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author | Jun Yao <yaojun8558363@gmail.com> | 2018-09-24 15:47:49 +0100 |
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committer | Catalin Marinas <catalin.marinas@arm.com> | 2018-09-25 15:10:54 +0100 |
commit | 2b5548b68199c17c1466d5798cf2c9cd806bdaa9 (patch) | |
tree | 88c8b8710b472236e0724ba3d18e92b7eec341ba /arch/arm64/mm | |
parent | 693d5639b44a8f3787444902d3600edc7e0105a2 (diff) | |
download | linux-2b5548b68199c17c1466d5798cf2c9cd806bdaa9.tar.gz linux-2b5548b68199c17c1466d5798cf2c9cd806bdaa9.tar.bz2 linux-2b5548b68199c17c1466d5798cf2c9cd806bdaa9.zip |
arm64/mm: Separate boot-time page tables from swapper_pg_dir
Since the address of swapper_pg_dir is fixed for a given kernel image,
it is an attractive target for manipulation via an arbitrary write. To
mitigate this we'd like to make it read-only by moving it into the
rodata section.
We require that swapper_pg_dir is at a fixed offset from tramp_pg_dir
and reserved_ttbr0, so these will also need to move into rodata.
However, swapper_pg_dir is allocated along with some transient page
tables used for boot which we do not want to move into rodata.
As a step towards this, this patch separates the boot-time page tables
into a new init_pg_dir, and reduces swapper_pg_dir to the single page it
needs to be. This allows us to retain the relationship between
swapper_pg_dir, tramp_pg_dir, and swapper_pg_dir, while cleanly
separating these from the boot-time page tables.
The init_pg_dir holds all of the pgd/pud/pmd/pte levels needed during
boot, and all of these levels will be freed when we switch to the
swapper_pg_dir, which is initialized by the existing code in
paging_init(). Since we start off on the init_pg_dir, we no longer need
to allocate a transient page table in paging_init() in order to ensure
that swapper_pg_dir isn't live while we initialize it.
There should be no functional change as a result of this patch.
Signed-off-by: Jun Yao <yaojun8558363@gmail.com>
Reviewed-by: James Morse <james.morse@arm.com>
[Mark: place init_pg_dir after BSS, fold mm changes, commit message]
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64/mm')
-rw-r--r-- | arch/arm64/mm/mmu.c | 30 |
1 files changed, 5 insertions, 25 deletions
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index 65f86271f02b..8a5491053717 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -629,34 +629,14 @@ static void __init map_kernel(pgd_t *pgdp) */ void __init paging_init(void) { - phys_addr_t pgd_phys = early_pgtable_alloc(); - pgd_t *pgdp = pgd_set_fixmap(pgd_phys); + map_kernel(swapper_pg_dir); + map_mem(swapper_pg_dir); - map_kernel(pgdp); - map_mem(pgdp); - - /* - * We want to reuse the original swapper_pg_dir so we don't have to - * communicate the new address to non-coherent secondaries in - * secondary_entry, and so cpu_switch_mm can generate the address with - * adrp+add rather than a load from some global variable. - * - * To do this we need to go via a temporary pgd. - */ - cpu_replace_ttbr1(__va(pgd_phys)); - memcpy(swapper_pg_dir, pgdp, PGD_SIZE); cpu_replace_ttbr1(lm_alias(swapper_pg_dir)); + init_mm.pgd = swapper_pg_dir; - pgd_clear_fixmap(); - memblock_free(pgd_phys, PAGE_SIZE); - - /* - * We only reuse the PGD from the swapper_pg_dir, not the pud + pmd - * allocated with it. - */ - memblock_free(__pa_symbol(swapper_pg_dir) + PAGE_SIZE, - __pa_symbol(swapper_pg_end) - __pa_symbol(swapper_pg_dir) - - PAGE_SIZE); + memblock_free(__pa_symbol(init_pg_dir), + __pa_symbol(init_pg_end) - __pa_symbol(init_pg_dir)); } /* |