9 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 4d0f545fb3ec..52742fab49a9 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1119,7 +1119,7 @@ Kernel parameters
 			It will be ignored when crashkernel=X,high is not used
 			or memory reserved is below 4G.
 	crashkernel=size[KMG],cma
-			[KNL, X86, ppc] Reserve additional crash kernel memory from
+			[KNL, X86, ARM64, PPC] Reserve additional crash kernel memory from
 			CMA. This reservation is usable by the first system's
 			userspace memory and kernel movable allocations (memory
 			balloon, zswap). Pages allocated from this memory range
diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c
index 66fbfbaec1c6..d2985ce62306 100644
--- a/arch/arm64/kernel/machine_kexec_file.c
+++ b/arch/arm64/kernel/machine_kexec_file.c
@@ -42,7 +42,7 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image)
 #ifdef CONFIG_CRASH_DUMP
 unsigned int arch_get_system_nr_ranges(void)
 {
-	unsigned int nr_ranges = 2; /* for exclusion of crashkernel region */
+	unsigned int nr_ranges = 2 + crashk_cma_cnt; /* for exclusion of crashkernel region */
 	phys_addr_t start, end;
 	u64 i;
 
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 97987f850a33..227f58522dad 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -96,8 +96,8 @@ phys_addr_t __ro_after_init arm64_dma_phys_limit;
 
 static void __init arch_reserve_crashkernel(void)
 {
+	unsigned long long crash_base, crash_size, cma_size = 0;
 	unsigned long long low_size = 0;
-	unsigned long long crash_base, crash_size;
 	bool high = false;
 	int ret;
 
@@ -106,11 +106,12 @@ static void __init arch_reserve_crashkernel(void)
 
 	ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
 				&crash_size, &crash_base,
-				&low_size, NULL, &high);
+				&low_size, &cma_size, &high);
 	if (ret)
 		return;
 
 	reserve_crashkernel_generic(crash_size, crash_base, low_size, high);
+	reserve_crashkernel_cma(cma_size);
 }
 
 static phys_addr_t __init max_zone_phys(phys_addr_t zone_limit)
diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 82f7327c59ea..0470acbd1fcf 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -880,11 +880,12 @@ static unsigned long chosen_node_offset = -FDT_ERR_NOTFOUND;
 /*
  * The main usage of linux,usable-memory-range is for crash dump kernel.
  * Originally, the number of usable-memory regions is one. Now there may
- * be two regions, low region and high region.
- * To make compatibility with existing user-space and older kdump, the low
- * region is always the last range of linux,usable-memory-range if exist.
+ * be 2 + CRASHK_CMA_RANGES_MAX regions, low region, high region and cma
+ * regions. To make compatibility with existing user-space and older kdump,
+ * the high and low region are always the first two ranges of
+ * linux,usable-memory-range if exist.
  */
-#define MAX_USABLE_RANGES		2
+#define MAX_USABLE_RANGES		(2 + CRASHK_CMA_RANGES_MAX)
 
 /**
  * early_init_dt_check_for_usable_mem_range - Decode usable memory range
diff --git a/drivers/of/kexec.c b/drivers/of/kexec.c
index b6837e299e7f..029903b986cb 100644
--- a/drivers/of/kexec.c
+++ b/drivers/of/kexec.c
@@ -458,6 +458,15 @@ void *of_kexec_alloc_and_setup_fdt(const struct kimage *image,
 			if (ret)
 				goto out;
 		}
+
+		for (int i = 0; i < crashk_cma_cnt; i++) {
+			ret = fdt_appendprop_addrrange(fdt, 0, chosen_node,
+					"linux,usable-memory-range",
+					crashk_cma_ranges[i].start,
+					crashk_cma_ranges[i].end - crashk_cma_ranges[i].start + 1);
+			if (ret)
+				goto out;
+		}
 #endif
 	}
 
diff --git a/include/linux/crash_reserve.h b/include/linux/crash_reserve.h
index f0dc03d94ca2..30864d90d7f5 100644
--- a/include/linux/crash_reserve.h
+++ b/include/linux/crash_reserve.h
@@ -14,9 +14,11 @@
 extern struct resource crashk_res;
 extern struct resource crashk_low_res;
 extern struct range crashk_cma_ranges[];
+
+#define CRASHK_CMA_RANGES_MAX 4
 #if defined(CONFIG_CMA) && defined(CONFIG_ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION)
 #define CRASHKERNEL_CMA
-#define CRASHKERNEL_CMA_RANGES_MAX 4
+#define CRASHKERNEL_CMA_RANGES_MAX (CRASHK_CMA_RANGES_MAX)
 extern int crashk_cma_cnt;
 #else
 #define crashk_cma_cnt 0
-- 
2.34.1

[PATCH v14 16/17] riscv: kexec: Add support for crashkernel CMA reservation

[Jinjie Ruan]

Commit 35c18f2933c5 ("Add a new optional ",cma" suffix to the
crashkernel= command line option") and commit ab475510e042 ("kdump:
implement reserve_crashkernel_cma") added CMA support for kdump
crashkernel reservation. This allows the kernel to dynamically allocate
contiguous memory for crash dumping when needed, rather than permanently
reserving a fixed region at boot time.

