> -----Original Message-----
> From: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> Sent: 14 October 2019 18:33
> To: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> Cc: linux-efi@xxxxxxxxxxxxxxx; Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>;
> Guillaume Gardet <Guillaume.Gardet@xxxxxxx>; Chester Lin <clin@xxxxxxxx>
> Subject: [PATCH] efi: libstub/arm: account for firmware reserved memory at the
> base of RAM
>
> The EFI stubloader for ARM starts out by allocating a 32 MB window at the base of
> RAM, in order to ensure that the decompressor (which blindly copies the
> uncompressed kernel into that window) does not overwrite other allocations
> that are made while running in the context of the EFI firmware.
>
> In some cases, (e.g., U-Boot running on the Raspberry Pi 2), this is causing boot
> failures because this initial allocation conflicts with a page of reserved memory at
> the base of RAM that contains the SMP spin tables and other pieces of firmware
> data and which was put there by the bootloader under the assumption that the
> TEXT_OFFSET window right below the kernel is only used partially during early
> boot, and will be left alone once the memory reservations are processed and
> taken into account.
>
> So let's permit reserved memory regions to exist in the region starting at the base
> of RAM, and ending at TEXT_OFFSET - 5 * PAGE_SIZE, which is the window below
> the kernel that is not touched by the early boot code.
>
> Cc: Guillaume Gardet <Guillaume.Gardet@xxxxxxx>
> Cc: Chester Lin <clin@xxxxxxxx>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
Tested-by: Guillaume Gardet <Guillaume.Gardet@xxxxxxx>
> ---
> drivers/firmware/efi/libstub/Makefile | 1 +
> drivers/firmware/efi/libstub/arm32-stub.c | 16 +++++++++++++---
> 2 files changed, 14 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/firmware/efi/libstub/Makefile
> b/drivers/firmware/efi/libstub/Makefile
> index 0460c7581220..ee0661ddb25b 100644
> --- a/drivers/firmware/efi/libstub/Makefile
> +++ b/drivers/firmware/efi/libstub/Makefile
> @@ -52,6 +52,7 @@ lib-$(CONFIG_EFI_ARMSTUB) += arm-stub.o fdt.o
> string.o random.o \
>
> lib-$(CONFIG_ARM) += arm32-stub.o
> lib-$(CONFIG_ARM64) += arm64-stub.o
> +CFLAGS_arm32-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
> CFLAGS_arm64-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
>
> #
> diff --git a/drivers/firmware/efi/libstub/arm32-stub.c
> b/drivers/firmware/efi/libstub/arm32-stub.c
> index e8f7aefb6813..47aafeff3e01 100644
> --- a/drivers/firmware/efi/libstub/arm32-stub.c
> +++ b/drivers/firmware/efi/libstub/arm32-stub.c
> @@ -195,6 +195,7 @@ efi_status_t handle_kernel_image(efi_system_table_t
> *sys_table,
> unsigned long dram_base,
> efi_loaded_image_t *image)
> {
> + unsigned long kernel_base;
> efi_status_t status;
>
> /*
> @@ -204,9 +205,18 @@ efi_status_t handle_kernel_image(efi_system_table_t
> *sys_table,
> * loaded. These assumptions are made by the decompressor,
> * before any memory map is available.
> */
> - dram_base = round_up(dram_base, SZ_128M);
> + kernel_base = round_up(dram_base, SZ_128M);
>
> - status = reserve_kernel_base(sys_table, dram_base, reserve_addr,
> + /*
> + * Note that some platforms (notably, the Raspberry Pi 2) put
> + * spin-tables and other pieces of firmware at the base of RAM,
> + * abusing the fact that the window of TEXT_OFFSET bytes at the
> + * base of the kernel image is only partially used at the moment.
> + * (Up to 5 pages are used for the swapper page table)
> + */
> + kernel_base += TEXT_OFFSET - 5 * PAGE_SIZE;
> +
> + status = reserve_kernel_base(sys_table, kernel_base, reserve_addr,
> reserve_size);
> if (status != EFI_SUCCESS) {
> pr_efi_err(sys_table, "Unable to allocate memory for
> uncompressed kernel.\n"); @@ -220,7 +230,7 @@ efi_status_t
> handle_kernel_image(efi_system_table_t *sys_table,
> *image_size = image->image_size;
> status = efi_relocate_kernel(sys_table, image_addr, *image_size,
> *image_size,
> - dram_base + MAX_UNCOMP_KERNEL_SIZE, 0);
> + kernel_base + MAX_UNCOMP_KERNEL_SIZE,
> 0);
> if (status != EFI_SUCCESS) {
> pr_efi_err(sys_table, "Failed to relocate kernel.\n");
> efi_free(sys_table, *reserve_size, *reserve_addr);
> --
> 2.20.1
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