dirty fix to merging

1 files changed, 74 insertions, 0 deletions

diff --git a/arch/x86/um/bugs_32.c b/arch/x86/um/bugs_32.c
new file mode 100644
index 00000000..17d88cf2
--- /dev/null
+++ b/arch/x86/um/bugs_32.c
@@ -0,0 +1,74 @@
+/*
+ * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+ * Licensed under the GPL
+ */
+
+#include <signal.h>
+#include "kern_util.h"
+#include "longjmp.h"
+#include "sysdep/ptrace.h"
+#include <generated/asm-offsets.h>
+
+/* Set during early boot */
+static int host_has_cmov = 1;
+static jmp_buf cmov_test_return;
+
+static void cmov_sigill_test_handler(int sig)
+{
+	host_has_cmov = 0;
+	longjmp(cmov_test_return, 1);
+}
+
+void arch_check_bugs(void)
+{
+	struct sigaction old, new;
+
+	printk(UM_KERN_INFO "Checking for host processor cmov support...");
+	new.sa_handler = cmov_sigill_test_handler;
+
+	/* Make sure that SIGILL is enabled after the handler longjmps back */
+	new.sa_flags = SA_NODEFER;
+	sigemptyset(&new.sa_mask);
+	sigaction(SIGILL, &new, &old);
+
+	if (setjmp(cmov_test_return) == 0) {
+		unsigned long foo = 0;
+		__asm__ __volatile__("cmovz %0, %1" : "=r" (foo) : "0" (foo));
+		printk(UM_KERN_CONT "Yes\n");
+	} else
+		printk(UM_KERN_CONT "No\n");
+
+	sigaction(SIGILL, &old, &new);
+}
+
+void arch_examine_signal(int sig, struct uml_pt_regs *regs)
+{
+	unsigned char tmp[2];
+
+	/*
+	 * This is testing for a cmov (0x0f 0x4x) instruction causing a
+	 * SIGILL in init.
+	 */
+	if ((sig != SIGILL) || (get_current_pid() != 1))
+		return;
+
+	if (copy_from_user_proc(tmp, (void *) UPT_IP(regs), 2)) {
+		printk(UM_KERN_ERR "SIGILL in init, could not read "
+		       "instructions!\n");
+		return;
+	}
+
+	if ((tmp[0] != 0x0f) || ((tmp[1] & 0xf0) != 0x40))
+		return;
+
+	if (host_has_cmov == 0)
+		printk(UM_KERN_ERR "SIGILL caused by cmov, which this "
+		       "processor doesn't implement.  Boot a filesystem "
+		       "compiled for older processors");
+	else if (host_has_cmov == 1)
+		printk(UM_KERN_ERR "SIGILL caused by cmov, which this "
+		       "processor claims to implement");
+	else
+		printk(UM_KERN_ERR "Bad value for host_has_cmov (%d)",
+			host_has_cmov);
+}