diff options
| -rw-r--r-- | Documentation/admin-guide/hw-vuln/srso.rst | 24 | ||||
| -rw-r--r-- | arch/x86/entry/vdso/Makefile | 3 | ||||
| -rw-r--r-- | arch/x86/include/asm/nospec-branch.h | 67 | ||||
| -rw-r--r-- | arch/x86/kernel/callthunks.c | 5 | ||||
| -rw-r--r-- | arch/x86/kernel/cpu/bugs.c | 95 | ||||
| -rw-r--r-- | arch/x86/kernel/vmlinux.lds.S | 7 | ||||
| -rw-r--r-- | arch/x86/lib/retpoline.S | 186 | ||||
| -rw-r--r-- | arch/x86/mm/pti.c | 58 | ||||
| -rw-r--r-- | include/linux/objtool.h | 3 | ||||
| -rw-r--r-- | init/Makefile | 1 | ||||
| -rw-r--r-- | scripts/Makefile.vmlinux | 1 | ||||
| -rw-r--r-- | scripts/Makefile.vmlinux_o | 3 | ||||
| -rw-r--r-- | tools/objtool/check.c | 16 |
13 files changed, 258 insertions, 211 deletions
diff --git a/Documentation/admin-guide/hw-vuln/srso.rst b/Documentation/admin-guide/hw-vuln/srso.rst index b6cfb51cb0b469..e715bfc09879a7 100644 --- a/Documentation/admin-guide/hw-vuln/srso.rst +++ b/Documentation/admin-guide/hw-vuln/srso.rst @@ -46,12 +46,22 @@ The possible values in this file are: The processor is not vulnerable - * 'Vulnerable: no microcode': +* 'Vulnerable': + + The processor is vulnerable and no mitigations have been applied. + + * 'Vulnerable: No microcode': The processor is vulnerable, no microcode extending IBPB functionality to address the vulnerability has been applied. - * 'Mitigation: microcode': + * 'Vulnerable: Safe RET, no microcode': + + The "Safe RET" mitigation (see below) has been applied to protect the + kernel, but the IBPB-extending microcode has not been applied. User + space tasks may still be vulnerable. + + * 'Vulnerable: Microcode, no safe RET': Extended IBPB functionality microcode patch has been applied. It does not address User->Kernel and Guest->Host transitions protection but it @@ -72,11 +82,11 @@ The possible values in this file are: (spec_rstack_overflow=microcode) - * 'Mitigation: safe RET': + * 'Mitigation: Safe RET': - Software-only mitigation. It complements the extended IBPB microcode - patch functionality by addressing User->Kernel and Guest->Host - transitions protection. + Combined microcode/software mitigation. It complements the + extended IBPB microcode patch functionality by addressing + User->Kernel and Guest->Host transitions protection. Selected by default or by spec_rstack_overflow=safe-ret @@ -129,7 +139,7 @@ an indrect branch prediction barrier after having applied the required microcode patch for one's system. This mitigation comes also at a performance cost. -Mitigation: safe RET +Mitigation: Safe RET -------------------- The mitigation works by ensuring all RET instructions speculate to diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile index 6a1821bd7d5e9b..83c0afb7c74137 100644 --- a/arch/x86/entry/vdso/Makefile +++ b/arch/x86/entry/vdso/Makefile @@ -42,7 +42,8 @@ vdso_img-$(VDSO64-y) += 64 vdso_img-$(VDSOX32-y) += x32 vdso_img-$(VDSO32-y) += 32 -obj-$(VDSO32-y) += vdso32-setup.o +obj-$(VDSO32-y) += vdso32-setup.o +OBJECT_FILES_NON_STANDARD_vdso32-setup.o := n vobjs := $(foreach F,$(vobjs-y),$(obj)/$F) vobjs32 := $(foreach F,$(vobjs32-y),$(obj)/$F) diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h index c55cc243592e94..14cd3cd5f85a5b 100644 --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -271,7 +271,7 @@ .Lskip_rsb_\@: .endm -#ifdef CONFIG_CPU_UNRET_ENTRY +#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_SRSO) #define CALL_UNTRAIN_RET "call entry_untrain_ret" #else #define CALL_UNTRAIN_RET "" @@ -288,38 +288,24 @@ * As such, this must be placed after every *SWITCH_TO_KERNEL_CR3 at a point * where we have a stack but before any RET instruction. */ -.macro UNTRAIN_RET -#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \ - defined(CONFIG_CALL_DEPTH_TRACKING) || defined(CONFIG_CPU_SRSO) +.macro __UNTRAIN_RET ibpb_feature, call_depth_insns +#if defined(CONFIG_RETHUNK) || defined(CONFIG_CPU_IBPB_ENTRY) VALIDATE_UNRET_END ALTERNATIVE_3 "", \ CALL_UNTRAIN_RET, X86_FEATURE_UNRET, \ - "call entry_ibpb", X86_FEATURE_ENTRY_IBPB, \ - __stringify(RESET_CALL_DEPTH), X86_FEATURE_CALL_DEPTH + "call entry_ibpb", \ibpb_feature, \ + __stringify(\call_depth_insns), X86_FEATURE_CALL_DEPTH #endif .endm -.macro UNTRAIN_RET_VM -#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \ - defined(CONFIG_CALL_DEPTH_TRACKING) || defined(CONFIG_CPU_SRSO) - VALIDATE_UNRET_END - ALTERNATIVE_3 "", \ - CALL_UNTRAIN_RET, X86_FEATURE_UNRET, \ - "call entry_ibpb", X86_FEATURE_IBPB_ON_VMEXIT, \ - __stringify(RESET_CALL_DEPTH), X86_FEATURE_CALL_DEPTH -#endif -.endm +#define UNTRAIN_RET \ + __UNTRAIN_RET X86_FEATURE_ENTRY_IBPB, __stringify(RESET_CALL_DEPTH) -.macro UNTRAIN_RET_FROM_CALL -#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \ - defined(CONFIG_CALL_DEPTH_TRACKING) - VALIDATE_UNRET_END - ALTERNATIVE_3 "", \ - CALL_UNTRAIN_RET, X86_FEATURE_UNRET, \ - "call entry_ibpb", X86_FEATURE_ENTRY_IBPB, \ - __stringify(RESET_CALL_DEPTH_FROM_CALL), X86_FEATURE_CALL_DEPTH -#endif -.endm +#define UNTRAIN_RET_VM \ + __UNTRAIN_RET X86_FEATURE_IBPB_ON_VMEXIT, __stringify(RESET_CALL_DEPTH) + +#define UNTRAIN_RET_FROM_CALL \ + __UNTRAIN_RET X86_FEATURE_ENTRY_IBPB, __stringify(RESET_CALL_DEPTH_FROM_CALL) .macro CALL_DEPTH_ACCOUNT @@ -348,13 +334,23 @@ extern void __x86_return_thunk(void); static inline void __x86_return_thunk(void) {} #endif +#ifdef CONFIG_CPU_UNRET_ENTRY extern void retbleed_return_thunk(void); +#else +static inline void retbleed_return_thunk(void) {} +#endif + +#ifdef CONFIG_CPU_SRSO extern void srso_return_thunk(void); extern void srso_alias_return_thunk(void); +#else +static inline void srso_return_thunk(void) {} +static inline void srso_alias_return_thunk(void) {} +#endif -extern void retbleed_untrain_ret(void); -extern void srso_untrain_ret(void); -extern void srso_alias_untrain_ret(void); +extern void retbleed_return_thunk(void); +extern void srso_return_thunk(void); +extern void srso_alias_return_thunk(void); extern void entry_untrain_ret(void); extern void entry_ibpb(void); @@ -362,12 +358,7 @@ extern void entry_ibpb(void); extern void (*x86_return_thunk)(void); #ifdef CONFIG_CALL_DEPTH_TRACKING -extern void __x86_return_skl(void); - -static inline void x86_set_skl_return_thunk(void) -{ - x86_return_thunk = &__x86_return_skl; -} +extern void call_depth_return_thunk(void); #define CALL_DEPTH_ACCOUNT \ ALTERNATIVE("", \ @@ -380,12 +371,12 @@ DECLARE_PER_CPU(u64, __x86_ret_count); DECLARE_PER_CPU(u64, __x86_stuffs_count); DECLARE_PER_CPU(u64, __x86_ctxsw_count); #endif -#else -static inline void x86_set_skl_return_thunk(void) {} +#else /* !CONFIG_CALL_DEPTH_TRACKING */ +static inline void call_depth_return_thunk(void) {} #define CALL_DEPTH_ACCOUNT "" -#endif +#endif /* CONFIG_CALL_DEPTH_TRACKING */ #ifdef CONFIG_RETPOLINE diff --git a/arch/x86/kernel/callthunks.c b/arch/x86/kernel/callthunks.c index