In order to support kexec, the kernel needs to be able to deal with the
state of the UEFI firmware after SetVirtualAddressMap() has been called.
To avoid having separate code paths for non-kexec and kexec, let's move
the call to SetVirtualAddressMap() to the stub: this will guarantee us
that it will only be called once (since the stub is not executed during
kexec), and ensures that the UEFI state is identical between kexec and
normal boot.
This implies that the layout of the virtual mapping needs to be created
by the stub as well. All regions are rounded up to a naturally aligned
multiple of 64 KB (for compatibility with 64k pages kernels) and recorded
in the UEFI memory map. The kernel proper reads those values and installs
the mappings in a dedicated set of page tables that are swapped in during
UEFI Runtime Services calls.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
---
arch/arm64/include/asm/efi.h | 19 +++-
arch/arm64/kernel/efi.c | 205 +++++++++++++++++++------------------
drivers/firmware/efi/libstub/fdt.c | 104 ++++++++++++++++++-
3 files changed, 224 insertions(+), 104 deletions(-)
diff --git a/arch/arm64/include/asm/efi.h b/arch/arm64/include/asm/efi.h
index a34fd3b12e2b..d752e5480096 100644
--- a/arch/arm64/include/asm/efi.h
+++ b/arch/arm64/include/asm/efi.h
@@ -12,23 +12,32 @@ extern void efi_idmap_init(void);
#define efi_idmap_init()
#endif
+void efi_load_rt_mapping(void);
+void efi_unload_rt_mapping(void);
+
#define efi_call_virt(f, ...) \
({ \
- efi_##f##_t *__f = efi.systab->runtime->f; \
+ efi_##f##_t *__f; \
efi_status_t __s; \
\
- kernel_neon_begin(); \
+ kernel_neon_begin(); /* disables preemption */ \
+ efi_load_rt_mapping(); \
+ __f = efi.systab->runtime->f; \
__s = __f(__VA_ARGS__); \
+ efi_unload_rt_mapping(); \
kernel_neon_end(); \
__s; \
})
#define __efi_call_virt(f, ...) \
({ \
- efi_##f##_t *__f = efi.systab->runtime->f; \
+ efi_##f##_t *__f; \
\
- kernel_neon_begin(); \
+ kernel_neon_begin(); /* disables preemption */ \
+ efi_load_rt_mapping(); \
+ __f = efi.systab->runtime->f; \
__f(__VA_ARGS__); \
+ efi_unload_rt_mapping(); \
kernel_neon_end(); \
})
@@ -44,4 +53,6 @@ extern void efi_idmap_init(void);
#define efi_call_early(f, ...) sys_table_arg->boottime->f(__VA_ARGS__)
+#define EFI_VIRTMAP EFI_ARCH_1
+
#endif /* _ASM_EFI_H */
diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
index baab9344a32b..324398c03acd 100644
--- a/arch/arm64/kernel/efi.c
+++ b/arch/arm64/kernel/efi.c
@@ -20,16 +20,21 @@
#include <linux/of_fdt.h>
#include <linux/sched.h>
#include <linux/slab.h>
+#include <linux/mm_types.h>
+#include <linux/rbtree.h>
+#include <linux/rwsem.h>
+#include <linux/spinlock.h>
+#include <linux/atomic.h>
#include <asm/cacheflush.h>
#include <asm/efi.h>
#include <asm/tlbflush.h>
+#include <asm/pgtable.h>
#include <asm/mmu_context.h>
+#include <asm/mmu.h>
struct efi_memory_map memmap;
-static efi_runtime_services_t *runtime;
-
static u64 efi_system_table;
static int uefi_debug __initdata;
@@ -69,9 +74,36 @@ static void __init efi_setup_idmap(void)
}
}
+/*
+ * Translate a EFI virtual address into a physical address: this is necessary,
+ * as some data members of the EFI system table are virtually remapped after
+ * SetVirtualAddressMap() has been called.
