[Qemu-devel] [6096] User-mode GDB stub improvements - handle signals

[Aurelien Jarno]

Revision: 6096
          http://svn.sv.gnu.org/viewvc/?view=rev&root=qemu&revision=6096
Author:   aurel32
Date:     2008-12-18 22:44:13 +0000 (Thu, 18 Dec 2008)

Log Message:
-----------
User-mode GDB stub improvements - handle signals

Handle signals in the user-mode GDB stub.  Report them to GDB, and
allow it to change or cancel them.  Also correct the protocol numbering;
it happens to match Linux numbering for SIGINT and SIGTRAP, but that's
just good fortune.

Signed-off-by: Daniel Jacobowitz <address@hidden>
Acked-by: Edgar E. Iglesias <address@hidden>
Signed-off-by: Aurelien Jarno <address@hidden>

Modified Paths:
--------------
    trunk/gdbstub.c
    trunk/gdbstub.h
    trunk/linux-user/signal.c

Modified: trunk/gdbstub.c
===================================================================
--- trunk/gdbstub.c     2008-12-18 22:44:04 UTC (rev 6095)
+++ trunk/gdbstub.c     2008-12-18 22:44:13 UTC (rev 6096)
@@ -38,18 +38,213 @@
 #define MAX_PACKET_LENGTH 4096
 
