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SubjectRe: [PATCH v3 1/5] efi: Export boot-services code and data as debugfs-blobs
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Hi,

On 16-04-18 10:23, Ard Biesheuvel wrote:
> Hallo Hans,
>
> On 8 April 2018 at 19:40, Hans de Goede <hdegoede@redhat.com> wrote:
>> Sometimes it is useful to be able to dump the efi boot-services code and
>> data. This commit adds these as debugfs-blobs to /sys/kernel/debug/efi,
>> but only if efi=debug is passed on the kernel-commandline as this requires
>> not freeing those memory-regions, which costs 20+ MB of RAM.
>>
>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>> ---
>> Changes in v2:
>> -Do not call pr_err on debugfs call failures
>> ---
>> arch/x86/platform/efi/quirks.c | 4 +++
>> drivers/firmware/efi/efi.c | 53 ++++++++++++++++++++++++++++++++++
>> 2 files changed, 57 insertions(+)
>>
>> diff --git a/arch/x86/platform/efi/quirks.c b/arch/x86/platform/efi/quirks.c
>> index 5b513ccffde4..0f968c7bcfec 100644
>> --- a/arch/x86/platform/efi/quirks.c
>> +++ b/arch/x86/platform/efi/quirks.c
>> @@ -374,6 +374,10 @@ void __init efi_free_boot_services(void)
>> int num_entries = 0;
>> void *new, *new_md;
>>
>> + /* Keep all regions for /sys/kernel/debug/efi */
>> + if (efi_enabled(EFI_DBG))
>> + return;
>> +
>> for_each_efi_memory_desc(md) {
>> unsigned long long start = md->phys_addr;
>> unsigned long long size = md->num_pages << EFI_PAGE_SHIFT;
>> diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
>> index cd42f66a7c85..10c896e8b82b 100644
>> --- a/drivers/firmware/efi/efi.c
>> +++ b/drivers/firmware/efi/efi.c
>> @@ -18,6 +18,7 @@
>> #include <linux/kobject.h>
>> #include <linux/module.h>
>> #include <linux/init.h>
>> +#include <linux/debugfs.h>
>> #include <linux/device.h>
>> #include <linux/efi.h>
>> #include <linux/of.h>
>> @@ -316,6 +317,55 @@ 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;
>> + }
>> +}
>> +#else
>> +static inline void efi_debugfs_init(void) {}
>> +#endif
>> +
>> /*
>> * We register the efi subsystem with the firmware subsystem and the
>> * efivars subsystem with the efi subsystem, if the system was booted with
>> @@ -360,6 +410,9 @@ static int __init efisubsys_init(void)
>> goto err_remove_group;
>> }
>>
>> + if (efi_enabled(EFI_DBG))
>> + efi_debugfs_init();
>> +
>
> This doesn't really make any sense on non-x86. The boot services
> regions are released to the kernel for general allocation, and so
> exposing them this way only makes sense if you keep them as you do for
> x86.
>
> Could you please try to make this call specific to situations where it
> makes sense? I don't mind allocating a new EFI_xxx flag for preserving
> the boot services regions so we could decide to set it for ARM/arm64
> as well in certain cases in the future.

Ok, I've added a new EFI_BOOT_SERVICES flag for this for v4 of this
patchset, mirroring the existing EFI_RUNTIME_SERVICES flag in naming.

Regards,

Hans

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