faa9f229984887..e9ad518a5003cd 100644 --- a/arch/x86/kernel/callthunks.c +++ b/arch/x86/kernel/callthunks.c @@ -48,11 +48,6 @@ EXPORT_SYMBOL_GPL(__x86_call_count); extern s32 __call_sites[], __call_sites_end[]; -struct thunk_desc { - void *template; - unsigned int template_size; -}; - struct core_text { unsigned long base; unsigned long end; diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 10499bcd4e3962..bb0ab8466b9198 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -63,7 +63,7 @@ EXPORT_SYMBOL_GPL(x86_pred_cmd); static DEFINE_MUTEX(spec_ctrl_mutex); -void (*x86_return_thunk)(void) __ro_after_init = &__x86_return_thunk; +void (*x86_return_thunk)(void) __ro_after_init = __x86_return_thunk; /* Update SPEC_CTRL MSR and its cached copy unconditionally */ static void update_spec_ctrl(u64 val) @@ -717,7 +717,7 @@ void update_gds_msr(void) case GDS_MITIGATION_UCODE_NEEDED: case GDS_MITIGATION_HYPERVISOR: return; - }; + } wrmsrl(MSR_IA32_MCU_OPT_CTRL, mcu_ctrl); @@ -1019,7 +1019,6 @@ static void __init retbleed_select_mitigation(void) do_cmd_auto: case RETBLEED_CMD_AUTO: - default: if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD || boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) { if (IS_ENABLED(CONFIG_CPU_UNRET_ENTRY)) @@ -1042,8 +1041,7 @@ do_cmd_auto: setup_force_cpu_cap(X86_FEATURE_RETHUNK); setup_force_cpu_cap(X86_FEATURE_UNRET); - if (IS_ENABLED(CONFIG_RETHUNK)) - x86_return_thunk = retbleed_return_thunk; + x86_return_thunk = retbleed_return_thunk; if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD && boot_cpu_data.x86_vendor != X86_VENDOR_HYGON) @@ -1061,7 +1059,8 @@ do_cmd_auto: case RETBLEED_MITIGATION_STUFF: setup_force_cpu_cap(X86_FEATURE_RETHUNK); setup_force_cpu_cap(X86_FEATURE_CALL_DEPTH); - x86_set_skl_return_thunk(); + + x86_return_thunk = call_depth_return_thunk; break; default: @@ -1290,6 +1289,8 @@ spectre_v2_user_select_mitigation(void) spectre_v2_user_ibpb = mode; switch (cmd) { + case SPECTRE_V2_USER_CMD_NONE: + break; case SPECTRE_V2_USER_CMD_FORCE: case SPECTRE_V2_USER_CMD_PRCTL_IBPB: case SPECTRE_V2_USER_CMD_SECCOMP_IBPB: @@ -1301,8 +1302,6 @@ spectre_v2_user_select_mitigation(void) case SPECTRE_V2_USER_CMD_SECCOMP: static_branch_enable(&switch_mm_cond_ibpb); break; - default: - break; } pr_info("mitigation: Enabling %s Indirect Branch Prediction Barrier\n", @@ -2160,6 +2159,10 @@ static int l1d_flush_prctl_get(struct task_struct *task) static int ssb_prctl_get(struct task_struct *task) { switch (ssb_mode) { + case SPEC_STORE_BYPASS_NONE: + if (boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS)) + return PR_SPEC_ENABLE; + return PR_SPEC_NOT_AFFECTED; case SPEC_STORE_BYPASS_DISABLE: return PR_SPEC_DISABLE; case SPEC_STORE_BYPASS_SECCOMP: @@ -2171,11 +2174,8 @@ static int ssb_prctl_get(struct task_struct *task) if (task_spec_ssb_disable(task)) return PR_SPEC_PRCTL | PR_SPEC_DISABLE; return PR_SPEC_PRCTL | PR_SPEC_ENABLE; - default: - if (boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS)) - return PR_SPEC_ENABLE; - return PR_SPEC_NOT_AFFECTED; } + BUG(); } static int ib_prctl_get(struct task_struct *task) @@ -2353,6 +2353,8 @@ early_param("l1tf", l1tf_cmdline); enum srso_mitigation { SRSO_MITIGATION_NONE, + SRSO_MITIGATION_UCODE_NEEDED, + SRSO_MITIGATION_SAFE_RET_UCODE_NEEDED, SRSO_MITIGATION_MICROCODE, SRSO_MITIGATION_SAFE_RET, SRSO_MITIGATION_IBPB, @@ -2368,11 +2370,13 @@ enum srso_mitigation_cmd { }; static