efi: Allow drivers to reserve boot services forever
Today, it is not possible for drivers to reserve EFI boot services for
access after efi_free_boot_services() has been called on x86. For
ARM/arm64 it can be done simply by calling memblock_reserve().
Having this ability for all three architectures is desirable for a
couple of reasons,
1) It saves drivers copying data out of those regions
2) kexec reboot can now make use of things like ESRT
Instead of using the standard memblock_reserve() which is insufficient
to reserve the region on x86 (see efi_reserve_boot_services()), a new
API is introduced in this patch; efi_mem_reserve().
efi.memmap now always represents which EFI memory regions are
available. On x86 the EFI boot services regions that have not been
reserved via efi_mem_reserve() will be removed from efi.memmap during
efi_free_boot_services().
This has implications for kexec, since it is not possible for a newly
kexec'd kernel to access the same boot services regions that the
initial boot kernel had access to unless they are reserved by every
kexec kernel in the chain.
Tested-by: Dave Young <dyoung@redhat.com> [kexec/kdump]
Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> [arm]
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Leif Lindholm <leif.lindholm@linaro.org>
Cc: Peter Jones <pjones@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>
diff --git a/arch/x86/platform/efi/quirks.c b/arch/x86/platform/efi/quirks.c
index 9faf188..f14b7a9 100644
--- a/arch/x86/platform/efi/quirks.c
+++ b/arch/x86/platform/efi/quirks.c
@@ -164,6 +164,71 @@
EXPORT_SYMBOL_GPL(efi_query_variable_store);
/*
+ * The UEFI specification makes it clear that the operating system is
+ * free to do whatever it wants with boot services code after
+ * ExitBootServices() has been called. Ignoring this recommendation a
+ * significant bunch of EFI implementations continue calling into boot
+ * services code (SetVirtualAddressMap). In order to work around such
+ * buggy implementations we reserve boot services region during EFI
+ * init and make sure it stays executable. Then, after
+ * SetVirtualAddressMap(), it is discarded.
+ *
+ * However, some boot services regions contain data that is required
+ * by drivers, so we need to track which memory ranges can never be
+ * freed. This is done by tagging those regions with the
+ * EFI_MEMORY_RUNTIME attribute.
+ *
+ * Any driver that wants to mark a region as reserved must use
+ * efi_mem_reserve() which will insert a new EFI memory descriptor
+ * into efi.memmap (splitting existing regions if necessary) and tag
+ * it with EFI_MEMORY_RUNTIME.
+ */
+void __init efi_arch_mem_reserve(phys_addr_t addr, u64 size)
+{
+ phys_addr_t new_phys, new_size;
+ struct efi_mem_range mr;
+ efi_memory_desc_t md;
+ int num_entries;
+ void *new;
+
+ if (efi_mem_desc_lookup(addr, &md)) {
+ pr_err("Failed to lookup EFI memory descriptor for %pa\n", &addr);
+ return;
+ }
+
+ if (addr + size > md.phys_addr + (md.num_pages << EFI_PAGE_SHIFT)) {
+ pr_err("Region spans EFI memory descriptors, %pa\n", &addr);
+ return;
+ }
+
+ mr.range.start = addr;
+ mr.range.end = addr + size;
+ mr.attribute = md.attribute | EFI_MEMORY_RUNTIME;
+
+ num_entries = efi_memmap_split_count(&md, &mr.range);
+ num_entries += efi.memmap.nr_map;
+
+ new_size = efi.memmap.desc_size * num_entries;
+
+ new_phys = memblock_alloc(new_size, 0);
+ if (!new_phys) {
+ pr_err("Could not allocate boot services memmap\n");
+ return;
+ }
+
+ new = early_memremap(new_phys, new_size);
+ if (!new) {
+ pr_err("Failed to map new boot services memmap\n");
+ return;
+ }
+
+ efi_memmap_insert(&efi.memmap, new, &mr);
+ early_memunmap(new, new_size);
+
+ efi_memmap_install(new_phys, num_entries);
+}
+
+/*
* Helper function for efi_reserve_boot_services() to figure out if we
* can free regions in efi_free_boot_services().
*
@@ -184,15 +249,6 @@
return true;
}
-/*
- * The UEFI specification makes it clear that the operating system is free to do
- * whatever it wants with boot services code after ExitBootServices() has been
- * called. Ignoring this recommendation a significant bunch of EFI implementations
- * continue calling into boot services code (SetVirtualAddressMap). In order to
- * work around such buggy implementations we reserve boot services region during
- * EFI init and make sure it stays executable. Then, after SetVirtualAddressMap(), it
-* is discarded.
-*/
void __init efi_reserve_boot_services(void)
{
efi_memory_desc_t *md;
@@ -249,7 +305,10 @@
void __init efi_free_boot_services(void)
{
+ phys_addr_t new_phys, new_size;
efi_memory_desc_t *md;
+ int num_entries = 0;
+ void *new, *new_md;
for_each_efi_memory_desc(md) {
unsigned long long start = md->phys_addr;
@@ -257,12 +316,16 @@
size_t rm_size;
if (md->type != EFI_BOOT_SERVICES_CODE &&
- md->type != EFI_BOOT_SERVICES_DATA)
+ md->type != EFI_BOOT_SERVICES_DATA) {
+ num_entries++;
continue;
+ }
/* Do not free, someone else owns it: */
- if (md->attribute & EFI_MEMORY_RUNTIME)
+ if (md->attribute & EFI_MEMORY_RUNTIME) {
+ num_entries++;
continue;
+ }
/*
* Nasty quirk: if all sub-1MB memory is used for boot
@@ -286,6 +349,42 @@
free_bootmem_late(start, size);
}
+
+ new_size = efi.memmap.desc_size * num_entries;
+ new_phys = memblock_alloc(new_size, 0);
+ if (!new_phys) {
+ pr_err("Failed to allocate new EFI memmap\n");
+ return;
+ }
+
+ new = memremap(new_phys, new_size, MEMREMAP_WB);
+ if (!new) {
+ pr_err("Failed to map new EFI memmap\n");
+ return;
+ }
+
+ /*
+ * Build a new EFI memmap that excludes any boot services
+ * regions that are not tagged EFI_MEMORY_RUNTIME, since those
+ * regions have now been freed.
+ */
+ new_md = new;
+ for_each_efi_memory_desc(md) {
+ if (!(md->attribute & EFI_MEMORY_RUNTIME) &&
+ (md->type == EFI_BOOT_SERVICES_CODE ||
+ md->type == EFI_BOOT_SERVICES_DATA))
+ continue;
+
+ memcpy(new_md, md, efi.memmap.desc_size);
+ new_md += efi.memmap.desc_size;
+ }
+
+ memunmap(new);
+
+ if (efi_memmap_install(new_phys, num_entries)) {
+ pr_err("Could not install new EFI memmap\n");
+ return;
+ }
}
/*