+ */
+static phys_addr_t __init efi_to_phys(unsigned long addr)
+{
+ efi_memory_desc_t *md;
+
+ for_each_efi_memory_desc(&memmap, md) {
+ if (!(md->attribute & EFI_MEMORY_RUNTIME))
+ continue;
+ if (md->virt_addr == 0)
+ /* no virtual mapping has been installed by the stub */
+ break;
+ if (md->virt_addr < addr &&
+ (addr - md->virt_addr) < (md->num_pages << EFI_PAGE_SHIFT))
+ return md->phys_addr + addr - md->virt_addr;
+ }
+
+ WARN_ONCE(1, "UEFI virtual mapping incomplete or missing -- no entry found for 0x%lx\n",
+ addr);
+ return addr;
+}
+
static int __init uefi_init(void)
{
efi_char16_t *c16;
+ void *config_tables;
+ u64 table_size;
char vendor[100] = "unknown";
int i, retval;
@@ -99,7 +131,7 @@ static int __init uefi_init(void)
efi.systab->hdr.revision & 0xffff);
/* Show what we know for posterity */
- c16 = early_memremap(efi.systab->fw_vendor,
+ c16 = early_memremap(efi_to_phys(efi.systab->fw_vendor),
sizeof(vendor));
if (c16) {
for (i = 0; i < (int) sizeof(vendor) - 1 && *c16; ++i)
@@ -112,8 +144,14 @@ static int __init uefi_init(void)
efi.systab->hdr.revision >> 16,
efi.systab->hdr.revision & 0xffff, vendor);
- retval = efi_config_init(NULL);
+ table_size = sizeof(efi_config_table_64_t) * efi.systab->nr_tables;
+ config_tables = early_memremap(efi_to_phys(efi.systab->tables),
+ table_size);
+
+ retval = efi_config_parse_tables(config_tables,
+ efi.systab->nr_tables, NULL);
+ early_memunmap(config_tables, table_size);
out:
early_memunmap(efi.systab, sizeof(efi_system_table_t));
return retval;
@@ -319,60 +357,64 @@ void __init efi_init(void)
reserve_regions();
}
+static pgd_t efi_pgd[PTRS_PER_PGD] __page_aligned_bss;
+
+static struct mm_struct efi_mm = {
+ .mm_rb = RB_ROOT,
+ .pgd = efi_pgd,
+ .mm_users = ATOMIC_INIT(2),
+ .mm_count = ATOMIC_INIT(1),
+ .mmap_sem = __RWSEM_INITIALIZER(efi_mm.mmap_sem),
+ .page_table_lock = __SPIN_LOCK_UNLOCKED(efi_mm.page_table_lock),
+ .mmlist = LIST_HEAD_INIT(efi_mm.mmlist),
+ INIT_MM_CONTEXT(efi_mm)
+};
+
void __init efi_idmap_init(void)
{
+ efi_memory_desc_t *md;
+
if (!efi_enabled(EFI_BOOT))
return;
/* boot time idmap_pg_dir is incomplete, so fill in missing parts */
efi_setup_idmap();
-}
-
-static int __init remap_region(efi_memory_desc_t *md, void **new)
-{
- u64 paddr, vaddr, npages, size;
-
- paddr = md->phys_addr;
- npages = md->num_pages;
- memrange_efi_to_native(&paddr, &npages);
- size = npages << PAGE_SHIFT;
-
- if (is_normal_ram(md))
- vaddr = (__force u64)ioremap_cache(paddr, size);
- else
- vaddr = (__force u64)ioremap(paddr, size);
- if (!vaddr) {
- pr_err("Unable to remap 0x%llx pages @ %p\n",
- npages, (void *)paddr);
- return 0;
- }
+ for_each_efi_memory_desc(&memmap, md) {
+ u64 paddr, npages, size;
- /* adjust for any rounding when EFI and system pagesize differs */
- md->virt_addr = vaddr + (md->phys_addr - paddr);
+ if (!(md->attribute & EFI_MEMORY_RUNTIME))
+ continue;
+ if (md->virt_addr == 0)
+ /* no virtual mapping has been installed by the stub */
+ return;
- if (uefi_debug)
- pr_info(" EFI remap 0x%012llx => %p\n",
- md->phys_addr, (void *)md->virt_addr);
+ paddr = md->phys_addr;
+ npages = md->num_pages;
+ memrange_efi_to_native(&paddr, &npages);
+ size = npages << PAGE_SHIFT;
- memcpy(*new, md, memmap.desc_size);
- *new += memmap.desc_size;
+ if (uefi_debug)
+ pr_info(" EFI remap 0x%012llx => %p\n",
+ md->phys_addr, (void *)md->virt_addr);
- return 1;
+ /*
+ * Only regions of type EFI_RUNTIME_SERVICES_CODE need to be
+ * executable, everything else can be mapped with the XN bits
+ * set. Unfortunately, we cannot map those code regions write
+ * protect, as they may contain read-write .data sections as
+ * well.
