From 76a5eaa38b15dda92cd6964248c39b5a6f3a4e9d Mon Sep 17 00:00:00 2001 From: Diana Craciun Date: Wed, 12 Dec 2018 16:03:00 +0200 Subject: powerpc/fsl: Add infrastructure to fixup branch predictor flush In order to protect against speculation attacks (Spectre variant 2) on NXP PowerPC platforms, the branch predictor should be flushed when the privillege level is changed. This patch is adding the infrastructure to fixup at runtime the code sections that are performing the branch predictor flush depending on a boot arg parameter which is added later in a separate patch. Signed-off-by: Diana Craciun Signed-off-by: Michael Ellerman --- arch/powerpc/lib/feature-fixups.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) (limited to 'arch/powerpc/lib') diff --git a/arch/powerpc/lib/feature-fixups.c b/arch/powerpc/lib/feature-fixups.c index ca8478503f18..5169cc805464 100644 --- a/arch/powerpc/lib/feature-fixups.c +++ b/arch/powerpc/lib/feature-fixups.c @@ -347,6 +347,29 @@ void do_barrier_nospec_fixups_range(bool enable, void *fixup_start, void *fixup_ printk(KERN_DEBUG "barrier-nospec: patched %d locations\n", i); } + +static void patch_btb_flush_section(long *curr) +{ + unsigned int *start, *end; + + start = (void *)curr + *curr; + end = (void *)curr + *(curr + 1); + for (; start < end; start++) { + pr_devel("patching dest %lx\n", (unsigned long)start); + patch_instruction(start, PPC_INST_NOP); + } +} + +void do_btb_flush_fixups(void) +{ + long *start, *end; + + start = PTRRELOC(&__start__btb_flush_fixup); + end = PTRRELOC(&__stop__btb_flush_fixup); + + for (; start < end; start += 2) + patch_btb_flush_section(start); +} #endif /* CONFIG_PPC_FSL_BOOK3E */ void do_lwsync_fixups(unsigned long value, void *fixup_start, void *fixup_end) -- cgit v1.2.3