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c905a3680d
qemu/accel/tcg/cpu-exec.c
Daniele Buono c905a3680d cfi: Initial support for cfi-icall in QEMU 
LLVM/Clang, supports runtime checks for forward-edge Control-Flow
Integrity (CFI).

CFI on indirect function calls (cfi-icall) ensures that, in indirect
function calls, the function called is of the right signature for the
pointer type defined at compile time.

For this check to work, the code must always respect the function
signature when using function pointer, the function must be defined
at compile time, and be compiled with link-time optimization.

This rules out, for example, shared libraries that are dynamically loaded
(given that functions are not known at compile time), and code that is
dynamically generated at run-time.

This patch:

1) Introduces the CONFIG_CFI flag to support cfi in QEMU

2) Introduces a decorator to allow the definition of "sensitive"
functions, where a non-instrumented function may be called at runtime
through a pointer. The decorator will take care of disabling cfi-icall
checks on such functions, when cfi is enabled.

3) Marks functions currently in QEMU that exhibit such behavior,
in particular:
- The function in TCG that calls pre-compiled TBs
- The function in TCI that interprets instructions
- Functions in the plugin infrastructures that jump to callbacks
- Functions in util that directly call a signal handler

Signed-off-by: Daniele Buono <dbuono@linux.vnet.ibm.com>
Acked-by: Alex Bennée <alex.bennee@linaro.org
Message-Id: <20201204230615.2392-3-dbuono@linux.vnet.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-01-02 21:03:35 +01:00

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/*
* emulator main execution loop
*
* 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 2.1 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 "qemu-common.h"
#include "qemu/qemu-print.h"
#include "cpu.h"
#include "trace.h"
#include "disas/disas.h"
#include "exec/exec-all.h"
#include "tcg/tcg.h"
#include "qemu/atomic.h"
#include "qemu/compiler.h"
#include "sysemu/qtest.h"
#include "qemu/timer.h"
#include "qemu/rcu.h"
#include "exec/tb-hash.h"
#include "exec/tb-lookup.h"
#include "exec/log.h"
#include "qemu/main-loop.h"
#if defined(TARGET_I386) && !defined(CONFIG_USER_ONLY)
#include "hw/i386/apic.h"
#endif
#include "sysemu/cpus.h"
#include "exec/cpu-all.h"
#include "sysemu/cpu-timers.h"
#include "sysemu/replay.h"
/* -icount align implementation. */
typedef struct SyncClocks {
int64_t diff_clk;
int64_t last_cpu_icount;
int64_t realtime_clock;
} SyncClocks;
#if !defined(CONFIG_USER_ONLY)
/* Allow the guest to have a max 3ms advance.
* The difference between the 2 clocks could therefore
* oscillate around 0.
*/
#define VM_CLOCK_ADVANCE 3000000
#define THRESHOLD_REDUCE 1.5
#define MAX_DELAY_PRINT_RATE 2000000000LL
#define MAX_NB_PRINTS 100
static int64_t max_delay;
static int64_t max_advance;
static void align_clocks(SyncClocks *sc, CPUState *cpu)
{
int64_t cpu_icount;
if (!icount_align_option) {
return;
}
cpu_icount = cpu->icount_extra + cpu_neg(cpu)->icount_decr.u16.low;
sc->diff_clk += icount_to_ns(sc->last_cpu_icount - cpu_icount);
sc->last_cpu_icount = cpu_icount;
if (sc->diff_clk > VM_CLOCK_ADVANCE) {
#ifndef _WIN32
struct timespec sleep_delay, rem_delay;
sleep_delay.tv_sec = sc->diff_clk / 1000000000LL;
