linux/arch/arm64/kernel/kaslr.c
Fuad Tabba fade9c2c6e arm64: Rename arm64-internal cache maintenance functions
Although naming across the codebase isn't that consistent, it
tends to follow certain patterns. Moreover, the term "flush"
isn't defined in the Arm Architecture reference manual, and might
be interpreted to mean clean, invalidate, or both for a cache.

Rename arm64-internal functions to make the naming internally
consistent, as well as making it consistent with the Arm ARM, by
specifying whether it applies to the instruction, data, or both
caches, whether the operation is a clean, invalidate, or both.
Also specify which point the operation applies to, i.e., to the
point of unification (PoU), coherency (PoC), or persistence
(PoP).

This commit applies the following sed transformation to all files
under arch/arm64:

"s/\b__flush_cache_range\b/caches_clean_inval_pou_macro/g;"\
"s/\b__flush_icache_range\b/caches_clean_inval_pou/g;"\
"s/\binvalidate_icache_range\b/icache_inval_pou/g;"\
"s/\b__flush_dcache_area\b/dcache_clean_inval_poc/g;"\
"s/\b__inval_dcache_area\b/dcache_inval_poc/g;"\
"s/__clean_dcache_area_poc\b/dcache_clean_poc/g;"\
"s/\b__clean_dcache_area_pop\b/dcache_clean_pop/g;"\
"s/\b__clean_dcache_area_pou\b/dcache_clean_pou/g;"\
"s/\b__flush_cache_user_range\b/caches_clean_inval_user_pou/g;"\
"s/\b__flush_icache_all\b/icache_inval_all_pou/g;"

Note that __clean_dcache_area_poc is deliberately missing a word
boundary check at the beginning in order to match the efistub
symbols in image-vars.h.

Also note that, despite its name, __flush_icache_range operates
on both instruction and data caches. The name change here
reflects that.

No functional change intended.

Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Fuad Tabba <tabba@google.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20210524083001.2586635-19-tabba@google.com
Signed-off-by: Will Deacon <will@kernel.org>
2021-05-25 19:27:49 +01:00

