[PATCH v11 01/10] efi: Export boot-services code and data as debugfs-blobs

Hans de Goede
2020-01-11T14:57:21Z

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>
---
Changes in v8:
-Add pr_warn if there are mode then EFI_DEBUGFS_MAX_BLOBS boot service segments
-Document how the boot_service_code? files can be used to check for embedded
firmware. Note since this is related to the firmware EFI embedded fw support,
these docs are added in the 4th patch of this patch-set, not in this one.

Changes in v5:
-Rename the EFI_BOOT_SERVICES flag to EFI_PRESERVE_BS_REGIONS

Changes in v4:
-Add new EFI_BOOT_SERVICES flag and use it to determine if the boot-services
memory segments are available (and thus if it makes sense to register the
debugfs bits for them)

Changes in v2:
-Do not call pr_err on debugfs call failures
---
arch/x86/platform/efi/efi.c | 1 +
arch/x86/platform/efi/quirks.c | 4 +++
drivers/firmware/efi/efi.c | 57 ++++++++++++++++++++++++++++++++++
include/linux/efi.h | 1 +
4 files changed, 63 insertions(+)

diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index 59f7f6d60cf6..51ee2e2a18d6 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -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;
}
diff --git a/arch/x86/platform/efi/quirks.c b/arch/x86/platform/efi/quirks.c
index 46807b7606da..d5e822373450 100644
--- a/arch/x86/platform/efi/quirks.c
+++ b/arch/x86/platform/efi/quirks.c
@@ -409,6 +409,10 @@ 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 621220ab3d0e..201a6799671d 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -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 @@ 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;
+ }
+
+ 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:
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 7efd7072cca5..a6e1a2d8511e 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -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
/*
--
2.24.1