sleep_delay.tv_nsec = sc->diff_clk % 1000000000LL;
if (nanosleep(&sleep_delay, &rem_delay) < 0) {
sc->diff_clk = rem_delay.tv_sec * 1000000000LL + rem_delay.tv_nsec;
} else {
sc->diff_clk = 0;
}
#else
Sleep(sc->diff_clk / SCALE_MS);
sc->diff_clk = 0;
#endif
}
}
static void print_delay(const SyncClocks *sc)
{
static float threshold_delay;
static int64_t last_realtime_clock;
static int nb_prints;
if (icount_align_option &&
sc->realtime_clock - last_realtime_clock >= MAX_DELAY_PRINT_RATE &&
nb_prints < MAX_NB_PRINTS) {
if ((-sc->diff_clk / (float)1000000000LL > threshold_delay) ||
(-sc->diff_clk / (float)1000000000LL <
(threshold_delay - THRESHOLD_REDUCE))) {
threshold_delay = (-sc->diff_clk / 1000000000LL) + 1;
qemu_printf("Warning: The guest is now late by %.1f to %.1f seconds\n",
threshold_delay - 1,
threshold_delay);
nb_prints++;
last_realtime_clock = sc->realtime_clock;
}
}
}
static void init_delay_params(SyncClocks *sc, CPUState *cpu)
{
if (!icount_align_option) {
return;
}
sc->realtime_clock = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL_RT);
sc->diff_clk = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) - sc->realtime_clock;
sc->last_cpu_icount
= cpu->icount_extra + cpu_neg(cpu)->icount_decr.u16.low;
if (sc->diff_clk < max_delay) {
max_delay = sc->diff_clk;
}
if (sc->diff_clk > max_advance) {
max_advance = sc->diff_clk;
}
/* Print every 2s max if the guest is late. We limit the number
of printed messages to NB_PRINT_MAX(currently 100) */
print_delay(sc);
}
#else
static void align_clocks(SyncClocks *sc, const CPUState *cpu)
{
}
static void init_delay_params(SyncClocks *sc, const CPUState *cpu)
{
}
#endif /* CONFIG USER ONLY */
/* Execute a TB, and fix up the CPU state afterwards if necessary */
/*
* Disable CFI checks.
* TCG creates binary blobs at runtime, with the transformed code.
* A TB is a blob of binary code, created at runtime and called with an
* indirect function call. Since such function did not exist at compile time,
* the CFI runtime has no way to verify its signature and would fail.
* TCG is not considered a security-sensitive part of QEMU so this does not
* affect the impact of CFI in environment with high security requirements
*/
QEMU_DISABLE_CFI
static inline tcg_target_ulong cpu_tb_exec(CPUState *cpu, TranslationBlock *itb)
{
CPUArchState *env = cpu->env_ptr;
uintptr_t ret;
TranslationBlock *last_tb;
int tb_exit;
uint8_t *tb_ptr = itb->tc.ptr;
qemu_log_mask_and_addr(CPU_LOG_EXEC, itb->pc,
"Trace %d: %p ["
TARGET_FMT_lx "/" TARGET_FMT_lx "/%#x] %s\n",
cpu->cpu_index, itb->tc.ptr,
itb->cs_base, itb->pc, itb->flags,
lookup_symbol(itb->pc));
#if defined(DEBUG_DISAS)
if (qemu_loglevel_mask(CPU_LOG_TB_CPU)
&& qemu_log_in_addr_range(itb->pc)) {
FILE *logfile = qemu_log_lock();
int flags = 0;
if (qemu_loglevel_mask(CPU_LOG_TB_FPU)) {
flags |= CPU_DUMP_FPU;
}
#if defined(TARGET_I386)
flags |= CPU_DUMP_CCOP;
#endif
log_cpu_state(cpu, flags);
qemu_log_unlock(logfile);
}
#endif /* DEBUG_DISAS */
ret = tcg_qemu_tb_exec(env, tb_ptr);
cpu->can_do_io = 1;
last_tb = (TranslationBlock *)(ret & ~TB_EXIT_MASK);
tb_exit = ret & TB_EXIT_MASK;
trace_exec_tb_exit(last_tb, tb_exit);
if (tb_exit > TB_EXIT_IDX1) {
/* We didn't start executing this TB (eg because the instruction
* counter hit zero); we must restore the guest PC to the address
* of the start of the TB.
