From: Nam Cao Date: Wed, 15 May 2024 05:50:39 +0000 (+0200) Subject: riscv: force PAGE_SIZE linear mapping if debug_pagealloc is enabled X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=c67ddf59ac44adc60649730bf8347e37c516b001;p=linux.git riscv: force PAGE_SIZE linear mapping if debug_pagealloc is enabled debug_pagealloc is a debug feature which clears the valid bit in page table entry for freed pages to detect illegal accesses to freed memory. For this feature to work, virtual mapping must have PAGE_SIZE resolution. (No, we cannot map with huge pages and split them only when needed; because pages can be allocated/freed in atomic context and page splitting cannot be done in atomic context) Force linear mapping to use small pages if debug_pagealloc is enabled. Note that it is not necessary to force the entire linear mapping, but only those that are given to memory allocator. Some parts of memory can keep using huge page mapping (for example, kernel's executable code). But these parts are minority, so keep it simple. This is just a debug feature, some extra overhead should be acceptable. Fixes: 5fde3db5eb02 ("riscv: add ARCH_SUPPORTS_DEBUG_PAGEALLOC support") Signed-off-by: Nam Cao Cc: stable@vger.kernel.org Reviewed-by: Alexandre Ghiti Link: https://lore.kernel.org/r/2e391fa6c6f9b3fcf1b41cefbace02ee4ab4bf59.1715750938.git.namcao@linutronix.de Signed-off-by: Palmer Dabbelt --- diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c index fe8e159394d8e..9020844f5189c 100644 --- a/arch/riscv/mm/init.c +++ b/arch/riscv/mm/init.c @@ -668,6 +668,9 @@ void __init create_pgd_mapping(pgd_t *pgdp, static uintptr_t __init best_map_size(phys_addr_t pa, uintptr_t va, phys_addr_t size) { + if (debug_pagealloc_enabled()) + return PAGE_SIZE; + if (pgtable_l5_enabled && !(pa & (P4D_SIZE - 1)) && !(va & (P4D_SIZE - 1)) && size >= P4D_SIZE) return P4D_SIZE;