Re: [PATCH 3/3] efi: Add support for using efivars as a pstore backend

[Mike Waychison <mikew@google.com>]

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@redhat.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;