pstore: Map PSTORE_TYPE_* to strings

In later patches we will need to map types to names, so create a
constant table for that which can also be used in different parts of
old and new code. This saves the type in the PRZ which will be useful
in later patches.

Instead of having an explicit PSTORE_TYPE_UNKNOWN, just use ..._MAX.

This includes removing the now redundant filename templates which can use
a single format string. Also, there's no reason to limit the "is it still
compressed?" test to only PSTORE_TYPE_DMESG when building the pstorefs
filename. Records are zero-initialized, so a backend would need to have
explicitly set compressed=1.

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Co-developed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>

drivers/acpi/apei/erst.c

@@ -1035,7 +1035,7 @@ skip:
 			     CPER_SECTION_TYPE_MCE) == 0)
 		record->type = PSTORE_TYPE_MCE;
 	else
-		record->type = PSTORE_TYPE_UNKNOWN;
+		record->type = PSTORE_TYPE_MAX;
 
 	if (rcd->hdr.validation_bits & CPER_VALID_TIMESTAMP)
 		record->time.tv_sec = rcd->hdr.timestamp;

fs/pstore/inode.c

@@ -335,53 +335,10 @@ int pstore_mkfile(struct dentry *root, struct pstore_record *record)
 		goto fail_alloc;
 	private->record = record;
 
-	switch (record->type) {
-	case PSTORE_TYPE_DMESG:
-		scnprintf(name, sizeof(name), "dmesg-%s-%llu%s",
-			  record->psi->name, record->id,
-			  record->compressed ? ".enc.z" : "");
-		break;
-	case PSTORE_TYPE_CONSOLE:
-		scnprintf(name, sizeof(name), "console-%s-%llu",
-			  record->psi->name, record->id);
-		break;
-	case PSTORE_TYPE_FTRACE:
-		scnprintf(name, sizeof(name), "ftrace-%s-%llu",
-			  record->psi->name, record->id);
-		break;
-	case PSTORE_TYPE_MCE:
-		scnprintf(name, sizeof(name), "mce-%s-%llu",
-			  record->psi->name, record->id);
-		break;
-	case PSTORE_TYPE_PPC_RTAS:
-		scnprintf(name, sizeof(name), "rtas-%s-%llu",
-			  record->psi->name, record->id);
-		break;
-	case PSTORE_TYPE_PPC_OF:
-		scnprintf(name, sizeof(name), "powerpc-ofw-%s-%llu",
-			  record->psi->name, record->id);
-		break;
-	case PSTORE_TYPE_PPC_COMMON:
-		scnprintf(name, sizeof(name), "powerpc-common-%s-%llu",
-			  record->psi->name, record->id);
-		break;
-	case PSTORE_TYPE_PMSG:
-		scnprintf(name, sizeof(name), "pmsg-%s-%llu",
-			  record->psi->name, record->id);
-		break;
-	case PSTORE_TYPE_PPC_OPAL:
-		scnprintf(name, sizeof(name), "powerpc-opal-%s-%llu",
-			  record->psi->name, record->id);
-		break;
-	case PSTORE_TYPE_UNKNOWN:
-		scnprintf(name, sizeof(name), "unknown-%s-%llu",
-			  record->psi->name, record->id);
-		break;
-	default:
-		scnprintf(name, sizeof(name), "type%d-%s-%llu",
-			  record->type, record->psi->name, record->id);
-		break;
-	}
+	scnprintf(name, sizeof(name), "%s-%s-%llu%s",
+			pstore_type_to_name(record->type),
+			record->psi->name, record->id,
+			record->compressed ? ".enc.z" : "");
 
 	dentry = d_alloc_name(root, name);
 	if (!dentry)

fs/pstore/platform.c

@@ -59,6 +59,19 @@ MODULE_PARM_DESC(update_ms, "milliseconds before pstore updates its content "
 		 "enabling this option is not safe, it may lead to further "
 		 "corruption on Oopses)");
 
+/* Names should be in the same order as the enum pstore_type_id */
+static const char * const pstore_type_names[] = {
+	"dmesg",
+	"mce",
+	"console",
+	"ftrace",
+	"rtas",
+	"powerpc-ofw",
+	"powerpc-common",
+	"pmsg",
+	"powerpc-opal",
+};
+
 static int pstore_new_entry;
 
 static void pstore_timefunc(struct timer_list *);
@@ -104,6 +117,30 @@ void pstore_set_kmsg_bytes(int bytes)
 /* Tag each group of saved records with a sequence number */
 static int	oopscount;
 