205 lines
5.8 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2016 Linaro Ltd <ard.biesheuvel@linaro.org>
*/
#include <linux/cache.h>
#include <linux/crc32.h>
#include <linux/init.h>
#include <linux/libfdt.h>
#include <linux/mm_types.h>
#include <linux/sched.h>
#include <linux/types.h>
#include <linux/pgtable.h>
#include <linux/random.h>
#include <asm/cacheflush.h>
#include <asm/fixmap.h>
#include <asm/kernel-pgtable.h>
#include <asm/memory.h>
#include <asm/mmu.h>
#include <asm/sections.h>
#include <asm/setup.h>
enum kaslr_status {
KASLR_ENABLED,
KASLR_DISABLED_CMDLINE,
KASLR_DISABLED_NO_SEED,
KASLR_DISABLED_FDT_REMAP,
};
static enum kaslr_status __initdata kaslr_status;
u64 __ro_after_init module_alloc_base;
u16 __initdata memstart_offset_seed;
static __init u64 get_kaslr_seed(void *fdt)
{
int node, len;
fdt64_t *prop;
u64 ret;
node = fdt_path_offset(fdt, "/chosen");
if (node < 0)
return 0;
prop = fdt_getprop_w(fdt, node, "kaslr-seed", &len);
if (!prop || len != sizeof(u64))
return 0;
ret = fdt64_to_cpu(*prop);
*prop = 0;
return ret;
}
struct arm64_ftr_override kaslr_feature_override __initdata;
/*
* This routine will be executed with the kernel mapped at its default virtual
* address, and if it returns successfully, the kernel will be remapped, and
* start_kernel() will be executed from a randomized virtual offset. The
* relocation will result in all absolute references (e.g., static variables
* containing function pointers) to be reinitialized, and zero-initialized
* .bss variables will be reset to 0.
*/
u64 __init kaslr_early_init(void)
{
void *fdt;
u64 seed, offset, mask, module_range;
unsigned long raw;
/*
* Set a reasonable default for module_alloc_base in case
* we end up running with module randomization disabled.
*/
module_alloc_base = (u64)_etext - MODULES_VSIZE;
dcache_clean_inval_poc((unsigned long)&module_alloc_base,
(unsigned long)&module_alloc_base +
sizeof(module_alloc_base));
/*
* Try to map the FDT early. If this fails, we simply bail,
* and proceed with KASLR disabled. We will make another
* attempt at mapping the FDT in setup_machine()
*/
fdt = get_early_fdt_ptr();
if (!fdt) {
kaslr_status = KASLR_DISABLED_FDT_REMAP;
return 0;
}
/*
* Retrieve (and wipe) the seed from the FDT
*/
seed = get_kaslr_seed(fdt);
/*
* Check if 'nokaslr' appears on the command line, and
* return 0 if that is the case.
*/
if (kaslr_feature_override.val & kaslr_feature_override.mask & 0xf) {
kaslr_status = KASLR_DISABLED_CMDLINE;
return 0;
}
/*
* Mix in any entropy obtainable architecturally if enabled
* and supported.
*/
if (arch_get_random_seed_long_early(&raw))
seed ^= raw;
if (!seed) {
kaslr_status = KASLR_DISABLED_NO_SEED;
return 0;
}
/*
* OK, so we are proceeding with KASLR enabled. Calculate a suitable
* kernel image offset from the seed. Let's place the kernel in the
* middle half of the VMALLOC area (VA_BITS_MIN - 2), and stay clear of
* the lower and upper quarters to avoid colliding with other
* allocations.
* Even if we could randomize at page granularity for 16k and 64k pages,
* let's always round to 2 MB so we don't interfere with the ability to
* map using contiguous PTEs
*/
mask = ((1UL << (VA_BITS_MIN - 2)) - 1) & ~(SZ_2M - 1);
offset = BIT(VA_BITS_MIN - 3) + (seed & mask);
/* use the top 16 bits to randomize the linear region */
memstart_offset_seed = seed >> 48;
if (!IS_ENABLED(CONFIG_KASAN_VMALLOC) &&
(IS_ENABLED(CONFIG_KASAN_GENERIC) ||
IS_ENABLED(CONFIG_KASAN_SW_TAGS)))
/*
* KASAN without KASAN_VMALLOC does not expect the module region
* to intersect the vmalloc region, since shadow memory is
* allocated for each module at load time, whereas the vmalloc
* region is shadowed by KASAN zero pages. So keep modules
* out of the vmalloc region if KASAN is enabled without
* KASAN_VMALLOC, and put the kernel well within 4 GB of the
* module region.
*/
return offset % SZ_2G;
if (IS_ENABLED(CONFIG_RANDOMIZE_MODULE_REGION_FULL)) {
/*
* Randomize the module region over a 2 GB window covering the
* kernel. This reduces the risk of modules leaking information
* about the address of the kernel itself, but results in
* branches between modules and the core kernel that are
* resolved via PLTs. (Branches between modules will be
* resolved normally.)
*/
module_range = SZ_2G - (u64)(_end - _stext);
module_alloc_base = max((u64)_end + offset - SZ_2G,
(u64)MODULES_VADDR);
} else {
/*
* Randomize the module region by setting module_alloc_base to
* a PAGE_SIZE multiple in the range [_etext - MODULES_VSIZE,
* _stext) . This guarantees that the resulting region still
* covers [_stext, _etext], and that all relative branches can
* be resolved without veneers.
*/
module_range = MODULES_VSIZE - (u64)(_etext - _stext);
module_alloc_base = (u64)_etext + offset - MODULES_VSIZE;
}
/* use the lower 21 bits to randomize the base of the module region */
module_alloc_base += (module_range * (seed & ((1 << 21) - 1))) >> 21;
module_alloc_base &= PAGE_MASK;
dcache_clean_inval_poc((unsigned long)&module_alloc_base,
(unsigned long)&module_alloc_base +
sizeof(module_alloc_base));
dcache_clean_inval_poc((unsigned long)&memstart_offset_seed,
(unsigned long)&memstart_offset_seed +
sizeof(memstart_offset_seed));
return offset;
}
static int __init kaslr_init(void)
{
switch (kaslr_status) {
case KASLR_ENABLED:
pr_info("KASLR enabled\n");
break;
case KASLR_DISABLED_CMDLINE:
pr_info("KASLR disabled on command line\n");
break;
case KASLR_DISABLED_NO_SEED:
pr_warn("KASLR disabled due to lack of seed\n");
break;
case KASLR_DISABLED_FDT_REMAP:
pr_warn("KASLR disabled due to FDT remapping failure\n");
break;
}
return 0;
}
core_initcall(kaslr_init)