+ */
+ create_pgd_mapping(&efi_mm, paddr, md->virt_addr, size,
+ !is_normal_ram(md),
+ md->type != EFI_RUNTIME_SERVICES_CODE);
+ }
+ set_bit(EFI_VIRTMAP, &efi.flags);
}
-/*
- * Switch UEFI from an identity map to a kernel virtual map
- */
static int __init arm64_enter_virtual_mode(void)
{
- efi_memory_desc_t *md;
- phys_addr_t virtmap_phys;
- void *virtmap, *virt_md;
- efi_status_t status;
u64 mapsize;
- int count = 0;
- unsigned long flags;
if (!efi_enabled(EFI_MEMMAP))
return 0;
@@ -393,79 +435,28 @@ static int __init arm64_enter_virtual_mode(void)
efi.memmap = &memmap;
- /* Map the runtime regions */
- virtmap = kmalloc(mapsize, GFP_KERNEL);
- if (!virtmap) {
- pr_err("Failed to allocate EFI virtual memmap\n");
- return -1;
- }
- virtmap_phys = virt_to_phys(virtmap);
- virt_md = virtmap;
-
- for_each_efi_memory_desc(&memmap, md) {
- if (!(md->attribute & EFI_MEMORY_RUNTIME))
- continue;
- if (!remap_region(md, &virt_md))
- goto err_unmap;
- ++count;
- }
-
- efi.systab = (__force void *)efi_lookup_mapped_addr(efi_system_table);
+ efi.systab = (__force void *)ioremap_cache(efi_system_table,
+ sizeof(efi_system_table_t));
if (!efi.systab) {
- /*
- * If we have no virtual mapping for the System Table at this
- * point, the memory map doesn't cover the physical offset where
- * it resides. This means the System Table will be inaccessible
- * to Runtime Services themselves once the virtual mapping is
- * installed.
- */
- pr_err("Failed to remap EFI System Table -- buggy firmware?\n");
- goto err_unmap;
+ pr_err("Failed to remap EFI System Table\n");
+ return -1;
}
set_bit(EFI_SYSTEM_TABLES, &efi.flags);
- local_irq_save(flags);
- cpu_switch_mm(idmap_pg_dir, &init_mm);
-
- /* Call SetVirtualAddressMap with the physical address of the map */
- runtime = efi.systab->runtime;
- efi.set_virtual_address_map = runtime->set_virtual_address_map;
-
- status = efi.set_virtual_address_map(count * memmap.desc_size,
- memmap.desc_size,
- memmap.desc_version,
- (efi_memory_desc_t *)virtmap_phys);
- cpu_set_reserved_ttbr0();
- flush_tlb_all();
- local_irq_restore(flags);
-
- kfree(virtmap);
-
free_boot_services();
- if (status != EFI_SUCCESS) {
- pr_err("Failed to set EFI virtual address map! [%lx]\n",
- status);
+ if (!efi_enabled(EFI_VIRTMAP)) {
+ pr_err("No UEFI virtual mapping was installed -- runtime services will not be available\n");
return -1;
}
/* Set up runtime services function pointers */
- runtime = efi.systab->runtime;
efi_native_runtime_setup();
set_bit(EFI_RUNTIME_SERVICES, &efi.flags);
efi.runtime_version = efi.systab->hdr.revision;
return 0;
-
-err_unmap:
- /* unmap all mappings that succeeded: there are 'count' of those */
- for (virt_md = virtmap; count--; virt_md += memmap.desc_size) {
- md = virt_md;
- iounmap((__force void __iomem *)md->virt_addr);
- }
- kfree(virtmap);
- return -1;
}
early_initcall(arm64_enter_virtual_mode);
@@ -482,3 +473,21 @@ static int __init arm64_dmi_init(void)
return 0;
}
core_initcall(arm64_dmi_init);
+
+static void efi_set_pgd(struct mm_struct *mm)
+{
+ cpu_switch_mm(mm->pgd, mm);
+ flush_tlb_all();
+ if (icache_is_aivivt())
+ __flush_icache_all();
+}
+
+void efi_load_rt_mapping(void)
+{
+ efi_set_pgd(&efi_mm);
+}
+
+void efi_unload_rt_mapping(void)
+{
+ efi_set_pgd(current->active_mm);
+}
diff --git a/drivers/firmware/efi/libstub/fdt.c b/drivers/firmware/efi/libstub/fdt.c
index c846a9608cbd..9a5f6e54a423 100644
--- a/drivers/firmware/efi/libstub/fdt.c
+++ b/drivers/firmware/efi/libstub/fdt.c
@@ -168,6 +168,68 @@ fdt_set_fail:
#endif
/*
+ * This is the base address at which to start allocating virtual memory ranges
+ * for UEFI Runtime Services. This is a userland range so that we can use any
+ * allocation we choose, and eliminate the risk of a conflict after kexec.