 #include "qemu_socket.h"
-#ifdef _WIN32
-/* XXX: these constants may be independent of the host ones even for Unix */
-#ifndef SIGTRAP
-#define SIGTRAP 5
-#endif
-#ifndef SIGINT
-#define SIGINT 2
-#endif
+
+
+enum {
+    GDB_SIGNAL_0 = 0,
+    GDB_SIGNAL_INT = 2,
+    GDB_SIGNAL_TRAP = 5,
+    GDB_SIGNAL_UNKNOWN = 143
+};
+
+#ifdef CONFIG_USER_ONLY
+
+/* Map target signal numbers to GDB protocol signal numbers and vice
+ * versa.  For user emulation's currently supported systems, we can
+ * assume most signals are defined.
+ */
+
+static int gdb_signal_table[] = {
+    0,
+    TARGET_SIGHUP,
+    TARGET_SIGINT,
+    TARGET_SIGQUIT,
+    TARGET_SIGILL,
+    TARGET_SIGTRAP,
+    TARGET_SIGABRT,
+    -1, /* SIGEMT */
+    TARGET_SIGFPE,
+    TARGET_SIGKILL,
+    TARGET_SIGBUS,
+    TARGET_SIGSEGV,
+    TARGET_SIGSYS,
+    TARGET_SIGPIPE,
+    TARGET_SIGALRM,
+    TARGET_SIGTERM,
+    TARGET_SIGURG,
+    TARGET_SIGSTOP,
+    TARGET_SIGTSTP,
+    TARGET_SIGCONT,
+    TARGET_SIGCHLD,
+    TARGET_SIGTTIN,
+    TARGET_SIGTTOU,
+    TARGET_SIGIO,
+    TARGET_SIGXCPU,
+    TARGET_SIGXFSZ,
+    TARGET_SIGVTALRM,
+    TARGET_SIGPROF,
+    TARGET_SIGWINCH,
+    -1, /* SIGLOST */
+    TARGET_SIGUSR1,
+    TARGET_SIGUSR2,
+    TARGET_SIGPWR,
+    -1, /* SIGPOLL */
+    -1,
+    -1,
+    -1,
+    -1,
+    -1,
+    -1,
+    -1,
+    -1,
+    -1,
+    -1,
+    -1,
+    __SIGRTMIN + 1,
+    __SIGRTMIN + 2,
+    __SIGRTMIN + 3,
+    __SIGRTMIN + 4,
+    __SIGRTMIN + 5,
+    __SIGRTMIN + 6,
+    __SIGRTMIN + 7,
+    __SIGRTMIN + 8,
+    __SIGRTMIN + 9,
+    __SIGRTMIN + 10,
+    __SIGRTMIN + 11,
+    __SIGRTMIN + 12,
+    __SIGRTMIN + 13,
+    __SIGRTMIN + 14,
+    __SIGRTMIN + 15,
+    __SIGRTMIN + 16,
+    __SIGRTMIN + 17,
+    __SIGRTMIN + 18,
+    __SIGRTMIN + 19,
+    __SIGRTMIN + 20,
+    __SIGRTMIN + 21,
+    __SIGRTMIN + 22,
+    __SIGRTMIN + 23,
+    __SIGRTMIN + 24,
+    __SIGRTMIN + 25,
+    __SIGRTMIN + 26,
+    __SIGRTMIN + 27,
+    __SIGRTMIN + 28,
+    __SIGRTMIN + 29,
+    __SIGRTMIN + 30,
+    __SIGRTMIN + 31,
+    -1, /* SIGCANCEL */
+    __SIGRTMIN,
+    __SIGRTMIN + 32,
+    __SIGRTMIN + 33,
+    __SIGRTMIN + 34,
+    __SIGRTMIN + 35,
+    __SIGRTMIN + 36,
+    __SIGRTMIN + 37,
+    __SIGRTMIN + 38,
+    __SIGRTMIN + 39,
+    __SIGRTMIN + 40,
+    __SIGRTMIN + 41,
+    __SIGRTMIN + 42,
+    __SIGRTMIN + 43,
+    __SIGRTMIN + 44,
+    __SIGRTMIN + 45,
+    __SIGRTMIN + 46,
+    __SIGRTMIN + 47,
+    __SIGRTMIN + 48,
+    __SIGRTMIN + 49,
+    __SIGRTMIN + 50,
+    __SIGRTMIN + 51,
+    __SIGRTMIN + 52,
+    __SIGRTMIN + 53,
+    __SIGRTMIN + 54,
+    __SIGRTMIN + 55,
+    __SIGRTMIN + 56,
+    __SIGRTMIN + 57,
+    __SIGRTMIN + 58,
+    __SIGRTMIN + 59,
+    __SIGRTMIN + 60,
+    __SIGRTMIN + 61,
+    __SIGRTMIN + 62,
+    __SIGRTMIN + 63,
+    __SIGRTMIN + 64,
+    __SIGRTMIN + 65,
+    __SIGRTMIN + 66,
+    __SIGRTMIN + 67,
+    __SIGRTMIN + 68,
+    __SIGRTMIN + 69,
+    __SIGRTMIN + 70,
+    __SIGRTMIN + 71,
+    __SIGRTMIN + 72,
+    __SIGRTMIN + 73,
+    __SIGRTMIN + 74,
+    __SIGRTMIN + 75,
+    __SIGRTMIN + 76,
+    __SIGRTMIN + 77,
+    __SIGRTMIN + 78,
+    __SIGRTMIN + 79,
+    __SIGRTMIN + 80,
+    __SIGRTMIN + 81,
+    __SIGRTMIN + 82,
+    __SIGRTMIN + 83,
+    __SIGRTMIN + 84,
+    __SIGRTMIN + 85,
+    __SIGRTMIN + 86,
+    __SIGRTMIN + 87,
+    __SIGRTMIN + 88,
+    __SIGRTMIN + 89,
+    __SIGRTMIN + 90,
+    __SIGRTMIN + 91,
+    __SIGRTMIN + 92,
+    __SIGRTMIN + 93,
+    __SIGRTMIN + 94,
+    __SIGRTMIN + 95,
+    -1, /* SIGINFO */
+    -1, /* UNKNOWN */
+    -1, /* DEFAULT */
+    -1,
+    -1,
+    -1,
+    -1,
+    -1,
+    -1
+};
 #else
-#include <signal.h>
+/* In system mode we only need SIGINT and SIGTRAP; other signals
+   are not yet supported.  */
+
+enum {
+    TARGET_SIGINT = 2,
+    TARGET_SIGTRAP = 5
+};
+
+static int gdb_signal_table[] = {
+    -1,
+    -1,
+    TARGET_SIGINT,
+    -1,
+    -1,
+    TARGET_SIGTRAP
+};
 #endif
 
+#ifdef CONFIG_USER_ONLY
+static int target_signal_to_gdb (int sig)
+{
+    int i;
+    for (i = 0; i < ARRAY_SIZE (gdb_signal_table); i++)
+        if (gdb_signal_table[i] == sig)
+            return i;
+    return GDB_SIGNAL_UNKNOWN;
+}
+#endif
+
+static int gdb_signal_to_target (int sig)
+{
+    if (sig < ARRAY_SIZE (gdb_signal_table))
+        return gdb_signal_table[sig];
+    else
+        return -1;
+}
+
 //#define DEBUG_GDB
 