So extend crashkernel CMA reservation support to riscv. The following
changes are made to enable CMA reservation:

- Parse and obtain the CMA reservation size along with other crashkernel
  parameters.
- Call reserve_crashkernel_cma() to allocate the CMA region for kdump.
- Include the CMA-reserved ranges for kdump kernel to use, which was
  already done in of_kexec_alloc_and_setup_fdt().
- Exclude the CMA-reserved ranges from the crash kernel memory to
  prevent them from being exported through /proc/vmcore, which was
  already done in the crash core.

Update kernel-parameters.txt to document CMA support for crashkernel on
riscv architecture.

Cc: Paul Walmsley <pjw@kernel.org>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Acked-by: Baoquan He <bhe@redhat.com>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Acked-by: Paul Walmsley <pjw@kernel.org> # arch/riscv
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 Documentation/admin-guide/kernel-parameters.txt | 16 ++++++++--------
 arch/riscv/kernel/machine_kexec_file.c          |  2 +-
 arch/riscv/mm/init.c                            |  5 +++--
 3 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 52742fab49a9..3ff3ddd516cf 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1119,14 +1119,14 @@ Kernel parameters
 			It will be ignored when crashkernel=X,high is not used
 			or memory reserved is below 4G.
 	crashkernel=size[KMG],cma
-			[KNL, X86, ARM64, PPC] Reserve additional crash kernel memory from
-			CMA. This reservation is usable by the first system's
-			userspace memory and kernel movable allocations (memory
-			balloon, zswap). Pages allocated from this memory range
-			will not be included in the vmcore so this should not
-			be used if dumping of userspace memory is intended and
-			it has to be expected that some movable kernel pages
-			may be missing from the dump.
+			[KNL, X86, ARM64, RISCV, PPC] Reserve additional crash
+			kernel memory from CMA. This reservation is usable by
+			the first system's userspace memory and kernel movable
+			allocations (memory balloon, zswap). Pages allocated
+			from this memory range will not be included in the vmcore
+			so this should not be used if dumping of userspace memory
+			is intended and it has to be expected that some movable
+			kernel pages may be missing from the dump.
 
 			A standard crashkernel reservation, as described above,
 			is still needed to hold the crash kernel and initrd.
diff --git a/arch/riscv/kernel/machine_kexec_file.c b/arch/riscv/kernel/machine_kexec_file.c
index d2bb61a8b6b6..075acf222fc0 100644
--- a/arch/riscv/kernel/machine_kexec_file.c
+++ b/arch/riscv/kernel/machine_kexec_file.c
@@ -46,7 +46,7 @@ static int get_nr_ram_ranges_callback(struct resource *res, void *arg)
 
 unsigned int arch_get_system_nr_ranges(void)
 {
-	unsigned int nr_ranges = 2; /* For exclusion of crashkernel region */
+	unsigned int nr_ranges = 2 + crashk_cma_cnt; /* For exclusion of crashkernel region */
 
 	walk_system_ram_res(0, -1, &nr_ranges, get_nr_ram_ranges_callback);
 
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index decd7df40fa4..c848454b8349 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -1295,7 +1295,7 @@ static inline void setup_vm_final(void)
  */
 static void __init arch_reserve_crashkernel(void)
 {
-	unsigned long long low_size = 0;
+	unsigned long long low_size = 0, cma_size = 0;
 	unsigned long long crash_base, crash_size;
 	bool high = false;
 	int ret;
@@ -1305,11 +1305,12 @@ static void __init arch_reserve_crashkernel(void)
 
 	ret = parse_crashkernel(boot_command_line, memblock_phys_mem_size(),
 				&crash_size, &crash_base,
-				&low_size, NULL, &high);
+				&low_size, &cma_size, &high);
 	if (ret)
 		return;
 
 	reserve_crashkernel_generic(crash_size, crash_base, low_size, high);
+	reserve_crashkernel_cma(cma_size);
 }
 
 void __init paging_init(void)
-- 
2.34.1

[PATCH v14 17/17] arm64/crash: Add crash hotplug support

[Jinjie Ruan]

Due to CPU/Memory hotplug or online/offline events, the elfcorehdr
(which describes the CPUs and memory of the crashed kernel) of kdump
image becomes outdated. Consequently, attempting dump collection with
an outdated elfcorehdr can lead to inaccurate dump collection.