*/
CPUClass *cc = CPU_GET_CLASS(cpu);
qemu_log_mask_and_addr(CPU_LOG_EXEC, last_tb->pc,
"Stopped execution of TB chain before %p ["
TARGET_FMT_lx "] %s\n",
last_tb->tc.ptr, last_tb->pc,
lookup_symbol(last_tb->pc));
if (cc->synchronize_from_tb) {
cc->synchronize_from_tb(cpu, last_tb);
} else {
assert(cc->set_pc);
cc->set_pc(cpu, last_tb->pc);
}
}
return ret;
}
#ifndef CONFIG_USER_ONLY
/* Execute the code without caching the generated code. An interpreter
could be used if available. */
static void cpu_exec_nocache(CPUState *cpu, int max_cycles,
TranslationBlock *orig_tb, bool ignore_icount)
{
TranslationBlock *tb;
uint32_t cflags = curr_cflags() | CF_NOCACHE;
if (ignore_icount) {
cflags &= ~CF_USE_ICOUNT;
}
/* Should never happen.
We only end up here when an existing TB is too long. */
cflags |= MIN(max_cycles, CF_COUNT_MASK);
mmap_lock();
tb = tb_gen_code(cpu, orig_tb->pc, orig_tb->cs_base,
orig_tb->flags, cflags);
tb->orig_tb = orig_tb;
mmap_unlock();
/* execute the generated code */
trace_exec_tb_nocache(tb, tb->pc);
cpu_tb_exec(cpu, tb);
mmap_lock();
tb_phys_invalidate(tb, -1);
mmap_unlock();
tcg_tb_remove(tb);
}
#endif
static void cpu_exec_enter(CPUState *cpu)
{
CPUClass *cc = CPU_GET_CLASS(cpu);
if (cc->cpu_exec_enter) {
cc->cpu_exec_enter(cpu);
}
}
static void cpu_exec_exit(CPUState *cpu)
{
CPUClass *cc = CPU_GET_CLASS(cpu);
if (cc->cpu_exec_exit) {
cc->cpu_exec_exit(cpu);
}
}
void cpu_exec_step_atomic(CPUState *cpu)
{
TranslationBlock *tb;
target_ulong cs_base, pc;
uint32_t flags;
uint32_t cflags = 1;
uint32_t cf_mask = cflags & CF_HASH_MASK;
if (sigsetjmp(cpu->jmp_env, 0) == 0) {
start_exclusive();
tb = tb_lookup__cpu_state(cpu, &pc, &cs_base, &flags, cf_mask);
if (tb == NULL) {
mmap_lock();
tb = tb_gen_code(cpu, pc, cs_base, flags, cflags);
mmap_unlock();
}
/* Since we got here, we know that parallel_cpus must be true. */
parallel_cpus = false;
cpu_exec_enter(cpu);
/* execute the generated code */
trace_exec_tb(tb, pc);
cpu_tb_exec(cpu, tb);
cpu_exec_exit(cpu);
} else {
/*
* The mmap_lock is dropped by tb_gen_code if it runs out of
* memory.
*/
#ifndef CONFIG_SOFTMMU
tcg_debug_assert(!have_mmap_lock());
#endif
if (qemu_mutex_iothread_locked()) {
qemu_mutex_unlock_iothread();
}
assert_no_pages_locked();
qemu_plugin_disable_mem_helpers(cpu);
}
/*
* As we start the exclusive region before codegen we must still
* be in the region if we longjump out of either the codegen or
* the execution.
