Merge tag 'pull-tcg-20231004' of https://gitlab.com/rth7680/qemu into staging

[mirror_qemu.git] / util / coroutine-sigaltstack.c

diff --git a/util/coroutine-sigaltstack.c b/util/coroutine-sigaltstack.c
index a7c33665538b6e8ad32e5fb13474b73f1cf03cb2..037d6416c4aead14a37afdfa054c222c0848f618 100644 (file)
--- a/util/coroutine-sigaltstack.c
+++ b/util/coroutine-sigaltstack.c
@@ -22,19 +22,23 @@
  */
 
 /* XXX Is there a nicer way to disable glibc's stack check for longjmp? */
-#ifdef _FORTIFY_SOURCE
 #undef _FORTIFY_SOURCE
-#endif
+#define _FORTIFY_SOURCE 0
+
 #include "qemu/osdep.h"
 #include <pthread.h>
-#include "qemu-common.h"
 #include "qemu/coroutine_int.h"
 
+#ifdef CONFIG_SAFESTACK
+#error "SafeStack is not compatible with code run in alternate signal stacks"
+#endif
+
 typedef struct {
     Coroutine base;
     void *stack;
+    size_t stack_size;
     sigjmp_buf env;
-} CoroutineUContext;
+} CoroutineSigAltStack;
 
 /**
  * Per-thread coroutine bookkeeping
@@ -44,7 +48,7 @@ typedef struct {
     Coroutine *current;
 
     /** The default coroutine */
-    CoroutineUContext leader;
+    CoroutineSigAltStack leader;
 
     /** Information for the signal handler (trampoline) */
     sigjmp_buf tr_reenter;
@@ -89,7 +93,7 @@ static void __attribute__((constructor)) coroutine_init(void)
  * (from the signal handler when it is not signal handling, read ahead
  * for more information).
  */
-static void coroutine_bootstrap(CoroutineUContext *self, Coroutine *co)
+static void coroutine_bootstrap(CoroutineSigAltStack *self, Coroutine *co)
 {
     /* Initialize longjmp environment and switch back the caller */
     if (!sigsetjmp(self->env, 0)) {
@@ -109,7 +113,7 @@ static void coroutine_bootstrap(CoroutineUContext *self, Coroutine *co)
  */
 static void coroutine_trampoline(int signal)
 {
-    CoroutineUContext *self;
+    CoroutineSigAltStack *self;
     Coroutine *co;
     CoroutineThreadState *coTS;
 
@@ -143,8 +147,7 @@ static void coroutine_trampoline(int signal)
 
 Coroutine *qemu_coroutine_new(void)
 {
-    const size_t stack_size = 1 << 20;
-    CoroutineUContext *co;
+    CoroutineSigAltStack *co;
     CoroutineThreadState *coTS;
     struct sigaction sa;
     struct sigaction osa;
@@ -153,6 +156,7 @@ Coroutine *qemu_coroutine_new(void)
     sigset_t sigs;
     sigset_t osigs;
     sigjmp_buf old_env;
+    static pthread_mutex_t sigusr2_mutex = PTHREAD_MUTEX_INITIALIZER;
 
     /* The way to manipulate stack is with the sigaltstack function. We
      * prepare a stack, with it delivering a signal to ourselves and then
@@ -164,7 +168,8 @@ Coroutine *qemu_coroutine_new(void)
      */
 
     co = g_malloc0(sizeof(*co));
-    co->stack = g_malloc(stack_size);
+    co->stack_size = COROUTINE_STACK_SIZE;
+    co->stack = qemu_alloc_stack(&co->stack_size);
     co->base.entry_arg = &old_env; /* stash away our jmp_buf */
 
     coTS = coroutine_get_thread_state();
@@ -181,6 +186,12 @@ Coroutine *qemu_coroutine_new(void)
     sa.sa_handler = coroutine_trampoline;
     sigfillset(&sa.sa_mask);
     sa.sa_flags = SA_ONSTACK;
+
+    /*
+     * sigaction() is a process-global operation.  We must not run
+     * this code in multiple threads at once.
+     */
+    pthread_mutex_lock(&sigusr2_mutex);
     if (sigaction(SIGUSR2, &sa, &osa) != 0) {
         abort();
     }
@@ -189,7 +200,7 @@ Coroutine *qemu_coroutine_new(void)
      * Set the new stack.
      */
     ss.ss_sp = co->stack;
-    ss.ss_size = stack_size;
+    ss.ss_size = co->stack_size;
     ss.ss_flags = 0;
     if (sigaltstack(&ss, &oss) < 0) {
         abort();
@@ -229,6 +240,8 @@ Coroutine *qemu_coroutine_new(void)
      * Restore the old SIGUSR2 signal handler and mask
      */
     sigaction(SIGUSR2, &osa, NULL);
+    pthread_mutex_unlock(&sigusr2_mutex);
+
     pthread_sigmask(SIG_SETMASK, &osigs, NULL);
 
     /*
@@ -251,17 +264,17 @@ Coroutine *qemu_coroutine_new(void)
 
 void qemu_coroutine_delete(Coroutine *co_)
 {
-    CoroutineUContext *co = DO_UPCAST(CoroutineUContext, base, co_);
+    CoroutineSigAltStack *co = DO_UPCAST(CoroutineSigAltStack, base, co_);
 
-    g_free(co->stack);
+    qemu_free_stack(co->stack, co->stack_size);
     g_free(co);
 }
 
 CoroutineAction qemu_coroutine_switch(Coroutine *from_, Coroutine *to_,
                                       CoroutineAction action)
 {
-    CoroutineUContext *from = DO_UPCAST(CoroutineUContext, base, from_);
-    CoroutineUContext *to = DO_UPCAST(CoroutineUContext, base, to_);
+    CoroutineSigAltStack *from = DO_UPCAST(CoroutineSigAltStack, base, from_);
+    CoroutineSigAltStack *to = DO_UPCAST(CoroutineSigAltStack, base, to_);
     CoroutineThreadState *s = coroutine_get_thread_state();
     int ret;