The current solution to address the above issue involves monitoring
the CPU/Memory add/remove events in userspace using udev rules and
whenever there are changes in CPU and memory resources, the entire
kdump image is loaded again. The kdump image includes kernel, initrd,
elfcorehdr, FDT, purgatory. Given that only elfcorehdr gets outdated
due to CPU/Memory add/remove events, reloading the entire kdump image
is inefficient. More importantly, kdump remains inactive for a
substantial amount of time until the kdump reload completes.

To address the aforementioned issue, commit 247262756121 ("crash: add
generic infrastructure for crash hotplug support") added a generic
infrastructure that allows architectures to selectively update the
kdump image component during CPU or memory add/remove events within
the kernel itself.

In the event of a CPU or memory add/remove events, the generic crash
hotplug event handler, crash_handle_hotplug_event(), is triggered. It
then acquires the necessary locks to update the kdump image and invokes
the architecture-specific crash hotplug handler,
arch_crash_handle_hotplug_event(), to update the required kdump image
components.

[1] has supported virtual CPU hotplug in virtual machines for ARM64,
allowing vCPUs to be added or removed at runtime to meet Kubernetes
demands.

On ARM64, only memory add/remove events are handled. Here's why:

1. Physical CPU hotplug: Not supported on ARM64 hardware.

2. ACPI vCPU hotplug (KVM virtual machine):
   - vCPU hotplug is implemented as a static firmware policy where all
     possible vCPUs are pre-described in the MADT table at boot.
   - The vCPU status will be automatically updated after vCPU hotplug.
   - No FDT or elfcorehdr update needed.

3. Device tree booted Virtual Machine vCPU hotplug:
  - The elfcorehdr is built using for_each_possible_cpu(), so it
    already includes all possible CPUs and doesn't need updates.

For memory add/remove events, the elfcorehdr is updated to reflect
the current memory layout.

This patch adds the ARCH_SUPPORTS_CRASH_HOTPLUG config option and
implements:
- arch_crash_hotplug_support(): Check if hotplug update is supported
- arch_crash_get_elfcorehdr_size(): Return elfcorehdr buffer size
- arch_crash_handle_hotplug_event(): Handle memory hotplug events

This follows the same approach as x86 commit
ea53ad9cf73b ("x86/crash: add x86 crash hotplug support") and powerpc
commit b741092d5976 ("powerpc/crash: add crash CPU hotplug support")
and commit 849599b702ef ("powerpc/crash: add crash memory hotplug
support").

The test is based on the following QEMU version:
	https://github.com/salil-mehta/qemu.git virt-cpuhp-armv8/rfc-v2

Replace your '-smp' argument with something like:
 | -smp cpus=1,maxcpus=3,cores=3,threads=1,sockets=1

then feed the following to the Qemu montior to hotplug vCPU;
 | (qemu) device_add driver=host-arm-cpu,core-id=1,id=cpu1
 | (qemu) device_del cpu1

feed the following to the Qemu montior to hotplug memory;
 | (qemu) object_add memory-backend-ram,id=mem1,size=256M
 | (qemu) device_add pc-dimm,id=dimm1,memdev=mem1
 | (qemu) device_del dimm1

The qemu startup configuration is as follows:
qemu-system-aarch64 \
		-M virt,gic-version=3,acpi=on,highmem=on \
		-enable-kvm \
		-cpu host \
		-kernel Image \
		-smp cpus=1,maxcpus=3,cores=3,threads=1,sockets=1 \
		-bios /usr/share/edk2/aarch64/QEMU_EFI.fd \
		-m 2G,slots=64,maxmem=16G \
		-nographic \
		-no-reboot \
		-device virtio-rng-pci \
		-append "root=/dev/vda rw console=ttyAMA0 kgdboc=ttyAMA0,115200 \
			earlycon acpi=on crashkernel=512M" \
		-drive if=none,file=images/rootfs.ext4,format=raw,id=hd0 \
		-device virtio-blk-device,drive=hd0 \

There are two system calls, `kexec_file_load` and `kexec_load`, used to
load the kdump image. Only kexec_file_load syscall way is tested now.

