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583 lines
15 KiB
583 lines
15 KiB
// SPDX-License-Identifier: GPL-2.0+ |
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// |
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// Security related flags and so on. |
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// |
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// Copyright 2018, Michael Ellerman, IBM Corporation. |
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#include <linux/cpu.h> |
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#include <linux/kernel.h> |
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#include <linux/device.h> |
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#include <linux/nospec.h> |
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#include <linux/prctl.h> |
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#include <linux/seq_buf.h> |
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#include <asm/asm-prototypes.h> |
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#include <asm/code-patching.h> |
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#include <asm/debugfs.h> |
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#include <asm/security_features.h> |
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#include <asm/setup.h> |
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#include <asm/inst.h> |
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u64 powerpc_security_features __read_mostly = SEC_FTR_DEFAULT; |
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enum branch_cache_flush_type { |
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BRANCH_CACHE_FLUSH_NONE = 0x1, |
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BRANCH_CACHE_FLUSH_SW = 0x2, |
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BRANCH_CACHE_FLUSH_HW = 0x4, |
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}; |
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static enum branch_cache_flush_type count_cache_flush_type = BRANCH_CACHE_FLUSH_NONE; |
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static enum branch_cache_flush_type link_stack_flush_type = BRANCH_CACHE_FLUSH_NONE; |
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bool barrier_nospec_enabled; |
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static bool no_nospec; |
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static bool btb_flush_enabled; |
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#if defined(CONFIG_PPC_FSL_BOOK3E) || defined(CONFIG_PPC_BOOK3S_64) |
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static bool no_spectrev2; |
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#endif |
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static void enable_barrier_nospec(bool enable) |
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{ |
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barrier_nospec_enabled = enable; |
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do_barrier_nospec_fixups(enable); |
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} |
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void setup_barrier_nospec(void) |
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{ |
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bool enable; |
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/* |
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* It would make sense to check SEC_FTR_SPEC_BAR_ORI31 below as well. |
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* But there's a good reason not to. The two flags we check below are |
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* both are enabled by default in the kernel, so if the hcall is not |
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* functional they will be enabled. |
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* On a system where the host firmware has been updated (so the ori |
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* functions as a barrier), but on which the hypervisor (KVM/Qemu) has |
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* not been updated, we would like to enable the barrier. Dropping the |
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* check for SEC_FTR_SPEC_BAR_ORI31 achieves that. The only downside is |
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* we potentially enable the barrier on systems where the host firmware |
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* is not updated, but that's harmless as it's a no-op. |
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*/ |
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enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) && |
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security_ftr_enabled(SEC_FTR_BNDS_CHK_SPEC_BAR); |
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if (!no_nospec && !cpu_mitigations_off()) |
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enable_barrier_nospec(enable); |
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} |
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static int __init handle_nospectre_v1(char *p) |
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{ |
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no_nospec = true; |
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return 0; |
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} |
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early_param("nospectre_v1", handle_nospectre_v1); |
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#ifdef CONFIG_DEBUG_FS |
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static int barrier_nospec_set(void *data, u64 val) |
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{ |
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switch (val) { |
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case 0: |
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case 1: |
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break; |
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default: |
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return -EINVAL; |
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} |
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if (!!val == !!barrier_nospec_enabled) |
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return 0; |
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enable_barrier_nospec(!!val); |
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return 0; |
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} |
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static int barrier_nospec_get(void *data, u64 *val) |
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{ |
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*val = barrier_nospec_enabled ? 1 : 0; |
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return 0; |
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} |
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DEFINE_DEBUGFS_ATTRIBUTE(fops_barrier_nospec, barrier_nospec_get, |
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barrier_nospec_set, "%llu\n"); |
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static __init int barrier_nospec_debugfs_init(void) |
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{ |
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debugfs_create_file_unsafe("barrier_nospec", 0600, |
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powerpc_debugfs_root, NULL, |
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&fops_barrier_nospec); |
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return 0; |
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} |
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device_initcall(barrier_nospec_debugfs_init); |
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static __init int security_feature_debugfs_init(void) |
