From: Nick Kossifidis <mick@xxxxxxxxxxxx> commit c6fe81191bd74f7e6ae9ce96a4837df9485f3ab8 upstream. 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: Nick Kossifidis <mick@xxxxxxxxxxxx> Link: https://lore.kernel.org/r/20220322132839.3653682-1-mick@xxxxxxxxxxxx Tested-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx> Fixes: f105aa940e78 ("riscv: add BUILTIN_DTB support for MMU-enabled targets") Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/riscv/mm/init.c | 21 +++++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-) --- a/arch/riscv/mm/init.c +++ b/arch/riscv/mm/init.c @@ -218,8 +218,25 @@ 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)) - memblock_reserve(dtb_early_pa, fdt_totalsize(dtb_early_va)); + 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);
