This series adds the ability for the MIPS kernel to relocate itself at runtime, optionally to an address determined at random each boot. This series is based on v4.4 and has been tested on the Malta, Boston and SEAD3 platforms. Here is a description of how relocation is achieved: * Kernel is compiled & statically linked as normal, with no position independent code. MIPS before R6 only has limited relative jump instructions so the vast majority of jumps are absolute. To compile the kernel position independent would introduce a highly undesireable overhead. Relocating the static binary gives a small startup time penalty but the kernel otherwise perforns normally. * The linker flag --emit-relocs is added to the linker command line, causing ld to include relocation sections in the output elf * A tool derived from the x86 relocs tool is used to parse the relocation sections and create a binary table of relocations. Each entry in the table is 32bits, comprised of a 24bit offset (in words) from _text and an 8bit relocation type. * The table is inserted into the vmlinux elf, into some space reserved for it in the linker script. Inserting the table into vmlinux means all boot targets will automatically include the relocation code and information. * At boot, the kernel memcpy()s itself elsewhere in memory, then goes through the table performing each relocation on the new image. * If all goes well, control is passed to the entry point of the new kernel. Restrictions: * The new kernel is not allowed to overlap the old kernel, such that the original kernel can still be booted if relocation fails. * Relocation is supported only by multiples of 64k bytes. This eliminates the need to handle R_MIPS_LO16 relocations as the bottom 16bits will remain the same at the relocated address. * In 64 bit kernels, relocation is supported only within the same 4Gb memory segment as the kernel link address (CONFIG_PHYSICAL_START). This eliminates the need to handle R_MIPS_HIGHEST and R_MIPS_HIGHER relocations as the top 32bits will remain the same at the relocated address. Changes in v2: - Added support for MIPSr6 - Accept the "nokaslr" command line option - Add a kernel panic notifier to print the relocation information - Accept entropy via the /chosen/kaslr-seed property in device tree - Tested on MIPS Malta, Boston and SEAD3 platforms Matt Redfearn (11): MIPS: tools: Add relocs tool MIPS: tools: Build relocs tool MIPS: Reserve space for relocation table MIPS: Generate relocation table when CONFIG_RELOCATABLE MIPS: Kernel: Add relocate.c MIPS: Call relocate_kernel if CONFIG_RELOCATABLE=y MIPS: bootmem: When relocatable, free memory below kernel MIPS: Add CONFIG_RELOCATABLE Kconfig option MIPS: Introduce plat_get_fdt a platform API to retrieve the FDT MIPS: Kernel: Implement KASLR using CONFIG_RELOCATABLE MIPS: KASLR: Print relocation Information on boot arch/mips/Kconfig | 64 ++++ arch/mips/Makefile | 19 ++ arch/mips/boot/tools/Makefile | 8 + arch/mips/boot/tools/relocs.c | 680 +++++++++++++++++++++++++++++++++++++ arch/mips/boot/tools/relocs.h | 45 +++ arch/mips/boot/tools/relocs_32.c | 17 + arch/mips/boot/tools/relocs_64.c | 27 ++ arch/mips/boot/tools/relocs_main.c | 84 +++++ arch/mips/include/asm/bootinfo.h | 18 + arch/mips/kernel/Makefile | 2 + arch/mips/kernel/head.S | 20 ++ arch/mips/kernel/relocate.c | 386 +++++++++++++++++++++ arch/mips/kernel/setup.c | 23 ++ arch/mips/kernel/vmlinux.lds.S | 21 ++ arch/mips/mti-malta/malta-setup.c | 7 +- arch/mips/mti-sead3/sead3-setup.c | 5 + 16 files changed, 1425 insertions(+), 1 deletion(-) create mode 100644 arch/mips/boot/tools/Makefile create mode 100644 arch/mips/boot/tools/relocs.c create mode 100644 arch/mips/boot/tools/relocs.h create mode 100644 arch/mips/boot/tools/relocs_32.c create mode 100644 arch/mips/boot/tools/relocs_64.c create mode 100644 arch/mips/boot/tools/relocs_main.c create mode 100644 arch/mips/kernel/relocate.c -- 2.5.0
