edac: reduce stack pressure by using a pre-allocated buffer

The number of variables at the stack is too big.
Reduces the stack usage by using a pre-allocated error
buffer.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

2 files changed, 104 insertions, 33 deletions

diff --git a/drivers/edac/edac_mc.c b/drivers/edac/edac_mc.c
index 34eb9703ed33..4f18dd755939 100644
--- a/drivers/edac/edac_mc.c
+++ b/drivers/edac/edac_mc.c
@@ -1065,7 +1065,6 @@ static void edac_ue_error(struct mem_ctl_info *mci,
         edac_inc_ue_error(mci, enable_per_layer_report, pos, error_count);
 }
 
-#define OTHER_LABEL " or "
 
 /**
  * edac_mc_handle_error - reports a memory event to userspace
@@ -1097,19 +1096,28 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type,
                           const char *msg,
                           const char *other_detail)
 {
-        /* FIXME: too much for stack: move it to some pre-alocated area */
-        char detail[80], location[80];
-        char label[(EDAC_MC_LABEL_LEN + 1 + sizeof(OTHER_LABEL)) * mci->tot_dimms];
+        char detail[80];
         char *p;
         int row = -1, chan = -1;
         int pos[EDAC_MAX_LAYERS] = { top_layer, mid_layer, low_layer };
-        int i;
-        long grain;
-        bool enable_per_layer_report = false;
+        int i, n_labels = 0;
         u8 grain_bits;
+        struct edac_raw_error_desc *e = &mci->error_desc;
 
         edac_dbg(3, "MC%d\n", mci->mc_idx);
 
+        /* Fills the error report buffer */
+        memset(e, 0, sizeof (*e));
+        e->error_count = error_count;
+        e->top_layer = top_layer;
+        e->mid_layer = mid_layer;
+        e->low_layer = low_layer;
+        e->page_frame_number = page_frame_number;
+        e->offset_in_page = offset_in_page;
+        e->syndrome = syndrome;
+        e->msg = msg;
+        e->other_detail = other_detail;
+
         /*
          * Check if the event report is consistent and if the memory
          * location is known. If it is known, enable_per_layer_report will be
@@ -1132,7 +1140,7 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type,
                         pos[i] = -1;
                 }
                 if (pos[i] >= 0)
-                        enable_per_layer_report = true;
+                        e->enable_per_layer_report = true;
         }
 
         /*
@@ -1146,8 +1154,7 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type,
          * where each memory belongs to a separate channel within the same
          * branch.
          */
-        grain = 0;
-        p = label;
+        p = e->label;
         *p = '\0';
 
         for (i = 0; i < mci->tot_dimms; i++) {
@@ -1161,8 +1168,8 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type,
                         continue;
 
                 /* get the max grain, over the error match range */
-                if (dimm->grain > grain)
-                        grain = dimm->grain;
+                if (dimm->grain > e->grain)
+                        e->grain = dimm->grain;
 
                 /*
                  * If the error is memory-controller wide, there's no need to
@@ -1170,8 +1177,13 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type,
                  * channel/memory controller/...  may be affected.
                  * Also, don't show errors for empty DIMM slots.
                  */
-                if (enable_per_layer_report && dimm->nr_pages) {
-                        if (p != label) {
+                if (e->enable_per_layer_report && dimm->nr_pages) {
+                        if (n_labels >= EDAC_MAX_LABELS) {
+                                e->enable_per_layer_report = false;
+                                break;
+                        }
+                        n_labels++;
+                        if (p != e->label) {
                                 strcpy(p, OTHER_LABEL);
                                 p += strlen(OTHER_LABEL);
                         }
@@ -1198,12 +1210,12 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type,
                 }
         }
 
-        if (!enable_per_layer_report) {
-                strcpy(label, "any memory");
+        if (!e->enable_per_layer_report) {
+                strcpy(e->label, "any memory");
         } else {
                 edac_dbg(4, "csrow/channel to increment: (%d,%d)\n", row, chan);
-                if (p == label)
-                        strcpy(label, "unknown memory");
+                if (p == e->label)
+                        strcpy(e->label, "unknown memory");
                 if (type == HW_EVENT_ERR_CORRECTED) {
                         if (row >= 0) {
                                 mci->csrows[row]->ce_count += error_count;
@@ -1216,7 +1228,7 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type,
         }
 
         /* Fill the RAM location data */
-        p = location;
+        p = e->location;
 
         for (i = 0; i < mci->n_layers; i++) {
                 if (pos[i] < 0)
@@ -1226,32 +1238,35 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type,
                              edac_layer_name[mci->layers[i].type],
                              pos[i]);
         }
-        if (p > location)
+        if (p > e->location)
                 *(p - 1) = '\0';
 
