leandrof/linux
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

efi: Allow drivers to reserve boot services forever

Browse Source 
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>
This commit is contained in:
Matt Fleming 2016-02-29 21:22:52 +00:00
parent c45f4da33a
commit 816e76129e
3 changed files with 141 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

121
arch/x86/platform/efi/quirks.c
View File

@ -163,6 +163,71 @@ efi_status_t efi_query_variable_store(u32 attributes, unsigned long size,
}
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 @@ static bool can_free_region(u64 start, u64 size)
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_reserve_boot_services(void)
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 @@ void __init efi_free_boot_services(void)
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 @@ void __init efi_free_boot_services(void)
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;
}
}
/*

30
drivers/firmware/efi/efi.c
View File

@ -27,6 +27,7 @@
#include <linux/slab.h>
#include <linux/acpi.h>
#include <linux/ucs2_string.h>
#include <linux/memblock.h>
#include <asm/early_ioremap.h>
@ -396,6 +397,35 @@ u64 __init efi_mem_desc_end(efi_memory_desc_t *md)
return end;
}
void __init __weak efi_arch_mem_reserve(phys_addr_t addr, u64 size) {}
/**
* efi_mem_reserve - Reserve an EFI memory region
* @addr: Physical address to reserve
* @size: Size of reservation
*
* Mark a region as reserved from general kernel allocation and
* prevent it being released by efi_free_boot_services().
*
* This function should be called drivers once they've parsed EFI
* configuration tables to figure out where their data lives, e.g.
* efi_esrt_init().
*/
void __init efi_mem_reserve(phys_addr_t addr, u64 size)
{
if (!memblock_is_region_reserved(addr, size))
memblock_reserve(addr, size);
/*
* Some architectures (x86) reserve all boot services ranges
* until efi_free_boot_services() because of buggy firmware
* implementations. This means the above memblock_reserve() is
* superfluous on x86 and instead what it needs to do is
* ensure the @start, @size is not freed.
*/
efi_arch_mem_reserve(addr, size);
}
static __initdata efi_config_table_type_t common_tables[] = {
{ACPI_20_TABLE_GUID, "ACPI 2.0", &efi.acpi20},
{ACPI_TABLE_GUID, "ACPI", &efi.acpi},

1
include/linux/efi.h
View File

@ -944,6 +944,7 @@ extern u64 efi_mem_attribute (unsigned long phys_addr, unsigned long size);
extern int __init efi_uart_console_only (void);
extern u64 efi_mem_desc_end(efi_memory_desc_t *md);
extern int efi_mem_desc_lookup(u64 phys_addr, efi_memory_desc_t *out_md);
extern void efi_mem_reserve(phys_addr_t addr, u64 size);
extern void efi_initialize_iomem_resources(struct resource *code_resource,
struct resource *data_resource, struct resource *bss_resource);
extern void efi_reserve_boot_services(void);