diff --git a/arch/powerpc/include/asm/security_features.h b/arch/powerpc/include/asm/security_features.h index 7c05e95a5c444768f67a40f3b7b40a734f1c5b59..fbb8fa32150fd969962ff9ee731e46c99bbb6f86 100644 --- a/arch/powerpc/include/asm/security_features.h +++ b/arch/powerpc/include/asm/security_features.h @@ -63,6 +63,8 @@ static inline bool security_ftr_enabled(u64 feature) // bcctr 2,0,0 triggers a hardware assisted count cache flush #define SEC_FTR_BCCTR_FLUSH_ASSIST 0x0000000000000800ull +// bcctr 2,0,0 triggers a hardware assisted link stack flush +#define SEC_FTR_BCCTR_LINK_FLUSH_ASSIST 0x0000000000002000ull // Features indicating need for Spectre/Meltdown mitigations diff --git a/arch/powerpc/kernel/security.c b/arch/powerpc/kernel/security.c index 05eeb22b3b978cbd18a3b2d9ec604edda4b00e7c..c9876aab31421aa8388692b94d8d0bdfb5364515 100644 --- a/arch/powerpc/kernel/security.c +++ b/arch/powerpc/kernel/security.c @@ -219,24 +219,25 @@ ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr, c if (ccd) seq_buf_printf(&s, "Indirect branch cache disabled"); - if (link_stack_flush_type == BRANCH_CACHE_FLUSH_SW) - seq_buf_printf(&s, ", Software link stack flush"); - } else if (count_cache_flush_type != BRANCH_CACHE_FLUSH_NONE) { seq_buf_printf(&s, "Mitigation: Software count cache flush"); if (count_cache_flush_type == BRANCH_CACHE_FLUSH_HW) seq_buf_printf(&s, " (hardware accelerated)"); - if (link_stack_flush_type == BRANCH_CACHE_FLUSH_SW) - seq_buf_printf(&s, ", Software link stack flush"); - } else if (btb_flush_enabled) { seq_buf_printf(&s, "Mitigation: Branch predictor state flush"); } else { seq_buf_printf(&s, "Vulnerable"); } + if (bcs || ccd || count_cache_flush_type != BRANCH_CACHE_FLUSH_NONE) { + if (link_stack_flush_type != BRANCH_CACHE_FLUSH_NONE) + seq_buf_printf(&s, ", Software link stack flush"); + if (link_stack_flush_type == BRANCH_CACHE_FLUSH_HW) + seq_buf_printf(&s, " (hardware accelerated)"); + } + seq_buf_printf(&s, "\n"); return s.len; @@ -435,6 +436,7 @@ static void update_branch_cache_flush(void) patch_instruction_site(&patch__call_kvm_flush_link_stack, ppc_inst(PPC_INST_NOP)); } else { + // Could use HW flush, but that could also flush count cache patch_branch_site(&patch__call_kvm_flush_link_stack, (u64)&kvm_flush_link_stack, BRANCH_SET_LINK); } @@ -445,6 +447,10 @@ static void update_branch_cache_flush(void) link_stack_flush_type == BRANCH_CACHE_FLUSH_NONE) { patch_instruction_site(&patch__call_flush_branch_caches, ppc_inst(PPC_INST_NOP)); + } else if (count_cache_flush_type == BRANCH_CACHE_FLUSH_HW && + link_stack_flush_type == BRANCH_CACHE_FLUSH_HW) { + patch_instruction_site(&patch__call_flush_branch_caches, + ppc_inst(PPC_INST_BCCTR_FLUSH)); } else { patch_branch_site(&patch__call_flush_branch_caches, (u64)&flush_branch_caches, BRANCH_SET_LINK); @@ -485,8 +491,13 @@ static void toggle_branch_cache_flush(bool enable) pr_info("link-stack-flush: flush disabled.\n"); } else { - link_stack_flush_type = BRANCH_CACHE_FLUSH_SW; - pr_info("link-stack-flush: software flush enabled.\n"); + if (security_ftr_enabled(SEC_FTR_BCCTR_LINK_FLUSH_ASSIST)) { + link_stack_flush_type = BRANCH_CACHE_FLUSH_HW; + pr_info("link-stack-flush: hardware flush enabled.\n"); + } else { + link_stack_flush_type = BRANCH_CACHE_FLUSH_SW; + pr_info("link-stack-flush: software flush enabled.\n"); + } } update_branch_cache_flush();