*/
g_assert(cpu_in_exclusive_context(cpu));
parallel_cpus = true;
end_exclusive();
}
struct tb_desc {
target_ulong pc;
target_ulong cs_base;
CPUArchState *env;
tb_page_addr_t phys_page1;
uint32_t flags;
uint32_t cf_mask;
uint32_t trace_vcpu_dstate;
};
static bool tb_lookup_cmp(const void *p, const void *d)
{
const TranslationBlock *tb = p;
const struct tb_desc *desc = d;
if (tb->pc == desc->pc &&
tb->page_addr[0] == desc->phys_page1 &&
tb->cs_base == desc->cs_base &&
tb->flags == desc->flags &&
tb->trace_vcpu_dstate == desc->trace_vcpu_dstate &&
(tb_cflags(tb) & (CF_HASH_MASK | CF_INVALID)) == desc->cf_mask) {
/* check next page if needed */
if (tb->page_addr[1] == -1) {
return true;
} else {
tb_page_addr_t phys_page2;
target_ulong virt_page2;
virt_page2 = (desc->pc & TARGET_PAGE_MASK) + TARGET_PAGE_SIZE;
phys_page2 = get_page_addr_code(desc->env, virt_page2);
if (tb->page_addr[1] == phys_page2) {
return true;
}
}
}
return false;
}
TranslationBlock *tb_htable_lookup(CPUState *cpu, target_ulong pc,
target_ulong cs_base, uint32_t flags,
uint32_t cf_mask)
{
tb_page_addr_t phys_pc;
struct tb_desc desc;
uint32_t h;
desc.env = (CPUArchState *)cpu->env_ptr;
desc.cs_base = cs_base;
desc.flags = flags;
desc.cf_mask = cf_mask;
desc.trace_vcpu_dstate = *cpu->trace_dstate;
desc.pc = pc;
phys_pc = get_page_addr_code(desc.env, pc);
if (phys_pc == -1) {
return NULL;
}
desc.phys_page1 = phys_pc & TARGET_PAGE_MASK;
h = tb_hash_func(phys_pc, pc, flags, cf_mask, *cpu->trace_dstate);
return qht_lookup_custom(&tb_ctx.htable, &desc, h, tb_lookup_cmp);
}
void tb_set_jmp_target(TranslationBlock *tb, int n, uintptr_t addr)
{
if (TCG_TARGET_HAS_direct_jump) {
uintptr_t offset = tb->jmp_target_arg[n];
uintptr_t tc_ptr = (uintptr_t)tb->tc.ptr;
tb_target_set_jmp_target(tc_ptr, tc_ptr + offset, addr);
} else {
tb->jmp_target_arg[n] = addr;
}
}
static inline void tb_add_jump(TranslationBlock *tb, int n,
TranslationBlock *tb_next)
{
uintptr_t old;
assert(n < ARRAY_SIZE(tb->jmp_list_next));
qemu_spin_lock(&tb_next->jmp_lock);
/* make sure the destination TB is valid */
if (tb_next->cflags & CF_INVALID) {
goto out_unlock_next;
}
/* Atomically claim the jump destination slot only if it was NULL */
old = qatomic_cmpxchg(&tb->jmp_dest[n], (uintptr_t)NULL,
(uintptr_t)tb_next);
if (old) {
goto out_unlock_next;
}
/* patch the native jump address */
tb_set_jmp_target(tb, n, (uintptr_t)tb_next->tc.ptr);
/* add in TB jmp list */
tb->jmp_list_next[n] = tb_next->jmp_list_head;
tb_next->jmp_list_head = (uintptr_t)tb | n;
qemu_spin_unlock(&tb_next->jmp_lock);
qemu_log_mask_and_addr(CPU_LOG_EXEC, tb->pc,
"Linking TBs %p [" TARGET_FMT_lx
"] index %d -> %p [" TARGET_FMT_lx "]\n",
tb->tc.ptr, tb->pc, n,
tb_next->tc.ptr, tb_next->pc);
return;
out_unlock_next:
qemu_spin_unlock(&tb_next->jmp_lock);
return;
}
static inline TranslationBlock *tb_find(CPUState *cpu,
TranslationBlock *last_tb,
int tb_exit, uint32_t cf_mask)
{
TranslationBlock *tb;
target_ulong cs_base, pc;
uint32_t flags;
tb = tb_lookup__cpu_state(cpu, &pc, &cs_base, &flags, cf_mask);
if (tb == NULL) {
mmap_lock();
tb = tb_gen_code(cpu, pc, cs_base, flags, cf_mask);
mmap_unlock();
/* We add the TB in the virtual pc hash table for the fast lookup */
qatomic_set(&cpu->tb_jmp_cache[tb_jmp_cache_hash_func(pc)], tb);
}
#ifndef CONFIG_USER_ONLY
/* We don't take care of direct jumps when address mapping changes in
* system emulation. So it's not safe to make a direct jump to a TB
* spanning two pages because the mapping for the second page can change.
