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qemu/user-exec.c
Alex Bennée 02bed6bd5f user-exec: handle synchronous signals from QEMU gracefully 
When "tcg: enable thread-per-vCPU" (commit 3725794) was merged the
lifetime of current_cpu was changed. Previously a broken linux-user
call might abort() which can eventually escalate into a SIGSEGV which
would then crash qemu as it attempted to deref a NULL current_cpu.
After commit 3725794 it would attempt to fixup state and re-start the
run-loop and much hilarity (i.e. a looping lockup) would ensue from
jumping into a stale jmp_env.

As we can actually tell if we are in the run-loop from looking at the
cpu->running flag we should catch this badness first and abort()
cleanly rather than try to soldier on. There is a theoretical race
between the flag being set and sigsetjmp refreshing the jump buffer
but we can try really hard to not introduce crashes into that code.

[LV: setgroups03 fails on powerpc LTP]
Reported-by: Laurent Vivier <laurent@vivier.eu>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
2017-03-28 10:50:35 +01:00

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/*
* User emulator execution
*
* Copyright (c) 2003-2005 Fabrice Bellard
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, see <http://www.gnu.org/licenses/>.
*/
#include "qemu/osdep.h"
#include "cpu.h"
#include "disas/disas.h"
#include "exec/exec-all.h"
#include "tcg.h"
#include "qemu/bitops.h"
#include "exec/cpu_ldst.h"
#include "translate-all.h"
#undef EAX
#undef ECX
#undef EDX
#undef EBX
#undef ESP
#undef EBP
#undef ESI
#undef EDI
#undef EIP
#ifdef __linux__
#include <sys/ucontext.h>
#endif
//#define DEBUG_SIGNAL
/* exit the current TB from a signal handler. The host registers are
restored in a state compatible with the CPU emulator
*/
static void cpu_exit_tb_from_sighandler(CPUState *cpu, sigset_t *old_set)
{
/* XXX: use siglongjmp ? */
sigprocmask(SIG_SETMASK, old_set, NULL);
cpu_loop_exit_noexc(cpu);
}
/* 'pc' is the host PC at which the exception was raised. 'address' is
the effective address of the memory exception. 'is_write' is 1 if a
write caused the exception and otherwise 0'. 'old_set' is the
signal set which should be restored */
static inline int handle_cpu_signal(uintptr_t pc, unsigned long address,
int is_write, sigset_t *old_set)
{
CPUState *cpu = current_cpu;
CPUClass *cc;
int ret;
/* For synchronous signals we expect to be coming from the vCPU
* thread (so current_cpu should be valid) and either from running
* code or during translation which can fault as we cross pages.
*
* If neither is true then something has gone wrong and we should
* abort rather than try and restart the vCPU execution.
*/
if (!cpu || !cpu->running) {
printf("qemu:%s received signal outside vCPU context @ pc=0x%"
PRIxPTR "\n", __func__, pc);
abort();
}
#if defined(DEBUG_SIGNAL)
printf("qemu: SIGSEGV pc=0x%08lx address=%08lx w=%d oldset=0x%08lx\n",
pc, address, is_write, *(unsigned long *)old_set);
#endif
/* XXX: locking issue */
if (is_write && h2g_valid(address)) {
switch (page_unprotect(h2g(address), pc)) {
case 0:
/* Fault not caused by a page marked unwritable to protect
* cached translations, must be the guest binary's problem
*/
break;
case 1:
/* Fault caused by protection of cached translation; TBs
* invalidated, so resume execution
*/
return 1;
case 2:
/* Fault caused by protection of cached translation, and the
* currently executing TB was modified and must be exited
* immediately.
