On Sun, Jun 21, 2009 at 11:20 AM, John David Anglin<dave@xxxxxxxxxxxxxxxxxx> wrote: > Looking at my email archive, I see the real cause involves kernel memory > maps: > > > > > On Wed, May 06, 2009 at 01:39:49PM -0400, John David Anglin wrote: > > > > > > The tombstone is: > > > > > > > > > > > > do_page_fault() pid=10205 command='strace' type=15 address=0x407d2f18 > > > > > > vm_start = 0x4068d000, vm_end = 0x4068f000 > > > > > > > > > > So, the pointer passed to __canonicalize_funcptr_for_compare is outside > > > > > the vm range. The strace problem is a compiler flaw. This is the problem: * Strace examines the applications syscall. * Strace extracts, via PTRACE, application addresses, addresses that don't exist in the strace address space (and should not exist). * Strace compares extracted address to a constant SIG_ERR. * Compiler generates a call to __c_f_f_c, which dereference the extracted address and strace faults. Strace and the application have completely different address spaces, and __c_f_f_c can't assume that an address is in the current address space. The solution is to detect that a comparison between two pointers is a comparison between pointer and small constant, and avoid calling __c_f_f_c for both. The workaround is to cast both long. I tested this and it works. I'll submit this to debian as the fix. Cheers, Carlos. -- To unsubscribe from this list: send the line "unsubscribe linux-parisc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
