open CONFIG_PAX_MPROTECT run java failed(openjdk)

[lynliuyan]

when I open pax mprotect, run java -version failed

root@debian7:~/java-pax-test# java -version
OpenJDK 64-Bit Server VM warning: INFO: os::commit_memory(0x00003fff7c000000, 2097152, 1) failed; error='Operation not permitted' (errno=1)




Analysis code found in the function do_mmap_pgoff(mm/mmap.c),

#ifdef CONFIG_PAX_MPROTECT
if (mm->pax_flags & MF_PAX_MPROTECT) {
if ((vm_flags & (VM_WRITE | VM_EXEC)) == (VM_WRITE | VM_EXEC))

#ifdef CONFIG_PAX_EMUPLT
vm_flags &= ~VM_EXEC;
#else
return -EPERM;
#endif

EMUPLT undefined, so return an error value，but I did not fount the definition CONFIG_PAX_EMUPLT?

[PaX Team]

you should read the config help about MPROTECT as it describes what restrictions it adds on top of the non-exec page feature. in your case it prevents one of the first steps of runtime code generation, the allocation of rwx memory. as for EMUPLT, it's in the usual place (security/Kconfig) and it doesn't apply to your architecture, that's why it doesn't show up in menuconfig.