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| author | Michael Ellerman <mpe@ellerman.id.au> | 2018-08-14 20:48:22 +1000 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2018-10-20 13:26:47 +1100 |
| commit | 3b5657ed5b4e27ccf593a41ff3c5aa27dae8df18 (patch) | |
| tree | f61e38527e3ed667b9e053f98ccd87f171b86414 /arch/powerpc | |
| parent | 5c6499b7041b43807dfaeda28aa87fc0e62558f7 (diff) | |
powerpc/mm/radix: Fix overuse of small pages in splitting logic
When we have CONFIG_STRICT_KERNEL_RWX enabled, we want to split the
linear mapping at the text/data boundary so we can map the kernel text
read only.
But the current logic uses small pages for the entire text section,
regardless of whether a larger page size would fit. eg. with the
boundary at 16M we could use 2M pages, but instead we use 64K pages up
to the 16M boundary:
Mapped 0x0000000000000000-0x0000000001000000 with 64.0 KiB pages
Mapped 0x0000000001000000-0x0000000040000000 with 2.00 MiB pages
Mapped 0x0000000040000000-0x0000000100000000 with 1.00 GiB pages
This is because the test is checking if addr is < __init_begin
and addr + mapping_size is >= _stext. But that is true for all pages
between _stext and __init_begin.
Instead what we want to check is if we are crossing the text/data
boundary, which is at __init_begin. With that fixed we see:
Mapped 0x0000000000000000-0x0000000000e00000 with 2.00 MiB pages
Mapped 0x0000000000e00000-0x0000000001000000 with 64.0 KiB pages
Mapped 0x0000000001000000-0x0000000040000000 with 2.00 MiB pages
Mapped 0x0000000040000000-0x0000000100000000 with 1.00 GiB pages
ie. we're correctly using 2MB pages below __init_begin, but we still
drop down to 64K pages unnecessarily at the boundary.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc')
| -rw-r--r-- | arch/powerpc/mm/pgtable-radix.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/powerpc/mm/pgtable-radix.c b/arch/powerpc/mm/pgtable-radix.c index d88d76231754..bb85c58b96c8 100644 --- a/arch/powerpc/mm/pgtable-radix.c +++ b/arch/powerpc/mm/pgtable-radix.c @@ -295,14 +295,14 @@ retry: if (split_text_mapping && (mapping_size == PUD_SIZE) && (addr < __pa_symbol(__init_begin)) && - (addr + mapping_size) >= __pa_symbol(_stext)) { + (addr + mapping_size) >= __pa_symbol(__init_begin)) { max_mapping_size = PMD_SIZE; goto retry; } if (split_text_mapping && (mapping_size == PMD_SIZE) && (addr < __pa_symbol(__init_begin)) && - (addr + mapping_size) >= __pa_symbol(_stext)) { + (addr + mapping_size) >= __pa_symbol(__init_begin)) { mapping_size = PAGE_SIZE; psize = mmu_virtual_psize; } |