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Message-ID: <4DFFEC3B.90001@google.com>
Date: Mon, 20 Jun 2011 17:56:27 -0700
From: Mike Waychison <mikew@...gle.com>
To: Matthew Garrett <mjg@...hat.com>
CC: tony.luck@...el.com, linux-kernel@...r.kernel.org,
Matt_Domsch@...l.com
Subject: Re: [PATCH 3/3] efi: Add support for using efivars as a pstore backend
On 06/06/11 12:38, Matthew Garrett wrote:
> EFI provides an area of nonvolatile storage managed by the firmware. We
> can use this as a pstore backend to maintain copies of oopses, aiding
> diagnosis.
How do I configure this thing?
Inline notes below. Sorry for the delayed response.
>
> Signed-off-by: Matthew Garrett<mjg@...hat.com>
> ---
> drivers/firmware/efivars.c | 158 +++++++++++++++++++++++++++++++++++++++++++-
> include/linux/efi.h | 3 +
> 2 files changed, 159 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c
> index 5f29aaf..89e6a3a 100644
> --- a/drivers/firmware/efivars.c
> +++ b/drivers/firmware/efivars.c
> @@ -78,6 +78,7 @@
> #include<linux/kobject.h>
> #include<linux/device.h>
> #include<linux/slab.h>
> +#include<linux/pstore.h>
>
> #include<asm/uaccess.h>
>
> @@ -89,6 +90,8 @@ MODULE_DESCRIPTION("sysfs interface to EFI Variables");
> MODULE_LICENSE("GPL");
> MODULE_VERSION(EFIVARS_VERSION);
>
> +#define DUMP_NAME_LEN 52
> +
> /*
> * The maximum size of VariableName + Data = 1024
> * Therefore, it's reasonable to save that much
> @@ -161,18 +164,28 @@ utf8_strsize(efi_char16_t *data, unsigned long maxlength)
> }
>
> static efi_status_t
> -get_var_data(struct efivars *efivars, struct efi_variable *var)
> +get_var_data_locked(struct efivars *efivars, struct efi_variable *var)
> {
> efi_status_t status;
>
> - spin_lock(&efivars->lock);
> var->DataSize = 1024;
> status = efivars->ops->get_variable(var->VariableName,
> &var->VendorGuid,
> &var->Attributes,
> &var->DataSize,
> var->Data);
> + return status;
> +}
> +
> +static efi_status_t
> +get_var_data(struct efivars *efivars, struct efi_variable *var)
> +{
> + efi_status_t status;
> +
> + spin_lock(&efivars->lock);
> + status = get_var_data_locked(efivars, var);
> spin_unlock(&efivars->lock);
> +
> if (status != EFI_SUCCESS) {
> printk(KERN_WARNING "efivars: get_variable() failed 0x%lx!\n",
> status);
> @@ -387,12 +400,145 @@ static struct kobj_type efivar_ktype = {
> .default_attrs = def_attrs,
> };
>
> +static struct efivar_entry *walk_entry;
> +
> +static struct pstore_info efi_pstore_info;
Can you move these into struct efivars in efi.h?
> +
> static inline void
> efivar_unregister(struct efivar_entry *var)
> {
> kobject_put(&var->kobj);
> }
>
> +static int efi_pstore_open(struct pstore_info *psi)
> +{
> + struct efivars *efivars = psi->data;
> +
> + spin_lock(&efivars->lock);
> + walk_entry = list_first_entry(&efivars->list, struct efivar_entry,
> + list);
> + return 0;
> +}
> +
> +static int efi_pstore_close(struct pstore_info *psi)
> +{
> + struct efivars *efivars = psi->data;
> +
> + spin_unlock(&efivars->lock);
> + return 0;
> +}
> +
> +static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
> + struct timespec *timespec, struct pstore_info *psi)
> +{
> + efi_guid_t vendor = LINUX_EFI_CRASH_GUID;
> + struct efivars *efivars = psi->data;
> + char name[DUMP_NAME_LEN];
> + int i;
> + unsigned int part, size;
> + unsigned long time;
> +
> + while (&walk_entry->list !=&efivars->list) {
> + if (!efi_guidcmp(walk_entry->var.VendorGuid, vendor)) {
> + for (i = 0; i< DUMP_NAME_LEN; i++) {
> + name[i] = walk_entry->var.VariableName[i];
> + }
> + if (sscanf(name, "dump-type%u-%u-%lu", type,&part,&time) == 3) {
> + *id = part;
> + timespec->tv_sec = time;
> + timespec->tv_nsec = 0;
> + get_var_data_locked(efivars,&walk_entry->var);
> + size = walk_entry->var.DataSize;
> + memcpy(psi->buf, walk_entry->var.Data, size);
> + walk_entry = list_entry(walk_entry->list.next,
> + struct efivar_entry, list);
> + return size;
> + }
> + }
> + walk_entry = list_entry(walk_entry->list.next,
> + struct efivar_entry, list);
> + }
> + return 0;
> +}
> +
> +static u64 efi_pstore_write(enum pstore_type_id type, 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;
> +
> + sprintf(stub_name, "dump-type%u-%u-", type, part);
The format specifier here uses an unsigned, but your series passes part
around as a signed int. If part is truely non-negative, consider
changing it to unsigned?
