[RFC PATCH 7/8] EDAC, mce_amd: Add a simple tracepoint dumping a decoded string

[Borislav Petkov]

From: Borislav Petkov <bp@xxxxxxx>

It is a single string which gets dynamically generated when the error
gets decoded. Dump it to userspace through that tracepoint so that
consumers can get the already decoded string and the kernel has the
decoding functionality too, even if there are no userspace consumers.

Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
 drivers/edac/mce_amd.c  |  7 ++++++-
 drivers/ras/ras.c       |  1 +
 include/ras/ras_event.h | 16 ++++++++++++++++
 3 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/drivers/edac/mce_amd.c b/drivers/edac/mce_amd.c
index 1f5e9bb161f3..ce7e20ca6773 100644
--- a/drivers/edac/mce_amd.c
+++ b/drivers/edac/mce_amd.c
@@ -1,6 +1,8 @@
 #include <linux/seq_buf.h>
 #include <linux/module.h>
 #include <linux/slab.h>
+#include <linux/ras.h>
+#include <ras/ras_event.h>
 
 #include <asm/cpu.h>
 
@@ -1053,7 +1055,10 @@ amd_decode_mce(struct notifier_block *nb, unsigned long val, void *data)
  err_code:
 	amd_decode_err_code(m->status & 0xffff);
 
-	pr_emerg("%.*s\n", (int)sb.len, sb.buffer);
+	if (ras_userspace_consumers())
+		trace_mce_decode(sb.buffer);
+	else
+		pr_emerg("%.*s\n", (int)sb.len, sb.buffer);
 
 	seq_buf_clear_buf(&sb);
 
diff --git a/drivers/ras/ras.c b/drivers/ras/ras.c
index 5429d3795732..a09e39b3f711 100644
--- a/drivers/ras/ras.c
+++ b/drivers/ras/ras.c
@@ -42,6 +42,7 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(extlog_mem_event);
 EXPORT_TRACEPOINT_SYMBOL_GPL(mc_event);
 EXPORT_TRACEPOINT_SYMBOL_GPL(non_standard_event);
 EXPORT_TRACEPOINT_SYMBOL_GPL(arm_event);
+EXPORT_TRACEPOINT_SYMBOL_GPL(mce_decode);
 
 static int __init parse_ras_param(char *str)
 {
diff --git a/include/ras/ras_event.h b/include/ras/ras_event.h
index 429f46fb61e4..113df73f7ba0 100644
--- a/include/ras/ras_event.h
+++ b/include/ras/ras_event.h
@@ -407,6 +407,22 @@ TRACE_EVENT(memory_failure_event,
 	)
 );
 #endif /* CONFIG_MEMORY_FAILURE */
+
+TRACE_EVENT(mce_decode,
+	TP_PROTO(const char *param_str),
+
+	TP_ARGS(param_str),
+
+	TP_STRUCT__entry(
+		__string(str, param_str)
+	),
+
+	TP_fast_assign(
+		__assign_str(str, param_str);
+	),
+
+	TP_printk("%s", __get_str(str))
+);
 #endif /* _TRACE_HW_EVENT_MC_H */
 
 /* This part must be outside protection */
-- 
2.14.0.rc0