From 7ab0b7cb8951d4095d73e203759b74d41916e455 Mon Sep 17 00:00:00 2001 From: Christophe Leroy Date: Fri, 16 Aug 2019 07:52:20 +0000 Subject: [PATCH] powerpc/32: Add warning on misaligned copy_page() or clear_page() copy_page() and clear_page() expect page aligned destination, and use dcbz instruction to clear entire cache lines based on the assumption that the destination is cache aligned. As shown during analysis of a bug in BTRFS filesystem, a misaligned copy_page() can create bugs that are difficult to locate (see Link). Add an explicit WARNING when copy_page() or clear_page() are called with misaligned destination. Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://bugzilla.kernel.org/show_bug.cgi?id=204371 Link: https://lore.kernel.org/r/c6cea38f90480268d439ca44a645647e260fff09.1565941808.git.christophe.leroy@c-s.fr --- arch/powerpc/include/asm/page_32.h | 4 ++++ arch/powerpc/kernel/misc_32.S | 5 +++++ 2 files changed, 9 insertions(+) diff --git a/arch/powerpc/include/asm/page_32.h b/arch/powerpc/include/asm/page_32.h index 683dfbc..d64dfe3 100644 --- a/arch/powerpc/include/asm/page_32.h +++ b/arch/powerpc/include/asm/page_32.h @@ -40,6 +40,8 @@ typedef unsigned long long pte_basic_t; typedef unsigned long pte_basic_t; #endif +#include + /* * Clear page using the dcbz instruction, which doesn't cause any * memory traffic (except to write out any cache lines which get @@ -49,6 +51,8 @@ static inline void clear_page(void *addr) { unsigned int i; + WARN_ON((unsigned long)addr & (L1_CACHE_BYTES - 1)); + for (i = 0; i < PAGE_SIZE / L1_CACHE_BYTES; i++, addr += L1_CACHE_BYTES) dcbz(addr); } diff --git a/arch/powerpc/kernel/misc_32.S b/arch/powerpc/kernel/misc_32.S index fe4bd32..02d90e1 100644 --- a/arch/powerpc/kernel/misc_32.S +++ b/arch/powerpc/kernel/misc_32.S @@ -452,7 +452,12 @@ END_FTR_SECTION_IFSET(CPU_FTR_COHERENT_ICACHE) stwu r9,16(r3) _GLOBAL(copy_page) + rlwinm r5, r3, 0, L1_CACHE_BYTES - 1 addi r3,r3,-4 + +0: twnei r5, 0 /* WARN if r3 is not cache aligned */ + EMIT_BUG_ENTRY 0b,__FILE__,__LINE__, BUGFLAG_WARNING + addi r4,r4,-4 li r5,4 -- 2.7.4