Merge tag 'pull-maintainer-updates-060324-1' of https://gitlab.com/stsquad/qemu into staging

maintainer updates (tests, gdbstub, plugins):

  - expand QOS_PATH_MAX_ELEMENT_SIZE to avoid LTO issues
  - support fork-follow-mode in gdbstub
  - new thread-safe scoreboard API for TCG plugins
  - suppress showing opcodes in plugin disassembly

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* tag 'pull-maintainer-updates-060324-1' of https://gitlab.com/stsquad/qemu: (29 commits)
  target/riscv: honour show_opcodes when disassembling
  target/loongarch: honour show_opcodes when disassembling
  disas/hppa: honour show_opcodes
  disas: introduce show_opcodes
  plugins: cleanup codepath for previous inline operation
  plugins: remove non per_vcpu inline operation from API
  contrib/plugins/howvec: migrate to new per_vcpu API
  contrib/plugins/hotblocks: migrate to new per_vcpu API
  tests/plugin/bb: migrate to new per_vcpu API
  tests/plugin/insn: migrate to new per_vcpu API
  tests/plugin/mem: migrate to new per_vcpu API
  tests/plugin: add test plugin for inline operations
  plugins: add inline operation per vcpu
  plugins: implement inline operation relative to cpu_index
  plugins: define qemu_plugin_u64
  plugins: scoreboard API
  tests/tcg: Add two follow-fork-mode tests
  gdbstub: Implement follow-fork-mode child
  gdbstub: Introduce gdb_handle_detach_user()
  gdbstub: Introduce gdb_handle_set_thread_user()
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 240 insertions, 4 deletions

diff --git a/gdbstub/user.c b/gdbstub/user.c
index 14918d1a21..7f9f19a124 100644
--- a/gdbstub/user.c
+++ b/gdbstub/user.c
@@ -25,6 +25,61 @@
 #define GDB_NR_SYSCALLS 1024
 typedef unsigned long GDBSyscallsMask[BITS_TO_LONGS(GDB_NR_SYSCALLS)];
 
+/*
+ * Forked child talks to its parent in order to let GDB enforce the
+ * follow-fork-mode. This happens inside a start_exclusive() section, so that
+ * the other threads, which may be forking too, do not interfere. The
+ * implementation relies on GDB not sending $vCont until it has detached
+ * either from the parent (follow-fork-mode child) or from the child
+ * (follow-fork-mode parent).
+ *
+ * The parent and the child share the GDB socket; at any given time only one
+ * of them is allowed to use it, as is reflected in the respective fork_state.
+ * This is negotiated via the fork_sockets pair as a reaction to $Hg.
+ *
+ * Below is a short summary of the possible state transitions:
+ *
+ *     ENABLED                     : Terminal state.
+ *     DISABLED                    : Terminal state.
+ *     ACTIVE                      : Parent initial state.
+ *     INACTIVE                    : Child initial state.
+ *     ACTIVE       -> DEACTIVATING: On $Hg.
+ *     ACTIVE       -> ENABLING    : On $D.
+ *     ACTIVE       -> DISABLING   : On $D.
+ *     ACTIVE       -> DISABLED    : On communication error.
+ *     DEACTIVATING -> INACTIVE    : On gdb_read_byte() return.
+ *     DEACTIVATING -> DISABLED    : On communication error.
+ *     INACTIVE     -> ACTIVE      : On $Hg in the peer.
+ *     INACTIVE     -> ENABLE      : On $D in the peer.
+ *     INACTIVE     -> DISABLE     : On $D in the peer.
+ *     INACTIVE     -> DISABLED    : On communication error.
+ *     ENABLING     -> ENABLED     : On gdb_read_byte() return.
+ *     ENABLING     -> DISABLED    : On communication error.
+ *     DISABLING    -> DISABLED    : On gdb_read_byte() return.
+ */
+enum GDBForkState {
+    /* Fully owning the GDB socket. */
+    GDB_FORK_ENABLED,
+    /* Working with the GDB socket; the peer is inactive. */
+    GDB_FORK_ACTIVE,
+    /* Handing off the GDB socket to the peer. */
+    GDB_FORK_DEACTIVATING,
+    /* The peer is working with the GDB socket. */
+    GDB_FORK_INACTIVE,
+    /* Asking the peer to close its GDB socket fd. */
+    GDB_FORK_ENABLING,
+    /* Asking the peer to take over, closing our GDB socket fd. */
+    GDB_FORK_DISABLING,
+    /* The peer has taken over, our GDB socket fd is closed. */
+    GDB_FORK_DISABLED,
+};
+
+enum GDBForkMessage {
+    GDB_FORK_ACTIVATE = 'a',
+    GDB_FORK_ENABLE = 'e',
+    GDB_FORK_DISABLE = 'd',
+};
+
 /* User-mode specific state */
 typedef struct {
     int fd;
@@ -36,6 +91,10 @@ typedef struct {
      */
     bool catch_all_syscalls;
     GDBSyscallsMask catch_syscalls_mask;
+    bool fork_events;
+    enum GDBForkState fork_state;
+    int fork_sockets[2];
+    pid_t fork_peer_pid, fork_peer_tid;
 } GDBUserState;
 
