Date: Fri, 24 Aug 2012 09:17:22 -0600 From: John Hein <jhein@symmetricom.com> To: hackers@freebsd.org Subject: LD_PRELOADed code before or after exec - different behavior after 6.x Message-ID: <20535.39682.330250.337503@gromit.timing.com>
next in thread | raw e-mail | index | archive | help
head sl.cc pe.c
==> sl.cc <==
#include <cstdio>
#include <cstdlib>
class C
{
public:
C(){
printf("C\n");
unsetenv("XXX");
}
};
static C c;
==> pe.c <==
#include <stdio.h>
#include <stdlib.h>
int
main()
{
char *p=getenv("XXX");
if (p != NULL)
printf("XXX=%s\n",p);
return 0;
}
% g++ -fpic -shared sl.cc -o sl.so
% gcc pe.c -o pe
7.x & 8.x ...
% sh -c 'XXX=1 LD_PRELOAD=$(pwd)/sl.so pe'
C
XXX=1
6.x & 4.x ...
% sh -c 'XXX=1 LD_PRELOAD=$(pwd)/sl.so pe'
C
In 6.x and earlier (fedora 16, too), the unsetenv clears the XXX env
var apparently in time to affect the exec'd process. In 8.x & 9.x, it
seems the environment is set and passed to the exec'd process and the
LD_PRELOADed code does not affect that despite its best efforts.
It seems to me that 6.x behavior is more correct, but I'm seeking
opinions before contemplating if / how to put together a fix.
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20535.39682.330250.337503>