[tip: efi/urgent] firmware/efi: Tell memblock about EFI iomem reservations

[tip-bot2 for Marc Zyngier]

The following commit has been merged into the efi/urgent branch of tip:

Commit-ID:     2bab693a608bdf614b9fcd44083c5100f34b9f77
Gitweb:        https://git.kernel.org/tip/2bab693a608bdf614b9fcd44083c5100f34b9f77
Author:        Marc Zyngier <maz@xxxxxxxxxx>
AuthorDate:    Tue, 13 Jul 2021 19:43:26 +01:00
Committer:     Ard Biesheuvel <ardb@xxxxxxxxxx>
CommitterDate: Fri, 16 Jul 2021 18:05:49 +02:00

firmware/efi: Tell memblock about EFI iomem reservations

kexec_load_file() relies on the memblock infrastructure to avoid
stamping over regions of memory that are essential to the survival
of the system.

However, nobody seems to agree how to flag these regions as reserved,
and (for example) EFI only publishes its reservations in /proc/iomem
for the benefit of the traditional, userspace based kexec tool.

On arm64 platforms with GICv3, this can result in the payload being
placed at the location of the LPI tables. Shock, horror!

Let's augment the EFI reservation code with a memblock_reserve() call,
protecting our dear tables from the secondary kernel invasion.

Reported-by: Moritz Fischer <mdf@xxxxxxxxxx>
Tested-by: Moritz Fischer <mdf@xxxxxxxxxx>
Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Cc: Ard Biesheuvel <ardb@xxxxxxxxxx>
Cc: James Morse <james.morse@xxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
---
 drivers/firmware/efi/efi.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 4b7ee3f..847f33f 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -896,6 +896,7 @@ static int __init efi_memreserve_map_root(void)
 static int efi_mem_reserve_iomem(phys_addr_t addr, u64 size)
 {
 	struct resource *res, *parent;
+	int ret;
 
 	res = kzalloc(sizeof(struct resource), GFP_ATOMIC);
 	if (!res)
@@ -908,7 +909,17 @@ static int efi_mem_reserve_iomem(phys_addr_t addr, u64 size)
 
 	/* we expect a conflict with a 'System RAM' region */
 	parent = request_resource_conflict(&iomem_resource, res);
-	return parent ? request_resource(parent, res) : 0;
+	ret = parent ? request_resource(parent, res) : 0;
+
+	/*
+	 * Given that efi_mem_reserve_iomem() can be called at any
+	 * time, only call memblock_reserve() if the architecture
+	 * keeps the infrastructure around.
+	 */
+	if (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK) && !ret)
+		memblock_reserve(addr, size);
+
+	return ret;
 }
 
 int __ref efi_mem_reserve_persistent(phys_addr_t addr, u64 size)