[PATCH v7 08/12] efi: export efi runtime memory mapping to sysfs

Dave Young
2013-12-20T10:06:56Z

kexec kernel will need exactly same mapping for
efi runtime memory ranges. Thus here export the
runtime ranges mapping to sysfs, kexec-tools
will assemble them and pass to 2nd kernel via
setup_data.

Introducing a new directory /sys/firmware/efi/runtime-map
Just like /sys/firmware/memmap. Containing below attribute
in each file of that directory:
attribute num_pages phys_addr type virt_addr

Changelog:
- Cleaup code, add function efi_save_runtime_map
- Improve err handling
- Add macros for sysfs _show functions
- Remove forward declarations.
Matt:
- s/efi-runtime-map.c/runtime-map.c
- Change dir name to runtime-map
- Changelog and documentation fixes.
- Documentation fixes.
- Update to use desc_size in efi_runtime_map
- Kconfig EFI_RUNTIME_MAP depends on X86 && KEXEC && EFI
Boris:
- Documentation grammar/spelling fix
- krealloc fix.
- Move efi_runtime_map_init to efisubsys_initcall.
- Remove 'if EXPERT' for EFI_RUNTIME_MAP Kconfig option
- save_runtime_map: move error handling code into the function itself.
- other code improvement.
Me:
- userspace prepares valid memmap in boot_params thus in this version
cleanup and improve save_runtime_map as a standalone function which
iterate the memmap again. In this way code looks better also it is
easier for later efi_kexec splitting.

Signed-off-by: Dave Young <dyoung@redhat.com>
---
.../ABI/testing/sysfs-firmware-efi-runtime-map | 34 ++++
arch/x86/platform/efi/efi.c | 46 +++++-
drivers/firmware/efi/Kconfig | 11 ++
drivers/firmware/efi/Makefile | 1 +
drivers/firmware/efi/efi.c | 4 +
drivers/firmware/efi/runtime-map.c | 181 +++++++++++++++++++++
include/linux/efi.h | 13 ++
7 files changed, 287 insertions(+), 3 deletions(-)
create mode 100644 Documentation/ABI/testing/sysfs-firmware-efi-runtime-map
create mode 100644 drivers/firmware/efi/runtime-map.c

diff --git a/Documentation/ABI/testing/sysfs-firmware-efi-runtime-map b/Documentation/ABI/testing/sysfs-firmware-efi-runtime-map
new file mode 100644
index 0000000..c61b9b3
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-firmware-efi-runtime-map
@@ -0,0 +1,34 @@
+What: /sys/firmware/efi/runtime-map/
+Date: December 2013
+Contact: Dave Young <dyoung@redhat.com>
+Description: Switching efi runtime services to virtual mode requires
+ that all efi memory ranges which have the runtime attribute
+ bit set to be mapped to virtual addresses.
+
+ The efi runtime services can only be switched to virtual
+ mode once without rebooting. The kexec kernel must maintain
+ the same physical to virtual address mappings as the first
+ kernel. The mappings are exported to sysfs so userspace tools
+ can reassemble them and pass them into the kexec kernel.
+
+ /sys/firmware/efi/runtime-map/ is the directory the kernel
+ exports that information in.
+
+ subdirectories are named with the number of the memory range:
+
+ /sys/firmware/efi/runtime-map/0
+ /sys/firmware/efi/runtime-map/1
+ /sys/firmware/efi/runtime-map/2
+ /sys/firmware/efi/runtime-map/3
+ ...
+
+ Each subdirectory contains five files:
+
+ attribute : The attributes of the memory range.
+ num_pages : The size of the memory range in pages.
+ phys_addr : The physical address of the memory range.
+ type : The type of the memory range.
+ virt_addr : The virtual address of the memory range.
+
+ Above values are all hexadecimal numbers with the '0x' prefix.
+Users: Kexec
diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index d12d145..0690a25 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -76,6 +76,9 @@ static __initdata efi_config_table_type_t arch_tables[] = {
{NULL_GUID, NULL, NULL},
};