This patch is based on following rework:
	https://lore.kernel.org/all/20260328074013.3589544-1-ruanjinjie@huawei.com/

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Breno Leitao <leitao@debian.org>
Cc: Kees Cook <kees@kernel.org>
[1]: https://lore.kernel.org/all/20240529133446.28446-1-Jonathan.Cameron@huawei.com/
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 arch/arm64/Kconfig                     |   3 +
 arch/arm64/include/asm/kexec.h         |  11 +++
 arch/arm64/kernel/Makefile             |   1 +
 arch/arm64/kernel/crash.c              | 125 +++++++++++++++++++++++++
 arch/arm64/kernel/machine_kexec_file.c |  23 ++++-
 5 files changed, 161 insertions(+), 2 deletions(-)
 create mode 100644 arch/arm64/kernel/crash.c

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index fe60738e5943..9091c67e1cc2 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1609,6 +1609,9 @@ config ARCH_DEFAULT_CRASH_DUMP
 config ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION
 	def_bool CRASH_RESERVE
 
+config ARCH_SUPPORTS_CRASH_HOTPLUG
+	def_bool y
+
 config TRANS_TABLE
 	def_bool y
 	depends on HIBERNATION || KEXEC_CORE
diff --git a/arch/arm64/include/asm/kexec.h b/arch/arm64/include/asm/kexec.h
index cc2f36b1b0d4..f338d162dec1 100644
--- a/arch/arm64/include/asm/kexec.h
+++ b/arch/arm64/include/asm/kexec.h
@@ -131,6 +131,17 @@ extern int load_other_segments(struct kimage *image,
 extern int prepare_elf_headers(void **addr, unsigned long *sz);
 #endif
 
+#ifdef CONFIG_CRASH_HOTPLUG
+void arch_crash_handle_hotplug_event(struct kimage *image, void *arg);
+#define arch_crash_handle_hotplug_event arch_crash_handle_hotplug_event
+
+int arch_crash_hotplug_support(struct kimage *image, unsigned long kexec_flags);
+#define arch_crash_hotplug_support arch_crash_hotplug_support
+
+unsigned int arch_crash_get_elfcorehdr_size(void);
+#define crash_get_elfcorehdr_size arch_crash_get_elfcorehdr_size
+#endif
+
 #endif /* __ASSEMBLER__ */
 
