On Wed, Oct 24, 2012 at 6:54 PM, Seiji Aguchi <seiji.aguchi@xxxxxxx> wrote:
> [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 removes a logic erasing existing entries in a write callback
> because the logic is not needed in the write callback to support holding multiple logs.
>
> Signed-off-by: Seiji Aguchi <seiji.aguchi@xxxxxxx>
> ---
> drivers/firmware/efivars.c | 39 ++-------------------------------------
> 1 files changed, 2 insertions(+), 37 deletions(-)
>
> diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c
> index bee14cc..fbe9202 100644
> --- a/drivers/firmware/efivars.c
> +++ b/drivers/firmware/efivars.c
> @@ -701,18 +701,13 @@ static int efi_pstore_write(enum pstore_type_id type,
> unsigned int part, size_t size, struct pstore_info *psi)
> {
> char name[DUMP_NAME_LEN];
> - 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, ret = 0;
> u64 storage_space, remaining_space, max_variable_size;
> efi_status_t status = EFI_NOT_FOUND;
>
> - sprintf(stub_name, "dump-type%u-%u-", type, part);
> - sprintf(name, "%s%lu", stub_name, get_seconds());
> -
> spin_lock(&efivars->lock);
>
> /*
> @@ -730,35 +725,8 @@ static int efi_pstore_write(enum pstore_type_id type,
> return -ENOSPC;
> }
>
> - 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);
> + sprintf(name, "dump-type%u-%u-%lu", type, part,
> + get_seconds());
Actually, nothing seems to be ensuring that the value used here ends
up being the same as the ctime :\ Consider what happens if the
get_seconds() call here happens at second N, and the i_ctime is
collected at time N+1. The object wouldn't be able to be deleted after
patch 4/5 is applied. How can we better ensure that the i_ctime is
the same value as serialized into the efi var name here?
>
> for (i = 0; i < DUMP_NAME_LEN; i++)
> efi_name[i] = name[i];
> @@ -768,9 +736,6 @@ static int efi_pstore_write(enum pstore_type_id type,
>
> spin_unlock(&efivars->lock);
>
> - if (found)
> - efivar_unregister(found);
> -
> if (size)
> ret = efivar_create_sysfs_entry(efivars,
> utf16_strsize(efi_name,
> -- 1.7.1
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