*/
cpu_exit_tb_from_sighandler(cpu, old_set);
g_assert_not_reached();
default:
g_assert_not_reached();
}
}
/* Convert forcefully to guest address space, invalid addresses
are still valid segv ones */
address = h2g_nocheck(address);
cc = CPU_GET_CLASS(cpu);
/* see if it is an MMU fault */
g_assert(cc->handle_mmu_fault);
ret = cc->handle_mmu_fault(cpu, address, is_write, MMU_USER_IDX);
if (ret < 0) {
return 0; /* not an MMU fault */
}
if (ret == 0) {
return 1; /* the MMU fault was handled without causing real CPU fault */
}
/* Now we have a real cpu fault. Since this is the exact location of
* the exception, we must undo the adjustment done by cpu_restore_state
* for handling call return addresses. */
cpu_restore_state(cpu, pc + GETPC_ADJ);
sigprocmask(SIG_SETMASK, old_set, NULL);
cpu_loop_exit(cpu);
/* never comes here */
return 1;
}
#if defined(__i386__)
#if defined(__NetBSD__)
#include <ucontext.h>
#define EIP_sig(context) ((context)->uc_mcontext.__gregs[_REG_EIP])
#define TRAP_sig(context) ((context)->uc_mcontext.__gregs[_REG_TRAPNO])
#define ERROR_sig(context) ((context)->uc_mcontext.__gregs[_REG_ERR])
#define MASK_sig(context) ((context)->uc_sigmask)
#elif defined(__FreeBSD__) || defined(__DragonFly__)
#include <ucontext.h>
#define EIP_sig(context) (*((unsigned long *)&(context)->uc_mcontext.mc_eip))
#define TRAP_sig(context) ((context)->uc_mcontext.mc_trapno)
#define ERROR_sig(context) ((context)->uc_mcontext.mc_err)
#define MASK_sig(context) ((context)->uc_sigmask)
#elif defined(__OpenBSD__)
#define EIP_sig(context) ((context)->sc_eip)
#define TRAP_sig(context) ((context)->sc_trapno)
#define ERROR_sig(context) ((context)->sc_err)
#define MASK_sig(context) ((context)->sc_mask)
#else
#define EIP_sig(context) ((context)->uc_mcontext.gregs[REG_EIP])
#define TRAP_sig(context) ((context)->uc_mcontext.gregs[REG_TRAPNO])
#define ERROR_sig(context) ((context)->uc_mcontext.gregs[REG_ERR])
#define MASK_sig(context) ((context)->uc_sigmask)
#endif
int cpu_signal_handler(int host_signum, void *pinfo,
void *puc)
{
siginfo_t *info = pinfo;
#if defined(__NetBSD__) || defined(__FreeBSD__) || defined(__DragonFly__)
ucontext_t *uc = puc;
#elif defined(__OpenBSD__)
struct sigcontext *uc = puc;
#else
struct ucontext *uc = puc;
#endif
unsigned long pc;
int trapno;
#ifndef REG_EIP
/* for glibc 2.1 */
#define REG_EIP EIP
#define REG_ERR ERR
#define REG_TRAPNO TRAPNO
#endif
pc = EIP_sig(uc);
trapno = TRAP_sig(uc);
return handle_cpu_signal(pc, (unsigned long)info->si_addr,
trapno == 0xe ?
(ERROR_sig(uc) >> 1) & 1 : 0,
&MASK_sig(uc));
}
#elif defined(__x86_64__)
#ifdef __NetBSD__
#define PC_sig(context) _UC_MACHINE_PC(context)
#define TRAP_sig(context) ((context)->uc_mcontext.__gregs[_REG_TRAPNO])
#define ERROR_sig(context) ((context)->uc_mcontext.__gregs[_REG_ERR])
#define MASK_sig(context) ((context)->uc_sigmask)
#elif defined(__OpenBSD__)
#define PC_sig(context) ((context)->sc_rip)
#define TRAP_sig(context) ((context)->sc_trapno)
#define ERROR_sig(context) ((context)->sc_err)
#define MASK_sig(context) ((context)->sc_mask)
#elif defined(__FreeBSD__) || defined(__DragonFly__)
#include <ucontext.h>
#define PC_sig(context) (*((unsigned long *)&(context)->uc_mcontext.mc_rip))
#define TRAP_sig(context) ((context)->uc_mcontext.mc_trapno)
#define ERROR_sig(context) ((context)->uc_mcontext.mc_err)
#define MASK_sig(context) ((context)->uc_sigmask)
#else
#define PC_sig(context) ((context)->uc_mcontext.gregs[REG_RIP])
#define TRAP_sig(context) ((context)->uc_mcontext.gregs[REG_TRAPNO])
#define ERROR_sig(context) ((context)->uc_mcontext.gregs[REG_ERR])
#define MASK_sig(context) ((context)->uc_sigmask)
#endif
int cpu_signal_handler(int host_signum, void *pinfo,
void *puc)
{
siginfo_t *info = pinfo;
unsigned long pc;
#if defined(__NetBSD__) || defined(__FreeBSD__) || defined(__DragonFly__)
ucontext_t *uc = puc;
#elif defined(__OpenBSD__)
struct sigcontext *uc = puc;
#else
struct ucontext *uc = puc;
#endif
pc = PC_sig(uc);
return handle_cpu_signal(pc, (unsigned long)info->si_addr,
TRAP_sig(uc) == 0xe ?
