Add a sysfs directory at /sys/kernel/hwerr_recovery_stats/ to expose
hardware error recovery statistics that are already tracked by the
kernel. This allows userspace monitoring tools to track recovered
hardware errors without requiring kernel crashes.

This is useful to track recoverable hardware errors in a time series,
even if the host doesn't crash.

The sysfs directory contains one file per error subsystem:

  /sys/kernel/hwerr_recovery_stats/cpu     - CPU-related errors (MCE, ARM errors)
  /sys/kernel/hwerr_recovery_stats/memory  - Memory-related errors
  /sys/kernel/hwerr_recovery_stats/pci     - PCI/PCIe AER non-fatal errors
  /sys/kernel/hwerr_recovery_stats/cxl     - CXL errors
  /sys/kernel/hwerr_recovery_stats/others  - Other hardware errors

Each file contains a single integer representing the count of recovered
errors for that subsystem.

These statistics provide visibility into the health of the system's
hardware and can be used by system administrators to proactively detect
failing components before they cause system crashes.

Signed-off-by: Breno Leitao <leitao@debian.org>
---
 kernel/vmcore_info.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

diff --git a/kernel/vmcore_info.c b/kernel/vmcore_info.c
index e2784038bbed7..b7fcd21be7c59 100644
--- a/kernel/vmcore_info.c
+++ b/kernel/vmcore_info.c

@@ -6,6 +6,8 @@
 
 #include <linux/buildid.h>
 #include <linux/init.h>
+#include <linux/kobject.h>
+#include <linux/sysfs.h>
 #include <linux/utsname.h>
 #include <linux/vmalloc.h>
 #include <linux/sizes.h>

@@ -139,6 +141,56 @@ void hwerr_log_error_type(enum hwerr_error_type src)
 }
 EXPORT_SYMBOL_GPL(hwerr_log_error_type);
 
+/* sysfs interface for hardware error recovery statistics */
+#define HWERR_ATTR_RO(_name, _type)					\
+static ssize_t _name##_show(struct kobject *kobj,			\
+			    struct kobj_attribute *attr, char *buf)	\
+{									\
+	return sysfs_emit(buf, "%d\n",					\
+			  atomic_read(&hwerr_data[_type].count));	\
+}									\
+static struct kobj_attribute hwerr_##_name##_attr = __ATTR_RO(_name)
+
+HWERR_ATTR_RO(cpu, HWERR_RECOV_CPU);
+HWERR_ATTR_RO(memory, HWERR_RECOV_MEMORY);
+HWERR_ATTR_RO(pci, HWERR_RECOV_PCI);
+HWERR_ATTR_RO(cxl, HWERR_RECOV_CXL);
+HWERR_ATTR_RO(others, HWERR_RECOV_OTHERS);
+
+static struct attribute *hwerr_recovery_stats_attrs[] = {
+	&hwerr_cpu_attr.attr,
+	&hwerr_memory_attr.attr,
+	&hwerr_pci_attr.attr,
+	&hwerr_cxl_attr.attr,
+	&hwerr_others_attr.attr,
+	NULL,
+};
+
+static const struct attribute_group hwerr_recovery_stats_group = {
+	.attrs = hwerr_recovery_stats_attrs,
+};
+
+static struct kobject *hwerr_recovery_stats_kobj;
+
+static int __init hwerr_recovery_stats_init(void)
+{
+	hwerr_recovery_stats_kobj = kobject_create_and_add("hwerr_recovery_stats",
+							   kernel_kobj);
+	if (!hwerr_recovery_stats_kobj) {
+		pr_warn("Failed to create hwerr_recovery_stats kobject\n");
+		return -ENOMEM;
+	}
+
+	if (sysfs_create_group(hwerr_recovery_stats_kobj,
+			       &hwerr_recovery_stats_group)) {
+		kobject_put(hwerr_recovery_stats_kobj);
+		pr_warn("Failed to create hwerr_recovery_stats sysfs group\n");
+		return -ENOMEM;
+	}
+
+	return 0;
+}
+
 static int __init crash_save_vmcoreinfo_init(void)
 {
 	vmcoreinfo_data = (unsigned char *)get_zeroed_page(GFP_KERNEL);

@@ -248,6 +300,9 @@ static int __init crash_save_vmcoreinfo_init(void)
 	arch_crash_save_vmcoreinfo();
 	update_vmcoreinfo_note();
 
+	/* Create /sys/kernel/hwerr_recovery_stats/ directory */
+	hwerr_recovery_stats_init();
+
 	return 0;
 }
 

-- 
2.47.3