efi_pstore: Add a logic erasing entries to an erase callback

[Issue]

Currently, efi_pstore driver simply overwrites existing panic messages in NVRAM.
So, in the following scenario, we will lose 1st panic messages.

 1. kernel panics.
 2. efi_pstore is kicked and writes panic messages to NVRAM.
 3. system reboots.
 4. kernel panics again before a user checks the 1st panic messages in NVRAM.

[Solution]

A reasonable solution to fix the issue is just holding multiple logs without erasing
existing entries.

This patch freshly adds a logic erasing existing entries, which shared with a write callback,
to an erase callback.
To support holding multiple logs, the write callback doesn't need to erase any entries and
it will be removed in a subsequent patch.

Signed-off-by: Seiji Aguchi <seiji.aguchi@hds.com>
Acked-by: Mike Waychison <mikew@google.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

1 files changed, 45 insertions, 1 deletions

diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c
index 37ac21a08751..bee14cc47c03 100644
--- a/drivers/firmware/efivars.c
+++ b/drivers/firmware/efivars.c
@@ -784,7 +784,51 @@ static int efi_pstore_write(enum pstore_type_id type,
 static int efi_pstore_erase(enum pstore_type_id type, u64 id,
                             struct pstore_info *psi)
 {
-        efi_pstore_write(type, 0, &id, (unsigned int)id, 0, psi);
+        char stub_name[DUMP_NAME_LEN];
+        efi_char16_t efi_name[DUMP_NAME_LEN];
+        efi_guid_t vendor = LINUX_EFI_CRASH_GUID;
+        struct efivars *efivars = psi->data;
+        struct efivar_entry *entry, *found = NULL;
+        int i;
+
+        sprintf(stub_name, "dump-type%u-%u-", type, (unsigned int)id);
+
+        spin_lock(&efivars->lock);
+
+        for (i = 0; i < DUMP_NAME_LEN; i++)
+                efi_name[i] = stub_name[i];
+
+        /*
+         * Clean up any entries with the same name
+         */
+
+        list_for_each_entry(entry, &efivars->list, list) {
+                get_var_data_locked(efivars, &entry->var);
+
+                if (efi_guidcmp(entry->var.VendorGuid, vendor))
+                        continue;
+                if (utf16_strncmp(entry->var.VariableName, efi_name,
+                                  utf16_strlen(efi_name)))
+                        continue;
+                /* Needs to be a prefix */
+                if (entry->var.VariableName[utf16_strlen(efi_name)] == 0)
+                        continue;
+
+                /* found */
+                found = entry;
+                efivars->ops->set_variable(entry->var.VariableName,
+                                           &entry->var.VendorGuid,
+                                           PSTORE_EFI_ATTRIBUTES,
+                                           0, NULL);
+        }
+
+        if (found)
+                list_del(&found->list);
+
+        spin_unlock(&efivars->lock);
+
+        if (found)
+                efivar_unregister(found);
 
         return 0;
 }