From 37926f96302d8b6c2bc97990d33e316a3ed6d67f Mon Sep 17 00:00:00 2001
From: Ard Biesheuvel <ardb@kernel.org>
Date: Thu, 20 Oct 2022 15:16:09 +0200
Subject: [PATCH] efi: runtime: Don't assume virtual mappings are missing if VA
== PA == 0
The generic EFI stub can be instructed to avoid SetVirtualAddressMap(),
and simply run with the firmware's 1:1 mapping. In this case, it
populates the virtual address fields of the runtime regions in the
memory map with the physical address of each region, so that the mapping
code has to be none the wiser. Only if SetVirtualAddressMap() fails, the
virtual addresses are wiped and the kernel code knows that the regions
cannot be mapped.
However, wiping amounts to setting it to zero, and if a runtime region
happens to live at physical address 0, its valid 1:1 mapped virtual
address could be mistaken for a wiped field, resulting on loss of access
to the EFI services at runtime.
So let's only assume that VA == 0 means 'no runtime services' if the
region in question does not live at PA 0x0.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
drivers/firmware/efi/arm-runtime.c | 2 +-
drivers/firmware/efi/libstub/fdt.c | 8 ++++----
drivers/firmware/efi/riscv-runtime.c | 2 +-
3 files changed, 6 insertions(+), 6 deletions(-)
diff --git a/drivers/firmware/efi/arm-runtime.c b/drivers/firmware/efi/arm-runtime.c
index 3359ae2adf24b..7c48c380d722c 100644
--- a/drivers/firmware/efi/arm-runtime.c
+++ b/drivers/firmware/efi/arm-runtime.c
@@ -63,7 +63,7 @@ static bool __init efi_virtmap_init(void)
if (!(md->attribute & EFI_MEMORY_RUNTIME))
continue;
- if (md->virt_addr == 0)
+ if (md->virt_addr == U64_MAX)
return false;
ret = efi_create_mapping(&efi_mm, md);
diff --git a/drivers/firmware/efi/libstub/fdt.c b/drivers/firmware/efi/libstub/fdt.c
index 4f4d98e51fbfd..70e9789ff9de0 100644
--- a/drivers/firmware/efi/libstub/fdt.c
+++ b/drivers/firmware/efi/libstub/fdt.c
@@ -313,16 +313,16 @@ efi_status_t allocate_new_fdt_and_exit_boot(void *handle,
/*
* 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.
+ * EFI_MEMORY_RUNTIME entries to U64_MAX. This will
+ * signal the incoming kernel that no virtual
+ * translation has been installed.
*/
for (l = 0; l < priv.boot_memmap->map_size;
l += priv.boot_memmap->desc_size) {
p = (void *)priv.boot_memmap->map + l;
if (p->attribute & EFI_MEMORY_RUNTIME)
- p->virt_addr = 0;
+ p->virt_addr = U64_MAX;
}
}
return EFI_SUCCESS;
diff --git a/drivers/firmware/efi/riscv-runtime.c b/drivers/firmware/efi/riscv-runtime.c
index d28e715d2bcc8..d0daacd2c903f 100644
--- a/drivers/firmware/efi/riscv-runtime.c
+++ b/drivers/firmware/efi/riscv-runtime.c
@@ -41,7 +41,7 @@ static bool __init efi_virtmap_init(void)
if (!(md->attribute & EFI_MEMORY_RUNTIME))
continue;
- if (md->virt_addr == 0)
+ if (md->virt_addr == U64_MAX)
return false;
ret = efi_create_mapping(&efi_mm, md);
--
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