From c0036549a9d9a060fa8bc24e31f85503ce08ad5e Mon Sep 17 00:00:00 2001 From: Nicholas Piggin Date: Tue, 9 Jun 2020 17:06:07 +1000 Subject: [PATCH] powerpc/security: split branch cache flush toggle from code patching Branch cache flushing code patching has inter-dependencies on both the link stack and the count cache flushing state. To make the code clearer and to separate the link stack and count cache handling, split the "toggle" (setting up variables and printing enable/disable) from the code patching. Signed-off-by: Nicholas Piggin [mpe: Always print something, even if the flush is disabled] Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20200609070610.846703-5-npiggin@gmail.com --- arch/powerpc/kernel/security.c | 100 ++++++++++++++++++--------------- 1 file changed, 54 insertions(+), 46 deletions(-) diff --git a/arch/powerpc/kernel/security.c b/arch/powerpc/kernel/security.c index 659ef6a92bb9..05eeb22b3b97 100644 --- a/arch/powerpc/kernel/security.c +++ b/arch/powerpc/kernel/security.c @@ -427,61 +427,69 @@ static __init int stf_barrier_debugfs_init(void) device_initcall(stf_barrier_debugfs_init); #endif /* CONFIG_DEBUG_FS */ -static void no_count_cache_flush(void) +static void update_branch_cache_flush(void) { - count_cache_flush_type = BRANCH_CACHE_FLUSH_NONE; - pr_info("count-cache-flush: flush disabled.\n"); +#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE + // This controls the branch from guest_exit_cont to kvm_flush_link_stack + if (link_stack_flush_type == BRANCH_CACHE_FLUSH_NONE) { + patch_instruction_site(&patch__call_kvm_flush_link_stack, + ppc_inst(PPC_INST_NOP)); + } else { + patch_branch_site(&patch__call_kvm_flush_link_stack, + (u64)&kvm_flush_link_stack, BRANCH_SET_LINK); + } +#endif + + // This controls the branch from _switch to flush_branch_caches + if (count_cache_flush_type == BRANCH_CACHE_FLUSH_NONE && + link_stack_flush_type == BRANCH_CACHE_FLUSH_NONE) { + patch_instruction_site(&patch__call_flush_branch_caches, + ppc_inst(PPC_INST_NOP)); + } else { + patch_branch_site(&patch__call_flush_branch_caches, + (u64)&flush_branch_caches, BRANCH_SET_LINK); + + // If we just need to flush the link stack, early return + if (count_cache_flush_type == BRANCH_CACHE_FLUSH_NONE) { + patch_instruction_site(&patch__flush_link_stack_return, + ppc_inst(PPC_INST_BLR)); + + // If we have flush instruction, early return + } else if (count_cache_flush_type == BRANCH_CACHE_FLUSH_HW) { + patch_instruction_site(&patch__flush_count_cache_return, + ppc_inst(PPC_INST_BLR)); + } + } } static void toggle_branch_cache_flush(bool enable) { - if (!security_ftr_enabled(SEC_FTR_FLUSH_COUNT_CACHE) && - !security_ftr_enabled(SEC_FTR_FLUSH_LINK_STACK)) - enable = false; + if (!enable || !security_ftr_enabled(SEC_FTR_FLUSH_COUNT_CACHE)) { + if (count_cache_flush_type != BRANCH_CACHE_FLUSH_NONE) + count_cache_flush_type = BRANCH_CACHE_FLUSH_NONE; + + pr_info("count-cache-flush: flush disabled.\n"); + } else { + if (security_ftr_enabled(SEC_FTR_BCCTR_FLUSH_ASSIST)) { + count_cache_flush_type = BRANCH_CACHE_FLUSH_HW; + pr_info("count-cache-flush: hardware flush enabled.\n"); + } else { + count_cache_flush_type = BRANCH_CACHE_FLUSH_SW; + pr_info("count-cache-flush: software flush enabled.\n"); + } + } + + if (!enable || !security_ftr_enabled(SEC_FTR_FLUSH_LINK_STACK)) { + if (link_stack_flush_type != BRANCH_CACHE_FLUSH_NONE) + link_stack_flush_type = BRANCH_CACHE_FLUSH_NONE; - if (!enable) { - patch_instruction_site(&patch__call_flush_branch_caches, - ppc_inst(PPC_INST_NOP)); -#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE - patch_instruction_site(&patch__call_kvm_flush_link_stack, - ppc_inst(PPC_INST_NOP)); -#endif pr_info("link-stack-flush: flush disabled.\n"); - link_stack_flush_type = BRANCH_CACHE_FLUSH_NONE; - no_count_cache_flush(); - return; + } else { + link_stack_flush_type = BRANCH_CACHE_FLUSH_SW; + pr_info("link-stack-flush: software flush enabled.\n"); } - // This enables the branch from _switch to flush_branch_caches - patch_branch_site(&patch__call_flush_branch_caches, - (u64)&flush_branch_caches, BRANCH_SET_LINK); - -#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE - // This enables the branch from guest_exit_cont to kvm_flush_link_stack - patch_branch_site(&patch__call_kvm_flush_link_stack, - (u64)&kvm_flush_link_stack, BRANCH_SET_LINK); -#endif - - pr_info("link-stack-flush: software flush enabled.\n"); - link_stack_flush_type = BRANCH_CACHE_FLUSH_SW; - - // If we just need to flush the link stack, patch an early return - if (!security_ftr_enabled(SEC_FTR_FLUSH_COUNT_CACHE)) { - patch_instruction_site(&patch__flush_link_stack_return, - ppc_inst(PPC_INST_BLR)); - no_count_cache_flush(); - return; - } - - if (!security_ftr_enabled(SEC_FTR_BCCTR_FLUSH_ASSIST)) { - count_cache_flush_type = BRANCH_CACHE_FLUSH_SW; - pr_info("count-cache-flush: software flush enabled.\n"); - return; - } - - patch_instruction_site(&patch__flush_count_cache_return, ppc_inst(PPC_INST_BLR)); - count_cache_flush_type = BRANCH_CACHE_FLUSH_HW; - pr_info("count-cache-flush: hardware flush enabled.\n"); + update_branch_cache_flush(); } void setup_count_cache_flush(void)