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{ |
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debugfs_create_x64("security_features", 0400, powerpc_debugfs_root, |
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&powerpc_security_features); |
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return 0; |
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} |
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device_initcall(security_feature_debugfs_init); |
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#endif /* CONFIG_DEBUG_FS */ |
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#if defined(CONFIG_PPC_FSL_BOOK3E) || defined(CONFIG_PPC_BOOK3S_64) |
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static int __init handle_nospectre_v2(char *p) |
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{ |
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no_spectrev2 = true; |
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return 0; |
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} |
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early_param("nospectre_v2", handle_nospectre_v2); |
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#endif /* CONFIG_PPC_FSL_BOOK3E || CONFIG_PPC_BOOK3S_64 */ |
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#ifdef CONFIG_PPC_FSL_BOOK3E |
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void setup_spectre_v2(void) |
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{ |
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if (no_spectrev2 || cpu_mitigations_off()) |
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do_btb_flush_fixups(); |
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else |
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btb_flush_enabled = true; |
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} |
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#endif /* CONFIG_PPC_FSL_BOOK3E */ |
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#ifdef CONFIG_PPC_BOOK3S_64 |
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ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr, char *buf) |
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{ |
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bool thread_priv; |
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thread_priv = security_ftr_enabled(SEC_FTR_L1D_THREAD_PRIV); |
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if (rfi_flush) { |
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struct seq_buf s; |
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seq_buf_init(&s, buf, PAGE_SIZE - 1); |
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seq_buf_printf(&s, "Mitigation: RFI Flush"); |
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if (thread_priv) |
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seq_buf_printf(&s, ", L1D private per thread"); |
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seq_buf_printf(&s, "\n"); |
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return s.len; |
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} |
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if (thread_priv) |
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return sprintf(buf, "Vulnerable: L1D private per thread\n"); |
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if (!security_ftr_enabled(SEC_FTR_L1D_FLUSH_HV) && |
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!security_ftr_enabled(SEC_FTR_L1D_FLUSH_PR)) |
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return sprintf(buf, "Not affected\n"); |
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return sprintf(buf, "Vulnerable\n"); |
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} |
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ssize_t cpu_show_l1tf(struct device *dev, struct device_attribute *attr, char *buf) |
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{ |
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return cpu_show_meltdown(dev, attr, buf); |
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} |
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#endif |
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ssize_t cpu_show_spectre_v1(struct device *dev, struct device_attribute *attr, char *buf) |
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{ |
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struct seq_buf s; |
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seq_buf_init(&s, buf, PAGE_SIZE - 1); |
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if (security_ftr_enabled(SEC_FTR_BNDS_CHK_SPEC_BAR)) { |
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if (barrier_nospec_enabled) |
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seq_buf_printf(&s, "Mitigation: __user pointer sanitization"); |
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else |
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seq_buf_printf(&s, "Vulnerable"); |
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if (security_ftr_enabled(SEC_FTR_SPEC_BAR_ORI31)) |
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seq_buf_printf(&s, ", ori31 speculation barrier enabled"); |
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seq_buf_printf(&s, "\n"); |
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} else |
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seq_buf_printf(&s, "Not affected\n"); |
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return s.len; |
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} |
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ssize_t cpu_show_spectre_v2(struct device *dev, struct device_attribute *attr, char *buf) |
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{ |
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struct seq_buf s; |
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bool bcs, ccd; |
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seq_buf_init(&s, buf, PAGE_SIZE - 1); |
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bcs = security_ftr_enabled(SEC_FTR_BCCTRL_SERIALISED); |
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ccd = security_ftr_enabled(SEC_FTR_COUNT_CACHE_DISABLED); |
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if (bcs || ccd) { |
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seq_buf_printf(&s, "Mitigation: "); |
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if (bcs) |
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seq_buf_printf(&s, "Indirect branch serialisation (kernel only)"); |
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if (bcs && ccd) |
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seq_buf_printf(&s, ", "); |
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if (ccd) |
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seq_buf_printf(&s, "Indirect branch cache disabled"); |
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} else if (count_cache_flush_type != BRANCH_CACHE_FLUSH_NONE) { |
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seq_buf_printf(&s, "Mitigation: Software count cache flush"); |
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if (count_cache_flush_type == BRANCH_CACHE_FLUSH_HW) |
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seq_buf_printf(&s, " (hardware accelerated)"); |
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} else if (btb_flush_enabled) { |
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seq_buf_printf(&s, "Mitigation: Branch predictor state flush"); |
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} else { |
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seq_buf_printf(&s, "Vulnerable"); |
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} |
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if (bcs || ccd || count_cache_flush_type != BRANCH_CACHE_FLUSH_NONE) { |
