From: Paul Burton Date: Wed, 18 Sep 2019 22:03:30 +0000 (+0000) Subject: MIPS: Detect bad _PFN_SHIFT values X-Git-Tag: v5.4-rc1~80^2 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=05d013a0366d50f4f0dbebf8c1b22b42020bf49a;p=platform%2Fkernel%2Flinux-rpi.git 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 --- diff --git a/arch/mips/mm/init.c b/arch/mips/mm/init.c index 6fea3b5..090fa65 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"