diff options
Diffstat (limited to 'arch/x86/kernel/sev-es.c')
| -rw-r--r-- | arch/x86/kernel/sev-es.c | 119 |
1 files changed, 79 insertions, 40 deletions
diff --git a/arch/x86/kernel/sev-es.c b/arch/x86/kernel/sev-es.c index 84c1821819af..73873b007838 100644 --- a/arch/x86/kernel/sev-es.c +++ b/arch/x86/kernel/sev-es.c @@ -121,35 +121,57 @@ static void __init setup_vc_stacks(int cpu) cea_set_pte((void *)vaddr, pa, PAGE_KERNEL); } -static __always_inline bool on_vc_stack(unsigned long sp) +static __always_inline bool on_vc_stack(struct pt_regs *regs) { + unsigned long sp = regs->sp; + + /* User-mode RSP is not trusted */ + if (user_mode(regs)) + return false; + + /* SYSCALL gap still has user-mode RSP */ + if (ip_within_syscall_gap(regs)) + return false; + return ((sp >= __this_cpu_ist_bottom_va(VC)) && (sp < __this_cpu_ist_top_va(VC))); } /* - * This function handles the case when an NMI is raised in the #VC exception - * handler entry code. In this case, the IST entry for #VC must be adjusted, so - * that any subsequent #VC exception will not overwrite the stack contents of the - * interrupted #VC handler. + * This function handles the case when an NMI is raised in the #VC + * exception handler entry code, before the #VC handler has switched off + * its IST stack. In this case, the IST entry for #VC must be adjusted, + * so that any nested #VC exception will not overwrite the stack + * contents of the interrupted #VC handler. * * The IST entry is adjusted unconditionally so that it can be also be - * unconditionally adjusted back in sev_es_ist_exit(). Otherwise a nested - * sev_es_ist_exit() call may adjust back the IST entry too early. + * unconditionally adjusted back in __sev_es_ist_exit(). Otherwise a + * nested sev_es_ist_exit() call may adjust back the IST entry too + * early. + * + * The __sev_es_ist_enter() and __sev_es_ist_exit() functions always run + * on the NMI IST stack, as they are only called from NMI handling code + * right now. */ void noinstr __sev_es_ist_enter(struct pt_regs *regs) { unsigned long old_ist, new_ist; /* Read old IST entry */ - old_ist = __this_cpu_read(cpu_tss_rw.x86_tss.ist[IST_INDEX_VC]); + new_ist = old_ist = __this_cpu_read(cpu_tss_rw.x86_tss.ist[IST_INDEX_VC]); - /* Make room on the IST stack */ - if (on_vc_stack(regs->sp)) - new_ist = ALIGN_DOWN(regs->sp, 8) - sizeof(old_ist); - else - new_ist = old_ist - sizeof(old_ist); + /* + * If NMI happened while on the #VC IST stack, set the new IST + * value below regs->sp, so that the interrupted stack frame is + * not overwritten by subsequent #VC exceptions. + */ + if (on_vc_stack(regs)) + new_ist = regs->sp; - /* Store old IST entry */ + /* + * Reserve additional 8 bytes and store old IST value so this + * adjustment can be unrolled in __sev_es_ist_exit(). + */ + new_ist -= sizeof(old_ist); *(unsigned long *)new_ist = old_ist; /* Set new IST entry */ @@ -241,39 +263,54 @@ static int vc_fetch_insn_kernel(struct es_em_ctxt *ctxt, return copy_from_kernel_nofault(buffer, (unsigned char *)ctxt->regs->ip, MAX_INSN_SIZE); } -static enum es_result vc_decode_insn(struct es_em_ctxt *ctxt) +static enum es_result __vc_decode_user_insn(struct es_em_ctxt *ctxt) { char buffer[MAX_INSN_SIZE]; - enum es_result ret; int res; - if (user_mode(ctxt->regs)) { - res = insn_fetch_from_user(ctxt->regs, buffer); - if (!res) { - ctxt->fi.vector = X86_TRAP_PF; - ctxt->fi.error_code = X86_PF_INSTR | X86_PF_USER; - ctxt->fi.cr2 = ctxt->regs->ip; - return ES_EXCEPTION; - } + res = insn_fetch_from_user_inatomic(ctxt->regs, buffer); + if (!res) { + ctxt->fi.vector = X86_TRAP_PF; + ctxt->fi.error_code = X86_PF_INSTR | X86_PF_USER; + ctxt->fi.cr2 = ctxt->regs->ip; + return ES_EXCEPTION; + } - if (!insn_decode(&ctxt->insn, ctxt->regs, buffer, res)) - return ES_DECODE_FAILED; - } else { - res = vc_fetch_insn_kernel(ctxt, buffer); - if (res) { - ctxt->fi.vector = X86_TRAP_PF; - ctxt->fi.error_code = X86_PF_INSTR; - ctxt->fi.cr2 = ctxt->regs->ip; - return ES_EXCEPTION; - } + if (!insn_decode_from_regs(&ctxt->insn, ctxt->regs, buffer, res)) + return ES_DECODE_FAILED; - insn_init(&ctxt->insn, buffer, MAX_INSN_SIZE - res, 1); - insn_get_length(&ctxt->insn); + if (ctxt->insn.immediate.got) + return ES_OK; + else + return ES_DECODE_FAILED; +} + +static enum es_result __vc_decode_kern_insn(struct es_em_ctxt *ctxt) +{ + char buffer[MAX_INSN_SIZE]; + int res, ret; + + res = vc_fetch_insn_kernel(ctxt, buffer); + if (res) { + ctxt->fi.vector = X86_TRAP_PF; + ctxt->fi.error_code = X86_PF_INSTR; + ctxt->fi.cr2 = ctxt->regs->ip; + return ES_EXCEPTION; } - ret = ctxt->insn.immediate.got ? ES_OK : ES_DECODE_FAILED; + ret = insn_decode(&ctxt->insn, buffer, MAX_INSN_SIZE, INSN_MODE_64); + if (ret < 0) + return ES_DECODE_FAILED; + else + return ES_OK; +} - return ret; +static enum es_result vc_decode_insn(struct es_em_ctxt *ctxt) +{ + if (user_mode(ctxt->regs)) + return __vc_decode_user_insn(ctxt); + else + return __vc_decode_kern_insn(ctxt); } static enum es_result vc_write_mem(struct es_em_ctxt *ctxt, @@ -1248,13 +1285,12 @@ static __always_inline bool on_vc_fallback_stack(struct pt_regs *regs) DEFINE_IDTENTRY_VC_SAFE_STACK(exc_vmm_communication) { struct sev_es_runtime_data *data = this_cpu_read(runtime_data); + irqentry_state_t irq_state; struct ghcb_state state; struct es_em_ctxt ctxt; enum es_result result; struct ghcb *ghcb; - lockdep_assert_irqs_disabled(); - /* * Handle #DB before calling into !noinstr code to avoid recursive #DB. */ @@ -1263,6 +1299,8 @@ DEFINE_IDTENTRY_VC_SAFE_STACK(exc_vmm_communication) return; } + irq_state = irqentry_nmi_enter(regs); + lockdep_assert_irqs_disabled(); instrumentation_begin(); /* @@ -1325,6 +1363,7 @@ DEFINE_IDTENTRY_VC_SAFE_STACK(exc_vmm_communication) out: instrumentation_end(); + irqentry_nmi_exit(regs, irq_state); return; |