*/
if (tb->page_addr[1] != -1) {
last_tb = NULL;
}
#endif
/* See if we can patch the calling TB. */
if (last_tb) {
tb_add_jump(last_tb, tb_exit, tb);
}
return tb;
}
static inline bool cpu_handle_halt(CPUState *cpu)
{
if (cpu->halted) {
#if defined(TARGET_I386) && !defined(CONFIG_USER_ONLY)
if (cpu->interrupt_request & CPU_INTERRUPT_POLL) {
X86CPU *x86_cpu = X86_CPU(cpu);
qemu_mutex_lock_iothread();
apic_poll_irq(x86_cpu->apic_state);
cpu_reset_interrupt(cpu, CPU_INTERRUPT_POLL);
qemu_mutex_unlock_iothread();
}
#endif
if (!cpu_has_work(cpu)) {
return true;
}
cpu->halted = 0;
}
return false;
}
static inline void cpu_handle_debug_exception(CPUState *cpu)
{
CPUClass *cc = CPU_GET_CLASS(cpu);
CPUWatchpoint *wp;
if (!cpu->watchpoint_hit) {
QTAILQ_FOREACH(wp, &cpu->watchpoints, entry) {
wp->flags &= ~BP_WATCHPOINT_HIT;
}
}
if (cc->debug_excp_handler) {
cc->debug_excp_handler(cpu);
}
}
static inline bool cpu_handle_exception(CPUState *cpu, int *ret)
{
if (cpu->exception_index < 0) {
#ifndef CONFIG_USER_ONLY
if (replay_has_exception()
&& cpu_neg(cpu)->icount_decr.u16.low + cpu->icount_extra == 0) {
/* try to cause an exception pending in the log */
cpu_exec_nocache(cpu, 1, tb_find(cpu, NULL, 0, curr_cflags()), true);
}
#endif
if (cpu->exception_index < 0) {
return false;
}
}
if (cpu->exception_index >= EXCP_INTERRUPT) {
/* exit request from the cpu execution loop */
*ret = cpu->exception_index;
if (*ret == EXCP_DEBUG) {
cpu_handle_debug_exception(cpu);
}
cpu->exception_index = -1;
return true;
} else {
#if defined(CONFIG_USER_ONLY)
/* if user mode only, we simulate a fake exception
which will be handled outside the cpu execution
loop */
#if defined(TARGET_I386)
CPUClass *cc = CPU_GET_CLASS(cpu);
cc->do_interrupt(cpu);
#endif
*ret = cpu->exception_index;
cpu->exception_index = -1;
return true;
#else
if (replay_exception()) {
CPUClass *cc = CPU_GET_CLASS(cpu);
qemu_mutex_lock_iothread();
cc->do_interrupt(cpu);
qemu_mutex_unlock_iothread();
cpu->exception_index = -1;
if (unlikely(cpu->singlestep_enabled)) {
/*
* After processing the exception, ensure an EXCP_DEBUG is
* raised when single-stepping so that GDB doesn't miss the
* next instruction.
*/
*ret = EXCP_DEBUG;
cpu_handle_debug_exception(cpu);
return true;
}
} else if (!replay_has_interrupt()) {
/* give a chance to iothread in replay mode */
*ret = EXCP_INTERRUPT;
return true;
}
#endif
}
return false;
}
/*
* CPU_INTERRUPT_POLL is a virtual event which gets converted into a
* "real" interrupt event later. It does not need to be recorded for
* replay purposes.
*/
static inline bool need_replay_interrupt(int interrupt_request)
{
#if defined(TARGET_I386)
return !(interrupt_request & CPU_INTERRUPT_POLL);
#else
return true;
#endif
}
static inline bool cpu_handle_interrupt(CPUState *cpu,
TranslationBlock **last_tb)
{
CPUClass *cc = CPU_GET_CLASS(cpu);
/* Clear the interrupt flag now since we're processing
* cpu->interrupt_request and cpu->exit_request.
