tjh.dev
x86-64: fix int $0x80 -ENOSYS return
One of my past fixes to this code introduced a different new bug.
When using 32-bit "int $0x80" entry for a bogus syscall number,
the return value is not correctly set to -ENOSYS. This only happens
when neither syscall-audit nor syscall tracing is enabled (i.e., never
seen if auditd ever started). Test program:
/* gcc -o int80-badsys -m32 -g int80-badsys.c
Run on x86-64 kernel.
Note to reproduce the bug you need auditd never to have started. */
#include <errno.h>
#include <stdio.h>
int
main (void)
{
long res;
asm ("int $0x80" : "=a" (res) : "0" (99999));
printf ("bad syscall returns %ld\n", res);
return res != -ENOSYS;
}
The fix makes the int $0x80 path match the sysenter and syscall paths.
Reported-by: Dmitry V. Levin <ldv@altlinux.org>
Signed-off-by: Roland McGrath <roland@redhat.com>