const char * const srso_strings[] = { - [SRSO_MITIGATION_NONE] = "Vulnerable", - [SRSO_MITIGATION_MICROCODE] = "Mitigation: microcode", - [SRSO_MITIGATION_SAFE_RET] = "Mitigation: safe RET", - [SRSO_MITIGATION_IBPB] = "Mitigation: IBPB", - [SRSO_MITIGATION_IBPB_ON_VMEXIT] = "Mitigation: IBPB on VMEXIT only" + [SRSO_MITIGATION_NONE] = "Vulnerable", + [SRSO_MITIGATION_UCODE_NEEDED] = "Vulnerable: No microcode", + [SRSO_MITIGATION_SAFE_RET_UCODE_NEEDED] = "Vulnerable: Safe RET, no microcode", + [SRSO_MITIGATION_MICROCODE] = "Vulnerable: Microcode, no safe RET", + [SRSO_MITIGATION_SAFE_RET] = "Mitigation: Safe RET", + [SRSO_MITIGATION_IBPB] = "Mitigation: IBPB", + [SRSO_MITIGATION_IBPB_ON_VMEXIT] = "Mitigation: IBPB on VMEXIT only" }; static enum srso_mitigation srso_mitigation __ro_after_init = SRSO_MITIGATION_NONE; @@ -2406,34 +2410,44 @@ static void __init srso_select_mitigation(void) { bool has_microcode = boot_cpu_has(X86_FEATURE_IBPB_BRTYPE); - if (!boot_cpu_has_bug(X86_BUG_SRSO) || cpu_mitigations_off()) - goto pred_cmd; + if (cpu_mitigations_off()) + return; - if (!has_microcode) { - pr_warn("IBPB-extending microcode not applied!\n"); - pr_warn(SRSO_NOTICE); - } else { + if (!boot_cpu_has_bug(X86_BUG_SRSO)) { + if (boot_cpu_has(X86_FEATURE_SBPB)) + x86_pred_cmd = PRED_CMD_SBPB; + return; + } + + if (has_microcode) { /* * Zen1/2 with SMT off aren't vulnerable after the right * IBPB microcode has been applied. + * + * Zen1/2 don't have SBPB, no need to try to enable it here. */ if (boot_cpu_data.x86 < 0x19 && !cpu_smt_possible()) { setup_force_cpu_cap(X86_FEATURE_SRSO_NO); return; } - } - if (retbleed_mitigation == RETBLEED_MITIGATION_IBPB) { - if (has_microcode) { - pr_err("Retbleed IBPB mitigation enabled, using same for SRSO\n"); + if (retbleed_mitigation == RETBLEED_MITIGATION_IBPB) { srso_mitigation = SRSO_MITIGATION_IBPB; - goto pred_cmd; + goto out; } + } else { + pr_warn("IBPB-extending microcode not applied!\n"); + pr_warn(SRSO_NOTICE); + + /* may be overwritten by SRSO_CMD_SAFE_RET below */ + srso_mitigation = SRSO_MITIGATION_UCODE_NEEDED; } switch (srso_cmd) { case SRSO_CMD_OFF: - goto pred_cmd; + if (boot_cpu_has(X86_FEATURE_SBPB)) + x86_pred_cmd = PRED_CMD_SBPB; + return; case SRSO_CMD_MICROCODE: if (has_microcode) { @@ -2458,10 +2472,12 @@ static void __init srso_select_mitigation(void) setup_force_cpu_cap(X86_FEATURE_SRSO); x86_return_thunk = srso_return_thunk; } - srso_mitigation = SRSO_MITIGATION_SAFE_RET; + if (has_microcode) + srso_mitigation = SRSO_MITIGATION_SAFE_RET; + else + srso_mitigation = SRSO_MITIGATION_SAFE_RET_UCODE_NEEDED; } else { pr_err("WARNING: kernel not compiled with CPU_SRSO.\n"); - goto pred_cmd; } break; @@ -2473,7 +2489,6 @@ static void __init srso_select_mitigation(void) } } else { pr_err("WARNING: kernel not compiled with CPU_IBPB_ENTRY.\n"); - goto pred_cmd; } break; @@ -2485,20 +2500,12 @@ static void __init srso_select_mitigation(void) } } else { pr_err("WARNING: kernel not compiled with CPU_SRSO.