The Hash MMU already supports XOM (i.e. mmap with PROT_EXEC only) through the execute-only pkey. A PROT_ONLY mapping will actually map to RX, and then the pkey will be applied on top of it.
Radix doesn't have pkeys, but it does have execute permissions built-in to the MMU, so all we have to do to support XOM is expose it. Signed-off-by: Russell Currey <rus...@russell.cc> --- quick test: https://raw.githubusercontent.com/ruscur/junkcode/main/mmap_test.c I can make it a selftest. arch/powerpc/include/asm/book3s/64/radix.h | 3 +++ arch/powerpc/mm/book3s64/radix_pgtable.c | 4 ++++ arch/powerpc/mm/fault.c | 10 ++++++++++ 3 files changed, 17 insertions(+) diff --git a/arch/powerpc/include/asm/book3s/64/radix.h b/arch/powerpc/include/asm/book3s/64/radix.h index 686001eda936..bf316b773d73 100644 --- a/arch/powerpc/include/asm/book3s/64/radix.h +++ b/arch/powerpc/include/asm/book3s/64/radix.h @@ -19,6 +19,9 @@ #include <asm/cpu_has_feature.h> #endif +/* Execute-only page protections, Hash can use RX + execute-only pkey */ +#define PAGE_EXECONLY __pgprot(_PAGE_BASE | _PAGE_EXEC) + /* An empty PTE can still have a R or C writeback */ #define RADIX_PTE_NONE_MASK (_PAGE_DIRTY | _PAGE_ACCESSED) diff --git a/arch/powerpc/mm/book3s64/radix_pgtable.c b/arch/powerpc/mm/book3s64/radix_pgtable.c index 698274109c91..2edb56169805 100644 --- a/arch/powerpc/mm/book3s64/radix_pgtable.c +++ b/arch/powerpc/mm/book3s64/radix_pgtable.c @@ -617,6 +617,10 @@ void __init radix__early_init_mmu(void) __pmd_frag_nr = RADIX_PMD_FRAG_NR; __pmd_frag_size_shift = RADIX_PMD_FRAG_SIZE_SHIFT; + /* Radix directly supports execute-only page protections */ + protection_map[VM_EXEC] = PAGE_EXECONLY; + protection_map[VM_EXEC | VM_SHARED] = PAGE_EXECONLY; + radix_init_pgtable(); if (!firmware_has_feature(FW_FEATURE_LPAR)) { diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c index 014005428687..887c0cc45ca6 100644 --- a/arch/powerpc/mm/fault.c +++ b/arch/powerpc/mm/fault.c @@ -270,6 +270,16 @@ static bool access_error(bool is_write, bool is_exec, struct vm_area_struct *vma return false; } + if (unlikely(!(vma->vm_flags & VM_READ))) { + /* + * If we're on Radix, then this could be a read attempt on + * execute-only memory. On other MMUs, an "exec-only" page + * will be given RX flags, so this might be redundant. + */ + if (radix_enabled()) + return true; + } + if (unlikely(!vma_is_accessible(vma))) return true; /* -- 2.37.1
