From 0673cb38951215060d7993b43ad3c45cd413c2c3 Mon Sep 17 00:00:00 2001 From: Geert Uytterhoeven Date: Mon, 4 Jan 2021 14:00:52 +0100 Subject: ARM: 9045/1: uncompress: Validate start of physical memory against passed DTB Currently, the start address of physical memory is obtained by masking the program counter with a fixed mask of 0xf8000000. This mask value was chosen as a balance between the requirements of different platforms. However, this does require that the start address of physical memory is a multiple of 128 MiB, precluding booting Linux on platforms where this requirement is not fulfilled. Fix this limitation by validating the masked address against the memory information in the passed DTB. Only use the start address from DTB when masking would yield an out-of-range address, prefer the traditional method in all other cases. Note that this applies only to the explicitly passed DTB on modern systems, and not to a DTB appended to the kernel, or to ATAGS. The appended DTB may need to be augmented by information from ATAGS, which may need to rely on knowledge of the start address of physical memory itself. This allows to boot Linux on r7s9210/rza2mevb using the 64 MiB of SDRAM on the RZA2MEVB sub board, which is located at 0x0C000000 (CS3 space), i.e. not at a multiple of 128 MiB. Suggested-by: Nicolas Pitre Suggested-by: Ard Biesheuvel Signed-off-by: Geert Uytterhoeven Reviewed-by: Ard Biesheuvel Acked-by: Nicolas Pitre Signed-off-by: Russell King --- arch/arm/Kconfig | 7 +- arch/arm/boot/compressed/Makefile | 5 +- arch/arm/boot/compressed/fdt_check_mem_start.c | 131 +++++++++++++++++++++++++ arch/arm/boot/compressed/head.S | 36 ++++++- 4 files changed, 172 insertions(+), 7 deletions(-) create mode 100644 arch/arm/boot/compressed/fdt_check_mem_start.c (limited to 'arch/arm') diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 138248999df7..9860057775ee 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -1875,9 +1875,10 @@ config AUTO_ZRELADDR help ZRELADDR is the physical address where the decompressed kernel image will be placed. If AUTO_ZRELADDR is selected, the address - will be determined at run-time by masking the current IP with - 0xf8000000. This assumes the zImage being placed in the first 128MB - from start of memory. + will be determined at run-time, either by masking the current IP + with 0xf8000000, or, if invalid, from the DTB passed in r2. + This assumes the zImage being placed in the first 128MB from + start of memory. config EFI_STUB bool diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile index fb521efcc6c2..fd94e27ba4fa 100644 --- a/arch/arm/boot/compressed/Makefile +++ b/arch/arm/boot/compressed/Makefile @@ -87,10 +87,13 @@ libfdt_objs := fdt_rw.o fdt_ro.o fdt_wip.o fdt.o ifeq ($(CONFIG_ARM_ATAG_DTB_COMPAT),y) OBJS += $(libfdt_objs) atags_to_fdt.o endif +ifeq ($(CONFIG_USE_OF),y) +OBJS += $(libfdt_objs) fdt_check_mem_start.o +endif # -fstack-protector-strong triggers protection checks in this code, # but it is being used too early to link to meaningful stack_chk logic. -$(foreach o, $(libfdt_objs) atags_to_fdt.o, \ +$(foreach o, $(libfdt_objs) atags_to_fdt.o fdt_check_mem_start.o, \ $(eval CFLAGS_$(o) := -I $(srctree)/scripts/dtc/libfdt -fno-stack-protector)) # These were previously generated C files. When you are building the kernel 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..62450d824c3c --- /dev/null +++ b/arch/arm/boot/compressed/fdt_check_mem_start.c @@ -0,0 +1,131 @@ +// SPDX-License-Identifier: GPL-2.0-only + +#include +#include +#include + +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 + * always used if it yields a valid address. + * + * 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 fdt_mem_start = 0xffffffff; + const fdt32_t *reg, *endp; + uint64_t size, 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; + + /* 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 (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. + * 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); +} diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S index d4837c2d0359..262b5b6e45d1 100644 --- a/arch/arm/boot/compressed/head.S +++ b/arch/arm/boot/compressed/head.S @@ -279,10 +279,40 @@ not_angel: * are already placing their zImage in (eg) the top 64MB * of this range. */ - mov r4, pc - and r4, r4, #0xf8000000 + mov r0, pc + and r0, r0, #0xf8000000 +#ifdef CONFIG_USE_OF + adr r1, LC1 +#ifdef CONFIG_ARM_APPENDED_DTB + /* + * Look for an appended DTB. If found, we cannot use it to + * validate the calculated start of physical memory, as its + * memory nodes may need to be augmented by ATAGS stored at + * an offset from the same start of physical memory. + */ + ldr r2, [r1, #4] @ get &_edata + add r2, r2, r1 @ relocate it + ldr r2, [r2] @ get DTB signature + ldr r3, =OF_DT_MAGIC + cmp r2, r3 @ do we have a DTB there? + beq 1f @ if yes, skip validation +#endif /* CONFIG_ARM_APPENDED_DTB */ + + /* + * Make sure we have some stack before calling C code. + * No GOT fixup has occurred yet, but none of the code we're + * about to call uses any global variables. + */ + ldr sp, [r1] @ get stack location + add sp, sp, r1 @ apply relocation + + /* Validate calculated start against passed DTB */ + mov r1, r8 + bl fdt_check_mem_start +1: +#endif /* CONFIG_USE_OF */ /* Determine final kernel image address. */ - add r4, r4, #TEXT_OFFSET + add r4, r0, #TEXT_OFFSET #else ldr r4, =zreladdr #endif -- cgit