         /* Report the error via the trace interface */
-        grain_bits = fls_long(grain) + 1;
-        trace_mc_event(type, msg, label, error_count,
-                       mci->mc_idx, top_layer, mid_layer, low_layer,
-                       PAGES_TO_MiB(page_frame_number) | offset_in_page,
-                       grain_bits, syndrome, other_detail);
+        grain_bits = fls_long(e->grain) + 1;
+        trace_mc_event(type, e->msg, e->label, e->error_count,
+                       mci->mc_idx, e->top_layer, e->mid_layer, e->low_layer,
+                       PAGES_TO_MiB(e->page_frame_number) | e->offset_in_page,
+                       grain_bits, e->syndrome, other_detail);
 
         /* Memory type dependent details about the error */
         if (type == HW_EVENT_ERR_CORRECTED) {
                 snprintf(detail, sizeof(detail),
                         "page:0x%lx offset:0x%lx grain:%ld syndrome:0x%lx",
-                        page_frame_number, offset_in_page,
-                        grain, syndrome);
-                edac_ce_error(mci, error_count, pos, msg, location, label,
-                              detail, other_detail, enable_per_layer_report,
-                              page_frame_number, offset_in_page, grain);
+                        e->page_frame_number, e->offset_in_page,
+                        e->grain, e->syndrome);
+                edac_ce_error(mci, e->error_count, pos, e->msg, e->location,
+                              e->label, detail, other_detail,
+                              e->enable_per_layer_report,
+                              e->page_frame_number, e->offset_in_page,
+                              e->grain);
         } else {
                 snprintf(detail, sizeof(detail),
                         "page:0x%lx offset:0x%lx grain:%ld",
-                        page_frame_number, offset_in_page, grain);
+                        page_frame_number, offset_in_page, e->grain);
 
-                edac_ue_error(mci, error_count, pos, msg, location, label,
-                              detail, other_detail, enable_per_layer_report);
+                edac_ue_error(mci, e->error_count, pos, e->msg, e->location,
+                              e->label, detail, other_detail,
+                              e->enable_per_layer_report);
         }
 }
 EXPORT_SYMBOL_GPL(edac_mc_handle_error);
diff --git a/include/linux/edac.h b/include/linux/edac.h
index ff18efc754f3..096b7fcdf484 100644
--- a/include/linux/edac.h
+++ b/include/linux/edac.h
@@ -47,8 +47,18 @@ static inline void opstate_init(void)
         return;
 }
 
+/* Max length of a DIMM label*/
 #define EDAC_MC_LABEL_LEN       31
 
+/* Maximum size of the location string */
+#define LOCATION_SIZE 80
+
+/* Defines the maximum number of labels that can be reported */
+#define EDAC_MAX_LABELS         8
+
+/* String used to join two or more labels */
+#define OTHER_LABEL " or "
+
 /**
  * enum dev_type - describe the type of memory DRAM chips used at the stick
  * @DEV_UNKNOWN:        Can't be determined, or MC doesn't support detect it
@@ -553,6 +563,46 @@ struct errcount_attribute_data {
         int layer0, layer1, layer2;
 };
 
+/**
+ * edac_raw_error_desc - Raw error report structure
+ * @grain:                      minimum granularity for an error report, in bytes
+ * @error_count:                number of errors of the same type
+ * @top_layer:                  top layer of the error (layer[0])
+ * @mid_layer:                  middle layer of the error (layer[1])
+ * @low_layer:                  low layer of the error (layer[2])
+ * @page_frame_number:          page where the error happened
+ * @offset_in_page:             page offset
+ * @syndrome:                   syndrome of the error (or 0 if unknown or if
+ *                              the syndrome is not applicable)
+ * @msg:                        error message
+ * @location:                   location of the error
+ * @label:                      label of the affected DIMM(s)
+ * @other_detail:               other driver-specific detail about the error
+ * @enable_per_layer_report:    if false, the error affects all layers
+ *                              (typically, a memory controller error)
+ */
+struct edac_raw_error_desc {
+        /*
+         * NOTE: everything before grain won't be cleaned by
+         * edac_raw_error_desc_clean()
+         */
+        char location[LOCATION_SIZE];
+        char label[(EDAC_MC_LABEL_LEN + 1 + sizeof(OTHER_LABEL)) * EDAC_MAX_LABELS];
+        long grain;
+
+        /* the vars below and grain will be cleaned on every new error report */
+        u16 error_count;
+        int top_layer;
+        int mid_layer;
+        int low_layer;
+        unsigned long page_frame_number;
+        unsigned long offset_in_page;
+        unsigned long syndrome;
+        const char *msg;
+        const char *other_detail;
+        bool enable_per_layer_report;
+};
+
 /* MEMORY controller information structure
  */
 struct mem_ctl_info {
@@ -660,6 +710,12 @@ struct mem_ctl_info {
         /* work struct for this MC */
         struct delayed_work work;
 
+        /*
+         * Used to report an error - by being at the global struct
+         * makes the memory allocated by the EDAC core
+         */
+        struct edac_raw_error_desc error_desc;
+
         /* the internal state of this controller instance */
         int op_state;