[PATCH 07/11] of: reserved_mem: add no-dump crash_mem exclusion helpers

Chen Wandun
2026-04-29T06:59:53Z

Provide two kdump-oriented helpers so that arch kexec_file code does
not have to open-code the no-dump filtering loop:

- of_reserved_mem_no_dump_nr_ranges() returns the number of reserved
regions flagged with linux,no-dump. Each exclusion may split one
existing crash_mem range into two, so callers use this count to
pre-size their crash_mem allocation.

- of_reserved_mem_exclude_no_dump() walks the reserved_mem[] array
and calls crash_exclude_mem_range() for each no-dump region.

Both helpers are guarded by CONFIG_KEXEC_FILE; empty inline stubs are
provided for the !KEXEC_FILE case so architecture code can call them
unconditionally.

The consumers are added in the following arm64, riscv and loongarch
patches in this series.

Signed-off-by: Chen Wandun <chenwandun@lixiang.com>
Tested-by: Zhao Meijing <zhaomeijing@lixiang.com>
---
drivers/of/of_reserved_mem.c | 54 +++++++++++++++++++++++++++++++++
include/linux/of_reserved_mem.h | 15 +++++++++
2 files changed, 69 insertions(+)

diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c
index 4b80420da2d2..038056a6408a 100644
--- a/drivers/of/of_reserved_mem.c
+++ b/drivers/of/of_reserved_mem.c
@@ -27,6 +27,10 @@

#include "of_private.h"

+#ifdef CONFIG_KEXEC_FILE
+#include <linux/crash_core.h>
+#endif
+
static struct reserved_mem reserved_mem_array[MAX_RESERVED_REGIONS] __initdata;
static struct reserved_mem *reserved_mem __refdata = reserved_mem_array;
static int total_reserved_mem_cnt = MAX_RESERVED_REGIONS;
@@ -916,6 +920,56 @@ struct reserved_mem *of_reserved_mem_lookup(struct device_node *np)
}
EXPORT_SYMBOL_GPL(of_reserved_mem_lookup);

+#ifdef CONFIG_KEXEC_FILE
+/**
+ * of_reserved_mem_no_dump_nr_ranges() - count reserved regions flagged
+ * with the linux,no-dump property.
+ *
+ * Each such region may split an existing crash_mem range into two when
+ * it is excluded, so callers can use this count to pre-size their
+ * crash_mem allocation.
+ */
+unsigned int of_reserved_mem_no_dump_nr_ranges(void)
+{
+ unsigned int i, n = 0;
+
+ for (i = 0; i < reserved_mem_count; i++)
+ if (reserved_mem[i].no_dump)
+ n++;
+ return n;
+}
+
+/**
+ * of_reserved_mem_exclude_no_dump() - exclude no-dump reserved regions
+ * from a crash_mem list.
+ * @cmem: crash memory list to modify
+ *
+ * Walks the reserved_mem[] array and calls crash_exclude_mem_range() for
+ * every region with no_dump set. Intended to be called from arch kdump
+ * code when constructing the elfcorehdr.
+ *
+ * Returns 0 on success, or a negative error returned by
+ * crash_exclude_mem_range() on the first failure.
+ */
+int of_reserved_mem_exclude_no_dump(struct crash_mem *cmem)
+{
+ unsigned int i;
+ int ret;
+
+ for (i = 0; i < reserved_mem_count; i++) {
+ struct reserved_mem *r = &reserved_mem[i];
+
+ if (!r->no_dump || !r->size)
+ continue;
+ ret = crash_exclude_mem_range(cmem, r->base,
+ r->base + r->size - 1);
+ if (ret)
+ return ret;
+ }
+ return 0;
+}
+#endif /* CONFIG_KEXEC_FILE */
+
/**
* of_reserved_mem_region_to_resource() - Get a reserved memory region as a resource
* @np: node containing 'memory-region' property
diff --git a/include/linux/of_reserved_mem.h b/include/linux/of_reserved_mem.h
index 29674f572673..cd0f88f29579 100644
--- a/include/linux/of_reserved_mem.h
+++ b/include/linux/of_reserved_mem.h
@@ -8,6 +8,7 @@
struct of_phandle_args;
struct reserved_mem_ops;
struct resource;
+struct crash_mem;

struct reserved_mem {
const char *name;
@@ -94,6 +95,20 @@ static inline int of_reserved_mem_region_count(const struct device_node *np)
}
#endif

+#if defined(CONFIG_OF_RESERVED_MEM) && defined(CONFIG_KEXEC_FILE)
+unsigned int of_reserved_mem_no_dump_nr_ranges(void);
+int of_reserved_mem_exclude_no_dump(struct crash_mem *cmem);
+#else
+static inline unsigned int of_reserved_mem_no_dump_nr_ranges(void)
+{
+ return 0;
+}
+static inline int of_reserved_mem_exclude_no_dump(struct crash_mem *cmem)
+{
+ return 0;
+}
+#endif
+
/**
* of_reserved_mem_device_init() - assign reserved memory region to given device
* @dev: Pointer to the device to configure
--
2.43.0