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if (link_stack_flush_type != BRANCH_CACHE_FLUSH_NONE) |
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seq_buf_printf(&s, ", Software link stack flush"); |
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if (link_stack_flush_type == BRANCH_CACHE_FLUSH_HW) |
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seq_buf_printf(&s, " (hardware accelerated)"); |
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} |
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seq_buf_printf(&s, "\n"); |
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return s.len; |
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} |
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#ifdef CONFIG_PPC_BOOK3S_64 |
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/* |
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* Store-forwarding barrier support. |
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*/ |
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static enum stf_barrier_type stf_enabled_flush_types; |
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static bool no_stf_barrier; |
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bool stf_barrier; |
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static int __init handle_no_stf_barrier(char *p) |
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{ |
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pr_info("stf-barrier: disabled on command line."); |
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no_stf_barrier = true; |
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return 0; |
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} |
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early_param("no_stf_barrier", handle_no_stf_barrier); |
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/* This is the generic flag used by other architectures */ |
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static int __init handle_ssbd(char *p) |
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{ |
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if (!p || strncmp(p, "auto", 5) == 0 || strncmp(p, "on", 2) == 0 ) { |
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/* Until firmware tells us, we have the barrier with auto */ |
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return 0; |
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} else if (strncmp(p, "off", 3) == 0) { |
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handle_no_stf_barrier(NULL); |
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return 0; |
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} else |
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return 1; |
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return 0; |
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} |
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early_param("spec_store_bypass_disable", handle_ssbd); |
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/* This is the generic flag used by other architectures */ |
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static int __init handle_no_ssbd(char *p) |
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{ |
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handle_no_stf_barrier(NULL); |
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return 0; |
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} |
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early_param("nospec_store_bypass_disable", handle_no_ssbd); |
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static void stf_barrier_enable(bool enable) |
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{ |
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if (enable) |
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do_stf_barrier_fixups(stf_enabled_flush_types); |
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else |
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do_stf_barrier_fixups(STF_BARRIER_NONE); |
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stf_barrier = enable; |
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} |
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void setup_stf_barrier(void) |
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{ |
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enum stf_barrier_type type; |
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bool enable, hv; |
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hv = cpu_has_feature(CPU_FTR_HVMODE); |
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/* Default to fallback in case fw-features are not available */ |
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if (cpu_has_feature(CPU_FTR_ARCH_300)) |
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type = STF_BARRIER_EIEIO; |
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else if (cpu_has_feature(CPU_FTR_ARCH_207S)) |
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type = STF_BARRIER_SYNC_ORI; |
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else if (cpu_has_feature(CPU_FTR_ARCH_206)) |
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type = STF_BARRIER_FALLBACK; |
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else |
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type = STF_BARRIER_NONE; |
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enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) && |
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(security_ftr_enabled(SEC_FTR_L1D_FLUSH_PR) || |
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(security_ftr_enabled(SEC_FTR_L1D_FLUSH_HV) && hv)); |
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if (type == STF_BARRIER_FALLBACK) { |
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pr_info("stf-barrier: fallback barrier available\n"); |
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} else if (type == STF_BARRIER_SYNC_ORI) { |
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pr_info("stf-barrier: hwsync barrier available\n"); |
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} else if (type == STF_BARRIER_EIEIO) { |
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pr_info("stf-barrier: eieio barrier available\n"); |
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} |
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stf_enabled_flush_types = type; |
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if (!no_stf_barrier && !cpu_mitigations_off()) |
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stf_barrier_enable(enable); |
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} |
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ssize_t cpu_show_spec_store_bypass(struct device *dev, struct device_attribute *attr, char *buf) |
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{ |
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if (stf_barrier && stf_enabled_flush_types != STF_BARRIER_NONE) { |
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const char *type; |
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switch (stf_enabled_flush_types) { |
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case STF_BARRIER_EIEIO: |
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type = "eieio"; |
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break; |
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case STF_BARRIER_SYNC_ORI: |
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type = "hwsync"; |
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break; |
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case STF_BARRIER_FALLBACK: |
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type = "fallback"; |
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break; |
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default: |
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type = "unknown"; |
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} |
