On Dec 18, 11:40am, njoly@pasteur.fr (Nicolas Joly) wrote:
-- Subject: Re: mprotect(2) strange behaviour under compat linux

| On Tue, Dec 18, 2007 at 03:32:37AM +0000, Christos Zoulas wrote:
| > In article <20071217223029.GA31529@medusa.sis.pasteur.fr>,
| > Nicolas Joly  <njoly@pasteur.fr> wrote:
| > >
| > >While working on compat linux i encountered some strange mprotect(2)
| > >behaviour.
| > >
| > >The attached piece of code work on NetBSD i386/amd64, Linux
| > >i386/x86_64, but not under compat linux/i386 or linux32/amd64.
| [...]
| > Can you add a segv handler in the program so that ktrace prints more
| > info as it passes it to the signal handler? I am interested if it is
| > a protection error or an access error. If it is an access error, please
| > try to instrument line 771 in uvm_fault.c to see what's causing it.
| 
| Thank for the tip.
| 
| This is an access error:
| 
|    619      1 mprotect PSIG  SIGSEGV caught handler=0x8048518 mask=(8,11,12,13,14,15,19,20,22,25,27,28,30,33,38,39,45,47,48,49,50,51,52,53,54,55,57,58,59,60,61,62,63): code=SEGV_ACCERR, addr=0xbbaba000, trap=14)
| 
| Intrumenting uvm_fault.c show that protections are correct (check_prot
| = 0x2), but something (memset ?) is trying to access this area for
| reading (access_type = 0x1) ...
| 
| Could this be a bug in memset from suse 10.0 glibc (from
| pkgsrc/emulators/suse100_base) ?

Could be. Disassemble and look at the instruction... Good hunting :-)

christos