[PATCH v2 14/45] powerpc/32s: Don't warn when mapping RO data ROX.
From: Christophe Leroy <hidden>
Date: 2020-05-06 16:51:02
Also in:
lkml
Subsystem:
linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Michael Ellerman, Linus Torvalds
Mapping RO data as ROX is not an issue since that data cannot be modified to introduce an exploit. PPC64 accepts to have RO data mapped ROX, as a trade off between kernel size and strictness of protection. On PPC32, kernel size is even more critical as amount of memory is usually small. Depending on the number of available IBATs, the last IBATs might overflow the end of text. Only warn if it crosses the end of RO data. Signed-off-by: Christophe Leroy <redacted> --- arch/powerpc/mm/book3s32/mmu.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/mm/book3s32/mmu.c b/arch/powerpc/mm/book3s32/mmu.c
index 39ba53ca5bb5..a9b2cbc74797 100644
--- a/arch/powerpc/mm/book3s32/mmu.c
+++ b/arch/powerpc/mm/book3s32/mmu.c@@ -187,6 +187,7 @@ void mmu_mark_initmem_nx(void) int i; unsigned long base = (unsigned long)_stext - PAGE_OFFSET; unsigned long top = (unsigned long)_etext - PAGE_OFFSET; + unsigned long border = (unsigned long)__init_begin - PAGE_OFFSET; unsigned long size; if (IS_ENABLED(CONFIG_PPC_BOOK3S_601))
@@ -201,9 +202,10 @@ void mmu_mark_initmem_nx(void) size = block_size(base, top); size = max(size, 128UL << 10); if ((top - base) > size) { - if (strict_kernel_rwx_enabled()) - pr_warn("Kernel _etext not properly aligned\n"); size <<= 1; + if (strict_kernel_rwx_enabled() && base + size > border) + pr_warn("Some RW data is getting mapped X. " + "Adjust CONFIG_DATA_SHIFT to avoid that.\n"); } setibat(i++, PAGE_OFFSET + base, base, size, PAGE_KERNEL_TEXT); base += size;
--
2.25.0