 #endif
diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index 74b76bb70452..629e962813ab 100644
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -65,6 +65,7 @@ obj-$(CONFIG_KEXEC_FILE)		+= machine_kexec_file.o kexec_image.o
 obj-$(CONFIG_ARM64_RELOC_TEST)		+= arm64-reloc-test.o
 arm64-reloc-test-y := reloc_test_core.o reloc_test_syms.o
 obj-$(CONFIG_CRASH_DUMP)		+= crash_dump.o
+obj-$(CONFIG_CRASH_HOTPLUG)		+= crash.o
 obj-$(CONFIG_VMCORE_INFO)		+= vmcore_info.o
 obj-$(CONFIG_ARM_SDE_INTERFACE)		+= sdei.o
 obj-$(CONFIG_ARM64_PTR_AUTH)		+= pointer_auth.o
diff --git a/arch/arm64/kernel/crash.c b/arch/arm64/kernel/crash.c
new file mode 100644
index 000000000000..2114375820da
--- /dev/null
+++ b/arch/arm64/kernel/crash.c
@@ -0,0 +1,125 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Architecture specific functions for kexec based crash dumps.
+ */
+
+#define pr_fmt(fmt)	"crash hp: " fmt
+
+#include <linux/kexec.h>
+#include <linux/elf.h>
+#include <linux/vmalloc.h>
+#include <linux/crash_core.h>
+
+#include <asm/kexec.h>
+
+#ifdef CONFIG_CRASH_HOTPLUG
+
+int arch_crash_hotplug_support(struct kimage *image, unsigned long kexec_flags)
+{
+#ifdef CONFIG_KEXEC_FILE
+	if (image->file_mode)
+		return 1;
+#endif
+	/*
+	 * For kexec_load syscall, crash hotplug support requires
+	 * KEXEC_CRASH_HOTPLUG_SUPPORT flag to be passed by userspace.
+	 */
+	return kexec_flags & KEXEC_CRASH_HOTPLUG_SUPPORT;
+}
+
+unsigned int arch_crash_get_elfcorehdr_size(void)
+{
+	unsigned int phdr_cnt;
+
+	/* A program header for possible CPUs, vmcoreinfo and kernel_map */
+	phdr_cnt = 2 + num_possible_cpus();
+	if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG))
+		phdr_cnt += CONFIG_CRASH_MAX_MEMORY_RANGES;
+
+	return sizeof(Elf64_Ehdr) + phdr_cnt * sizeof(Elf64_Phdr);
+}
+
+/**
+ * update_crash_elfcorehdr() - Recreate the elfcorehdr and replace it with old
+ *			       elfcorehdr in the kexec segment array.
+ * @image: the active struct kimage
+ */
+static void update_crash_elfcorehdr(struct kimage *image)
+{
+	void *elfbuf = NULL, *old_elfcorehdr;
+	unsigned long mem, memsz;
+	unsigned long elfsz = 0;
+
+	/*
+	 * Create the new elfcorehdr reflecting the changes to CPU and/or
+	 * memory resources.
+	 */
+	if (crash_prepare_headers(true, &elfbuf, &elfsz, NULL)) {
+		pr_err("unable to create new elfcorehdr");
+		goto out;
+	}
+
+	/*
+	 * Obtain address and size of the elfcorehdr segment, and
+	 * check it against the new elfcorehdr buffer.
+	 */
+	mem = image->segment[image->elfcorehdr_index].mem;
+	memsz = image->segment[image->elfcorehdr_index].memsz;
+	if (elfsz > memsz) {
+		pr_err("update elfcorehdr elfsz %lu > memsz %lu",
+			elfsz, memsz);
+		goto out;
+	}
+
+	/*
+	 * Copy new elfcorehdr over the old elfcorehdr at destination.
+	 */
+	old_elfcorehdr = (void *)__va(mem);
+	if (!old_elfcorehdr) {
+		pr_err("mapping elfcorehdr segment failed\n");
+		goto out;
+	}
+
+	/*
+	 * Temporarily invalidate the crash image while the
+	 * elfcorehdr is updated.
+	 */
+	xchg(&kexec_crash_image, NULL);
+	memcpy_flushcache(old_elfcorehdr, elfbuf, elfsz);
+	xchg(&kexec_crash_image, image);
+	pr_debug("updated elfcorehdr\n");
+
+out:
+	vfree(elfbuf);
+}
+
+/**
+ * arch_crash_handle_hotplug_event() - Handle hotplug elfcorehdr changes
+ * @image: a pointer to kexec_crash_image
+ * @arg: struct memory_notify handler for memory hotplug case and
+ *       NULL for CPU hotplug case.
+ *
+ * Update the kdump image based on the type of hotplug event:
+ * - CPU add and remove: No action is needed.
+ * - Memory add/remove: Update the elfcorehdr to reflect the current memory layout.
+ *
+ * Prepare the new elfcorehdr and replace the existing elfcorehdr.
+ */
+void arch_crash_handle_hotplug_event(struct kimage *image, void *arg)
+{
+	switch (image->hp_action) {
+	case KEXEC_CRASH_HP_ADD_CPU:
+		fallthrough;
+	case KEXEC_CRASH_HP_REMOVE_CPU:
+		if (image->file_mode || image->elfcorehdr_updated)
+			return;
+		fallthrough;
+	case KEXEC_CRASH_HP_ADD_MEMORY:
+	case KEXEC_CRASH_HP_REMOVE_MEMORY:
+		update_crash_elfcorehdr(image);
+		return;
+	default:
+		pr_warn_once("Unknown hotplug action\n");
+	}
+}
+#endif /* CONFIG_CRASH_HOTPLUG */
diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c
index d2985ce62306..781febd0f6db 100644
--- a/arch/arm64/kernel/machine_kexec_file.c
+++ b/arch/arm64/kernel/machine_kexec_file.c
@@ -82,10 +82,11 @@ int load_other_segments(struct kimage *image,
 			char *cmdline, void *headers,
 			unsigned long headers_sz)
 {
-	struct kexec_buf kbuf = {};
-	void *dtb = NULL;
 	unsigned long initrd_load_addr = 0, dtb_len,
 		      orig_segments = image->nr_segments;
+	struct kexec_buf kbuf = {};
+	unsigned long pnum = 0;
+	void *dtb = NULL;
 	int ret = 0;
 
