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authorMichael Ellerman <mpe@ellerman.id.au>2018-08-14 12:48:22 +0200
committerMichael Ellerman <mpe@ellerman.id.au>2018-10-20 04:26:47 +0200
commit3b5657ed5b4e27ccf593a41ff3c5aa27dae8df18 (patch)
treef61e38527e3ed667b9e053f98ccd87f171b86414 /arch/powerpc/mm/pgtable-radix.c
parentpowerpc/mm/radix: Fix off-by-one in split mapping logic (diff)
downloadlinux-3b5657ed5b4e27ccf593a41ff3c5aa27dae8df18.tar.xz
linux-3b5657ed5b4e27ccf593a41ff3c5aa27dae8df18.zip
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/mm/pgtable-radix.c')
-rw-r--r--arch/powerpc/mm/pgtable-radix.c4
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;
}