+static void *efi_runtime_map;
+static int nr_efi_runtime_map;
+
/*
* Returns 1 if 'facility' is enabled, 0 otherwise.
*/
@@ -817,6 +820,39 @@ static void __init get_systab_virt_addr(efi_memory_desc_t *md)
}
}

+static int __init save_runtime_map(void)
+{
+ efi_memory_desc_t *md;
+ void *tmp, *p, *q = NULL;
+ int count = 0;
+
+ for (p = memmap.map; p < memmap.map_end; p += memmap.desc_size) {
+ md = p;
+
+ if (!(md->attribute & EFI_MEMORY_RUNTIME) ||
+ (md->type == EFI_BOOT_SERVICES_CODE) ||
+ (md->type == EFI_BOOT_SERVICES_DATA))
+ continue;
+ tmp = krealloc(q, (count + 1) * memmap.desc_size, GFP_KERNEL);
+ if (!tmp)
+ goto out;
+ q = tmp;
+
+ memcpy(q + count * memmap.desc_size, md, memmap.desc_size);
+ count++;
+ }
+
+ efi_runtime_map = q;
+ nr_efi_runtime_map = count;
+ efi_runtime_map_setup(efi_runtime_map, nr_efi_runtime_map,
+ boot_params.efi_info.efi_memdesc_size);
+
+ return 0;
+out:
+ kfree(q);
+ return -ENOMEM;
+}
+
/*
* Map efi memory ranges for runtime serivce and update new_memmap with virtual
* addresses.
@@ -842,7 +878,7 @@ static void * __init efi_map_regions(int *count)
tmp = krealloc(new_memmap, (*count + 1) * memmap.desc_size,
GFP_KERNEL);
if (!tmp)
- goto out_krealloc;
+ goto out;
new_memmap = tmp;
memcpy(new_memmap + (*count * memmap.desc_size), md,
memmap.desc_size);
@@ -850,7 +886,7 @@ static void * __init efi_map_regions(int *count)
}

return new_memmap;
-out_krealloc:
+out:
kfree(new_memmap);
return NULL;
}
@@ -876,7 +912,7 @@ void __init efi_enter_virtual_mode(void)
{
efi_status_t status;
void *new_memmap = NULL;
- int count = 0;
+ int err, count = 0;

efi.systab = NULL;

@@ -897,6 +933,10 @@ void __init efi_enter_virtual_mode(void)
return;
}

+ err = save_runtime_map();
+ if (err)
+ pr_err("Error saving runtime map, efi runtime on kexec non-functional!!\n");
+
BUG_ON(!efi.systab);

efi_setup_page_tables();
diff --git a/drivers/firmware/efi/Kconfig b/drivers/firmware/efi/Kconfig
index 6aecbc8..1e75f48 100644
--- a/drivers/firmware/efi/Kconfig
+++ b/drivers/firmware/efi/Kconfig
@@ -36,6 +36,17 @@ config EFI_VARS_PSTORE_DEFAULT_DISABLE
backend for pstore by default. This setting can be overridden
using the efivars module's pstore_disable parameter.

+config EFI_RUNTIME_MAP
+ bool "Export efi runtime maps to sysfs"
+ depends on X86 && EFI && KEXEC
+ default y
+ help
+ Export efi runtime memory maps to /sys/firmware/efi/runtime-map.
+ That memory map is used for example by kexec to set up efi virtual
+ mapping the 2nd kernel, but can also be used for debugging purposes.
+
+ See also Documentation/ABI/testing/sysfs-firmware-efi-runtime-map.
+
endmenu

