diff --git a/arch/arm/boot/compressed/fdt_check_mem_start.c b/arch/arm/boot/compressed/fdt_check_mem_start.c index 62450d824c3c..9291a2661bdf 100644 --- a/arch/arm/boot/compressed/fdt_check_mem_start.c +++ b/arch/arm/boot/compressed/fdt_check_mem_start.c @@ -55,16 +55,17 @@ static uint64_t get_val(const fdt32_t *cells, uint32_t ncells) * DTB, and, if out-of-range, replace it by the real start address. * To preserve backwards compatibility (systems reserving a block of memory * at the start of physical memory, kdump, ...), the traditional method is - * always used if it yields a valid address. + * used if it yields a valid address, unless the "linux,usable-memory-range" + * property is present. * * Return value: start address of physical memory to use */ uint32_t fdt_check_mem_start(uint32_t mem_start, const void *fdt) { - uint32_t addr_cells, size_cells, base; + uint32_t addr_cells, size_cells, usable_base, base; uint32_t fdt_mem_start = 0xffffffff; - const fdt32_t *reg, *endp; - uint64_t size, end; + const fdt32_t *usable, *reg, *endp; + uint64_t size, usable_end, end; const char *type; int offset, len; @@ -80,6 +81,27 @@ uint32_t fdt_check_mem_start(uint32_t mem_start, const void *fdt) if (addr_cells > 2 || size_cells > 2) return mem_start; + /* + * Usable memory in case of a crash dump kernel + * This property describes a limitation: memory within this range is + * only valid when also described through another mechanism + */ + usable = get_prop(fdt, "/chosen", "linux,usable-memory-range", + (addr_cells + size_cells) * sizeof(fdt32_t)); + if (usable) { + size = get_val(usable + addr_cells, size_cells); + if (!size) + return mem_start; + + if (addr_cells > 1 && fdt32_ld(usable)) { + /* Outside 32-bit address space */ + return mem_start; + } + + usable_base = fdt32_ld(usable + addr_cells - 1); + usable_end = usable_base + size; + } + /* Walk all memory nodes and regions */ for (offset = fdt_next_node(fdt, -1, NULL); offset >= 0; offset = fdt_next_node(fdt, offset, NULL)) { @@ -107,7 +129,20 @@ uint32_t fdt_check_mem_start(uint32_t mem_start, const void *fdt) base = fdt32_ld(reg + addr_cells - 1); end = base + size; - if (mem_start >= base && mem_start < end) { + if (usable) { + /* + * Clip to usable range, which takes precedence + * over mem_start + */ + if (base < usable_base) + base = usable_base; + + if (end > usable_end) + end = usable_end; + + if (end <= base) + continue; + } else if (mem_start >= base && mem_start < end) { /* Calculated address is valid, use it */ return mem_start; } @@ -123,7 +158,8 @@ uint32_t fdt_check_mem_start(uint32_t mem_start, const void *fdt) } /* - * The calculated address is not usable. + * The calculated address is not usable, or was overridden by the + * "linux,usable-memory-range" property. * Use the lowest usable physical memory address from the DTB instead, * and make sure this is a multiple of 2 MiB for phys/virt patching. */