(ERROR_sig(uc) >> 1) & 1 : 0,
&MASK_sig(uc));
}
#elif defined(_ARCH_PPC)
/***********************************************************************
* signal context platform-specific definitions
* From Wine
*/
#ifdef linux
/* All Registers access - only for local access */
#define REG_sig(reg_name, context) \
((context)->uc_mcontext.regs->reg_name)
/* Gpr Registers access */
#define GPR_sig(reg_num, context) REG_sig(gpr[reg_num], context)
/* Program counter */
#define IAR_sig(context) REG_sig(nip, context)
/* Machine State Register (Supervisor) */
#define MSR_sig(context) REG_sig(msr, context)
/* Count register */
#define CTR_sig(context) REG_sig(ctr, context)
/* User's integer exception register */
#define XER_sig(context) REG_sig(xer, context)
/* Link register */
#define LR_sig(context) REG_sig(link, context)
/* Condition register */
#define CR_sig(context) REG_sig(ccr, context)
/* Float Registers access */
#define FLOAT_sig(reg_num, context) \
(((double *)((char *)((context)->uc_mcontext.regs + 48 * 4)))[reg_num])
#define FPSCR_sig(context) \
(*(int *)((char *)((context)->uc_mcontext.regs + (48 + 32 * 2) * 4)))
/* Exception Registers access */
#define DAR_sig(context) REG_sig(dar, context)
#define DSISR_sig(context) REG_sig(dsisr, context)
#define TRAP_sig(context) REG_sig(trap, context)
#endif /* linux */
#if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
#include <ucontext.h>
#define IAR_sig(context) ((context)->uc_mcontext.mc_srr0)
#define MSR_sig(context) ((context)->uc_mcontext.mc_srr1)
#define CTR_sig(context) ((context)->uc_mcontext.mc_ctr)
#define XER_sig(context) ((context)->uc_mcontext.mc_xer)
#define LR_sig(context) ((context)->uc_mcontext.mc_lr)
#define CR_sig(context) ((context)->uc_mcontext.mc_cr)
/* Exception Registers access */
#define DAR_sig(context) ((context)->uc_mcontext.mc_dar)
#define DSISR_sig(context) ((context)->uc_mcontext.mc_dsisr)
#define TRAP_sig(context) ((context)->uc_mcontext.mc_exc)
#endif /* __FreeBSD__|| __FreeBSD_kernel__ */
int cpu_signal_handler(int host_signum, void *pinfo,
void *puc)
{
siginfo_t *info = pinfo;
#if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
ucontext_t *uc = puc;
#else
struct ucontext *uc = puc;
#endif
unsigned long pc;
int is_write;
pc = IAR_sig(uc);
is_write = 0;
#if 0
/* ppc 4xx case */
if (DSISR_sig(uc) & 0x00800000) {
is_write = 1;
}
#else
if (TRAP_sig(uc) != 0x400 && (DSISR_sig(uc) & 0x02000000)) {
is_write = 1;
}
#endif
return handle_cpu_signal(pc, (unsigned long)info->si_addr,
is_write, &uc->uc_sigmask);
}
#elif defined(__alpha__)
int cpu_signal_handler(int host_signum, void *pinfo,
void *puc)
