Re: [PATCH v7 1/8] efi: Export boot-services code and data as debugfs-blobs

Hans de Goede
2019-11-14T11:31:26Z

Hi,

On 14-10-2019 11:11, Luis Chamberlain wrote:
> On Fri, Oct 04, 2019 at 04:50:49PM +0200, Hans de Goede wrote:
>> diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
>> index 8d3e778e988b..abba49c4c46d 100644
>> --- a/drivers/firmware/efi/efi.c
>> +++ b/drivers/firmware/efi/efi.c
>> @@ -314,6 +315,55 @@ static __init int efivar_ssdt_load(void)
>> static inline int efivar_ssdt_load(void) { return 0; }
>> #endif
>>
>> +#ifdef CONFIG_DEBUG_FS
>> +
>> +#define EFI_DEBUGFS_MAX_BLOBS 32
>> +
>> +static struct debugfs_blob_wrapper debugfs_blob[EFI_DEBUGFS_MAX_BLOBS];
>> +
>> +static void __init efi_debugfs_init(void)
>> +{
>> + struct dentry *efi_debugfs;
>> + efi_memory_desc_t *md;
>> + char name[32];
>> + int type_count[EFI_BOOT_SERVICES_DATA + 1] = {};
>> + int i = 0;
>> +
>> + efi_debugfs = debugfs_create_dir("efi", NULL);
>> + if (IS_ERR_OR_NULL(efi_debugfs))
>> + return;
>> +
>> + for_each_efi_memory_desc(md) {
>> + switch (md->type) {
>> + case EFI_BOOT_SERVICES_CODE:
>> + snprintf(name, sizeof(name), "boot_services_code%d",
>> + type_count[md->type]++);
>> + break;
>> + case EFI_BOOT_SERVICES_DATA:
>> + snprintf(name, sizeof(name), "boot_services_data%d",
>> + type_count[md->type]++);
>> + break;
>> + default:
>> + continue;
>> + }
>> +
>> + debugfs_blob[i].size = md->num_pages << EFI_PAGE_SHIFT;
>> + debugfs_blob[i].data = memremap(md->phys_addr,
>> + debugfs_blob[i].size,
>> + MEMREMAP_WB);
>> + if (!debugfs_blob[i].data)
>> + continue;
>> +
>> + debugfs_create_blob(name, 0400, efi_debugfs, &debugfs_blob[i]);
>> + i++;
>> + if (i == EFI_DEBUGFS_MAX_BLOBS)
>> + break;
>
> Why do we silently ignore more entries ?

A valid remark, I agree that adding a pr_warn_once here would be good
I will do so for the next version.

> And could documentation be
> added for ways in which this could be used in practice?

I can write a little how to use this to get an embedded firmware,
I will add this to firmware/fallback-mechanisms.rst for the next
version.

Regards,

Hans