\n"); - goto pred_cmd; } break; - - default: - break; } - pr_info("%s%s\n", srso_strings[srso_mitigation], (has_microcode ? "" : ", no microcode")); - -pred_cmd: - if ((boot_cpu_has(X86_FEATURE_SRSO_NO) || srso_cmd == SRSO_CMD_OFF) && - boot_cpu_has(X86_FEATURE_SBPB)) - x86_pred_cmd = PRED_CMD_SBPB; +out: + pr_info("%s\n", srso_strings[srso_mitigation]); } #undef pr_fmt @@ -2704,9 +2711,7 @@ static ssize_t srso_show_state(char *buf) if (boot_cpu_has(X86_FEATURE_SRSO_NO)) return sysfs_emit(buf, "Mitigation: SMT disabled\n"); - return sysfs_emit(buf, "%s%s\n", - srso_strings[srso_mitigation], - boot_cpu_has(X86_FEATURE_IBPB_BRTYPE) ? "" : ", no microcode"); + return sysfs_emit(buf, "%s\n", srso_strings[srso_mitigation]); } static ssize_t gds_show_state(char *buf) diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S index f15fb71f280e24..54a5596adaa61e 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -139,10 +139,7 @@ SECTIONS STATIC_CALL_TEXT ALIGN_ENTRY_TEXT_BEGIN -#ifdef CONFIG_CPU_SRSO *(.text..__x86.rethunk_untrain) -#endif - ENTRY_TEXT #ifdef CONFIG_CPU_SRSO @@ -520,12 +517,12 @@ INIT_PER_CPU(irq_stack_backing_store); "fixed_percpu_data is not at start of per-cpu area"); #endif -#ifdef CONFIG_RETHUNK +#ifdef CONFIG_CPU_UNRET_ENTRY . = ASSERT((retbleed_return_thunk & 0x3f) == 0, "retbleed_return_thunk not cacheline-aligned"); -. = ASSERT((srso_safe_ret & 0x3f) == 0, "srso_safe_ret not cacheline-aligned"); #endif #ifdef CONFIG_CPU_SRSO +. = ASSERT((srso_safe_ret & 0x3f) == 0, "srso_safe_ret not cacheline-aligned"); /* * GNU ld cannot do XOR until 2.41. * https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=f6f78318fca803c4907fb8d7f6ded8295f1947b1 diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S index cd86aeb5fdd3ea..a48077c5ca619c 100644 --- a/arch/x86/lib/retpoline.S +++ b/arch/x86/lib/retpoline.S @@ -126,11 +126,19 @@ SYM_CODE_END(__x86_indirect_jump_thunk_array) #include <asm/GEN-for-each-reg.h> #undef GEN #endif + +#ifdef CONFIG_RETHUNK + /* - * This function name is magical and is used by -mfunction-return=thunk-extern - * for the compiler to generate JMPs to it. + * Be careful here: that label cannot really be removed because in + * some configurations and toolchains, the JMP __x86_return_thunk the + * compiler issues is either a short one or the compiler doesn't use + * relocations for same-section JMPs and that breaks the returns + * detection logic in apply_returns() and in objtool. */ -#ifdef CONFIG_RETHUNK + .section .text..__x86.return_thunk + +#ifdef CONFIG_CPU_SRSO /* * srso_alias_untrain_ret() and srso_alias_safe_ret() are placed at @@ -147,29 +155,18 @@ SYM_CODE_END(__x86_indirect_jump_thunk_array) * * As a result, srso_alias_safe_ret() becomes a safe return. */ -#ifdef CONFIG_CPU_SRSO - .section .text..__x86.rethunk_untrain - -SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE) + .pushsection .text..__x86.rethunk_untrain +SYM_CODE_START_NOALIGN(srso_alias_untrain_ret) UNWIND_HINT_FUNC ANNOTATE_NOENDBR ASM_NOP2 lfence jmp srso_alias_return_thunk SYM_FUNC_END(srso_alias_untrain_ret) -__EXPORT_THUNK(srso_alias_untrain_ret) - - .section .text..__x86.rethunk_safe -#else -/* dummy definition for alternatives */ -SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE) - ANNOTATE_UNRET_SAFE - ret - int3 -SYM_FUNC_END(srso_alias_untrain_ret) -#endif + .popsection -SYM_START(srso_alias_safe_ret, SYM_L_GLOBAL, SYM_A_NONE) + .pushsection .text..__x86.rethunk_safe +SYM_CODE_START_NOALIGN(srso_alias_safe_ret) lea 8(%_ASM_SP), %_ASM_SP UNWIND_HINT_FUNC ANNOTATE_UNRET_SAFE @@ -177,14 +174,63 @@ SYM_START(srso_alias_safe_ret, SYM_L_GLOBAL, SYM_A_NONE) int3 SYM_FUNC_END(srso_alias_safe_ret) - .section .text..