config UEFI_CPER
diff --git a/drivers/firmware/efi/Makefile b/drivers/firmware/efi/Makefile
index 6c2a41e..9553496 100644
--- a/drivers/firmware/efi/Makefile
+++ b/drivers/firmware/efi/Makefile
@@ -5,3 +5,4 @@ obj-$(CONFIG_EFI) += efi.o vars.o
obj-$(CONFIG_EFI_VARS) += efivars.o
obj-$(CONFIG_EFI_VARS_PSTORE) += efi-pstore.o
obj-$(CONFIG_UEFI_CPER) += cper.o
+obj-$(CONFIG_EFI_RUNTIME_MAP) += runtime-map.o
diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 6d0bc52..7910cd5 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -167,6 +167,10 @@ static int __init efisubsys_init(void)
goto err_unregister;
}

+ error = efi_runtime_map_init(efi_kobj);
+ if (error)
+ goto err_remove_group;
+
/* and the standard mountpoint for efivarfs */
efivars_kobj = kobject_create_and_add("efivars", efi_kobj);
if (!efivars_kobj) {
diff --git a/drivers/firmware/efi/runtime-map.c b/drivers/firmware/efi/runtime-map.c
new file mode 100644
index 0000000..97cdd16
--- /dev/null
+++ b/drivers/firmware/efi/runtime-map.c
@@ -0,0 +1,181 @@
+/*
+ * linux/drivers/efi/runtime-map.c
+ * Copyright (C) 2013 Red Hat, Inc., Dave Young <dyoung@redhat.com>
+ *
+ * This file is released under the GPLv2.
+ */
+
+#include <linux/string.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/efi.h>
+#include <linux/slab.h>
+
+#include <asm/setup.h>
+
+static void *efi_runtime_map;
+static int nr_efi_runtime_map;
+static u32 efi_memdesc_size;
+
+struct efi_runtime_map_entry {
+ efi_memory_desc_t md;
+ struct kobject kobj; /* kobject for each entry */
+};
+
+static struct efi_runtime_map_entry **map_entries;
+
+struct map_attribute {
+ struct attribute attr;
+ ssize_t (*show)(struct efi_runtime_map_entry *entry, char *buf);
+};
+
+static inline struct map_attribute *to_map_attr(struct attribute *attr)
+{
+ return container_of(attr, struct map_attribute, attr);
+}
+
+static ssize_t type_show(struct efi_runtime_map_entry *entry, char *buf)
+{
+ return snprintf(buf, PAGE_SIZE, "0x%x\n", entry->md.type);
+}
+
+#define EFI_RUNTIME_FIELD(var) entry->md.var
+
+#define EFI_RUNTIME_U64_ATTR_SHOW(name) \
+static ssize_t name##_show(struct efi_runtime_map_entry *entry, char *buf) \
+{ \
+ return snprintf(buf, PAGE_SIZE, "0x%llx\n", EFI_RUNTIME_FIELD(name)); \
+}
+
+EFI_RUNTIME_U64_ATTR_SHOW(phys_addr);
+EFI_RUNTIME_U64_ATTR_SHOW(virt_addr);
+EFI_RUNTIME_U64_ATTR_SHOW(num_pages);
+EFI_RUNTIME_U64_ATTR_SHOW(attribute);
+
+static inline struct efi_runtime_map_entry *to_map_entry(struct kobject *kobj)
+{
+ return container_of(kobj, struct efi_runtime_map_entry, kobj);
+}
+
+static ssize_t map_attr_show(struct kobject *kobj, struct attribute *attr,
+ char *buf)
+{
+ struct efi_runtime_map_entry *entry = to_map_entry(kobj);
+ struct map_attribute *map_attr = to_map_attr(attr);
+
+ return map_attr->show(entry, buf);
+}
+
+static struct map_attribute map_type_attr = __ATTR_RO(type);
+static struct map_attribute map_phys_addr_attr = __ATTR_RO(phys_addr);
+static struct map_attribute map_virt_addr_attr = __ATTR_RO(virt_addr);