{
siginfo_t *info = pinfo;
struct ucontext *uc = puc;
uint32_t *pc = uc->uc_mcontext.sc_pc;
uint32_t insn = *pc;
int is_write = 0;
/* XXX: need kernel patch to get write flag faster */
switch (insn >> 26) {
case 0x0d: /* stw */
case 0x0e: /* stb */
case 0x0f: /* stq_u */
case 0x24: /* stf */
case 0x25: /* stg */
case 0x26: /* sts */
case 0x27: /* stt */
case 0x2c: /* stl */
case 0x2d: /* stq */
case 0x2e: /* stl_c */
case 0x2f: /* stq_c */
is_write = 1;
}
return handle_cpu_signal(pc, (unsigned long)info->si_addr,
is_write, &uc->uc_sigmask);
}
#elif defined(__sparc__)
int cpu_signal_handler(int host_signum, void *pinfo,
void *puc)
{
siginfo_t *info = pinfo;
int is_write;
uint32_t insn;
#if !defined(__arch64__) || defined(CONFIG_SOLARIS)
uint32_t *regs = (uint32_t *)(info + 1);
void *sigmask = (regs + 20);
/* XXX: is there a standard glibc define ? */
unsigned long pc = regs[1];
#else
#ifdef __linux__
struct sigcontext *sc = puc;
unsigned long pc = sc->sigc_regs.tpc;
void *sigmask = (void *)sc->sigc_mask;
#elif defined(__OpenBSD__)
struct sigcontext *uc = puc;
unsigned long pc = uc->sc_pc;
void *sigmask = (void *)(long)uc->sc_mask;
#elif defined(__NetBSD__)
ucontext_t *uc = puc;
unsigned long pc = _UC_MACHINE_PC(uc);
void *sigmask = (void *)&uc->uc_sigmask;
#endif
#endif
/* XXX: need kernel patch to get write flag faster */
is_write = 0;
insn = *(uint32_t *)pc;
if ((insn >> 30) == 3) {
switch ((insn >> 19) & 0x3f) {
case 0x05: /* stb */
case 0x15: /* stba */
case 0x06: /* sth */
case 0x16: /* stha */
case 0x04: /* st */
case 0x14: /* sta */
case 0x07: /* std */
case 0x17: /* stda */
case 0x0e: /* stx */
case 0x1e: /* stxa */
case 0x24: /* stf */
case 0x34: /* stfa */
case 0x27: /* stdf */
case 0x37: /* stdfa */
case 0x26: /* stqf */
case 0x36: /* stqfa */
case 0x25: /* stfsr */
case 0x3c: /* casa */
case 0x3e: /* casxa */
is_write = 1;
break;
}
}
return handle_cpu_signal(pc, (unsigned long)info->si_addr,
is_write, sigmask);
}
#elif defined(__arm__)
#if defined(__NetBSD__)
#include <ucontext.h>
#endif
int cpu_signal_handler(int host_signum, void *pinfo,
void *puc)
{
siginfo_t *info = pinfo;
#if defined(__NetBSD__)
ucontext_t *uc = puc;
#else
struct ucontext *uc = puc;
#endif
unsigned long pc;
int is_write;
#if defined(__NetBSD__)
pc = uc->uc_mcontext.__gregs[_REG_R15];
#elif defined(__GLIBC__) && (__GLIBC__ < 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ <= 3))
pc = uc->uc_mcontext.gregs[R15];
#else
pc = uc->uc_mcontext.arm_pc;
#endif
/* error_code is the FSR value, in which bit 11 is WnR (assuming a v6 or
* later processor; on v5 we will always report this as a read).
