| Message ID | 1489047912-642-8-git-send-email-ard.biesheuvel@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, Mar 09, 2017 at 09:25:09AM +0100, Ard Biesheuvel wrote: > The debug_pagealloc facility manipulates kernel mappings in the linear > region at page granularity to detect out of bounds or use-after-free > accesses. Since the kernel segments are not allocated dynamically, > there is no point in taking the debug_pagealloc_enabled flag into > account for them, and we can use block mappings unconditionally. > > Note that this applies equally to the linear alias of text/rodata: > we will never have dynamic allocations there given that the same > memory is statically in use by the kernel image. > > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> This makes sense to me, and I haven't found anything this breaks. It may be worth noting that a similar reasoning already applies the the FDT mapping, where we use create_mapping_noalloc(), and never mandate page mappings. Regardless: Reviewed-by: Mark Rutland <mark.rutland@arm.com> Mark. > --- > arch/arm64/mm/mmu.c | 7 +++---- > 1 file changed, 3 insertions(+), 4 deletions(-) > > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > index c3963c592ec3..d3fecd20a136 100644 > --- a/arch/arm64/mm/mmu.c > +++ b/arch/arm64/mm/mmu.c > @@ -328,8 +328,7 @@ static void update_mapping_prot(phys_addr_t phys, unsigned long virt, > return; > } > > - __create_pgd_mapping(init_mm.pgd, phys, virt, size, prot, > - NULL, debug_pagealloc_enabled()); > + __create_pgd_mapping(init_mm.pgd, phys, virt, size, prot, NULL, false); > > /* flush the TLBs after updating live kernel mappings */ > flush_tlb_kernel_range(virt, virt + size); > @@ -381,7 +380,7 @@ static void __init __map_memblock(pgd_t *pgd, phys_addr_t start, phys_addr_t end > */ > __create_pgd_mapping(pgd, kernel_start, __phys_to_virt(kernel_start), > kernel_end - kernel_start, PAGE_KERNEL, > - early_pgtable_alloc, debug_pagealloc_enabled()); > + early_pgtable_alloc, false); > } > > void __init mark_linear_text_alias_ro(void) > @@ -437,7 +436,7 @@ static void __init map_kernel_segment(pgd_t *pgd, void *va_start, void *va_end, > BUG_ON(!PAGE_ALIGNED(size)); > > __create_pgd_mapping(pgd, pa_start, (unsigned long)va_start, size, prot, > - early_pgtable_alloc, debug_pagealloc_enabled()); > + early_pgtable_alloc, false); > > vma->addr = va_start; > vma->phys_addr = pa_start; > -- > 2.7.4 >
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index c3963c592ec3..d3fecd20a136 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -328,8 +328,7 @@ static void update_mapping_prot(phys_addr_t phys, unsigned long virt, return; } - __create_pgd_mapping(init_mm.pgd, phys, virt, size, prot, - NULL, debug_pagealloc_enabled()); + __create_pgd_mapping(init_mm.pgd, phys, virt, size, prot, NULL, false); /* flush the TLBs after updating live kernel mappings */ flush_tlb_kernel_range(virt, virt + size); @@ -381,7 +380,7 @@ static void __init __map_memblock(pgd_t *pgd, phys_addr_t start, phys_addr_t end */ __create_pgd_mapping(pgd, kernel_start, __phys_to_virt(kernel_start), kernel_end - kernel_start, PAGE_KERNEL, - early_pgtable_alloc, debug_pagealloc_enabled()); + early_pgtable_alloc, false); } void __init mark_linear_text_alias_ro(void) @@ -437,7 +436,7 @@ static void __init map_kernel_segment(pgd_t *pgd, void *va_start, void *va_end, BUG_ON(!PAGE_ALIGNED(size)); __create_pgd_mapping(pgd, pa_start, (unsigned long)va_start, size, prot, - early_pgtable_alloc, debug_pagealloc_enabled()); + early_pgtable_alloc, false); vma->addr = va_start; vma->phys_addr = pa_start;
The debug_pagealloc facility manipulates kernel mappings in the linear region at page granularity to detect out of bounds or use-after-free accesses. Since the kernel segments are not allocated dynamically, there is no point in taking the debug_pagealloc_enabled flag into account for them, and we can use block mappings unconditionally. Note that this applies equally to the linear alias of text/rodata: we will never have dynamic allocations there given that the same memory is statically in use by the kernel image. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> --- arch/arm64/mm/mmu.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-)