 	kbuf.image = image;
@@ -98,6 +99,23 @@ int load_other_segments(struct kimage *image,
 		kbuf.bufsz = headers_sz;
 		kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
 		kbuf.memsz = headers_sz;
+
+#ifdef CONFIG_CRASH_HOTPLUG
+		/*
+		 * The elfcorehdr segment size accounts for VMCOREINFO, kernel_map
+		 * maximum CPUs and maximum memory ranges.
+		 */
+		if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG))
+			pnum = 2 + num_possible_cpus() + CONFIG_CRASH_MAX_MEMORY_RANGES;
+		else
+			pnum += 2 + num_possible_cpus();
+
+		if (pnum < (unsigned long)PN_XNUM)
+			kbuf.memsz = pnum * sizeof(Elf64_Phdr) + sizeof(Elf64_Ehdr);
+		else
+			pr_err("number of Phdrs %lu exceeds max\n", pnum);
+#endif
+
 		kbuf.buf_align = SZ_64K; /* largest supported page size */
 		kbuf.buf_max = ULONG_MAX;
 		kbuf.top_down = true;
@@ -108,6 +126,7 @@ int load_other_segments(struct kimage *image,
 			goto out_err;
 		}
 		image->elf_load_addr = kbuf.mem;
+		image->elf_headers_sz = kbuf.memsz;
 
 		kexec_dprintk("Loaded elf core header at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
 			      image->elf_load_addr, kbuf.bufsz, kbuf.memsz);
-- 
2.34.1

Re: [PATCH v14 00/17] arm64/riscv: Add support for crashkernel CMA reservation

[Huacai Chen]

Hi, Jinjie,

On Mon, May 25, 2026 at 4:50 PM Jinjie Ruan <ruanjinjie@huawei.com> wrote:
>
> The crash memory allocation, and the exclude of crashk_res, crashk_low_res
> and crashk_cma memory are almost identical across different architectures,
> This patch set handle them in crash core in a general way, which eliminate
> a lot of duplication code.
>
> And add support for crashkernel CMA reservation for arm64 and riscv.
>
> Also add support for arm64 crash hotplug.
>
> This patch set is rebased on v7.1-rc1.
>
> Basic second kernel boot test were performed on QEMU platforms for x86,
> ARM64 and RISC-V architectures with the following parameters:
>
>         "cma=256M crashkernel=4G crashkernel=64M,cma"
>
> For first kernel, there will be such log:
>
>         # dmesg | grep crash
>         [    0.000000] crashkernel low memory reserved: 0xe8000000 - 0xf0000000 (128 MB)
>         [    0.000000] crashkernel reserved: 0x000000023e600000 - 0x000000033e600000 (4096 MB)
>         [    0.000000] crashkernel CMA reserved: 64 MB in 1 ranges
>
>         # dmesg | grep cma
>         [    0.000000] cma: Reserved 256 MiB at 0x00000000f0000000
>         [    0.000000] cma: Reserved 64 MiB at 0x0000000100000000
>
> For second kernel, there will be such log:
>
>         [    0.000000] OF: fdt: Looking for usable-memory-range property...
>         [    0.000000] OF: fdt: cap_mem_regions[0]: base=0x000000023e600000, size=0x0000000100000000
>         [    0.000000] OF: fdt: cap_mem_regions[1]: base=0x00000000e8000000, size=0x0000000008000000
>         [    0.000000] OF: fdt: cap_mem_regions[2]: base=0x0000000100000000, size=0x0000000004000000
>
> Changes in v14:
> - Fix image->elf_headers memory leak during retry loop for arm64 as Sashiko
>   AI code review pointed out.
> - Solve the hotplug notifier arch_crash_handle_hotplug_event() AA
>   self-deadlock problem as Sashiko AI code review pointed out.
> - Fix the TOCTOU issue in prepare_elf_headers() by get_online_mems().
> - -ENOMEM -> -EAGAIN as Breno suggested.
> - Add support for arm64 crash hotplug.
> - Link to v13: https://lore.kernel.org/all/20260511030454.1730881-1-ruanjinjie@huawei.com/
>
> Changes in v13:
> - Rebased on v7.1-rc1.
> - Update the commit message.
> - Add Reviewed-by.
> - Link to v12: https://lore.kernel.org/all/20260402072701.628293-1-ruanjinjie@huawei.com/
>
> Changes in v12:
> - Remove the unused "nr_mem_ranges" for x86.
> - Add "Fix crashk_low_res not exclude bug" test log.
> - Provide a separate patch for each architecture for using
>   crash_prepare_headers(), which will make the review more convenient.
> - Add Reviewed-by and Tested-by.
> - Link to v11: https://lore.kernel.org/all/20260328074013.3589544-1-ruanjinjie@huawei.com/
>
> Changes in v11:
> - Avoid silently drop crash memory if the crash kernel is built without
>   CONFIG_CMA.
> - Remove unnecessary "cmem->nr_ranges = 0" for arch_crash_populate_cmem()
>   as we use kvzalloc().
> - Provide a separate patch for each architecture to fix the existing
>   buffer overflow issue.
> - Add Acked-bys for arm64.
>
> Changes in v10:
> - Fix crashk_low_res not excluded bug in the existing
>   RISC-V code.
> - Fix an existing memory leak issue in the existing PowerPC code.
> - Fix the ordering issue of adding CMA ranges to
>   "linux,usable-memory-range".
> - Fix an existing concurrency issue. A Concurrent memory hotplug may occur
>   between reading memblock and attempting to fill cmem during kexec_load()
>   for almost all existing architectures.
> - Link to v9: https://lore.kernel.org/all/20260323072745.2481719-1-ruanjinjie@huawei.com/
>
> Changes in v9:
> - Collect Reviewed-by and Acked-by, and prepare for Sashiko AI review.
> - Link to v8: https://lore.kernel.org/all/20260302035315.3892241-1-ruanjinjie@huawei.com/
>
> Changes in v8:
> - Fix the build issues reported by kernel test robot and Sourabh.
> - Link to v7: https://lore.kernel.org/all/20260226130437.1867658-1-ruanjinjie@huawei.com/
>
> Changes in v7:
> - Correct the inclusion of CMA-reserved ranges for kdump kernel in of/kexec
>   for arm64 and riscv.
> - Add Acked-by.
> - Link to v6: https://lore.kernel.org/all/20260224085342.387996-1-ruanjinjie@huawei.com/
>
> Changes in v6:
> - Update the crash core exclude code as Mike suggested.
> - Rebased on v7.0-rc1.
> - Add acked-by.
> - Link to v5: https://lore.kernel.org/all/20260212101001.343158-1-ruanjinjie@huawei.com/
>
> Jinjie Ruan (16):
>   riscv: kexec_file: Fix crashk_low_res not exclude bug
>   powerpc/crash: Fix possible memory leak in update_crash_elfcorehdr()
>   arm64: kexec: Fix image->elf_headers memory leak during retry loop
>   x86/kexec: Fix potential buffer overflow in prepare_elf_headers()
>   arm64: kexec_file: Fix potential buffer overflow in
>     prepare_elf_headers()
>   riscv: kexec_file: Fix potential buffer overflow in
>     prepare_elf_headers()
>   LoongArch: kexec: Fix potential buffer overflow in
>     prepare_elf_headers()
>   crash: Add crash_prepare_headers() to exclude crash kernel memory
>   arm64: kexec_file: Use crash_prepare_headers() helper to simplify code
>   x86/kexec: Use crash_prepare_headers() helper to simplify code
>   riscv: kexec_file: Use crash_prepare_headers() helper to simplify code
>   LoongArch: kexec: Use crash_prepare_headers() helper to simplify code
>   crash: Use crash_exclude_core_ranges() on powerpc
>   arm64: kexec: Add support for crashkernel CMA reservation
>   riscv: kexec: Add support for crashkernel CMA reservation
>   arm64/crash: Add crash hotplug support
I have some bikesheedings about the subjects. Can we unify the prefix formats?
x86/kexec, arm64: kexec_file, riscv: kexec_file, LoongArch: kexec .....