* Ensure zeroing happens before reading cpu->exit_request or
* cpu->interrupt_request (see also smp_wmb in cpu_exit())
*/
qatomic_mb_set(&cpu_neg(cpu)->icount_decr.u16.high, 0);
if (unlikely(qatomic_read(&cpu->interrupt_request))) {
int interrupt_request;
qemu_mutex_lock_iothread();
interrupt_request = cpu->interrupt_request;
if (unlikely(cpu->singlestep_enabled & SSTEP_NOIRQ)) {
/* Mask out external interrupts for this step. */
interrupt_request &= ~CPU_INTERRUPT_SSTEP_MASK;
}
if (interrupt_request & CPU_INTERRUPT_DEBUG) {
cpu->interrupt_request &= ~CPU_INTERRUPT_DEBUG;
cpu->exception_index = EXCP_DEBUG;
qemu_mutex_unlock_iothread();
return true;
}
if (replay_mode == REPLAY_MODE_PLAY && !replay_has_interrupt()) {
/* Do nothing */
} else if (interrupt_request & CPU_INTERRUPT_HALT) {
replay_interrupt();
cpu->interrupt_request &= ~CPU_INTERRUPT_HALT;
cpu->halted = 1;
cpu->exception_index = EXCP_HLT;
qemu_mutex_unlock_iothread();
return true;
}
#if defined(TARGET_I386)
else if (interrupt_request & CPU_INTERRUPT_INIT) {
X86CPU *x86_cpu = X86_CPU(cpu);
CPUArchState *env = &x86_cpu->env;
replay_interrupt();
cpu_svm_check_intercept_param(env, SVM_EXIT_INIT, 0, 0);
do_cpu_init(x86_cpu);
cpu->exception_index = EXCP_HALTED;
qemu_mutex_unlock_iothread();
return true;
}
#else
else if (interrupt_request & CPU_INTERRUPT_RESET) {
replay_interrupt();
cpu_reset(cpu);
qemu_mutex_unlock_iothread();
return true;
}
#endif
/* The target hook has 3 exit conditions:
False when the interrupt isn't processed,
True when it is, and we should restart on a new TB,
and via longjmp via cpu_loop_exit. */
else {
if (cc->cpu_exec_interrupt &&
cc->cpu_exec_interrupt(cpu, interrupt_request)) {
if (need_replay_interrupt(interrupt_request)) {
replay_interrupt();
}
/*
* After processing the interrupt, ensure an EXCP_DEBUG is
* raised when single-stepping so that GDB doesn't miss the
* next instruction.
*/
cpu->exception_index =
(cpu->singlestep_enabled ? EXCP_DEBUG : -1);
*last_tb = NULL;
}
/* The target hook may have updated the 'cpu->interrupt_request';
* reload the 'interrupt_request' value */
interrupt_request = cpu->interrupt_request;
}
if (interrupt_request & CPU_INTERRUPT_EXITTB) {
cpu->interrupt_request &= ~CPU_INTERRUPT_EXITTB;
/* ensure that no TB jump will be modified as
the program flow was changed */
*last_tb = NULL;
}
/* If we exit via cpu_loop_exit/longjmp it is reset in cpu_exec */
qemu_mutex_unlock_iothread();
}
/* Finally, check if we need to exit to the main loop. */
if (unlikely(qatomic_read(&cpu->exit_request))
|| (icount_enabled()
&& cpu_neg(cpu)->icount_decr.u16.low + cpu->icount_extra == 0)) {
qatomic_set(&cpu->exit_request, 0);
if (cpu->exception_index == -1) {
cpu->exception_index = EXCP_INTERRUPT;
}
return true;
}
return false;
}
static inline void cpu_loop_exec_tb(CPUState *cpu, TranslationBlock *tb,
TranslationBlock **last_tb, int *tb_exit)
{
uintptr_t ret;
int32_t insns_left;
trace_exec_tb(tb, tb->pc);
ret = cpu_tb_exec(cpu, tb);
tb = (TranslationBlock *)(ret & ~TB_EXIT_MASK);
*tb_exit = ret & TB_EXIT_MASK;
if (*tb_exit != TB_EXIT_REQUESTED) {
*last_tb = tb;
return;
}
*last_tb = NULL;
insns_left = qatomic_read(&cpu_neg(cpu)->icount_decr.u32);
if (insns_left < 0) {
/* Something asked us to stop executing chained TBs; just
* continue round the main loop. Whatever requested the exit
* will also have set something else (eg exit_request or
* interrupt_request) which will be handled by
* cpu_handle_interrupt. cpu_handle_interrupt will also
* clear cpu->icount_decr.u16.high.
