x86/selftests, x86/vm86: Improve entry_from_vm86 selftest
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 <luto@kernel.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Denys Vlasenko <vda.linux@googlemail.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Kees Cook <keescook@chromium.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rik van Riel <riel@redhat.com> Cc: Shuah Khan <shuahkh@osg.samsung.com> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/d8ef1d7368ac70d8342481563ed50f9a7d2eea6f.1436492057.git.luto@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
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@ -28,6 +28,55 @@
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static unsigned long load_addr = 0x10000;
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static unsigned long load_addr = 0x10000;
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static int nerrs = 0;
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static int nerrs = 0;
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static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
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int flags)
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{
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struct sigaction sa;
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memset(&sa, 0, sizeof(sa));
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sa.sa_sigaction = handler;
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sa.sa_flags = SA_SIGINFO | flags;
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sigemptyset(&sa.sa_mask);
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if (sigaction(sig, &sa, 0))
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err(1, "sigaction");
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}
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static void clearhandler(int sig)
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{
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struct sigaction sa;
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memset(&sa, 0, sizeof(sa));
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sa.sa_handler = SIG_DFL;
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sigemptyset(&sa.sa_mask);
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if (sigaction(sig, &sa, 0))
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err(1, "sigaction");
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}
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static sig_atomic_t got_signal;
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static void sighandler(int sig, siginfo_t *info, void *ctx_void)
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{
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ucontext_t *ctx = (ucontext_t*)ctx_void;
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if (ctx->uc_mcontext.gregs[REG_EFL] & X86_EFLAGS_VM ||
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(ctx->uc_mcontext.gregs[REG_CS] & 3) != 3) {
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printf("[FAIL]\tSignal frame should not reflect vm86 mode\n");
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nerrs++;
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}
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const char *signame;
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if (sig == SIGSEGV)
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signame = "SIGSEGV";
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else if (sig == SIGILL)
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signame = "SIGILL";
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else
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signame = "unexpected signal";
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printf("[INFO]\t%s: FLAGS = 0x%lx, CS = 0x%hx\n", signame,
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(unsigned long)ctx->uc_mcontext.gregs[REG_EFL],
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(unsigned short)ctx->uc_mcontext.gregs[REG_CS]);
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got_signal = 1;
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}
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asm (
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asm (
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".pushsection .rodata\n\t"
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".pushsection .rodata\n\t"
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".type vmcode_bound, @object\n\t"
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".type vmcode_bound, @object\n\t"
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@ -38,6 +87,14 @@ asm (
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"int3\n\t"
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"int3\n\t"
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"vmcode_sysenter:\n\t"
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"vmcode_sysenter:\n\t"
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"sysenter\n\t"
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"sysenter\n\t"
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"vmcode_syscall:\n\t"
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"syscall\n\t"
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"vmcode_sti:\n\t"
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"sti\n\t"
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"vmcode_int3:\n\t"
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"int3\n\t"
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"vmcode_int80:\n\t"
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"int $0x80\n\t"
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".size vmcode, . - vmcode\n\t"
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".size vmcode, . - vmcode\n\t"
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"end_vmcode:\n\t"
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"end_vmcode:\n\t"
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".code32\n\t"
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".code32\n\t"
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@ -45,9 +102,11 @@ asm (
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);
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);
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extern unsigned char vmcode[], end_vmcode[];
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extern unsigned char vmcode[], end_vmcode[];
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extern unsigned char vmcode_bound[], vmcode_sysenter[];
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extern unsigned char vmcode_bound[], vmcode_sysenter[], vmcode_syscall[],
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vmcode_sti[], vmcode_int3[], vmcode_int80[];
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static void do_test(struct vm86plus_struct *v86, unsigned long eip,
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static void do_test(struct vm86plus_struct *v86, unsigned long eip,
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unsigned int rettype, unsigned int retarg,
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const char *text)
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const char *text)
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{
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{
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long ret;
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long ret;
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@ -73,13 +132,28 @@ static void do_test(struct vm86plus_struct *v86, unsigned long eip,
