Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752842AbbGJCSX (ORCPT ); Thu, 9 Jul 2015 22:18:23 -0400 Received: from mail.kernel.org ([198.145.29.136]:54427 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751688AbbGJCRm (ORCPT ); Thu, 9 Jul 2015 22:17:42 -0400 From: Andy Lutomirski To: x86@kernel.org, linux-kernel@vger.kernel.org Cc: =?UTF-8?q?Fr=C3=A9d=C3=A9ric=20Weisbecker?= , Rik van Riel , Oleg Nesterov , Denys Vlasenko , Borislav Petkov , Kees Cook , Brian Gerst , Linus Torvalds , Andy Lutomirski Subject: [RFC/PATCH v2 v2 1/6] x86/selftests, x86/vm86: Improve entry_from_vm86 selftest Date: Thu, 9 Jul 2015 19:17:29 -0700 Message-Id: X-Mailer: git-send-email 2.4.3 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6124 Lines: 197 The entry_from_vm86 selftest was very weak. Improve it: test more types of kernel entries from vm86 mode and test them more carefully. While we're at it, try to improve behavior on non-SEP CPUs. The old code was buggy because I misunderstood the intended semantics of #UD in vm86, so I didn't handle a possible signal. Signed-off-by: Andy Lutomirski --- tools/testing/selftests/x86/entry_from_vm86.c | 132 ++++++++++++++++++++++++-- 1 file changed, 124 insertions(+), 8 deletions(-) diff --git a/tools/testing/selftests/x86/entry_from_vm86.c b/tools/testing/selftests/x86/entry_from_vm86.c index 5c38a187677b..f004b2a09916 100644 --- a/tools/testing/selftests/x86/entry_from_vm86.c +++ b/tools/testing/selftests/x86/entry_from_vm86.c @@ -28,6 +28,55 @@ static unsigned long load_addr = 0x10000; static int nerrs = 0; +static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *), + int flags) +{ + struct sigaction sa; + memset(&sa, 0, sizeof(sa)); + sa.sa_sigaction = handler; + sa.sa_flags = SA_SIGINFO | flags; + sigemptyset(&sa.sa_mask); + if (sigaction(sig, &sa, 0)) + err(1, "sigaction"); +} + +static void clearhandler(int sig) +{ + struct sigaction sa; + memset(&sa, 0, sizeof(sa)); + sa.sa_handler = SIG_DFL; + sigemptyset(&sa.sa_mask); + if (sigaction(sig, &sa, 0)) + err(1, "sigaction"); +} + +static sig_atomic_t got_signal; + +static void sighandler(int sig, siginfo_t *info, void *ctx_void) +{ + ucontext_t *ctx = (ucontext_t*)ctx_void; + + if (ctx->uc_mcontext.gregs[REG_EFL] & X86_EFLAGS_VM || + (ctx->uc_mcontext.gregs[REG_CS] & 3) != 3) { + printf("[FAIL]\tSignal frame should not reflect vm86 mode\n"); + nerrs++; + } + + const char *signame; + if (sig == SIGSEGV) + signame = "SIGSEGV"; + else if (sig == SIGILL) + signame = "SIGILL"; + else + signame = "unexpected signal"; + + printf("[INFO]\t%s: FLAGS = 0x%lx, CS = 0x%hx\n", signame, + (unsigned long)ctx->uc_mcontext.gregs[REG_EFL], + (unsigned short)ctx->uc_mcontext.gregs[REG_CS]); + + got_signal = 1; +} + asm ( ".pushsection .rodata\n\t" ".type vmcode_bound, @object\n\t" @@ -38,6 +87,14 @@ asm ( "int3\n\t" "vmcode_sysenter:\n\t" "sysenter\n\t" + "vmcode_syscall:\n\t" + "syscall\n\t" + "vmcode_sti:\n\t" + "sti\n\t" + "vmcode_int3:\n\t" + "int3\n\t" + "vmcode_int80:\n\t" + "int $0x80\n\t" ".size vmcode, . - vmcode\n\t" "end_vmcode:\n\t" ".code32\n\t" @@ -45,9 +102,11 @@ asm ( ); extern unsigned char vmcode[], end_vmcode[]; -extern unsigned char vmcode_bound[], vmcode_sysenter[]; +extern unsigned char