Re: [tip:efi/core] efibc: Add EFI Bootloader Control module

Compostella, Jeremy
2016-04-30T08:35:11Z

Ingo Molnar <mingo@kernel.org> writes:

> * Compostella, Jeremy <jeremy.compostella@intel.com> wrote:
>
>> -static void efibc_set_variable(const char *name, const char *value)
>> +static int efibc_set_variable(const char *name, const char *value)
>> {
>> int ret;
>> efi_guid_t guid = LINUX_EFI_LOADER_ENTRY_GUID;
>> - struct efivar_entry entry;
>> + struct efivar_entry *entry;
>> size_t size = (strlen(value) + 1) * sizeof(efi_char16_t);
>>
>> - if (size > sizeof(entry.var.Data))
>> + if (size > sizeof(entry->var.Data)) {
>> pr_err("value is too large");
>> + return -1;
>> + }
>>
>> - efibc_str_to_str16(name, entry.var.VariableName);
>> - efibc_str_to_str16(value, (efi_char16_t *)entry.var.Data);
>> - memcpy(&entry.var.VendorGuid, &guid, sizeof(guid));
>> + entry = kmalloc(sizeof(*entry), GFP_KERNEL);
>> + if (!entry) {
>> + pr_err("failed to allocate efivar entry");
>> + return -1;
>> + }
>>
>> - ret = efivar_entry_set(&entry,
>> + efibc_str_to_str16(name, entry->var.VariableName);
>> + efibc_str_to_str16(value, (efi_char16_t *)entry->var.Data);
>> + memcpy(&entry->var.VendorGuid, &guid, sizeof(guid));
>> +
>> + ret = efivar_entry_set(entry,
>> EFI_VARIABLE_NON_VOLATILE
>> | EFI_VARIABLE_BOOTSERVICE_ACCESS
>> | EFI_VARIABLE_RUNTIME_ACCESS,
>> - size, entry.var.Data, NULL);
>> + size, entry->var.Data, NULL);
>> if (ret)
>> pr_err("failed to set %s EFI variable: 0x%x\n",
>> name, ret);
>> +
>> + kfree(entry);
>> + return ret;
>> }
>>
>> static int efibc_reboot_notifier_call(struct notifier_block *notifier,
>> unsigned long event, void *data)
>> {
>> const char *reason = "shutdown";
>> + int ret;
>>
>> if (event == SYS_RESTART)
>> reason = "reboot";
>>
>> - efibc_set_variable("LoaderEntryRebootReason", reason);
>> -
>> - if (!data)
>> - return NOTIFY_DONE;
>> + ret = efibc_set_variable("LoaderEntryRebootReason", reason);
>> + if (ret || !data)
>> + return NOTIFY_DONE;
>>
>> efibc_set_variable("LoaderEntryOneShot", (char *)data);
>
> Hm, can reboot notifiers do non-atomic allocations?
The reboot notifier chain is a blocking notifier chain. AFAIK, it
allows non-atomic allocation, right ?

> Why is efivar_entry so huge?
efivar_entry structure include two "big" arrays of 1024 bytes each for
the EFI variable name and data.

Thanks,

Jérémy
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