Currently, we infer the UEFI memory region mapping permissions
from the memory region type (i.e., runtime services code are
mapped RWX and runtime services data mapped RW-). This appears to
work fine but is not entirely UEFI spec compliant. So instead, use
the designated permission attributes to decide how these regions
should be mapped.
Since UEFIv2.5 introduces a new EFI_MEMORY_RO permission attribute,
and redefines EFI_MEMORY_WP as a cacheability attribute, use only
the former as a read-only attribute. For setting the PXN bit, the
corresponding EFI_MEMORY_XP attribute is used.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
---
Changes since v1:
- rewrote page size and alignment check to be more legible
- use code that is STRICT_MM_TYPECHECKS compliant
Example output of a recent Tianocore build on FVP Foundation model
is attached below.
arch/arm64/kernel/efi.c | 37 +++++++++++++-------
1 file changed, 24 insertions(+), 13 deletions(-)
diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
index ab21e0d58278..c8d587f46f3e 100644
--- a/arch/arm64/kernel/efi.c
+++ b/arch/arm64/kernel/efi.c
@@ -235,7 +235,7 @@ static bool __init efi_virtmap_init(void)
for_each_efi_memory_desc(&memmap, md) {
u64 paddr, npages, size;
- pgprot_t prot;
+ pteval_t prot_val;
if (!(md->attribute & EFI_MEMORY_RUNTIME))
continue;
@@ -247,22 +247,33 @@ static bool __init efi_virtmap_init(void)
memrange_efi_to_native(&paddr, &npages);
size = npages << PAGE_SHIFT;
- pr_info(" EFI remap 0x%016llx => %p\n",
- md->phys_addr, (void *)md->virt_addr);
+ if (!is_normal_ram(md))
+ prot_val = PROT_DEVICE_nGnRE;
+ else
+ prot_val = pgprot_val(PAGE_KERNEL_EXEC);
/*
- * Only regions of type EFI_RUNTIME_SERVICES_CODE need to be
- * executable, everything else can be mapped with the XN bits
- * set.
+ * On 64 KB granule kernels, only use strict permissions when
+ * the region does not share a 64 KB page frame with another
+ * region at either end.
*/
- if (!is_normal_ram(md))
- prot = __pgprot(PROT_DEVICE_nGnRE);
- else if (md->type == EFI_RUNTIME_SERVICES_CODE)
- prot = PAGE_KERNEL_EXEC;
- else
- prot = PAGE_KERNEL;
+ if (PAGE_SIZE == EFI_PAGE_SIZE ||
+ (PAGE_ALIGNED(md->virt_addr) &&
+ PAGE_ALIGNED(md->phys_addr + md->num_pages * EFI_PAGE_SIZE))) {
+
+ if (md->attribute & EFI_MEMORY_RO)
+ prot_val |= PTE_RDONLY;
+ if (md->attribute & EFI_MEMORY_XP)
+ prot_val |= PTE_PXN;
+ }
+
+ pr_info(" EFI remap 0x%016llx => %p (R%c%c)\n",
+ md->phys_addr, (void *)md->virt_addr,
+ prot_val & PTE_RDONLY ? '-' : 'W',
+ prot_val & PTE_PXN ? '-' : 'X');
- create_pgd_mapping(&efi_mm, paddr, md->virt_addr, size, prot);
+ create_pgd_mapping(&efi_mm, paddr, md->virt_addr, size,
+ __pgprot(prot_val));
}
return true;
}
--
1.9.1
Processing EFI memory map:
0x00000c000000-0x00000ffeffff [Memory Mapped I/O |RUN|XP| | | | | | | |UC]
0x00001c170000-0x00001c170fff [Memory Mapped I/O |RUN|XP| | | | | | | |UC]
...
