On Fri, Mar 9, 2018 at 12:45 AM, Ram Pai <linux...@us.ibm.com> wrote:
> On Thu, Mar 08, 2018 at 11:19:12PM +1100, Michael Ellerman wrote: > > Li Wang <liw...@redhat.com> writes: > > > Hi, > > > > > > ltp/mprotect04[1] crashed by SEGV_PKUERR on ppc64(LPAR on P730, Power 8 > > > 8247-22L) with kernel-v4.16.0-rc4. > > > > > > 10000000-10020000 r-xp 00000000 fd:00 167223 mprotect04 > > > 10020000-10030000 r--p 00010000 fd:00 167223 mprotect04 > > > 10030000-10040000 rw-p 00020000 fd:00 167223 mprotect04 > > > 1001a380000-1001a3b0000 rw-p 00000000 00:00 0 [heap] > > > 7fffa6c60000-7fffa6c80000 --xp 00000000 00:00 0 > > > > > > &exec_func = 0x10030170 > > > > > > &func = 0x7fffa6c60170 > > > > > > While perform > > > "(*func)();" we get the > > > segmentation fault. > > > > > > > > > strace log: > > > > > > ------------------- > > > mprotect(0x7fffaed00000, 131072, PROT_EXEC) = 0 > > > rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 > > > --- SIGSEGV {si_signo=SIGSEGV, si_code=SEGV_PKUERR, > si_addr=0x7fffaed00170} > > > --- > > > > Looks like a bug to me. > > > > Please Cc linuxppc-dev on powerpc bugs. > > > > I also can't reproduce this failure on my machine. > > Not sure what's going on? > > I could reproduce it on a power7 lpar. But not on a power8 lpar. > > The problem seems to be that the cpu generates a key exception if > the page with Read/Write-disable-but-execute-enable key is executed > on power7. If I enable read on that key, the exception disappears. > After adding read permission on that key, reproducer get PASS on my power8 machine too. (mprotect(..,PROT_READ | PROT_EXEC)) > > BTW: the testcase executes > > mprotect(..,PROT_EXEC). > The mprotect(, PROT_EXEC) system call internally generates a > execute-only key and associates it with the pages in the address-range. > Now since Li Wang claims that he can reproduce it on power8 as well, i > am wondering if the slightly different cpu behavior is dependent on the > version of the firmware/microcode? > I also run this reproducer on series ppc kvm machines, but none of them get the FAIL. If you need some more HW info, pls let me know. > > > RP > > -- Li Wang liw...@redhat.com