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Subject[PATCH 2/3] x86, RAS: Add a decoded msg buffer
Date
From: Borislav Petkov <borislav.petkov@amd.com>

Echoing 1 into /sys/devices/system/ras/agent causes the ras_printk()
function to buffer a string describing a hardware error. This is meant
for userspace daemons which are running on the system and are going to
consume decoded information through the MCE tracepoint.

Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
---
arch/x86/Kconfig | 9 +++
arch/x86/Makefile | 3 +
arch/x86/include/asm/ras.h | 15 +++++
arch/x86/ras/Makefile | 1 +
arch/x86/ras/ras.c | 145 ++++++++++++++++++++++++++++++++++++++++++++
5 files changed, 173 insertions(+), 0 deletions(-)
create mode 100644 arch/x86/include/asm/ras.h
create mode 100644 arch/x86/ras/Makefile
create mode 100644 arch/x86/ras/ras.c

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 5bed94e189fa..bda1480241b2 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -657,6 +657,15 @@ config X86_CYCLONE_TIMER
def_bool y
depends on X86_SUMMIT

+config X86_RAS
+ def_bool y
+ prompt "X86 RAS features"
+ ---help---
+ A collection of Reliability, Availability and Serviceability
+ software features which aim to enable hardware error logging
+ and reporting. Leave it at 'y' unless you really know what
+ you're doing
+
source "arch/x86/Kconfig.cpu"

config HPET_TIMER
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 209ba1294592..a6b6bb1f308b 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -146,6 +146,9 @@ drivers-$(CONFIG_OPROFILE) += arch/x86/oprofile/
# suspend and hibernation support
drivers-$(CONFIG_PM) += arch/x86/power/

+# RAS support
+core-y += arch/x86/ras/
+
drivers-$(CONFIG_FB) += arch/x86/video/

####
diff --git a/arch/x86/include/asm/ras.h b/arch/x86/include/asm/ras.h
new file mode 100644
index 000000000000..b51838514259
--- /dev/null
+++ b/arch/x86/include/asm/ras.h
@@ -0,0 +1,15 @@
+#ifndef _ASM_X86_RAS_H
+#define _ASM_X86_RAS_H
+
+#define ERR_BUF_SZ 500
+
+extern bool ras_agent;
+
+#define PR_EMERG BIT(0)
+#define PR_WARNING BIT(4)
+#define PR_CONT BIT(8)
+
+extern const char *ras_get_decoded_err(void);
+extern void ras_printk(unsigned long flags, const char *fmt, ...);
+
+#endif /* _ASM_X86_RAS_H */
diff --git a/arch/x86/ras/Makefile b/arch/x86/ras/Makefile
new file mode 100644
index 000000000000..7a70bb5cd057
--- /dev/null
+++ b/arch/x86/ras/Makefile
@@ -0,0 +1 @@
+obj-y := ras.o
diff --git a/arch/x86/ras/ras.c b/arch/x86/ras/ras.c
new file mode 100644
index 000000000000..868d732c6cd4
--- /dev/null
+++ b/arch/x86/ras/ras.c
@@ -0,0 +1,145 @@
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <asm/ras.h>
+
+static size_t dec_len;
+static char *err_str;
+
+/*
+ * If true, userspace has an agent running and eating all the
+ * tracing data we're sending out so there's no dmesg output
+ */
+bool ras_agent;
+EXPORT_SYMBOL_GPL(ras_agent);
+
+/* getting the string implies the current buffer is emptied */
+const char *ras_get_decoded_err(void)
+{
+ dec_len = 0;
+ return err_str;
+}
+
+void ras_printk(unsigned long flags, const char *fmt, ...)
+{
+ va_list args;
+ char *buf;
+ size_t left;
+ int i;
+
+ /* add a HW_ERR prefix to a newly started line */
+ if (!(flags & PR_CONT)) {
+ strcpy(err_str + dec_len, HW_ERR);
+ dec_len += strlen(HW_ERR);
+ }
+
+ left = ERR_BUF_SZ - dec_len - 1;
+ buf = err_str + dec_len;
+
+ va_start(args, fmt);
+ i = vsnprintf(buf, left, fmt, args);
+ va_end(args);
+
+ if (i >= left) {
+ pr_err("Error decode buffer truncated.\n");
+ dec_len = ERR_BUF_SZ-1;
+ err_str[dec_len] = '\n';
+ } else
+ dec_len += i;
+
+ if (!ras_agent) {
+ if (flags & PR_EMERG)
+ pr_emerg("%s", buf);
+ else if (flags & PR_WARNING)
+ pr_warning("%s", buf);
+ else if (flags & PR_CONT)
+ pr_cont("%s", buf);
+
+ dec_len = 0;
+ }
+}
+EXPORT_SYMBOL_GPL(ras_printk);
+
+struct bus_type ras_subsys = {
+ .name = "ras",
+ .dev_name = "ras",
+};
+
+struct ras_attr {
+ struct attribute attr;
+ ssize_t (*show) (struct kobject *kobj, struct ras_attr *attr, char *bf);
+ ssize_t (*store)(struct kobject *kobj, struct ras_attr *attr,
+ const char *buf, size_t count);
+};
+
+#define RAS_ATTR(_name, _mode, _show, _store) \
+static struct ras_attr ras_attr_##_name = __ATTR(_name, _mode, _show, _store)
+
+static ssize_t ras_agent_show(struct kobject *kobj,
+ struct ras_attr *attr,
+ char *buf)
+{
+ return sprintf(buf, "%.1d\n", ras_agent);
+}
+
+static ssize_t ras_agent_store(struct kobject *kobj,
+ struct ras_attr *attr,
+ const char *buf, size_t count)
+{
+ int ret = 0;
+ unsigned long value;
+
+ ret = kstrtoul(buf, 10, &value);
+ if (ret < 0) {
+ printk(KERN_ERR "Wrong value for ras_agent field.\n");
+ return ret;
+ }
+
+ ras_agent = !!value;
+
+ return count;
+}
+
+RAS_ATTR(agent, 0644, ras_agent_show, ras_agent_store);
+
+static struct attribute *ras_root_attrs[] = {
+ &ras_attr_agent.attr,
+ NULL
+};
+
+static const struct attribute_group ras_root_attr_group = {
+ .attrs = ras_root_attrs,
+};
+
+static const struct attribute_group *ras_root_attr_groups[] = {
+ &ras_root_attr_group,
+ NULL,
+};
+
+static int __init ras_init(void)
+{
+ int err = 0;
+
+ err = subsys_system_register(&ras_subsys, ras_root_attr_groups);
+ if (err) {
+ printk(KERN_ERR "Error registering toplevel RAS sysfs node.\n");
+ return err;
+ }
+
+ /* no freeing of this since it ras.c is compiled-on only */
+ err_str = kzalloc(ERR_BUF_SZ, GFP_KERNEL);
+ if (!err_str) {
+ err = -ENOMEM;
+ goto err_alloc;
+ }
+
+ return 0;
+
+err_alloc:
+ bus_unregister(&ras_subsys);
+
+ return err;
+}
+subsys_initcall(ras_init);
--
1.7.8.rc0


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