diff options
| author | Alexandre Ghiti <alexghiti@rivosinc.com> | 2023-07-22 14:38:46 +0200 |
|---|---|---|
| committer | Palmer Dabbelt <palmer@rivosinc.com> | 2023-09-05 19:49:27 -0700 |
| commit | 84fe419dc7578b03e721b9bd6eb07947db70fd0e (patch) | |
| tree | d8a270fb5d5b0248452f47ca4669ac3eb278a41e /arch/riscv/mm/init.c | |
| parent | 06c2afb862f9da8dc5efa4b6076a0e48c3fbaaa5 (diff) | |
riscv: Introduce virtual kernel mapping KASLR
KASLR implementation relies on a relocatable kernel so that we can move
the kernel mapping.
The seed needed to virtually move the kernel is taken from the device tree,
so we rely on the bootloader to provide a correct seed. Zkr could be used
unconditionnally instead if implemented, but that's for another patch.
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Tested-by: Conor Dooley <conor.dooley@microchip.com>
Tested-by: Song Shuai <songshuaishuai@tinylab.org>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Tested-by: Sami Tolvanen <samitolvanen@google.com>
Link: https://lore.kernel.org/r/20230722123850.634544-2-alexghiti@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Diffstat (limited to 'arch/riscv/mm/init.c')
| -rw-r--r-- | arch/riscv/mm/init.c | 36 |
1 files changed, 35 insertions, 1 deletions
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c index 70fb31960b63..ff926531236e 100644 --- a/arch/riscv/mm/init.c +++ b/arch/riscv/mm/init.c @@ -1012,11 +1012,45 @@ static void __init pt_ops_set_late(void) #endif } +#ifdef CONFIG_RANDOMIZE_BASE +extern bool __init __pi_set_nokaslr_from_cmdline(uintptr_t dtb_pa); +extern u64 __init __pi_get_kaslr_seed(uintptr_t dtb_pa); + +static int __init print_nokaslr(char *p) +{ + pr_info("Disabled KASLR"); + return 0; +} +early_param("nokaslr", print_nokaslr); + +unsigned long kaslr_offset(void) +{ + return kernel_map.virt_offset; +} +#endif + asmlinkage void __init setup_vm(uintptr_t dtb_pa) { pmd_t __maybe_unused fix_bmap_spmd, fix_bmap_epmd; - kernel_map.virt_addr = KERNEL_LINK_ADDR; +#ifdef CONFIG_RANDOMIZE_BASE + if (!__pi_set_nokaslr_from_cmdline(dtb_pa)) { + u64 kaslr_seed = __pi_get_kaslr_seed(dtb_pa); + u32 kernel_size = (uintptr_t)(&_end) - (uintptr_t)(&_start); + u32 nr_pos; + + /* + * Compute the number of positions available: we are limited + * by the early page table that only has one PUD and we must + * be aligned on PMD_SIZE. + */ + nr_pos = (PUD_SIZE - kernel_size) / PMD_SIZE; + + kernel_map.virt_offset = (kaslr_seed % nr_pos) * PMD_SIZE; + } +#endif + + kernel_map.virt_addr = KERNEL_LINK_ADDR + kernel_map.virt_offset; kernel_map.page_offset = _AC(CONFIG_PAGE_OFFSET, UL); #ifdef CONFIG_XIP_KERNEL |