 typedef struct GDBRegisterState {
@@ -1300,7 +1495,7 @@
     switch(ch) {
     case '?':
         /* TODO: Make this return the correct value for user-mode.  */
-        snprintf(buf, sizeof(buf), "T%02xthread:%02x;", SIGTRAP,
+        snprintf(buf, sizeof(buf), "T%02xthread:%02x;", GDB_SIGNAL_TRAP,
                  s->c_cpu->cpu_index+1);
         put_packet(s, buf);
         /* Remove all the breakpoints when this query is issued,
@@ -1331,10 +1526,13 @@
             s->c_cpu->pc = addr;
 #endif
         }
+        s->signal = 0;
         gdb_continue(s);
        return RS_IDLE;
     case 'C':
-        s->signal = strtoul(p, (char **)&p, 16);
+        s->signal = gdb_signal_to_target (strtoul(p, (char **)&p, 16));
+        if (s->signal == -1)
+            s->signal = 0;
         gdb_continue(s);
         return RS_IDLE;
     case 'k':
@@ -1692,16 +1890,16 @@
             }
             snprintf(buf, sizeof(buf),
                      "T%02xthread:%02x;%swatch:" TARGET_FMT_lx ";",
-                     SIGTRAP, env->cpu_index+1, type,
+                     GDB_SIGNAL_TRAP, env->cpu_index+1, type,
                      env->watchpoint_hit->vaddr);
             put_packet(s, buf);
             env->watchpoint_hit = NULL;
             return;
         }
        tb_flush(env);
-        ret = SIGTRAP;
+        ret = GDB_SIGNAL_TRAP;
     } else if (reason == EXCP_INTERRUPT) {
-        ret = SIGINT;
+        ret = GDB_SIGNAL_INT;
     } else {
         ret = 0;
     }
@@ -1853,6 +2051,19 @@
 
 #ifdef CONFIG_USER_ONLY
 int
+gdb_queuesig (void)
+{
+    GDBState *s;
+
+    s = gdbserver_state;
+
+    if (gdbserver_fd < 0 || s->fd < 0)
+        return 0;
+    else
+        return 1;
+}
+
+int
 gdb_handlesig (CPUState *env, int sig)
 {
   GDBState *s;
@@ -1869,7 +2080,7 @@
 
   if (sig != 0)
     {
-      snprintf(buf, sizeof(buf), "S%02x", sig);
+      snprintf(buf, sizeof(buf), "S%02x", target_signal_to_gdb (sig));
       put_packet(s, buf);
     }
   /* put_packet() might have detected that the peer terminated the 
@@ -1915,7 +2126,20 @@
   put_packet(s, buf);
 }
 
+/* Tell the remote gdb that the process has exited due to SIG.  */
+void gdb_signalled(CPUState *env, int sig)
+{
+  GDBState *s;
+  char buf[4];
 
+  s = gdbserver_state;
+  if (gdbserver_fd < 0 || s->fd < 0)
+    return;
+
+  snprintf(buf, sizeof(buf), "X%02x", target_signal_to_gdb (sig));
+  put_packet(s, buf);
+}
+
 static void gdb_accept(void)
 {
     GDBState *s;

Modified: trunk/gdbstub.h
===================================================================
--- trunk/gdbstub.h     2008-12-18 22:44:04 UTC (rev 6095)
+++ trunk/gdbstub.h     2008-12-18 22:44:13 UTC (rev 6096)
@@ -10,8 +10,10 @@
 int use_gdb_syscalls(void);
 void gdb_set_stop_cpu(CPUState *env);
 #ifdef CONFIG_USER_ONLY
+int gdb_queuesig (void);
 int gdb_handlesig (CPUState *, int);
 void gdb_exit(CPUState *, int);
+void gdb_signalled(CPUState *, int);
 int gdbserver_start(int);
 void gdbserver_fork(CPUState *);
 #else

Modified: trunk/linux-user/signal.c
===================================================================
--- trunk/linux-user/signal.c   2008-12-18 22:44:04 UTC (rev 6095)
+++ trunk/linux-user/signal.c   2008-12-18 22:44:13 UTC (rev 6096)
@@ -264,6 +264,26 @@
             (void *)(long)tswapl(tinfo->_sifields._rt._sigval.sival_ptr);
 }
 