*/
is_write = extract32(uc->uc_mcontext.error_code, 11, 1);
return handle_cpu_signal(pc, (unsigned long)info->si_addr,
is_write,
&uc->uc_sigmask);
}
#elif defined(__aarch64__)
int cpu_signal_handler(int host_signum, void *pinfo, void *puc)
{
siginfo_t *info = pinfo;
struct ucontext *uc = puc;
uintptr_t pc = uc->uc_mcontext.pc;
uint32_t insn = *(uint32_t *)pc;
bool is_write;
/* XXX: need kernel patch to get write flag faster. */
is_write = ( (insn & 0xbfff0000) == 0x0c000000 /* C3.3.1 */
|| (insn & 0xbfe00000) == 0x0c800000 /* C3.3.2 */
|| (insn & 0xbfdf0000) == 0x0d000000 /* C3.3.3 */
|| (insn & 0xbfc00000) == 0x0d800000 /* C3.3.4 */
|| (insn & 0x3f400000) == 0x08000000 /* C3.3.6 */
|| (insn & 0x3bc00000) == 0x39000000 /* C3.3.13 */
|| (insn & 0x3fc00000) == 0x3d800000 /* ... 128bit */
/* Ingore bits 10, 11 & 21, controlling indexing. */
|| (insn & 0x3bc00000) == 0x38000000 /* C3.3.8-12 */
|| (insn & 0x3fe00000) == 0x3c800000 /* ... 128bit */
/* Ignore bits 23 & 24, controlling indexing. */
|| (insn & 0x3a400000) == 0x28000000); /* C3.3.7,14-16 */
return handle_cpu_signal(pc, (uintptr_t)info->si_addr,
is_write, &uc->uc_sigmask);
}
#elif defined(__ia64)
#ifndef __ISR_VALID
/* This ought to be in <bits/siginfo.h>... */
# define __ISR_VALID 1
#endif
int cpu_signal_handler(int host_signum, void *pinfo, void *puc)
{
siginfo_t *info = pinfo;
struct ucontext *uc = puc;
unsigned long ip;
int is_write = 0;
ip = uc->uc_mcontext.sc_ip;
switch (host_signum) {
case SIGILL:
case SIGFPE:
case SIGSEGV:
case SIGBUS:
case SIGTRAP:
if (info->si_code && (info->si_segvflags & __ISR_VALID)) {
/* ISR.W (write-access) is bit 33: */
is_write = (info->si_isr >> 33) & 1;
}
break;
default:
break;
}
return handle_cpu_signal(ip, (unsigned long)info->si_addr,
is_write,
(sigset_t *)&uc->uc_sigmask);
}
#elif defined(__s390__)
int cpu_signal_handler(int host_signum, void *pinfo,
void *puc)
{
siginfo_t *info = pinfo;
struct ucontext *uc = puc;
unsigned long pc;
uint16_t *pinsn;
int is_write = 0;
pc = uc->uc_mcontext.psw.addr;
/* ??? On linux, the non-rt signal handler has 4 (!) arguments instead
of the normal 2 arguments. The 3rd argument contains the "int_code"
from the hardware which does in fact contain the is_write value.
The rt signal handler, as far as I can tell, does not give this value
at all. Not that we could get to it from here even if it were. */
/* ??? This is not even close to complete, since it ignores all
of the read-modify-write instructions. */
pinsn = (uint16_t *)pc;
switch (pinsn[0] >> 8) {
case 0x50: /* ST */
case 0x42: /* STC */
case 0x40: /* STH */
is_write = 1;
break;
case 0xc4: /* RIL format insns */
switch (pinsn[0] & 0xf) {
case 0xf: /* STRL */
case 0xb: /* STGRL */
case 0x7: /* STHRL */
is_write = 1;
}
break;
case 0xe3: /* RXY format insns */
switch (pinsn[2] & 0xff) {
case 0x50: /* STY */
case 0x24: /* STG */
case 0x72: /* STCY */
case 0x70: /* STHY */
case 0x8e: /* STPQ */
case 0x3f: /* STRVH */
case 0x3e: /* STRV */
case 0x2f: /* STRVG */
is_write = 1;
}
break;
}
return handle_cpu_signal(pc, (unsigned long)info->si_addr,
is_write, &uc->uc_sigmask);
}
#elif defined(__mips__)
int cpu_signal_handler(int host_signum, void *pinfo,
void *puc)
{
siginfo_t *info = pinfo;
struct ucontext *uc = puc;
greg_t pc = uc->uc_mcontext.pc;
int is_write;
/* XXX: compute is_write */
is_write = 0;
return handle_cpu_signal(pc, (unsigned long)info->si_addr,
is_write, &uc->uc_sigmask);
}
#else
#error host CPU specific signal handler needed
#endif
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