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return sprintf(buf, "Mitigation: Kernel entry/exit barrier (%s)\n", type); |
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} |
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if (!security_ftr_enabled(SEC_FTR_L1D_FLUSH_HV) && |
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!security_ftr_enabled(SEC_FTR_L1D_FLUSH_PR)) |
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return sprintf(buf, "Not affected\n"); |
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return sprintf(buf, "Vulnerable\n"); |
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} |
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static int ssb_prctl_get(struct task_struct *task) |
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{ |
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if (stf_enabled_flush_types == STF_BARRIER_NONE) |
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/* |
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* We don't have an explicit signal from firmware that we're |
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* vulnerable or not, we only have certain CPU revisions that |
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* are known to be vulnerable. |
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* |
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* We assume that if we're on another CPU, where the barrier is |
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* NONE, then we are not vulnerable. |
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*/ |
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return PR_SPEC_NOT_AFFECTED; |
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else |
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/* |
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* If we do have a barrier type then we are vulnerable. The |
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* barrier is not a global or per-process mitigation, so the |
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* only value we can report here is PR_SPEC_ENABLE, which |
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* appears as "vulnerable" in /proc. |
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*/ |
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return PR_SPEC_ENABLE; |
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return -EINVAL; |
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} |
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int arch_prctl_spec_ctrl_get(struct task_struct *task, unsigned long which) |
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{ |
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switch (which) { |
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case PR_SPEC_STORE_BYPASS: |
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return ssb_prctl_get(task); |
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default: |
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return -ENODEV; |
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} |
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} |
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#ifdef CONFIG_DEBUG_FS |
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static int stf_barrier_set(void *data, u64 val) |
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{ |
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bool enable; |
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if (val == 1) |
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enable = true; |
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else if (val == 0) |
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enable = false; |
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else |
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return -EINVAL; |
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/* Only do anything if we're changing state */ |
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if (enable != stf_barrier) |
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stf_barrier_enable(enable); |
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return 0; |
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} |
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static int stf_barrier_get(void *data, u64 *val) |
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{ |
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*val = stf_barrier ? 1 : 0; |
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return 0; |
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} |
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DEFINE_DEBUGFS_ATTRIBUTE(fops_stf_barrier, stf_barrier_get, stf_barrier_set, |
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"%llu\n"); |
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static __init int stf_barrier_debugfs_init(void) |
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{ |
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debugfs_create_file_unsafe("stf_barrier", 0600, powerpc_debugfs_root, |
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NULL, &fops_stf_barrier); |
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return 0; |
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} |
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device_initcall(stf_barrier_debugfs_init); |
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#endif /* CONFIG_DEBUG_FS */ |
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static void update_branch_cache_flush(void) |
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{ |
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u32 *site; |
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#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE |
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site = &patch__call_kvm_flush_link_stack; |
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// This controls the branch from guest_exit_cont to kvm_flush_link_stack |
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if (link_stack_flush_type == BRANCH_CACHE_FLUSH_NONE) { |
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patch_instruction_site(site, ppc_inst(PPC_INST_NOP)); |
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} else { |
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// Could use HW flush, but that could also flush count cache |
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patch_branch_site(site, (u64)&kvm_flush_link_stack, BRANCH_SET_LINK); |
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} |
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#endif |
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// Patch out the bcctr first, then nop the rest |
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site = &patch__call_flush_branch_caches3; |
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patch_instruction_site(site, ppc_inst(PPC_INST_NOP)); |
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site = &patch__call_flush_branch_caches2; |
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patch_instruction_site(site, ppc_inst(PPC_INST_NOP)); |
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site = &patch__call_flush_branch_caches1; |
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patch_instruction_site(site, ppc_inst(PPC_INST_NOP)); |
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// This controls the branch from _switch to flush_branch_caches |
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if (count_cache_flush_type == BRANCH_CACHE_FLUSH_NONE && |
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link_stack_flush_type == BRANCH_CACHE_FLUSH_NONE) { |
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// Nothing to be done |
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|