vmcode_bound[], vmcode_sysenter[], vmcode_syscall[], + vmcode_sti[], vmcode_int3[], vmcode_int80[]; static void do_test(struct vm86plus_struct *v86, unsigned long eip, + unsigned int rettype, unsigned int retarg, const char *text) { long ret; @@ -73,13 +132,28 @@ static void do_test(struct vm86plus_struct *v86, unsigned long eip, else sprintf(trapname, "%d", trapno); - printf("[OK]\tExited vm86 mode due to #%s\n", trapname); + printf("[INFO]\tExited vm86 mode due to #%s\n", trapname); } else if (VM86_TYPE(ret) == VM86_UNKNOWN) { - printf("[OK]\tExited vm86 mode due to unhandled GP fault\n"); + printf("[INFO]\tExited vm86 mode due to unhandled GP fault\n"); + } else if (VM86_TYPE(ret) == VM86_TRAP) { + printf("[INFO]\tExited vm86 mode due to a trap (arg=%ld)\n", + VM86_ARG(ret)); + } else if (VM86_TYPE(ret) == VM86_SIGNAL) { + printf("[INFO]\tExited vm86 mode due to a signal\n"); + } else if (VM86_TYPE(ret) == VM86_STI) { + printf("[INFO]\tExited vm86 mode due to STI\n"); } else { - printf("[OK]\tExited vm86 mode due to type %ld, arg %ld\n", + printf("[INFO]\tExited vm86 mode due to type %ld, arg %ld\n", VM86_TYPE(ret), VM86_ARG(ret)); } + + if (rettype == -1 || + (VM86_TYPE(ret) == rettype && VM86_ARG(ret) == retarg)) { + printf("[OK]\tReturned correctly\n"); + } else { + printf("[FAIL]\tIncorrect return reason\n"); + nerrs++; + } } int main(void) @@ -105,10 +179,52 @@ int main(void) assert((v86.regs.cs & 3) == 0); /* Looks like RPL = 0 */ /* #BR -- should deliver SIG??? */ - do_test(&v86, vmcode_bound - vmcode, "#BR"); - - /* SYSENTER -- should cause #GP or #UD depending on CPU */ - do_test(&v86, vmcode_sysenter - vmcode, "SYSENTER"); + do_test(&v86, vmcode_bound - vmcode, VM86_INTx, 5, "#BR"); + + /* + * SYSENTER -- should cause #GP or #UD depending on CPU. + * Expected return type -1 means that we shouldn't validate + * the vm86 return value. This will avoid problems on non-SEP + * CPUs. + */ + sethandler(SIGILL, sighandler, 0); + do_test(&v86, vmcode_sysenter - vmcode, -1, 0, "SYSENTER"); + clearhandler(SIGILL); + + /* + * SYSCALL would be a disaster in VM86 mode. Fortunately, + * there is no kernel that both enables SYSCALL and sets + * EFER.SCE, so it's #UD on all systems. But vm86 is + * buggy (or has a "feature"), so the SIGILL will actually + * be delivered. + */ + sethandler(SIGILL, sighandler, 0); + do_test(&v86, vmcode_syscall - vmcode, VM86_SIGNAL, 0, "SYSCALL"); + clearhandler(SIGILL); + + /* STI with VIP set */ + v86.regs.eflags |= X86_EFLAGS_VIP; + v86.regs.eflags &= ~X86_EFLAGS_IF; + do_test(&v86, vmcode_sti - vmcode, VM86_STI, 0, "STI with VIP set"); + + /* INT3 -- should cause #BP */ + do_test(&v86, vmcode_int3 - vmcode, VM86_TRAP, 3, "INT3"); + + /* INT80 -- should exit with "INTx 0x80" */ + v86.regs.eax = (unsigned int)-1; + do_test(&v86, vmcode_int80 - vmcode, VM86_INTx, 0x80, "int80"); + + /* Execute a null pointer */ + v86.regs.cs = 0; + v86.regs.ss = 0; + sethandler(SIGSEGV, sighandler, 0); + got_signal = 0; + do_test(&v86, 0, VM86_SIGNAL, 0, "Execute null pointer"); + if (!got_signal) { + printf("[FAIL]\tDid not receive SIGSEGV\n"); + nerrs++; + } + clearhandler(SIGSEGV); return (nerrs == 0 ? 0 : 1); } -- 2.4.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/