+static int fatal_signal (int sig)
+{
+    switch (sig) {
+    case TARGET_SIGCHLD:
+    case TARGET_SIGURG:
+    case TARGET_SIGWINCH:
+        /* Ignored by default.  */
+        return 0;
+    case TARGET_SIGCONT:
+    case TARGET_SIGSTOP:
+    case TARGET_SIGTSTP:
+    case TARGET_SIGTTIN:
+    case TARGET_SIGTTOU:
+        /* Job control signals.  */
+        return 0;
+    default:
+        return 1;
+    }
+}
+
 void signal_init(void)
 {
     struct sigaction act;
@@ -298,10 +318,12 @@
         }
         /* If there's already a handler installed then something has
            gone horribly wrong, so don't even try to handle that case.  */
-        /* Install some handlers for our own use.  */
-        if (host_sig == SIGSEGV || host_sig == SIGBUS) {
+        /* Install some handlers for our own use.  We need at least
+           SIGSEGV and SIGBUS, to detect exceptions.  We can not just
+           trap all signals because it affects syscall interrupt
+           behavior.  But do trap all default-fatal signals.  */
+        if (fatal_signal (i))
             sigaction(host_sig, &act, NULL);
-        }
     }
 }
 
@@ -332,6 +354,7 @@
     fprintf(stderr, "qemu: uncaught target signal %d (%s) - exiting\n",
             sig, strsignal(host_sig));
 #if 1
+    gdb_signalled(thread_env, sig);
     _exit(-host_sig);
 #else
     {
@@ -353,14 +376,16 @@
     struct emulated_sigtable *k;
     struct sigqueue *q, **pq;
     abi_ulong handler;
+    int queue;
 
 #if defined(DEBUG_SIGNAL)
     fprintf(stderr, "queue_signal: sig=%d\n",
             sig);
 #endif
     k = &ts->sigtab[sig - 1];
+    queue = gdb_queuesig ();
     handler = sigact_table[sig - 1]._sa_handler;
-    if (handler == TARGET_SIG_DFL) {
+    if (!queue && handler == TARGET_SIG_DFL) {
         if (sig == TARGET_SIGTSTP || sig == TARGET_SIGTTIN || sig == 
TARGET_SIGTTOU) {
             kill(getpid(),SIGSTOP);
             return 0;
@@ -374,10 +399,10 @@
         } else {
             return 0; /* indicate ignored */
         }
-    } else if (handler == TARGET_SIG_IGN) {
+    } else if (!queue && handler == TARGET_SIG_IGN) {
         /* ignore signal */
         return 0;
-    } else if (handler == TARGET_SIG_ERR) {
+    } else if (!queue && handler == TARGET_SIG_ERR) {
         force_sig(sig);
     } else {
         pq = &k->first;
@@ -417,7 +442,8 @@
 
     /* the CPU emulator uses some host signals to detect exceptions,
        we we forward to it some signals */
-    if (host_signum == SIGSEGV || host_signum == SIGBUS) {
+    if ((host_signum == SIGSEGV || host_signum == SIGBUS)
+        && info->si_code == SI_KERNEL) {
         if (cpu_signal_handler(host_signum, info, puc))
             return;
     }
@@ -544,7 +570,10 @@
             if (k->_sa_handler == TARGET_SIG_IGN) {
                 act1.sa_sigaction = (void *)SIG_IGN;
             } else if (k->_sa_handler == TARGET_SIG_DFL) {
-                act1.sa_sigaction = (void *)SIG_DFL;
+                if (fatal_signal (sig))
+                    act1.sa_sigaction = host_signal_handler;
+                else
+                    act1.sa_sigaction = (void *)SIG_DFL;
             } else {
                 act1.sa_sigaction = host_signal_handler;
             }
@@ -3107,17 +3136,21 @@
 
     sig = gdb_handlesig (cpu_env, sig);
     if (!sig) {
-        fprintf (stderr, "Lost signal\n");
-        abort();
+        sa = NULL;
+        handler = TARGET_SIG_IGN;
+    } else {
+        sa = &sigact_table[sig - 1];
+        handler = sa->_sa_handler;
     }
 
-    sa = &sigact_table[sig - 1];
-    handler = sa->_sa_handler;
     if (handler == TARGET_SIG_DFL) {
-        /* default handler : ignore some signal. The other are fatal */
-        if (sig != TARGET_SIGCHLD &&
-            sig != TARGET_SIGURG &&
-            sig != TARGET_SIGWINCH) {
+        /* default handler : ignore some signal. The other are job control or 
fatal */
+        if (sig == TARGET_SIGTSTP || sig == TARGET_SIGTTIN || sig == 
TARGET_SIGTTOU) {
+            kill(getpid(),SIGSTOP);
+        } else if (sig != TARGET_SIGCHLD &&
+                   sig != TARGET_SIGURG &&
+                   sig != TARGET_SIGWINCH &&
+                   sig != TARGET_SIGCONT) {
             force_sig(sig);
         }
     } else if (handler == TARGET_SIG_IGN) {