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efi: Export boot-services code and data as debugfs-blobs 

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.

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20200115163554.101315-2-hdegoede@redhat.com
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
This commit is contained in:
Hans de Goede 2020-01-15 17:35:45 +01:00 committed by Ard Biesheuvel
parent bb6d3fb354
commit 0e72a6a3cf
4 changed files with 63 additions and 0 deletions
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1
arch/x86/platform/efi/efi.c
View File

@ -243,6 +243,7 @@ int __init efi_memblock_x86_reserve_range(void)
efi.memmap.desc_version);
memblock_reserve(pmap, efi.memmap.nr_map * efi.memmap.desc_size);
set_bit(EFI_PRESERVE_BS_REGIONS, &efi.flags);
return 0;
}

4
arch/x86/platform/efi/quirks.c
View File

@ -410,6 +410,10 @@ 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;

57
drivers/firmware/efi/efi.c
View File

@ -17,6 +17,7 @@
#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>
@ -325,6 +326,59 @@ free_entry:
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;
}
if (i >= EFI_DEBUGFS_MAX_BLOBS) {
pr_warn("More then %d EFI boot service segments, only showing first %d in debugfs\n",
EFI_DEBUGFS_MAX_BLOBS, EFI_DEBUGFS_MAX_BLOBS);
break;
}
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++;
}
}
#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
@ -381,6 +435,9 @@ static int __init efisubsys_init(void)
goto err_remove_group;
}
if (efi_enabled(EFI_DBG) && efi_enabled(EFI_PRESERVE_BS_REGIONS))
efi_debugfs_init();
return 0;
err_remove_group:

1
include/linux/efi.h
View File

@ -1124,6 +1124,7 @@ extern int __init efi_setup_pcdp_console(char *);
#define EFI_NX_PE_DATA 9 /* Can runtime data regions be mapped non-executable? */
#define EFI_MEM_ATTR 10 /* Did firmware publish an EFI_MEMORY_ATTRIBUTES table? */
#define EFI_MEM_NO_SOFT_RESERVE 11 /* Is the kernel configured to ignore soft reservations? */
#define EFI_PRESERVE_BS_REGIONS 12 /* Are EFI boot-services memory segments available? */
#ifdef CONFIG_EFI
/*