If the final page table entry we walk is a valid mapping, the page table
dumping code will not log the region this entry is part of, as the final
note_page call in ptdump_show will trigger an early return. Luckily this
isn't seen on contemporary systems as they typically don't have enough
RAM to extend the linear mapping right to the end of the address space.
In note_page, we log a region when we reach its end (i.e. we hit an
entry immediately afterwards which has different prot bits or is
invalid). The final entry has no subsequent entry, so we will not log
this immediately. We try to cater for this with a subsequent call to
note_page in ptdump_show, but this returns early as 0 < LOWEST_ADDR, and
hence we will skip a valid mapping if it spans to the final entry we
note.
Unlike 32-bit ARM, the pgd with the kernel mapping is never shared with
user mappings, so we do not need the check to ensure we don't log user
page tables. Due to the way addr is constructed in the walk_* functions,
it can never be less than LOWEST_ADDR when walking the page tables, so
it is not necessary to avoid dereferencing invalid table addresses. The
existing checks for st->current_prot and st->marker[1].start_address are
sufficient to ensure we will not print and/or dereference garbage when
trying to log information.
This patch removes the unnecessary check against LOWEST_ADDR, ensuring
we log all regions in the kernel page table, including those which span
right to the end of the address space.
Cc: Kees Cook <keescook@chromium.org>
Acked-by: Laura Abbott <lauraa@codeaurora.org>
Acked-by: Steve Capper <steve.capper@linaro.org>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
When building with 48-bit VAs, it's possible to get the following
warning when building the arm64 page table dumping code:
arch/arm64/mm/dump.c: In function ‘walk_pgd’:
arch/arm64/mm/dump.c:266:2: warning: right shift count >= width of type
pgd_t *pgd = pgd_offset(mm, 0);
^
As pgd_offset is a macro and the second argument is not cast to any
particular type, the zero will be given integer type by the compiler.
As pgd_offset passes the pargument to pgd_index, we then try to shift
the 32-bit integer by at least 39 bits (for 4k pages).
Elsewhere the pgd_offset is passed a second argument of unsigned long
type, so let's do the same here by passing '0UL' rather than '0'.
Cc: Kees Cook <keescook@chromium.org>
Acked-by: Laura Abbott <lauraa@codeaurora.org>
Acked-by: Steve Capper <steve.capper@arm.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
In a similar manner to arm, it's useful to be able to dump the page
tables to verify permissions and memory types. Add a debugfs file
to check the page tables.
Acked-by: Steve Capper <steve.capper@linaro.org>
Tested-by: Steve Capper <steve.capper@linaro.org>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>
[will: s/BUFFERABLE/NORMAL-NC/]
Signed-off-by: Will Deacon <will.deacon@arm.com>
Mark Rutland