Unverified Commit c6fe8119 authored by Nick Kossifidis's avatar Nick Kossifidis Committed by Palmer Dabbelt
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RISC-V: relocate DTB if it's outside memory region 



In case the DTB provided by the bootloader/BootROM is before the kernel
image or outside /memory, we won't be able to access it through the
linear mapping, and get a segfault on setup_arch(). Currently OpenSBI
relocates DTB but that's not always the case (e.g. if FW_JUMP_FDT_ADDR
is not specified), and it's also not the most portable approach since
the default FW_JUMP_FDT_ADDR of the generic platform relocates the DTB
at a specific offset that may not be available. To avoid this situation
copy DTB so that it's visible through the linear mapping.

Signed-off-by: default avatarNick Kossifidis <mick@ics.forth.gr>
Link: https://lore.kernel.org/r/20220322132839.3653682-1-mick@ics.forth.gr


Tested-by: default avatarConor Dooley <conor.dooley@microchip.com>
Fixes: f105aa94 ("riscv: add BUILTIN_DTB support for MMU-enabled targets")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarPalmer Dabbelt <palmer@rivosinc.com>
parent ac0280a9

arch/riscv/mm/init.c

+19 −2
Original line number Diff line number Diff line
@@ -208,8 +208,25 @@ static void __init setup_bootmem(void) 
	 * early_init_fdt_reserve_self() since __pa() does

	 * not work for DTB pointers that are fixmap addresses

	 */

	if (!IS_ENABLED(CONFIG_BUILTIN_DTB))

	if (!IS_ENABLED(CONFIG_BUILTIN_DTB)) {

		/*

		 * In case the DTB is not located in a memory region we won't

		 * be able to locate it later on via the linear mapping and

		 * get a segfault when accessing it via __va(dtb_early_pa).

		 * To avoid this situation copy DTB to a memory region.

		 * Note that memblock_phys_alloc will also reserve DTB region.

		 */

		if (!memblock_is_memory(dtb_early_pa)) {

			size_t fdt_size = fdt_totalsize(dtb_early_va);

			phys_addr_t new_dtb_early_pa = memblock_phys_alloc(fdt_size, PAGE_SIZE);

			void *new_dtb_early_va = early_memremap(new_dtb_early_pa, fdt_size);



			memcpy(new_dtb_early_va, dtb_early_va, fdt_size);

			early_memunmap(new_dtb_early_va, fdt_size);

			_dtb_early_pa = new_dtb_early_pa;

		} else

			memblock_reserve(dtb_early_pa, fdt_totalsize(dtb_early_va));

	}



	early_init_fdt_scan_reserved_mem();

	dma_contiguous_reserve(dma32_phys_limit);