Messages in this thread | | | Date | Thu, 27 May 2010 21:17:05 +0400 | From | Michael Tokarev <> | Subject | personality(ADDR_LIMIT_3GB) results in EFAULT |
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Hello.
I noticed an.. interesting issue here.
Running a 32bit executable on a 64bit kernel, and doing
personality(ADDR_LIMIT_3GB);
That call succedes, but any further execve() and friends results in EFAULT, unless whole argv[] and envp[] are copied to a malloc'ed space. alloca sometimes helps and sometimes not.
This simple program demonstrates the issue:
===== cut ===== #include <sys/types.h> #include <unistd.h> #include <stdlib.h> #include <string.h> #include <stdio.h>
int main(int ac, char **av, char **ev) { int i;
personality(ADDR_LIMIT_3GB);
++av; --ac;
for (i = 0; i < ac; ++i) av[i] = strdup(av[i]);
for(i = 0; ev[i]; ++i) ev[i] = strdup(ev[i]);
execve(av[0], av, ev); printf("unable to execute %s: %m\n", av[0]); return 1; } ===== cut =====
Run as ./a.out /bin/echo (or any other 32bit program).
Without the two for() loops it fails with EFAULT error. Changing strdup into strdupa results in it working in the above simplest case, but failing in more complex situation as a part of larger program.
For now, in order to set this personality, I use a 64bit helper program that executes the 32bit binary (for which that personality is important). Which look a bit ugly, esp. since it is in a chain of other, all 32bit, programs.
Is it easy enough to fix? :)
The issue here, original issue, is a need to run some legacy application (oracle database v.8 in in this particular example), so it's not very interesting to fix. But doing ugly workarounds aren't good either :)
Thanks!
/mjt
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