From: Mark Rutland mark.rutland@arm.com
commit 90268574a3e8a6b883bd802d702a2738577e1006 upstream.
The `compute_indices` and `populate_entries` macros operate on inclusive bounds, and thus the `map_memory` macro which uses them also operates on inclusive bounds.
We pass `_end` and `_idmap_text_end` to `map_memory`, but these are exclusive bounds, and if one of these is sufficiently aligned (as a result of kernel configuration, physical placement, and KASLR), then:
* In `compute_indices`, the computed `iend` will be in the page/block *after* the final byte of the intended mapping.
* In `populate_entries`, an unnecessary entry will be created at the end of each level of table. At the leaf level, this entry will map up to SWAPPER_BLOCK_SIZE bytes of physical addresses that we did not intend to map.
As we may map up to SWAPPER_BLOCK_SIZE bytes more than intended, we may violate the boot protocol and map physical address past the 2MiB-aligned end address we are permitted to map. As we map these with Normal memory attributes, this may result in further problems depending on what these physical addresses correspond to.
The final entry at each level may require an additional table at that level. As EARLY_ENTRIES() calculates an inclusive bound, we allocate enough memory for this.
Avoid the extraneous mapping by having map_memory convert the exclusive end address to an inclusive end address by subtracting one, and do likewise in EARLY_ENTRIES() when calculating the number of required tables. For clarity, comments are updated to more clearly document which boundaries the macros operate on. For consistency with the other macros, the comments in map_memory are also updated to describe `vstart` and `vend` as virtual addresses.
Fixes: 0370b31e4845 ("arm64: Extend early page table code to allow for larger kernels") Cc: stable@vger.kernel.org # 4.16.x Signed-off-by: Mark Rutland mark.rutland@arm.com Cc: Anshuman Khandual anshuman.khandual@arm.com Cc: Ard Biesheuvel ard.biesheuvel@linaro.org Cc: Steve Capper steve.capper@arm.com Cc: Will Deacon will@kernel.org Acked-by: Will Deacon will@kernel.org Link: https://lore.kernel.org/r/20210823101253.55567-1-mark.rutland@arm.com Signed-off-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/arm64/include/asm/kernel-pgtable.h | 4 ++-- arch/arm64/kernel/head.S | 11 ++++++----- 2 files changed, 8 insertions(+), 7 deletions(-)
--- a/arch/arm64/include/asm/kernel-pgtable.h +++ b/arch/arm64/include/asm/kernel-pgtable.h @@ -65,8 +65,8 @@ #define EARLY_KASLR (0) #endif
-#define EARLY_ENTRIES(vstart, vend, shift) (((vend) >> (shift)) \ - - ((vstart) >> (shift)) + 1 + EARLY_KASLR) +#define EARLY_ENTRIES(vstart, vend, shift) \ + ((((vend) - 1) >> (shift)) - ((vstart) >> (shift)) + 1 + EARLY_KASLR)
#define EARLY_PGDS(vstart, vend) (EARLY_ENTRIES(vstart, vend, PGDIR_SHIFT))
--- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -177,7 +177,7 @@ SYM_CODE_END(preserve_boot_args) * to be composed of multiple pages. (This effectively scales the end index). * * vstart: virtual address of start of range - * vend: virtual address of end of range + * vend: virtual address of end of range - we map [vstart, vend] * shift: shift used to transform virtual address into index * ptrs: number of entries in page table * istart: index in table corresponding to vstart @@ -214,17 +214,18 @@ SYM_CODE_END(preserve_boot_args) * * tbl: location of page table * rtbl: address to be used for first level page table entry (typically tbl + PAGE_SIZE) - * vstart: start address to map - * vend: end address to map - we map [vstart, vend] + * vstart: virtual address of start of range + * vend: virtual address of end of range - we map [vstart, vend - 1] * flags: flags to use to map last level entries * phys: physical address corresponding to vstart - physical memory is contiguous * pgds: the number of pgd entries * * Temporaries: istart, iend, tmp, count, sv - these need to be different registers - * Preserves: vstart, vend, flags - * Corrupts: tbl, rtbl, istart, iend, tmp, count, sv + * Preserves: vstart, flags + * Corrupts: tbl, rtbl, vend, istart, iend, tmp, count, sv */ .macro map_memory, tbl, rtbl, vstart, vend, flags, phys, pgds, istart, iend, tmp, count, sv + sub \vend, \vend, #1 add \rtbl, \tbl, #PAGE_SIZE mov \sv, \rtbl mov \count, #0