+ */
+#define EFI_RT_VIRTUAL_BASE 0x40000000
+
+static void update_memory_map(efi_memory_desc_t *memory_map,
+ unsigned long map_size, unsigned long desc_size,
+ int *count)
+{
+ u64 efi_virt_base = EFI_RT_VIRTUAL_BASE;
+ union {
+ efi_memory_desc_t entry;
+ u8 pad[desc_size];
+ } *p, *q, tmp;
+ int i = map_size / desc_size;
+
+ p = (void *)memory_map;
+ for (q = p; i >= 0; i--, q++) {
+ u64 paddr, size;
+
+ if (!(q->entry.attribute & EFI_MEMORY_RUNTIME))
+ continue;
+
+ /*
+ * Swap the entries around so that all EFI_MEMORY_RUNTIME
+ * entries bubble to the top. This will allow us to reuse the
+ * table as input to SetVirtualAddressMap().
+ */
+ if (q != p) {
+ tmp = *p;
+ *p = *q;
+ *q = tmp;
+ }
+
+ /*
+ * Make the mapping compatible with 64k pages: this allows
+ * a 4k page size kernel to kexec a 64k page size kernel and
+ * vice versa.
+ */
+ paddr = round_down(p->entry.phys_addr, SZ_64K);
+ size = round_up(p->entry.num_pages * EFI_PAGE_SIZE +
+ p->entry.phys_addr - paddr, SZ_64K);
+
+ /*
+ * Avoid wasting memory on PTEs by choosing a virtual base that
+ * is compatible with section mappings if this region has the
+ * appropriate size and physical alignment. (Sections are 2 MB
+ * on 4k granule kernels)
+ */
+ if (IS_ALIGNED(p->entry.phys_addr, SZ_2M) && size >= SZ_2M)
+ efi_virt_base = round_up(efi_virt_base, SZ_2M);
+
+ p->entry.virt_addr = efi_virt_base + p->entry.phys_addr - paddr;
+ efi_virt_base += size;
+
+ ++p;
+ ++*count;
+ }
+}
+
+/*
* Allocate memory for a new FDT, then add EFI, commandline, and
* initrd related fields to the FDT. This routine increases the
* FDT allocation size until the allocated memory is large
@@ -196,6 +258,7 @@ efi_status_t allocate_new_fdt_and_exit_boot(efi_system_table_t *sys_table,
efi_memory_desc_t *memory_map;
unsigned long new_fdt_size;
efi_status_t status;
+ int runtime_entry_count = 0;
/*
* Estimate size of new FDT, and allocate memory for it. We
@@ -248,12 +311,49 @@ efi_status_t allocate_new_fdt_and_exit_boot(efi_system_table_t *sys_table,
}
}
+ /*
+ * Update the memory map with virtual addresses, and reorder the entries
+ * so that we can pass it straight into SetVirtualAddressMap()
+ */
+ update_memory_map(memory_map, map_size, desc_size,
+ &runtime_entry_count);
+
/* Now we are ready to exit_boot_services.*/
status = sys_table->boottime->exit_boot_services(handle, mmap_key);
+ if (status == EFI_SUCCESS) {
+ efi_set_virtual_address_map_t *svam;
+
+ /* Install the new virtual address map */
+ svam = sys_table->runtime->set_virtual_address_map;
+ status = svam(runtime_entry_count * desc_size, desc_size,
+ desc_ver, memory_map);
- if (status == EFI_SUCCESS)
- return status;
+ /*
+ * We are beyond the point of no return here, so if the call to
+ * SetVirtualAddressMap() failed, we need to signal that to the
+ * incoming kernel but proceed normally otherwise.
+ */
+ if (status != EFI_SUCCESS) {
+ int i;
+
+ /*
+ * Set the virtual address field of all
+ * EFI_MEMORY_RUNTIME entries to 0. This will signal
+ * the incoming kernel that no virtual translation has
+ * been installed.
+ */
+ for (i = 0; i < map_size; i += desc_size) {
+ efi_memory_desc_t *p;
+
+ p = (efi_memory_desc_t *)((u8 *)memory_map + i);
+ if (!(p->attribute & EFI_MEMORY_RUNTIME))
+ break;
+ p->virt_addr = 0;
+ }
+ }
+ return EFI_SUCCESS;
+ }
pr_efi_err(sys_table, "Exit boot services failed.\n");
--
1.8.3.2
--
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