Add a sysfs entry /sys/kernel/kexec/crash_cma_ranges to expose all CMA crashkernel ranges.
This allows userspace tools configuring kdump to determine how much memory is reserved for crashkernel. If CMA is used, tools can warn users when attempting to capture user pages with CMA reservation. The new sysfs hold the CMA ranges in below format: cat /sys/kernel/kexec/crash_cma_ranges 100000000-10c7fffff Cc: Aditya Gupta <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Baoquan he <[email protected]> Cc: Dave Young <[email protected]> Cc: Hari Bathini <[email protected]> Cc: Jiri Bohac <[email protected]> Cc: Madhavan Srinivasan <[email protected]> Cc: Mahesh J Salgaonkar <[email protected]> Cc: Pingfan Liu <[email protected]> Cc: Ritesh Harjani (IBM) <[email protected]> Cc: Shivang Upadhyay <[email protected]> Cc: Vivek Goyal <[email protected]> Cc: [email protected] Cc: [email protected] Signed-off-by: Sourabh Jain <[email protected]> --- Changelog: - Add the missing hunk to export crash_cma_ranges sysfs --- .../ABI/testing/sysfs-kernel-kexec-kdump | 10 ++++++++++ kernel/kexec_core.c | 17 +++++++++++++++++ 2 files changed, 27 insertions(+) diff --git a/Documentation/ABI/testing/sysfs-kernel-kexec-kdump b/Documentation/ABI/testing/sysfs-kernel-kexec-kdump index 00c00f380fea..f59051b5d96d 100644 --- a/Documentation/ABI/testing/sysfs-kernel-kexec-kdump +++ b/Documentation/ABI/testing/sysfs-kernel-kexec-kdump @@ -49,3 +49,13 @@ Description: read only is used by the user space utility kexec to support updating the in-kernel kdump image during hotplug operations. User: Kexec tools + +What: /sys/kernel/kexec/crash_cma_ranges +Date: Nov 2025 +Contact: [email protected] +Description: read only + Provides information about the memory ranges reserved from + the Contiguous Memory Allocator (CMA) area that are allocated + to the crash (kdump) kernel. It lists the start and end physical + addresses of CMA regions assigned for crashkernel use. +User: kdump service diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c index 7476a46de5d6..da6ff72b4669 100644 --- a/kernel/kexec_core.c +++ b/kernel/kexec_core.c @@ -1271,6 +1271,22 @@ static ssize_t crash_size_store(struct kobject *kobj, } static struct kobj_attribute crash_size_attr = __ATTR_RW(crash_size); +static ssize_t crash_cma_ranges_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + + ssize_t len = 0; + int i; + + for (i = 0; i < crashk_cma_cnt; ++i) { + len += sysfs_emit_at(buf, len, "%08llx-%08llx\n", + crashk_cma_ranges[i].start, + crashk_cma_ranges[i].end); + } + return len; +} +static struct kobj_attribute crash_cma_ranges_attr = __ATTR_RO(crash_cma_ranges); + #ifdef CONFIG_CRASH_HOTPLUG static ssize_t crash_elfcorehdr_size_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) @@ -1289,6 +1305,7 @@ static struct attribute *kexec_attrs[] = { #ifdef CONFIG_CRASH_DUMP &crash_loaded_attr.attr, &crash_size_attr.attr, + &crash_cma_ranges_attr.attr, #ifdef CONFIG_CRASH_HOTPLUG &crash_elfcorehdr_size_attr.attr, #endif -- 2.51.1
