jstack from JDK7 b123 (hs20-b05) launched with -m option reports the following on linux-i586 for one of threads:

0xb78aa424              ????????
0x0e80dc30              ????????
sun.jvm.hotspot.debugger.UnmappedAddressException
        at sun.jvm.hotspot.debugger.PageCache.checkPage(PageCache.java:208)
        at sun.jvm.hotspot.debugger.PageCache.getData(PageCache.java:63)
        at sun.jvm.hotspot.debugger.DebuggerBase.readBytes(DebuggerBase.java:217)
        at sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal.readCInteger(LinuxDebuggerLocal.java:482)
        at sun.jvm.hotspot.debugger.DebuggerBase.readAddressValue(DebuggerBase.java:454)
        at sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal.readAddress(LinuxDebuggerLocal.java:423)
        at sun.jvm.hotspot.debugger.linux.LinuxAddress.getAddressAt(LinuxAddress.java:74)
        at sun.jvm.hotspot.debugger.linux.x86.LinuxX86CFrame.sender(LinuxX86CFrame.java:60)
        at sun.jvm.hotspot.tools.PStack.run(PStack.java:161)
        at sun.jvm.hotspot.tools.PStack.run(PStack.java:53)
        at sun.jvm.hotspot.tools.PStack.run(PStack.java:48)
        at sun.jvm.hotspot.tools.JStack.run(JStack.java:60)
        at sun.jvm.hotspot.tools.Tool.start(Tool.java:221)
        at sun.jvm.hotspot.tools.JStack.main(JStack.java:86)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:613)
        at sun.tools.jstack.JStack.runJStackTool(JStack.java:136)
        at sun.tools.jstack.JStack.main(JStack.java:102)

To reproduce:

$ jconsole localhost:0 &
$ jps | grep JConsole
<pid> JConsole
$ jstack -m <pid>