From 9abcc981de9775659a0f6e4a52a3448ea72e59da Mon Sep 17 00:00:00 2001 From: Michael Ellerman Date: Tue, 6 Jun 2017 15:48:57 +1000 Subject: [PATCH] powerpc/mm/radix: Only add X for pages overlapping kernel text Currently we map the whole linear mapping with PAGE_KERNEL_X. Instead we should check if the page overlaps the kernel text and only then add PAGE_KERNEL_X. Note that we still use 1G pages if they're available, so this will typically still result in a 1G executable page at KERNELBASE. So this fix is primarily useful for catching stray branches to high linear mapping addresses. Without this patch, we can execute at 1G in xmon using: 0:mon> m c000000040000000 c000000040000000 00 l c000000040000000 00000000 01006038 c000000040000004 00000000 2000804e c000000040000008 00000000 x 0:mon> di c000000040000000 c000000040000000 38600001 li r3,1 c000000040000004 4e800020 blr 0:mon> p c000000040000000 return value is 0x1 After we get a 400 as expected: 0:mon> p c000000040000000 *** 400 exception occurred Fixes: 2bfd65e45e87 ("powerpc/mm/radix: Add radix callbacks for early init routines") Cc: stable@vger.kernel.org # v4.7+ Signed-off-by: Michael Ellerman Reviewed-by: Aneesh Kumar K.V Acked-by: Balbir Singh --- arch/powerpc/mm/pgtable-radix.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/arch/powerpc/mm/pgtable-radix.c b/arch/powerpc/mm/pgtable-radix.c index c28165d8970b..6c062f92b9e4 100644 --- a/arch/powerpc/mm/pgtable-radix.c +++ b/arch/powerpc/mm/pgtable-radix.c @@ -19,6 +19,7 @@ #include #include #include +#include #include @@ -121,7 +122,8 @@ static inline void __meminit print_mapping(unsigned long start, static int __meminit create_physical_mapping(unsigned long start, unsigned long end) { - unsigned long addr, mapping_size = 0; + unsigned long vaddr, addr, mapping_size = 0; + pgprot_t prot; start = _ALIGN_UP(start, PAGE_SIZE); for (addr = start; addr < end; addr += mapping_size) { @@ -145,8 +147,14 @@ static int __meminit create_physical_mapping(unsigned long start, start = addr; } - rc = radix__map_kernel_page((unsigned long)__va(addr), addr, - PAGE_KERNEL_X, mapping_size); + vaddr = (unsigned long)__va(addr); + + if (overlaps_kernel_text(vaddr, vaddr + mapping_size)) + prot = PAGE_KERNEL_X; + else + prot = PAGE_KERNEL; + + rc = radix__map_kernel_page(vaddr, addr, prot, mapping_size); if (rc) return rc; } -- 2.20.1