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

Hans de Goede
2019-10-04T14:51:17Z

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 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 | 53 ++++++++++++++++++++++++++++++++++
include/linux/efi.h | 1 +
4 files changed, 59 insertions(+)

diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index c202e1b07e29..847730f7e74b 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -232,6 +232,7 @@ 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 3b9fd679cea9..fab12ebf0ada 100644
--- a/arch/x86/platform/efi/quirks.c
+++ b/arch/x86/platform/efi/quirks.c
@@ -411,6 +411,10 @@ 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 8d3e778e988b..abba49c4c46d 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>
@@ -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;
+ }
+}
+#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
@@ -370,6 +420,9 @@ 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 bd3837022307..2a30a1bd8bdf 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -1202,6 +1202,7 @@ extern int __init efi_setup_pcdp_console(char *);
#define EFI_DBG 8 /* Print additional debug info at runtime */
#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_PRESERVE_BS_REGIONS 11 /* Are EFI boot-services memory segments available? */

#ifdef CONFIG_EFI
/*
--
2.23.0