forked from Minki/linux
a318beea22
Setting TF prevents fastpath returns in most cases, which causes the test to fail on 32-bit kernels because 32-bit kernels do not, in fact, handle NT correctly on SYSENTER entries. The next patch will fix 32-bit kernels. Signed-off-by: Andy Lutomirski <luto@kernel.org> Cc: Andrew Cooper <andrew.cooper3@citrix.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/bd4bb48af6b10c0dc84aec6dbcf487ed25683495.1457578375.git.luto@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
96 lines
2.3 KiB
C
96 lines
2.3 KiB
C
/*
|
|
* syscall_nt.c - checks syscalls with NT set
|
|
* Copyright (c) 2014-2015 Andrew Lutomirski
|
|
*
|
|
* This program is free software; you can redistribute it and/or modify
|
|
* it under the terms and conditions of the GNU General Public License,
|
|
* version 2, as published by the Free Software Foundation.
|
|
*
|
|
* This program is distributed in the hope it will be useful, but
|
|
* WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
* General Public License for more details.
|
|
*
|
|
* Some obscure user-space code requires the ability to make system calls
|
|
* with FLAGS.NT set. Make sure it works.
|
|
*/
|
|
|
|
#include <stdio.h>
|
|
#include <unistd.h>
|
|
#include <string.h>
|
|
#include <signal.h>
|
|
#include <err.h>
|
|
#include <sys/syscall.h>
|
|
#include <asm/processor-flags.h>
|
|
|
|
#ifdef __x86_64__
|
|
# define WIDTH "q"
|
|
#else
|
|
# define WIDTH "l"
|
|
#endif
|
|
|
|
static unsigned int nerrs;
|
|
|
|
static unsigned long get_eflags(void)
|
|
{
|
|
unsigned long eflags;
|
|
asm volatile ("pushf" WIDTH "\n\tpop" WIDTH " %0" : "=rm" (eflags));
|
|
return eflags;
|
|
}
|
|
|
|
static void set_eflags(unsigned long eflags)
|
|
{
|
|
asm volatile ("push" WIDTH " %0\n\tpopf" WIDTH
|
|
: : "rm" (eflags) : "flags");
|
|
}
|
|
|
|
static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
|
|
int flags)
|
|
{
|
|
struct sigaction sa;
|
|
memset(&sa, 0, sizeof(sa));
|
|
sa.sa_sigaction = handler;
|
|
sa.sa_flags = SA_SIGINFO | flags;
|
|
sigemptyset(&sa.sa_mask);
|
|
if (sigaction(sig, &sa, 0))
|
|
err(1, "sigaction");
|
|
}
|
|
|
|
static void sigtrap(int sig, siginfo_t *si, void *ctx_void)
|
|
{
|
|
}
|
|
|
|
static void do_it(unsigned long extraflags)
|
|
{
|
|
unsigned long flags;
|
|
|
|
set_eflags(get_eflags() | extraflags);
|
|
syscall(SYS_getpid);
|
|
flags = get_eflags();
|
|
if ((flags & extraflags) == extraflags) {
|
|
printf("[OK]\tThe syscall worked and flags are still set\n");
|
|
} else {
|
|
printf("[FAIL]\tThe syscall worked but flags were cleared (flags = 0x%lx but expected 0x%lx set)\n",
|
|
flags, extraflags);
|
|
nerrs++;
|
|
}
|
|
}
|
|
|
|
int main(void)
|
|
{
|
|
printf("[RUN]\tSet NT and issue a syscall\n");
|
|
do_it(X86_EFLAGS_NT);
|
|
|
|
/*
|
|
* Now try it again with TF set -- TF forces returns via IRET in all
|
|
* cases except non-ptregs-using 64-bit full fast path syscalls.
|
|
*/
|
|
|
|
sethandler(SIGTRAP, sigtrap, 0);
|
|
|
|
printf("[RUN]\tSet NT|TF and issue a syscall\n");
|
|
do_it(X86_EFLAGS_NT | X86_EFLAGS_TF);
|
|
|
|
return nerrs == 0 ? 0 : 1;
|
|
}
|