> + sprintf(name, "%s%lu", stub_name, get_seconds());
> +
> + 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);
> +
> + for (i = 0; i< DUMP_NAME_LEN; i++) {
> + if (efi_name[i] == 0) {
Test for entry->var.VariableName[i] == 0 too. Actually, could we just
turn this string comparing loop into a strncmp test?
> + found = entry;
> + efi.set_variable(entry->var.VariableName,&entry->var.VendorGuid,
space after comma
> + EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS,
> + 0, NULL);
We shouldn't be calling the global efi ops structure here. Instead, we
should be using efivars->ops->set_variable(...)
> + break;
> + } else if (efi_name[i] != entry->var.VariableName[i]) {
> + break;
> + }
> + }
> + }
> +
> + if (found)
> + list_del(&found->list);
> +
> + for (i = 0; i< DUMP_NAME_LEN; i++)
> + efi_name[i] = name[i];
> +
> + efi.set_variable(efi_name,&vendor,
> + EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS,
> + size, psi->buf);
efivars->ops->set_variable.
> +
> + spin_unlock(&efivars->lock);
> +
> + if (found)
> + efivar_unregister(found);
> +
> + if (size)
> + efivar_create_sysfs_entry(efivars, utf8_strsize(efi_name, DUMP_NAME_LEN * 2),
> + efi_name,&vendor);
> +
> + return part;
> +};
> +
> +static int efi_pstore_erase(enum pstore_type_id type, u64 id,
> + struct pstore_info *psi)
> +{
> + efi_pstore_write(type, id, 0, psi);
> +
> + return 0;
> +}
> +
> +static struct pstore_info efi_pstore_info = {
> + .owner = THIS_MODULE,
> + .name = "efi",
> + .open = efi_pstore_open,
> + .close = efi_pstore_close,
> + .read = efi_pstore_read,
> + .write = efi_pstore_write,
> + .erase = efi_pstore_erase,
> +};
>
> static ssize_t efivar_create(struct file *filp, struct kobject *kobj,
> struct bin_attribute *bin_attr,
> @@ -763,6 +909,14 @@ int register_efivars(struct efivars *efivars,
> if (error)
> unregister_efivars(efivars);
>
> + efi_pstore_info.buf = kmalloc(4096, GFP_KERNEL);
> + if (efi_pstore_info.buf) {
> + efi_pstore_info.bufsize = 1024;
> + efi_pstore_info.data = efivars;
> + mutex_init(&efi_pstore_info.buf_mutex);
> + pstore_register(&efi_pstore_info);
> + }
> +
Hmm. pstore doesn't have a pstore_unregister? This is unfortunate
because this breaks efivars module unloading :(
> out:
> kfree(variable_name);
>
> diff --git a/include/linux/efi.h b/include/linux/efi.h
> index ec25726..8dd9a01 100644
> --- a/include/linux/efi.h
> +++ b/include/linux/efi.h
> @@ -232,6 +232,9 @@ typedef efi_status_t efi_query_capsule_caps_t(efi_capsule_header_t **capsules,
> #define UV_SYSTEM_TABLE_GUID \
> EFI_GUID( 0x3b13a7d4, 0x633e, 0x11dd, 0x93, 0xec, 0xda, 0x25, 0x56, 0xd8, 0x95, 0x93 )
>
> +#define LINUX_EFI_CRASH_GUID \
> + EFI_GUID( 0xcfc8fc79, 0xbe2e, 0x4ddc, 0x97, 0xf0, 0x9f, 0x98, 0xbf, 0xe2, 0x98, 0xa0 )
> +
> typedef struct {
> efi_guid_t guid;
> unsigned long table;
--
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