Huacai

>
> Sourabh Jain (1):
>   powerpc/crash: sort crash memory ranges before preparing elfcorehdr
>
>  .../admin-guide/kernel-parameters.txt         |  16 +--
>  arch/arm64/Kconfig                            |   3 +
>  arch/arm64/include/asm/kexec.h                |  14 +-
>  arch/arm64/kernel/Makefile                    |   1 +
>  arch/arm64/kernel/crash.c                     | 125 ++++++++++++++++++
>  arch/arm64/kernel/kexec_image.c               |  22 ++-
>  arch/arm64/kernel/machine_kexec_file.c        |  78 ++++++-----
>  arch/arm64/mm/init.c                          |   5 +-
>  arch/loongarch/kernel/machine_kexec_file.c    |  43 +++---
>  arch/powerpc/include/asm/kexec_ranges.h       |   1 -
>  arch/powerpc/kexec/crash.c                    |   7 +-
>  arch/powerpc/kexec/ranges.c                   | 101 +-------------
>  arch/riscv/kernel/machine_kexec_file.c        |  42 +++---
>  arch/riscv/mm/init.c                          |   5 +-
>  arch/x86/kernel/crash.c                       |  92 ++-----------
>  drivers/of/fdt.c                              |   9 +-
>  drivers/of/kexec.c                            |   9 ++
>  include/linux/crash_core.h                    |  11 ++
>  include/linux/crash_reserve.h                 |   4 +-
>  kernel/crash_core.c                           | 102 +++++++++++++-
>  20 files changed, 392 insertions(+), 298 deletions(-)
>  create mode 100644 arch/arm64/kernel/crash.c
>
> --
> 2.34.1
>