+const char *pstore_type_to_name(enum pstore_type_id type)
+{
+	BUILD_BUG_ON(ARRAY_SIZE(pstore_type_names) != PSTORE_TYPE_MAX);
+
+	if (WARN_ON_ONCE(type >= PSTORE_TYPE_MAX))
+		return "unknown";
+
+	return pstore_type_names[type];
+}
+EXPORT_SYMBOL_GPL(pstore_type_to_name);
+
+enum pstore_type_id pstore_name_to_type(const char *name)
+{
+	int i;
+
+	for (i = 0; i < PSTORE_TYPE_MAX; i++) {
+		if (!strcmp(pstore_type_names[i], name))
+			return i;
+	}
+
+	return PSTORE_TYPE_MAX;
+}
+EXPORT_SYMBOL_GPL(pstore_name_to_type);
+
 static const char *get_reason_str(enum kmsg_dump_reason reason)
 {
 	switch (reason) {

fs/pstore/ram.c

@@ -611,6 +611,7 @@ static int ramoops_init_przs(const char *name,
 			goto fail;
 		}
 		*paddr += zone_sz;
+		prz_ar[i]->type = pstore_name_to_type(name);
 	}
 
 	*przs = prz_ar;
@@ -650,6 +651,7 @@ static int ramoops_init_prz(const char *name,
 	}
 
 	*paddr += sz;
+	(*prz)->type = pstore_name_to_type(name);
 
 	return 0;
 }
@@ -785,7 +787,7 @@ static int ramoops_probe(struct platform_device *pdev)
 
 	dump_mem_sz = cxt->size - cxt->console_size - cxt->ftrace_size
 			- cxt->pmsg_size;
-	err = ramoops_init_przs("dump", dev, cxt, &cxt->dprzs, &paddr,
+	err = ramoops_init_przs("dmesg", dev, cxt, &cxt->dprzs, &paddr,
 				dump_mem_sz, cxt->record_size,
 				&cxt->max_dump_cnt, 0, 0);
 	if (err)

include/linux/pstore.h

@@ -32,21 +32,32 @@
 
 struct module;
 
-/* pstore record types (see fs/pstore/inode.c for filename templates) */
+/*
+ * pstore record types (see fs/pstore/platform.c for pstore_type_names[])
+ * These values may be written to storage (see EFI vars backend), so
+ * they are kind of an ABI. Be careful changing the mappings.
+ */
 enum pstore_type_id {
+	/* Frontend storage types */
 	PSTORE_TYPE_DMESG	= 0,
 	PSTORE_TYPE_MCE		= 1,
 	PSTORE_TYPE_CONSOLE	= 2,
 	PSTORE_TYPE_FTRACE	= 3,
-	/* PPC64 partition types */
+
+	/* PPC64-specific partition types */
 	PSTORE_TYPE_PPC_RTAS	= 4,
 	PSTORE_TYPE_PPC_OF	= 5,
 	PSTORE_TYPE_PPC_COMMON	= 6,
 	PSTORE_TYPE_PMSG	= 7,
 	PSTORE_TYPE_PPC_OPAL	= 8,
-	PSTORE_TYPE_UNKNOWN	= 255
+
+	/* End of the list */
+	PSTORE_TYPE_MAX
 };
 
+const char *pstore_type_to_name(enum pstore_type_id type);
+enum pstore_type_id pstore_name_to_type(const char *name);
+
 struct pstore_info;
 /**
  * struct pstore_record - details of a pstore record entry

include/linux/pstore_ram.h

@@ -22,6 +22,7 @@
 #include <linux/init.h>
 #include <linux/kernel.h>
 #include <linux/list.h>
+#include <linux/pstore.h>
 #include <linux/types.h>
 
 /*
@@ -54,6 +55,7 @@ struct persistent_ram_ecc_info {
  * @paddr:	physical address of the mapped RAM area
  * @size:	size of mapping
  * @label:	unique name of this PRZ
+ * @type:	frontend type for this PRZ
  * @flags:	holds PRZ_FLAGS_* bits
  *
  * @buffer_lock:
@@ -88,6 +90,7 @@ struct persistent_ram_zone {
 	size_t size;
 	void *vaddr;
 	char *label;
+	enum pstore_type_id type;
 	u32 flags;
 
 	raw_spinlock_t buffer_lock;