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Subject[RFC][Patch]efi_pstore:Introduce an efi_pstore_overwrite parameter to avoid missing messages in NVRAM

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 shutdowns and boots up.
4. kernel panics again before a user checks the 1st panic messages in NVRAM.


To avoid missing 1st panic messages, this patch adds a new parameter ,efi_pstore_overwrite,
to efi_pstore so that we can specify whether efi_pstore overwrites existing entries in NVRAM or not.


Signed-off-by: Seiji Aguchi <seiji.aguchi@hds.com>

---
Documentation/kernel-parameters.txt | 6 ++++
drivers/firmware/efivars.c | 55 +++++++++++++++++++---------------
2 files changed, 37 insertions(+), 24 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index a92c5eb..990befa 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -786,6 +786,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
edd= [EDD]
Format: {"off" | "on" | "skip[mbr]"}

+ efivars.efi_pstore_overwrite=
+ Specify whether efi_pstore overwrites existing entries
+ in NVRAM
+ Format: <bool> (1/Y/y=yes, 0/N/n=no)
+ default: yes
+
eisa_irq_edge= [PARISC,HW]
See header of drivers/parisc/eisa.c.

diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c index 47408e8..94fbd1d 100644
--- a/drivers/firmware/efivars.c
+++ b/drivers/firmware/efivars.c
@@ -685,6 +685,10 @@ static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
return 0;
}

+static bool efi_pstore_overwrite = 1;
+module_param_named(efi_pstore_overwrite, efi_pstore_overwrite,
+ bool, S_IRUGO | S_IWUSR);
+
static int efi_pstore_write(enum pstore_type_id type,
enum kmsg_dump_reason reason, u64 *id,
unsigned int part, size_t size, struct pstore_info *psi) @@ -705,33 +709,36 @@ static int efi_pstore_write(enum pstore_type_id type,
for (i = 0; i < DUMP_NAME_LEN; i++)
efi_name[i] = stub_name[i];

- /*
- * Clean up any entries with the same name
- */
+ if (efi_pstore_overwrite) {
+ /*
+ * 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);
+ }

- 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);
}

- if (found)
- list_del(&found->list);
-
for (i = 0; i < DUMP_NAME_LEN; i++)
efi_name[i] = name[i];
--
1.7.1


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