diff options
Diffstat (limited to '')
| -rw-r--r-- | arch/arm/boot/compressed/fdt_check_mem_start.c | 167 |
1 files changed, 167 insertions, 0 deletions
diff --git a/arch/arm/boot/compressed/fdt_check_mem_start.c b/arch/arm/boot/compressed/fdt_check_mem_start.c new file mode 100644 index 000000000000..9291a2661bdf --- /dev/null +++ b/arch/arm/boot/compressed/fdt_check_mem_start.c @@ -0,0 +1,167 @@ +// SPDX-License-Identifier: GPL-2.0-only + +#include <linux/kernel.h> +#include <linux/libfdt.h> +#include <linux/sizes.h> + +static const void *get_prop(const void *fdt, const char *node_path, + const char *property, int minlen) +{ + const void *prop; + int offset, len; + + offset = fdt_path_offset(fdt, node_path); + if (offset < 0) + return NULL; + + prop = fdt_getprop(fdt, offset, property, &len); + if (!prop || len < minlen) + return NULL; + + return prop; +} + +static uint32_t get_cells(const void *fdt, const char *name) +{ + const fdt32_t *prop = get_prop(fdt, "/", name, sizeof(fdt32_t)); + + if (!prop) { + /* default */ + return 1; + } + + return fdt32_ld(prop); +} + +static uint64_t get_val(const fdt32_t *cells, uint32_t ncells) +{ + uint64_t r; + + r = fdt32_ld(cells); + if (ncells > 1) + r = (r << 32) | fdt32_ld(cells + 1); + + return r; +} + +/* + * Check the start of physical memory + * + * Traditionally, the start address of physical memory is obtained by masking + * the program counter. However, this does require that this address is a + * multiple of 128 MiB, precluding booting Linux on platforms where this + * requirement is not fulfilled. + * Hence validate the calculated address against the memory information in the + * 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 + * 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, usable_base, base; + uint32_t fdt_mem_start = 0xffffffff; + const fdt32_t *usable, *reg, *endp; + uint64_t size, usable_end, end; + const char *type; + int offset, len; + + if (!fdt) + return mem_start; + + if (fdt_magic(fdt) != FDT_MAGIC) + return mem_start; + + /* There may be multiple cells on LPAE platforms */ + addr_cells = get_cells(fdt, "#address-cells"); + size_cells = get_cells(fdt, "#size-cells"); + 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)) { + type = fdt_getprop(fdt, offset, "device_type", NULL); + if (!type || strcmp(type, "memory")) + continue; + + reg = fdt_getprop(fdt, offset, "linux,usable-memory", &len); + if (!reg) + reg = fdt_getprop(fdt, offset, "reg", &len); + if (!reg) + continue; + + for (endp = reg + (len / sizeof(fdt32_t)); + endp - reg >= addr_cells + size_cells; + reg += addr_cells + size_cells) { + size = get_val(reg + addr_cells, size_cells); + if (!size) + continue; + + if (addr_cells > 1 && fdt32_ld(reg)) { + /* Outside 32-bit address space, skipping */ + continue; + } + + base = fdt32_ld(reg + addr_cells - 1); + end = base + size; + 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; + } + + if (base < fdt_mem_start) + fdt_mem_start = base; + } + } + + if (fdt_mem_start == 0xffffffff) { + /* No usable memory found, falling back to default */ + return mem_start; + } + + /* + * 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. + */ + return round_up(fdt_mem_start, SZ_2M); +} |