+static struct map_attribute map_num_pages_attr = __ATTR_RO(num_pages);
+static struct map_attribute map_attribute_attr = __ATTR_RO(attribute);
+
+/*
+ * These are default attributes that are added for every memmap entry.
+ */
+static struct attribute *def_attrs[] = {
+ &map_type_attr.attr,
+ &map_phys_addr_attr.attr,
+ &map_virt_addr_attr.attr,
+ &map_num_pages_attr.attr,
+ &map_attribute_attr.attr,
+ NULL
+};
+
+static const struct sysfs_ops map_attr_ops = {
+ .show = map_attr_show,
+};
+
+static void map_release(struct kobject *kobj)
+{
+ struct efi_runtime_map_entry *entry;
+
+ entry = to_map_entry(kobj);
+ kfree(entry);
+}
+
+static struct kobj_type __refdata map_ktype = {
+ .sysfs_ops = &map_attr_ops,
+ .default_attrs = def_attrs,
+ .release = map_release,
+};
+
+static struct kset *map_kset;
+
+static struct efi_runtime_map_entry *
+add_sysfs_runtime_map_entry(struct kobject *kobj, int nr)
+{
+ int ret;
+ struct efi_runtime_map_entry *entry;
+
+ if (!map_kset) {
+ map_kset = kset_create_and_add("runtime-map", NULL, kobj);
+ if (!map_kset)
+ return ERR_PTR(-ENOMEM);
+ }
+
+ entry = kzalloc(sizeof(*entry), GFP_KERNEL);
+ if (!entry) {
+ kset_unregister(map_kset);
+ return entry;
+ }
+
+ memcpy(&entry->md, efi_runtime_map + nr * efi_memdesc_size,
+ sizeof(efi_memory_desc_t));
+
+ kobject_init(&entry->kobj, &map_ktype);
+ entry->kobj.kset = map_kset;
+ ret = kobject_add(&entry->kobj, NULL, "%d", nr);
+ if (ret) {
+ kobject_put(&entry->kobj);
+ kset_unregister(map_kset);
+ return ERR_PTR(ret);
+ }
+
+ return entry;
+}
+
+void efi_runtime_map_setup(void *map, int nr_entries, u32 desc_size)
+{
+ efi_runtime_map = map;
+ nr_efi_runtime_map = nr_entries;
+ efi_memdesc_size = desc_size;
+}
+
+int __init efi_runtime_map_init(struct kobject *efi_kobj)
+{
+ int i, j, ret = 0;
+ struct efi_runtime_map_entry *entry;
+
+ if (!efi_runtime_map)
+ return 0;
+
+ map_entries = kzalloc(nr_efi_runtime_map * sizeof(entry), GFP_KERNEL);
+ if (!map_entries) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ for (i = 0; i < nr_efi_runtime_map; i++) {
+ entry = add_sysfs_runtime_map_entry(efi_kobj, i);
+ if (IS_ERR(entry)) {
+ ret = PTR_ERR(entry);
+ goto out_add_entry;
+ }
+ *(map_entries + i) = entry;
+ }
+
+ return 0;
+out_add_entry:
+ for (j = i - 1; j > 0; j--) {
+ entry = *(map_entries + j);
+ kobject_put(&entry->kobj);
+ }
+ if (map_kset)
+ kset_unregister(map_kset);
+out:
+ return ret;
+}
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 988af61..0a819e7 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -876,4 +876,17 @@ int efivars_sysfs_init(void);

#endif /* CONFIG_EFI_VARS */

+#ifdef CONFIG_EFI_RUNTIME_MAP
+int efi_runtime_map_init(struct kobject *);
+void efi_runtime_map_setup(void *, int, u32);
+#else
+static inline int efi_runtime_map_init(struct kobject *kobj)
+{
+ return 0;
+}
+
+static inline void
+efi_runtime_map_setup(void *map, int nr_entries, u32 desc_size) {}
+#endif
+
#endif /* _LINUX_EFI_H */
--
1.8.3.1