Seems to me it drops permissions instead of not allowing the trace.
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dmg@jolt:[pts/4]:~$ cat euid.c
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
int main() { printf("euid=%d\n", geteuid()); }
dmg@jolt:[pts/4]:~$ ls -l ./euid
-rwsr-sr-x 1 root root 5039 Dec 6 01:46 ./euid
dmg@jolt:[pts/4]:~$ ./euid
euid=0
dmg@jolt:[pts/4]:~$ strace -o /dev/null ./euid
euid=1000
dmg@jolt:[pts/4]:~$
--- 8< --- cut here --- 8< ---
Damian
-- Damian Gryski ==> dgryski@uwaterloo.ca | Linux, the choice of a GNU generation 512 pt Hacker Test score = 37% | 500 pt Nerd Test score = 56% geek / linux zealot / coder / juggler - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/