__x86.return_thunk - -SYM_CODE_START(srso_alias_return_thunk) +SYM_CODE_START_NOALIGN(srso_alias_return_thunk) UNWIND_HINT_FUNC ANNOTATE_NOENDBR call srso_alias_safe_ret ud2 SYM_CODE_END(srso_alias_return_thunk) + .popsection + +/* + * SRSO untraining sequence for Zen1/2, similar to retbleed_untrain_ret() + * above. On kernel entry, srso_untrain_ret() is executed which is a + * + * movabs $0xccccc30824648d48,%rax + * + * and when the return thunk executes the inner label srso_safe_ret() + * later, it is a stack manipulation and a RET which is mispredicted and + * thus a "safe" one to use. + */ + .align 64 + .skip 64 - (srso_safe_ret - srso_untrain_ret), 0xcc +SYM_CODE_START_LOCAL_NOALIGN(srso_untrain_ret) + ANNOTATE_NOENDBR + .byte 0x48, 0xb8 + +/* + * This forces the function return instruction to speculate into a trap + * (UD2 in srso_return_thunk() below). This RET will then mispredict + * and execution will continue at the return site read from the top of + * the stack. + */ +SYM_INNER_LABEL(srso_safe_ret, SYM_L_GLOBAL) + lea 8(%_ASM_SP), %_ASM_SP + ret + int3 + int3 + /* end of movabs */ + lfence + call srso_safe_ret + ud2 +SYM_CODE_END(srso_safe_ret) +SYM_FUNC_END(srso_untrain_ret) + +SYM_CODE_START(srso_return_thunk) + UNWIND_HINT_FUNC + ANNOTATE_NOENDBR + call srso_safe_ret + ud2 +SYM_CODE_END(srso_return_thunk) + +#define JMP_SRSO_UNTRAIN_RET "jmp srso_untrain_ret" +#define JMP_SRSO_ALIAS_UNTRAIN_RET "jmp srso_alias_untrain_ret" +#else /* !CONFIG_CPU_SRSO */ +#define JMP_SRSO_UNTRAIN_RET "ud2" +#define JMP_SRSO_ALIAS_UNTRAIN_RET "ud2" +#endif /* CONFIG_CPU_SRSO */ + +#ifdef CONFIG_CPU_UNRET_ENTRY /* * Some generic notes on the untraining sequences: @@ -216,7 +262,7 @@ SYM_CODE_END(srso_alias_return_thunk) */ .align 64 .skip 64 - (retbleed_return_thunk - retbleed_untrain_ret), 0xcc -SYM_START(retbleed_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE) +SYM_CODE_START_LOCAL_NOALIGN(retbleed_untrain_ret) ANNOTATE_NOENDBR /* * As executed from retbleed_untrain_ret, this is: @@ -264,72 +310,27 @@ SYM_CODE_END(retbleed_return_thunk) jmp retbleed_return_thunk int3 SYM_FUNC_END(retbleed_untrain_ret) -__EXPORT_THUNK(retbleed_untrain_ret) -/* - * SRSO untraining sequence for Zen1/2, similar to retbleed_untrain_ret() - * above. On kernel entry, srso_untrain_ret() is executed which is a - * - * movabs $0xccccc30824648d48,%rax - * - * and when the return thunk executes the inner label srso_safe_ret() - * later, it is a stack manipulation and a RET which is mispredicted and - * thus a "safe" one to use. - */ - .align 64 - .skip 64 - (srso_safe_ret - srso_untrain_ret), 0xcc -SYM_START(srso_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE) - ANNOTATE_NOENDBR - .byte 0x48, 0xb8 +#define JMP_RETBLEED_UNTRAIN_RET "jmp retbleed_untrain_ret" +#else /* !CONFIG_CPU_UNRET_ENTRY */ +#define JMP_RETBLEED_UNTRAIN_RET "ud2" +#endif /* CONFIG_CPU_UNRET_ENTRY */ -/* - * This forces the function return instruction to speculate into a trap - * (UD2 in srso_return_thunk() below). This RET will then mispredict - * and execution will continue at the return site read from the top of - * the stack. - */ -SYM_INNER_LABEL(srso_safe_ret, SYM_L_GLOBAL) - lea 8(%_ASM_SP), %_ASM_SP - ret - int3 - int3 - /* end of movabs */ - lfence - call srso_safe_ret - ud2 -SYM_CODE_END(srso_safe_ret) -SYM_FUNC_END(srso_untrain_ret) -__EXPORT_THUNK(srso_untrain_ret) - -SYM_CODE_START(srso_return_thunk) - UNWIND_HINT_FUNC - ANNOTATE_NOENDBR - call srso_safe_ret - ud2 -SYM_CODE_END(srso_return_thunk) +#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_SRSO) SYM_FUNC_START(entry_untrain_ret) - ALTERNATIVE_2 "jmp retbleed_untrain_ret", \ - "jmp srso_untrain_ret", X86_FEATURE_SRSO, \ - "jmp srso_alias_untrain_ret", X86_FEATURE_SRSO_ALIAS + ALTERNATIVE_2 JMP_RETBLEED_UNTRAIN_RET, \ + JMP_SRSO_UNTRAIN_RET, X86_FEATURE_SRSO, \ + JMP_SRSO_ALIAS_UNTRAIN_RET, X86_FEATURE_SRSO_ALIAS SYM_FUNC_END(entry_untrain_ret) __EXPORT_THUNK(entry_untrain_ret) -SYM_CODE_START(__x86_return_thunk) - UNWIND_HINT_FUNC - ANNOTATE_NOENDBR - ANNOTATE_UNRET_SAFE - ret - int3 -SYM_CODE_END(__x86_return_thunk) -EXPORT_SYMBOL(__x86_return_thunk) - -#endif /* CONFIG_RETHUNK */ +#endif /* CONFIG_CPU_UNRET_ENTRY || CONFIG_CPU_SRSO */ #ifdef CONFIG_CALL_DEPTH_TRACKING .align 64 -SYM_FUNC_START(__x86_return_skl) +SYM_FUNC_START(call_depth_return_thunk) ANNOTATE_NOENDBR /* * Keep the hotpath in a 16byte I-fetch for the non-debug @@ -356,6 +357,33 @@ SYM_FUNC_START(__x86_return_skl) ANNOTATE_UNRET_SAFE ret int3 -SYM_FUNC_END(__x86_return_skl) +SYM_FUNC_END(call_depth_return_thunk) #endif /* CONFIG_CALL_DEPTH_TRACKING */ + +/* + * This function name is magical and is used by -mfunction-return=thunk-extern + * for the compiler to generate JMPs to it. + * + * This code is only used during kernel boot or module init. All + * 'JMP __x86_return_thunk' sites are changed to something else by + * apply_returns(). + * + * This should be converted eventually to call a warning function which + * should scream loudly when the default return thunk is called after + * alternatives have been applied. + * + * That warning function cannot BUG() because the bug splat cannot be + * displayed in all possible configurations, leading to users not really + * knowing why the machine froze. + */ +SYM_CODE_START(__x86_return_thunk) + UNWIND_HINT_FUNC + ANNOTATE_NOENDBR + ANNOTATE_UNRET_SAFE + ret + int3 +SYM_CODE_END(__x86_return_thunk) +EXPORT_SYMBOL(__x86_return_thunk) + +#endif /* CONFIG_RETHUNK */ diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c index 78414c6d1b5ed1..5dd733944629fa 100644 --- a/arch/x86/mm/pti.c +++ b/arch/x86/mm/pti.c @@ -69,6 +69,7 @@ static void __init pti_print_if_secure(const char *reason) pr_info("%s\n", reason); } +/* Assume mode is auto unless overridden via cmdline below. */ static enum pti_mode { PTI_AUTO = 0, PTI_FORCE_OFF, @@ -77,50 +78,49 @@ static enum pti_mode { void __init pti_check_boottime_disable(void) { - char arg[5]; - int ret; - - /* Assume mode is auto unless overridden. */ - pti_mode = PTI_AUTO; - if (hypervisor_is_type(X86_HYPER_XEN_PV)) { pti_mode = PTI_FORCE_OFF; pti_print_if_insecure("disabled on XEN PV."); return; } - ret = cmdline_find_option(boot_command_line, "pti", arg, sizeof(arg)); - if (ret > 0) { - if (ret == 3 && !strncmp(arg, "off", 3)) { - pti_mode = PTI_FORCE_OFF; - pti_print_if_insecure("disabled on command line."); - return; - } - if (ret == 2 && !strncmp(arg, "on", 2)) { - pti_mode = PTI_FORCE_ON; - pti_print_if_secure("force enabled on command line."); - goto enable; - } - if (ret == 4 && !strncmp(arg, "auto", 4)) { - pti_mode = PTI_AUTO; - goto autosel; - } - } - - if (cmdline_find_option_bool(boot_command_line, "nopti") || - cpu_mitigations_off()) { + if (cpu_mitigations_off()) pti_mode = PTI_FORCE_OFF; + if (pti_mode == PTI_FORCE_OFF) { pti_print_if_insecure("disabled on command line."); return; } -autosel: - if (!boot_cpu_has_bug(X86_BUG_CPU_MELTDOWN)) + if (pti_mode == PTI_FORCE_ON) + pti_print_if_secure("force