[PATCH v7 2/5] crash: Exclude crash kernel memory in crash core

Jinjie Ruan
2026-02-26T13:05:55Z

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
do 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.

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/machine_kexec_file.c | 39 +++-------
arch/loongarch/kernel/machine_kexec_file.c | 39 +++-------
arch/riscv/kernel/machine_kexec_file.c | 38 +++------
arch/x86/kernel/crash.c | 89 +++-------------------
include/linux/crash_core.h | 5 ++
kernel/crash_core.c | 82 +++++++++++++++++++-
6 files changed, 132 insertions(+), 160 deletions(-)

diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c
index fba260ad87a9..c338506a580b 100644
--- a/arch/arm64/kernel/machine_kexec_file.c
+++ b/arch/arm64/kernel/machine_kexec_file.c
@@ -40,23 +40,23 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image)
}

#ifdef CONFIG_CRASH_DUMP
-static 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) {
cmem->ranges[cmem->nr_ranges].start = start;
@@ -64,22 +64,7 @@ static int prepare_elf_headers(void **addr, unsigned long *sz)
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

@@ -109,7 +94,7 @@ int load_other_segments(struct kimage *image,
void *headers;
unsigned long headers_sz;
if (image->type == KEXEC_TYPE_CRASH) {
- ret = prepare_elf_headers(&headers, &headers_sz);
+ ret = crash_prepare_headers(true, &headers, &headers_sz, NULL);
if (ret) {
pr_err("Preparing elf core header failed\n");
goto out_err;
diff --git a/arch/loongarch/kernel/machine_kexec_file.c b/arch/loongarch/kernel/machine_kexec_file.c
index 5584b798ba46..4b318a94b564 100644
--- a/arch/loongarch/kernel/machine_kexec_file.c
+++ b/arch/loongarch/kernel/machine_kexec_file.c
@@ -56,23 +56,23 @@ 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) {
cmem->ranges[cmem->nr_ranges].start = start;
@@ -80,22 +80,7 @@ static int prepare_elf_headers(void **addr, unsigned long *sz)
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;
}

/*
@@ -163,7 +148,7 @@ int load_other_segments(struct kimage *image,
void *headers;
unsigned long headers_sz;

- ret = prepare_elf_headers(&headers, &headers_sz);
+ ret = crash_prepare_headers(true, &headers, &headers_sz, NULL);
if (ret < 0) {
pr_err("Preparing elf core header failed\n");
goto out_err;
diff --git a/arch/riscv/kernel/machine_kexec_file.c b/arch/riscv/kernel/machine_kexec_file.c
index 54e2d9552e93..d0e331d87155 100644
--- a/arch/riscv/kernel/machine_kexec_file.c
+++ b/arch/riscv/kernel/machine_kexec_file.c
@@ -44,6 +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 = 1; /* 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;
@@ -55,33 +64,10 @@ 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 = 1; /* 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)
- 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,
@@ -273,7 +259,7 @@ int load_extra_segments(struct kimage *image, unsigned long kernel_start,
if (image->type == KEXEC_TYPE_CRASH) {
void *headers;
unsigned long headers_sz;
- ret = prepare_elf_headers(&headers, &headers_sz);
+ ret = crash_prepare_headers(true, &headers, &headers_sz, NULL);
if (ret) {
pr_err("Preparing elf core header failed\n");
goto out;
diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index 335fd2ee9766..3ad3f8b758a4 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -152,16 +152,8 @@ 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.
@@ -176,49 +168,16 @@ 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)
@@ -232,35 +191,9 @@ 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

@@ -418,7 +351,8 @@ int crash_load_segments(struct kimage *image)
.buf_max = ULONG_MAX, .top_down = false };

/* Prepare elf headers and add a segment */
- ret = prepare_elf_headers(&kbuf.buffer, &kbuf.bufsz, &pnum);
+ ret = crash_prepare_headers(IS_ENABLED(CONFIG_X86_64), &kbuf.buffer,
+ &kbuf.bufsz, &pnum);
if (ret)
return ret;

@@ -529,7 +463,8 @@ 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,
+ &nr_mem_ranges)) {
pr_err("unable to create new elfcorehdr");
goto out;
}
diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
index d35726d6a415..033b20204aca 100644
--- a/include/linux/crash_core.h
+++ b/include/linux/crash_core.h
@@ -66,6 +66,8 @@ 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);

struct kimage;
struct kexec_segment;
@@ -83,6 +85,9 @@ 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 2c1a3791e410..96a96e511f5a 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -170,9 +170,6 @@ 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)
{
@@ -274,6 +271,85 @@ 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;
+}
+
/**
* crash_exclude_mem_range - exclude a mem range for existing ranges
* @mem: mem->range contains an array of ranges sorted in ascending order