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else
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else
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sprintf(trapname, "%d", trapno);
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sprintf(trapname, "%d", trapno);
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printf("[OK]\tExited vm86 mode due to #%s\n", trapname);
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printf("[INFO]\tExited vm86 mode due to #%s\n", trapname);
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} else if (VM86_TYPE(ret) == VM86_UNKNOWN) {
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} else if (VM86_TYPE(ret) == VM86_UNKNOWN) {
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printf("[OK]\tExited vm86 mode due to unhandled GP fault\n");
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printf("[INFO]\tExited vm86 mode due to unhandled GP fault\n");
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} else if (VM86_TYPE(ret) == VM86_TRAP) {
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printf("[INFO]\tExited vm86 mode due to a trap (arg=%ld)\n",
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VM86_ARG(ret));
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} else if (VM86_TYPE(ret) == VM86_SIGNAL) {
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printf("[INFO]\tExited vm86 mode due to a signal\n");
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} else if (VM86_TYPE(ret) == VM86_STI) {
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printf("[INFO]\tExited vm86 mode due to STI\n");
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} else {
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} else {
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printf("[OK]\tExited vm86 mode due to type %ld, arg %ld\n",
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printf("[INFO]\tExited vm86 mode due to type %ld, arg %ld\n",
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VM86_TYPE(ret), VM86_ARG(ret));
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VM86_TYPE(ret), VM86_ARG(ret));
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}
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}
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if (rettype == -1 ||
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(VM86_TYPE(ret) == rettype && VM86_ARG(ret) == retarg)) {
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printf("[OK]\tReturned correctly\n");
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} else {
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printf("[FAIL]\tIncorrect return reason\n");
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nerrs++;
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}
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}
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}
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int main(void)
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int main(void)
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@ -105,10 +179,52 @@ int main(void)
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assert((v86.regs.cs & 3) == 0); /* Looks like RPL = 0 */
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assert((v86.regs.cs & 3) == 0); /* Looks like RPL = 0 */
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/* #BR -- should deliver SIG??? */
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/* #BR -- should deliver SIG??? */
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do_test(&v86, vmcode_bound - vmcode, "#BR");
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do_test(&v86, vmcode_bound - vmcode, VM86_INTx, 5, "#BR");
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/* SYSENTER -- should cause #GP or #UD depending on CPU */
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/*
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do_test(&v86, vmcode_sysenter - vmcode, "SYSENTER");
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* SYSENTER -- should cause #GP or #UD depending on CPU.
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* Expected return type -1 means that we shouldn't validate
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* the vm86 return value. This will avoid problems on non-SEP
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* CPUs.
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*/
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sethandler(SIGILL, sighandler, 0);
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do_test(&v86, vmcode_sysenter - vmcode, -1, 0, "SYSENTER");
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clearhandler(SIGILL);
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/*
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* SYSCALL would be a disaster in VM86 mode. Fortunately,
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* there is no kernel that both enables SYSCALL and sets
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* EFER.SCE, so it's #UD on all systems. But vm86 is
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* buggy (or has a "feature"), so the SIGILL will actually
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* be delivered.
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*/
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sethandler(SIGILL, sighandler, 0);
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do_test(&v86, vmcode_syscall - vmcode, VM86_SIGNAL, 0, "SYSCALL");
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clearhandler(SIGILL);
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/* STI with VIP set */
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v86.regs.eflags |= X86_EFLAGS_VIP;
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v86.regs.eflags &= ~X86_EFLAGS_IF;
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do_test(&v86, vmcode_sti - vmcode, VM86_STI, 0, "STI with VIP set");
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/* INT3 -- should cause #BP */
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do_test(&v86, vmcode_int3 - vmcode, VM86_TRAP, 3, "INT3");
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/* INT80 -- should exit with "INTx 0x80" */
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v86.regs.eax = (unsigned int)-1;
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do_test(&v86, vmcode_int80 - vmcode, VM86_INTx, 0x80, "int80");
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/* Execute a null pointer */
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v86.regs.cs = 0;
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v86.regs.ss = 0;
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sethandler(SIGSEGV, sighandler, 0);
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got_signal = 0;
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do_test(&v86, 0, VM86_SIGNAL, 0, "Execute null pointer");
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if (!got_signal) {
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printf("[FAIL]\tDid not receive SIGSEGV\n");
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nerrs++;
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}
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clearhandler(SIGSEGV);
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return (nerrs == 0 ? 0 : 1);
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return (nerrs == 0 ? 0 : 1);
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}
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}
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