0x0008fabf0000-0x0008fac0ffff [Runtime Data |RUN|XP| | | | |WB|WT|WC|UC]*
0x0008fac10000-0x0008fac1ffff [Runtime Code |RUN| | | |RO| |WB|WT|WC|UC]*
0x0008fac20000-0x0008fac4ffff [Runtime Data |RUN|XP| | | | |WB|WT|WC|UC]*
0x0008fac50000-0x0008fac5ffff [Runtime Code |RUN| | | |RO| |WB|WT|WC|UC]*
0x0008fac60000-0x0008fac8ffff [Runtime Data |RUN|XP| | | | |WB|WT|WC|UC]*
0x0008fac90000-0x0008fac9ffff [Runtime Code |RUN| | | |RO| |WB|WT|WC|UC]*
0x0008faca0000-0x0008fad4ffff [Runtime Data |RUN|XP| | | | |WB|WT|WC|UC]*
0x0008fad50000-0x0008fad5ffff [Runtime Data |RUN|XP| | | | |WB|WT|WC|UC]*
0x0008fad60000-0x0008fad6ffff [Runtime Code |RUN| | | |RO| |WB|WT|WC|UC]*
0x0008fad70000-0x0008fae8ffff [Runtime Data |RUN|XP| | | | |WB|WT|WC|UC]*
0x0008fae90000-0x0008fae9ffff [Runtime Data |RUN|XP| | | | |WB|WT|WC|UC]*
0x0008faea0000-0x0008faeaffff [Runtime Code |RUN| | | |RO| |WB|WT|WC|UC]*
0x0008faeb0000-0x0008faf2ffff [Runtime Data |RUN|XP| | | | |WB|WT|WC|UC]*
0x0008faf30000-0x0008faf3ffff [Runtime Data |RUN|XP| | | | |WB|WT|WC|UC]*
0x0008faf40000-0x0008faf4ffff [Runtime Code |RUN| | | |RO| |WB|WT|WC|UC]*
0x0008faf50000-0x0008faf7ffff [Runtime Data |RUN|XP| | | | |WB|WT|WC|UC]*
...
0x0008fff50000-0x0008fff5ffff [Runtime Data |RUN|XP| | | | |WB|WT|WC|UC]*
0x0008fff60000-0x0008fff6ffff [Runtime Code |RUN| | | |RO| |WB|WT|WC|UC]*
0x0008fff70000-0x0008fff8ffff [Runtime Data |RUN|XP| | | | |WB|WT|WC|UC]*
0x0008fff90000-0x0008fff9ffff [Conventional Memory| | | | | | |WB|WT|WC|UC]
0x0008fffa0000-0x0008fffeffff [Runtime Data |RUN|XP| | | | |WB|WT|WC|UC]*
...
Remapping and enabling EFI services.
EFI remap 0x000000000c000000 => 0000000040000000 (RW-)
EFI remap 0x000000001c170000 => 0000000043ff0000 (RW-)
EFI remap 0x00000008fabf0000 => 0000000044000000 (RW-)
EFI remap 0x00000008fac10000 => 0000000044020000 (R-X)
EFI remap 0x00000008fac20000 => 0000000044030000 (RW-)
EFI remap 0x00000008fac50000 => 0000000044060000 (R-X)
EFI remap 0x00000008fac60000 => 0000000044070000 (RW-)
EFI remap 0x00000008fac90000 => 00000000440a0000 (R-X)
EFI remap 0x00000008faca0000 => 00000000440b0000 (RW-)
EFI remap 0x00000008fad50000 => 0000000044160000 (RW-)
EFI remap 0x00000008fad60000 => 0000000044170000 (R-X)
EFI remap 0x00000008fad70000 => 0000000044180000 (RW-)
EFI remap 0x00000008fae90000 => 00000000442a0000 (RW-)
EFI remap 0x00000008faea0000 => 00000000442b0000 (R-X)
EFI remap 0x00000008faeb0000 => 00000000442c0000 (RW-)
EFI remap 0x00000008faf30000 => 0000000044340000 (RW-)
EFI remap 0x00000008faf40000 => 0000000044350000 (R-X)
EFI remap 0x00000008faf50000 => 0000000044360000 (RW-)
EFI remap 0x00000008fff50000 => 0000000044390000 (RW-)
EFI remap 0x00000008fff60000 => 00000000443a0000 (R-X)
EFI remap 0x00000008fff70000 => 00000000443b0000 (RW-)
EFI remap 0x00000008fffa0000 => 00000000443d0000 (RW-)
--
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