Ensure that the EFI memreserve entries can be accessed, even if they
are located in memory that the kernel (e.g., a crashkernel) omits from
the linear map.
Reported-by: Jonathan Richardson <jonathan.richardson@xxxxxxxxxxxx>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
---
drivers/firmware/efi/efi.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 16b2137d117c..4b7cf7bc0ded 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -1009,14 +1009,16 @@ int __ref efi_mem_reserve_persistent(phys_addr_t addr, u64 size)
/* first try to find a slot in an existing linked list entry */
for (prsv = efi_memreserve_root->next; prsv; prsv = rsv->next) {
- rsv = __va(prsv);
+ rsv = memremap(prsv, sizeof(*rsv), MEMREMAP_WB);
index = atomic_fetch_add_unless(&rsv->count, 1, rsv->size);
if (index < rsv->size) {
rsv->entry[index].base = addr;
rsv->entry[index].size = size;
+ memunmap(rsv);
return 0;
}
+ memunmap(rsv);
}
/* no slot found - allocate a new linked list entry */
@@ -1024,7 +1026,13 @@ int __ref efi_mem_reserve_persistent(phys_addr_t addr, u64 size)
if (!rsv)
return -ENOMEM;
- rsv->size = EFI_MEMRESERVE_COUNT(PAGE_SIZE);
+ /*
+ * The memremap() call above assumes that a linux_efi_memreserve entry
+ * never crosses a page boundary, so let's ensure that this remains true
+ * even when kexec'ing a 4k pages kernel from a >4k pages kernel, by
+ * using SZ_4K explicitly in the size calculation below.
+ */
+ rsv->size = EFI_MEMRESERVE_COUNT(SZ_4K);
atomic_set(&rsv->count, 1);
rsv->entry[0].base = addr;
rsv->entry[0].size = size;
--
2.20.1
