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selftests/x86: Test SYSCALL and SYSENTER manually with TF set

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Make sure that both variants of the nasty TF-in-compat-syscall are
exercised regardless of what vendor's CPU is running the tests.

Also change the intentional signal after SYSCALL to use ud2, which
is a lot more comprehensible.

This crashes the kernel due to an FSGSBASE bug right now.

This test *also* detects a bug in KVM when run on an Intel host.  KVM
people, feel free to use it to help debug.  There's a bunch of code in this
test to warn instead of going into an infinite looping when the bug gets
triggered.

Reported-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc:  "BaeChang Seok" <chang.seok.bae@intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: kvm@vger.kernel.org
Cc: "Bae, Chang Seok" <chang.seok.bae@intel.com>
Link: https://lkml.kernel.org/r/5f5de10441ab2e3005538b4c33be9b1965d1bb63.1562035429.git.luto@kernel.org
This commit is contained in:
Andy Lutomirski 2019-07-01 20:43:19 -07:00 committed by Thomas Gleixner
parent fd329f276e
commit 9402eaf4c1
2 changed files with 110 additions and 7 deletions
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5
tools/testing/selftests/x86/Makefile
View File

@ -12,8 +12,9 @@ CAN_BUILD_WITH_NOPIE := $(shell ./check_cc.sh $(CC) trivial_program.c -no-pie)
TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs syscall_nt test_mremap_vdso \
check_initial_reg_state sigreturn iopl mpx-mini-test ioperm \
protection_keys test_vdso test_vsyscall mov_ss_trap
TARGETS_C_32BIT_ONLY := entry_from_vm86 syscall_arg_fault test_syscall_vdso unwind_vdso \
protection_keys test_vdso test_vsyscall mov_ss_trap \
syscall_arg_fault
TARGETS_C_32BIT_ONLY := entry_from_vm86 test_syscall_vdso unwind_vdso \
test_FCMOV test_FCOMI test_FISTTP \
vdso_restorer
TARGETS_C_64BIT_ONLY := fsgsbase sysret_rip

112
tools/testing/selftests/x86/syscall_arg_fault.c
View File

@ -15,9 +15,30 @@
#include <setjmp.h>
#include <errno.h>
#ifdef __x86_64__
# define WIDTH "q"
#else
# define WIDTH "l"
#endif
/* Our sigaltstack scratch space. */
static unsigned char altstack_data[SIGSTKSZ];
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");
}
#define X86_EFLAGS_TF (1UL << 8)
static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
int flags)
{
@ -35,13 +56,22 @@ static sigjmp_buf jmpbuf;
static volatile sig_atomic_t n_errs;
#ifdef __x86_64__
#define REG_AX REG_RAX
#define REG_IP REG_RIP
#else
#define REG_AX REG_EAX
#define REG_IP REG_EIP
#endif
static void sigsegv_or_sigbus(int sig, siginfo_t *info, void *ctx_void)
{
ucontext_t *ctx = (ucontext_t*)ctx_void;
long ax = (long)ctx->uc_mcontext.gregs[REG_AX];
if (ctx->uc_mcontext.gregs[REG_EAX] != -EFAULT) {
printf("[FAIL]\tAX had the wrong value: 0x%x\n",
ctx->uc_mcontext.gregs[REG_EAX]);
if (ax != -EFAULT && ax != -ENOSYS) {
printf("[FAIL]\tAX had the wrong value: 0x%lx\n",
(unsigned long)ax);
n_errs++;
} else {
printf("[OK]\tSeems okay\n");
@ -50,9 +80,42 @@ static void sigsegv_or_sigbus(int sig, siginfo_t *info, void *ctx_void)
siglongjmp(jmpbuf, 1);
}
static volatile sig_atomic_t sigtrap_consecutive_syscalls;
static void sigtrap(int sig, siginfo_t *info, void *ctx_void)
{
/*
* KVM has some bugs that can cause us to stop making progress.
* detect them and complain, but don't infinite loop or fail the
* test.
*/
ucontext_t *ctx = (ucontext_t*)ctx_void;
unsigned short *ip = (unsigned short *)ctx->uc_mcontext.gregs[REG_IP];
if (*ip == 0x340f || *ip == 0x050f) {
/* The trap was on SYSCALL or SYSENTER */
sigtrap_consecutive_syscalls++;
if (sigtrap_consecutive_syscalls > 3) {
printf("[WARN]\tGot stuck single-stepping -- you probably have a KVM bug\n");
siglongjmp(jmpbuf, 1);
}
} else {
sigtrap_consecutive_syscalls = 0;
}
}
static void sigill(int sig, siginfo_t *info, void *ctx_void)
{
printf("[SKIP]\tIllegal instruction\n");
ucontext_t *ctx = (ucontext_t*)ctx_void;
unsigned short *ip = (unsigned short *)ctx->uc_mcontext.gregs[REG_IP];
if (*ip == 0x0b0f) {
/* one of the ud2 instructions faulted */
printf("[OK]\tSYSCALL returned normally\n");
} else {
printf("[SKIP]\tIllegal instruction\n");
}
siglongjmp(jmpbuf, 1);
}
@ -120,9 +183,48 @@ int main()
"movl $-1, %%ebp\n\t"
"movl $-1, %%esp\n\t"
"syscall\n\t"
"pushl $0" /* make sure we segfault cleanly */
"ud2" /* make sure we recover cleanly */
: : : "memory", "flags");
}
printf("[RUN]\tSYSENTER with TF and invalid state\n");
sethandler(SIGTRAP, sigtrap, SA_ONSTACK);
if (sigsetjmp(jmpbuf, 1) == 0) {
sigtrap_consecutive_syscalls = 0;
set_eflags(get_eflags() | X86_EFLAGS_TF);
asm volatile (
"movl $-1, %%eax\n\t"
"movl $-1, %%ebx\n\t"
"movl $-1, %%ecx\n\t"
"movl $-1, %%edx\n\t"
"movl $-1, %%esi\n\t"
"movl $-1, %%edi\n\t"
"movl $-1, %%ebp\n\t"
"movl $-1, %%esp\n\t"
"sysenter"
: : : "memory", "flags");
}
set_eflags(get_eflags() & ~X86_EFLAGS_TF);
printf("[RUN]\tSYSCALL with TF and invalid state\n");
if (sigsetjmp(jmpbuf, 1) == 0) {
sigtrap_consecutive_syscalls = 0;
set_eflags(get_eflags() | X86_EFLAGS_TF);
asm volatile (
"movl $-1, %%eax\n\t"
"movl $-1, %%ebx\n\t"
"movl $-1, %%ecx\n\t"
"movl $-1, %%edx\n\t"
"movl $-1, %%esi\n\t"
"movl $-1, %%edi\n\t"
"movl $-1, %%ebp\n\t"
"movl $-1, %%esp\n\t"
"syscall\n\t"
"ud2" /* make sure we recover cleanly */
: : : "memory", "flags");
}
set_eflags(get_eflags() & ~X86_EFLAGS_TF);
return 0;
}