*/
return;
}
/* Instruction counter expired. */
assert(icount_enabled());
#ifndef CONFIG_USER_ONLY
/* Ensure global icount has gone forward */
icount_update(cpu);
/* Refill decrementer and continue execution. */
insns_left = MIN(0xffff, cpu->icount_budget);
cpu_neg(cpu)->icount_decr.u16.low = insns_left;
cpu->icount_extra = cpu->icount_budget - insns_left;
if (!cpu->icount_extra && insns_left < tb->icount) {
/* Execute any remaining instructions, then let the main loop
* handle the next event.
*/
if (insns_left > 0) {
cpu_exec_nocache(cpu, insns_left, tb, false);
}
}
#endif
}
/* main execution loop */
int cpu_exec(CPUState *cpu)
{
CPUClass *cc = CPU_GET_CLASS(cpu);
int ret;
SyncClocks sc = { 0 };
/* replay_interrupt may need current_cpu */
current_cpu = cpu;
if (cpu_handle_halt(cpu)) {
return EXCP_HALTED;
}
rcu_read_lock();
cpu_exec_enter(cpu);
/* Calculate difference between guest clock and host clock.
* This delay includes the delay of the last cycle, so
* what we have to do is sleep until it is 0. As for the
* advance/delay we gain here, we try to fix it next time.
*/
init_delay_params(&sc, cpu);
/* prepare setjmp context for exception handling */
if (sigsetjmp(cpu->jmp_env, 0) != 0) {
#if defined(__clang__)
/* Some compilers wrongly smash all local variables after
* siglongjmp. There were bug reports for gcc 4.5.0 and clang.
* Reload essential local variables here for those compilers.
* Newer versions of gcc would complain about this code (-Wclobbered). */
cpu = current_cpu;
cc = CPU_GET_CLASS(cpu);
#else /* buggy compiler */
/* Assert that the compiler does not smash local variables. */
g_assert(cpu == current_cpu);
g_assert(cc == CPU_GET_CLASS(cpu));
#endif /* buggy compiler */
#ifndef CONFIG_SOFTMMU
tcg_debug_assert(!have_mmap_lock());
#endif
if (qemu_mutex_iothread_locked()) {
qemu_mutex_unlock_iothread();
}
qemu_plugin_disable_mem_helpers(cpu);
assert_no_pages_locked();
}
/* if an exception is pending, we execute it here */
while (!cpu_handle_exception(cpu, &ret)) {
TranslationBlock *last_tb = NULL;
int tb_exit = 0;
while (!cpu_handle_interrupt(cpu, &last_tb)) {
uint32_t cflags = cpu->cflags_next_tb;
TranslationBlock *tb;
/* When requested, use an exact setting for cflags for the next
execution. This is used for icount, precise smc, and stop-
after-access watchpoints. Since this request should never
have CF_INVALID set, -1 is a convenient invalid value that
does not require tcg headers for cpu_common_reset. */
if (cflags == -1) {
cflags = curr_cflags();
} else {
cpu->cflags_next_tb = -1;
}
tb = tb_find(cpu, last_tb, tb_exit, cflags);
cpu_loop_exec_tb(cpu, tb, &last_tb, &tb_exit);
/* Try to align the host and virtual clocks
if the guest is in advance */
align_clocks(&sc, cpu);
}
}
cpu_exec_exit(cpu);
rcu_read_unlock();
return ret;
}
#ifndef CONFIG_USER_ONLY
void dump_drift_info(void)
{
if (!icount_enabled()) {
return;
}
qemu_printf("Host - Guest clock %"PRIi64" ms\n",
(cpu_get_clock() - icount_get()) / SCALE_MS);
if (icount_align_option) {
qemu_printf("Max guest delay %"PRIi64" ms\n",
-max_delay / SCALE_MS);
qemu_printf("Max guest advance %"PRIi64" ms\n",
max_advance / SCALE_MS);
} else {
qemu_printf("Max guest delay NA\n");
qemu_printf("Max guest advance NA\n");
}
}
#endif /* !CONFIG_USER_ONLY */
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