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>

diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index ae923ee..8391d3c 100644 (file)
--- 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 88d32c0..bada103 100644 (file)
--- a/arch/x86/platform/efi/quirks.c
+++ b/arch/x86/platform/efi/quirks.c
@@ -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;

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 621220a..201a679 100644 (file)
--- 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 @@ 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:

diff --git a/include/linux/efi.h b/include/linux/efi.h
index 7efd707..a6e1a2d 100644 (file)
--- 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
 /*