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} else if (count_cache_flush_type == BRANCH_CACHE_FLUSH_HW && |
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link_stack_flush_type == BRANCH_CACHE_FLUSH_HW) { |
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// Patch in the bcctr last |
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site = &patch__call_flush_branch_caches1; |
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patch_instruction_site(site, ppc_inst(0x39207fff)); // li r9,0x7fff |
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site = &patch__call_flush_branch_caches2; |
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patch_instruction_site(site, ppc_inst(0x7d2903a6)); // mtctr r9 |
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site = &patch__call_flush_branch_caches3; |
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patch_instruction_site(site, ppc_inst(PPC_INST_BCCTR_FLUSH)); |
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|
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} else { |
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patch_branch_site(site, (u64)&flush_branch_caches, BRANCH_SET_LINK); |
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|
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// If we just need to flush the link stack, early return |
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if (count_cache_flush_type == BRANCH_CACHE_FLUSH_NONE) { |
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patch_instruction_site(&patch__flush_link_stack_return, |
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ppc_inst(PPC_INST_BLR)); |
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|
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// If we have flush instruction, early return |
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} else if (count_cache_flush_type == BRANCH_CACHE_FLUSH_HW) { |
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patch_instruction_site(&patch__flush_count_cache_return, |
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ppc_inst(PPC_INST_BLR)); |
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} |
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} |
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} |
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|
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static void toggle_branch_cache_flush(bool enable) |
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{ |
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if (!enable || !security_ftr_enabled(SEC_FTR_FLUSH_COUNT_CACHE)) { |
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if (count_cache_flush_type != BRANCH_CACHE_FLUSH_NONE) |
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count_cache_flush_type = BRANCH_CACHE_FLUSH_NONE; |
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|
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pr_info("count-cache-flush: flush disabled.\n"); |
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} else { |
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if (security_ftr_enabled(SEC_FTR_BCCTR_FLUSH_ASSIST)) { |
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count_cache_flush_type = BRANCH_CACHE_FLUSH_HW; |
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pr_info("count-cache-flush: hardware flush enabled.\n"); |
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} else { |
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count_cache_flush_type = BRANCH_CACHE_FLUSH_SW; |
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pr_info("count-cache-flush: software flush enabled.\n"); |
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} |
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} |
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|
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if (!enable || !security_ftr_enabled(SEC_FTR_FLUSH_LINK_STACK)) { |
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if (link_stack_flush_type != BRANCH_CACHE_FLUSH_NONE) |
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link_stack_flush_type = BRANCH_CACHE_FLUSH_NONE; |
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|
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pr_info("link-stack-flush: flush disabled.\n"); |
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} else { |
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if (security_ftr_enabled(SEC_FTR_BCCTR_LINK_FLUSH_ASSIST)) { |
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link_stack_flush_type = BRANCH_CACHE_FLUSH_HW; |
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pr_info("link-stack-flush: hardware flush enabled.\n"); |
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} else { |
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link_stack_flush_type = BRANCH_CACHE_FLUSH_SW; |
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pr_info("link-stack-flush: software flush enabled.\n"); |
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} |
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} |
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|
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update_branch_cache_flush(); |
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} |
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|
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void setup_count_cache_flush(void) |
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{ |
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bool enable = true; |
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|
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if (no_spectrev2 || cpu_mitigations_off()) { |
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if (security_ftr_enabled(SEC_FTR_BCCTRL_SERIALISED) || |
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security_ftr_enabled(SEC_FTR_COUNT_CACHE_DISABLED)) |
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pr_warn("Spectre v2 mitigations not fully under software control, can't disable\n"); |
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|
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enable = false; |
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} |
|
|
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/* |
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* There's no firmware feature flag/hypervisor bit to tell us we need to |
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* flush the link stack on context switch. So we set it here if we see |
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* either of the Spectre v2 mitigations that aim to protect userspace. |
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*/ |
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if (security_ftr_enabled(SEC_FTR_COUNT_CACHE_DISABLED) || |
|
security_ftr_enabled(SEC_FTR_FLUSH_COUNT_CACHE)) |
|
security_ftr_set(SEC_FTR_FLUSH_LINK_STACK); |
|
|
|
toggle_branch_cache_flush(enable); |
|
} |
|
|
|
#ifdef CONFIG_DEBUG_FS |
|
static int count_cache_flush_set(void *data, u64 val) |
|
{ |
|
bool enable; |
|
|
|
if (val == 1) |
|
enable = true; |
|
else if (val == 0) |
|
enable = false; |
|
else |
|
return -EINVAL; |
|
|
|
toggle_branch_cache_flush(enable); |
|
|
|
return 0; |
|
} |
|
|
|
static int count_cache_flush_get(void *data, u64 *val) |
|
{ |
|
if (count_cache_flush_type == BRANCH_CACHE_FLUSH_NONE) |
|
*val = 0; |
|
else |
|
*val = 1; |
|
|
|
return 0; |
|
} |
|
|
|
DEFINE_DEBUGFS_ATTRIBUTE(fops_count_cache_flush, count_cache_flush_get, |
|
count_cache_flush_set, "%llu\n"); |
|
|
|
static __init int count_cache_flush_debugfs_init(void) |
|
{ |
|
debugfs_create_file_unsafe("count_cache_flush", 0600, |
|
powerpc_debugfs_root, NULL, |
|
&fops_count_cache_flush); |
|
return 0; |
|
} |
|
device_initcall(count_cache_flush_debugfs_init); |
|
#endif /* CONFIG_DEBUG_FS */ |
|
#endif /* CONFIG_PPC_BOOK3S_64 */
|
|
|