Re: [PATCH v14 00/17] arm64/riscv: Add support for crashkernel CMA reservation

[Mike Rapoport]

Hi Huacai,

On Mon, May 25, 2026 at 06:14:52PM +0800, Huacai Chen wrote:
> On Mon, May 25, 2026 at 4:50 PM Jinjie Ruan <ruanjinjie@huawei.com> wrote:
> >
> > Jinjie Ruan (16):
> >   riscv: kexec_file: Fix crashk_low_res not exclude bug
> >   powerpc/crash: Fix possible memory leak in update_crash_elfcorehdr()
> >   arm64: kexec: Fix image->elf_headers memory leak during retry loop
> >   x86/kexec: Fix potential buffer overflow in prepare_elf_headers()
> >   arm64: kexec_file: Fix potential buffer overflow in
> >     prepare_elf_headers()
> >   riscv: kexec_file: Fix potential buffer overflow in
> >     prepare_elf_headers()
> >   LoongArch: kexec: Fix potential buffer overflow in
> >     prepare_elf_headers()
> >   crash: Add crash_prepare_headers() to exclude crash kernel memory
> >   arm64: kexec_file: Use crash_prepare_headers() helper to simplify code
> >   x86/kexec: Use crash_prepare_headers() helper to simplify code
> >   riscv: kexec_file: Use crash_prepare_headers() helper to simplify code
> >   LoongArch: kexec: Use crash_prepare_headers() helper to simplify code
> >   crash: Use crash_exclude_core_ranges() on powerpc
> >   arm64: kexec: Add support for crashkernel CMA reservation
> >   riscv: kexec: Add support for crashkernel CMA reservation
> >   arm64/crash: Add crash hotplug support
> I have some bikesheedings about the subjects. Can we unify the prefix formats?
> x86/kexec, arm64: kexec_file, riscv: kexec_file, LoongArch: kexec .....

It might look weird in the series, but powerpc and x86 use '/' and arm64 and
riscv use ':' so in the logs in arch/ this would be actually fine.

With the only exception of arm64/crash that should have been arm64: crash:
 
> Huacai

-- 
Sincerely yours,
Mike.

Re: [PATCH v14 00/17] arm64/riscv: Add support for crashkernel CMA reservation

[Huacai Chen]

On Mon, May 25, 2026 at 7:37 PM Mike Rapoport <rppt@kernel.org> wrote:
>
> Hi Huacai,
>
> On Mon, May 25, 2026 at 06:14:52PM +0800, Huacai Chen wrote:
> > On Mon, May 25, 2026 at 4:50 PM Jinjie Ruan <ruanjinjie@huawei.com> wrote:
> > >
> > > Jinjie Ruan (16):
> > >   riscv: kexec_file: Fix crashk_low_res not exclude bug
> > >   powerpc/crash: Fix possible memory leak in update_crash_elfcorehdr()
> > >   arm64: kexec: Fix image->elf_headers memory leak during retry loop
> > >   x86/kexec: Fix potential buffer overflow in prepare_elf_headers()
> > >   arm64: kexec_file: Fix potential buffer overflow in
> > >     prepare_elf_headers()
> > >   riscv: kexec_file: Fix potential buffer overflow in
> > >     prepare_elf_headers()
> > >   LoongArch: kexec: Fix potential buffer overflow in
> > >     prepare_elf_headers()
> > >   crash: Add crash_prepare_headers() to exclude crash kernel memory
> > >   arm64: kexec_file: Use crash_prepare_headers() helper to simplify code
> > >   x86/kexec: Use crash_prepare_headers() helper to simplify code
> > >   riscv: kexec_file: Use crash_prepare_headers() helper to simplify code
> > >   LoongArch: kexec: Use crash_prepare_headers() helper to simplify code
> > >   crash: Use crash_exclude_core_ranges() on powerpc
> > >   arm64: kexec: Add support for crashkernel CMA reservation
> > >   riscv: kexec: Add support for crashkernel CMA reservation
> > >   arm64/crash: Add crash hotplug support
> > I have some bikesheedings about the subjects. Can we unify the prefix formats?
> > x86/kexec, arm64: kexec_file, riscv: kexec_file, LoongArch: kexec .....
>
> It might look weird in the series, but powerpc and x86 use '/' and arm64 and
> riscv use ':' so in the logs in arch/ this would be actually fine.
OK, but at least we can unify kexec and kexec_file.

Huacai

>
> With the only exception of arm64/crash that should have been arm64: crash:
>
> > Huacai
>
> --
> Sincerely yours,
> Mike.