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Message-Id: <d8ef1d7368ac70d8342481563ed50f9a7d2eea6f.1436492057.git.luto@kernel.org>
Date: Thu, 9 Jul 2015 19:17:29 -0700
From: Andy Lutomirski <luto@...nel.org>
To: x86@...nel.org, linux-kernel@...r.kernel.org
Cc: Frédéric Weisbecker <fweisbec@...il.com>,
Rik van Riel <riel@...hat.com>,
Oleg Nesterov <oleg@...hat.com>,
Denys Vlasenko <vda.linux@...glemail.com>,
Borislav Petkov <bp@...en8.de>,
Kees Cook <keescook@...omium.org>,
Brian Gerst <brgerst@...il.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Andy Lutomirski <luto@...nel.org>
Subject: [RFC/PATCH v2 v2 1/6] 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@...nel.org>
---
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
--
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