From 05d013a0366d50f4f0dbebf8c1b22b42020bf49a Mon Sep 17 00:00:00 2001 From: Paul Burton Date: Wed, 18 Sep 2019 22:03:30 +0000 Subject: [PATCH] MIPS: Detect bad _PFN_SHIFT values 2 recent commits have fixed issues where _PFN_SHIFT grew too large due to the introduction of too many pgprot bits in our PTEs for some MIPS32 kernel configurations. Tracking down such issues can be tricky, so add a BUILD_BUG_ON() to help. Signed-off-by: Paul Burton Cc: linux-mips@vger.kernel.org --- arch/mips/mm/init.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/arch/mips/mm/init.c b/arch/mips/mm/init.c index 6fea3b54c961..090fa653dfa9 100644 --- a/arch/mips/mm/init.c +++ b/arch/mips/mm/init.c @@ -446,6 +446,12 @@ static inline void __init mem_init_free_highmem(void) void __init mem_init(void) { + /* + * When _PFN_SHIFT is greater than PAGE_SHIFT we won't have enough PTE + * bits to hold a full 32b physical address on MIPS32 systems. + */ + BUILD_BUG_ON(IS_ENABLED(CONFIG_32BIT) && (_PFN_SHIFT > PAGE_SHIFT)); + #ifdef CONFIG_HIGHMEM #ifdef CONFIG_DISCONTIGMEM #error "CONFIG_HIGHMEM and CONFIG_DISCONTIGMEM dont work together yet"