enabled on command line."); + + if (pti_mode == PTI_AUTO && !boot_cpu_has_bug(X86_BUG_CPU_MELTDOWN)) return; -enable: + setup_force_cpu_cap(X86_FEATURE_PTI); } +static int __init pti_parse_cmdline(char *arg) +{ + if (!strcmp(arg, "off")) + pti_mode = PTI_FORCE_OFF; + else if (!strcmp(arg, "on")) + pti_mode = PTI_FORCE_ON; + else if (!strcmp(arg, "auto")) + pti_mode = PTI_AUTO; + else + return -EINVAL; + return 0; +} +early_param("pti", pti_parse_cmdline); + +static int __init pti_parse_cmdline_nopti(char *arg) +{ + pti_mode = PTI_FORCE_OFF; + return 0; +} +early_param("nopti", pti_parse_cmdline_nopti); + pgd_t __pti_set_user_pgtbl(pgd_t *pgdp, pgd_t pgd) { /* diff --git a/include/linux/objtool.h b/include/linux/objtool.h index 03f82c2c2ebf6f..b5440e7da55bfc 100644 --- a/include/linux/objtool.h +++ b/include/linux/objtool.h @@ -130,7 +130,8 @@ * it will be ignored. */ .macro VALIDATE_UNRET_BEGIN -#if defined(CONFIG_NOINSTR_VALIDATION) && defined(CONFIG_CPU_UNRET_ENTRY) +#if defined(CONFIG_NOINSTR_VALIDATION) && \ + (defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_SRSO)) .Lhere_\@: .pushsection .discard.validate_unret .long .Lhere_\@ - . diff --git a/init/Makefile b/init/Makefile index ec557ada3c12ef..cbac576c57d63f 100644 --- a/init/Makefile +++ b/init/Makefile @@ -60,4 +60,5 @@ include/generated/utsversion.h: FORCE $(obj)/version-timestamp.o: include/generated/utsversion.h CFLAGS_version-timestamp.o := -include include/generated/utsversion.h KASAN_SANITIZE_version-timestamp.o := n +KCSAN_SANITIZE_version-timestamp.o := n GCOV_PROFILE_version-timestamp.o := n diff --git a/scripts/Makefile.vmlinux b/scripts/Makefile.vmlinux index 3cd6ca15f390de..c9f3e03124d7f5 100644 --- a/scripts/Makefile.vmlinux +++ b/scripts/Makefile.vmlinux @@ -19,6 +19,7 @@ quiet_cmd_cc_o_c = CC $@ ifdef CONFIG_MODULES KASAN_SANITIZE_.vmlinux.export.o := n +KCSAN_SANITIZE_.vmlinux.export.o := n GCOV_PROFILE_.vmlinux.export.o := n targets += .vmlinux.export.o vmlinux: .vmlinux.export.o diff --git a/scripts/Makefile.vmlinux_o b/scripts/Makefile.vmlinux_o index 0edfdb40364b8c..25b3b587d37c00 100644 --- a/scripts/Makefile.vmlinux_o +++ b/scripts/Makefile.vmlinux_o @@ -37,7 +37,8 @@ objtool-enabled := $(or $(delay-objtool),$(CONFIG_NOINSTR_VALIDATION)) vmlinux-objtool-args-$(delay-objtool) += $(objtool-args-y) vmlinux-objtool-args-$(CONFIG_GCOV_KERNEL) += --no-unreachable -vmlinux-objtool-args-$(CONFIG_NOINSTR_VALIDATION) += --noinstr $(if $(CONFIG_CPU_UNRET_ENTRY), --unret) +vmlinux-objtool-args-$(CONFIG_NOINSTR_VALIDATION) += --noinstr \ + $(if $(or $(CONFIG_CPU_UNRET_ENTRY),$(CONFIG_CPU_SRSO)), --unret) objtool-args = $(vmlinux-objtool-args-y) --link diff --git a/tools/objtool/check.c b/tools/objtool/check.c index e308d1ba664ef9..e94756e09ca9f5 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -1611,6 +1611,22 @@ static int add_jump_destinations(struct objtool_file *file) } /* + * An intra-TU jump in retpoline.o might not have a relocation + * for its jump dest, in which case the above + * add_{retpoline,return}_call() didn't happen. + */ + if (jump_dest->sym && jump_dest->offset == jump_dest->sym->offset) { + if (jump_dest->sym->retpoline_thunk) { + add_retpoline_call(file, insn); + continue; + } + if (jump_dest->sym->return_thunk) { + add_return_call(file, insn, true); + continue; + } + } + + /* * Cross-function jump. */ if (insn_func(insn) && insn_func(jump_dest) && |