 static GDBUserState gdbserver_user_state;
@@ -356,16 +415,193 @@ int gdbserver_start(const char *port_or_path)
     return -1;
 }
 
-/* Disable gdb stub for child processes.  */
-void gdbserver_fork(CPUState *cpu)
+void gdbserver_fork_start(void)
 {
     if (!gdbserver_state.init || gdbserver_user_state.fd < 0) {
         return;
     }
+    if (!gdbserver_user_state.fork_events ||
+            qemu_socketpair(AF_UNIX, SOCK_STREAM, 0,
+                            gdbserver_user_state.fork_sockets) < 0) {
+        gdbserver_user_state.fork_state = GDB_FORK_DISABLED;
+        return;
+    }
+    gdbserver_user_state.fork_state = GDB_FORK_INACTIVE;
+    gdbserver_user_state.fork_peer_pid = getpid();
+    gdbserver_user_state.fork_peer_tid = qemu_get_thread_id();
+}
+
+static void disable_gdbstub(CPUState *thread_cpu)
+{
+    CPUState *cpu;
+
     close(gdbserver_user_state.fd);
     gdbserver_user_state.fd = -1;
-    cpu_breakpoint_remove_all(cpu, BP_GDB);
-    /* no cpu_watchpoint_remove_all for user-mode */
+    CPU_FOREACH(cpu) {
+        cpu_breakpoint_remove_all(cpu, BP_GDB);
+        /* no cpu_watchpoint_remove_all for user-mode */
+        cpu_single_step(cpu, 0);
+    }
+    tb_flush(thread_cpu);
+}
+
+void gdbserver_fork_end(CPUState *cpu, pid_t pid)
+{
+    char b;
+    int fd;
+
+    if (!gdbserver_state.init || gdbserver_user_state.fd < 0) {
+        return;
+    }
+
+    if (pid == -1) {
+        if (gdbserver_user_state.fork_state != GDB_FORK_DISABLED) {
+            g_assert(gdbserver_user_state.fork_state == GDB_FORK_INACTIVE);
+            close(gdbserver_user_state.fork_sockets[0]);
+            close(gdbserver_user_state.fork_sockets[1]);
+        }
+        return;
+    }
+
+    if (gdbserver_user_state.fork_state == GDB_FORK_DISABLED) {
+        if (pid == 0) {
+            disable_gdbstub(cpu);
+        }
+        return;
+    }
+
+    if (pid == 0) {
+        close(gdbserver_user_state.fork_sockets[0]);
+        fd = gdbserver_user_state.fork_sockets[1];
+        g_assert(gdbserver_state.process_num == 1);
+        g_assert(gdbserver_state.processes[0].pid ==
+                     gdbserver_user_state.fork_peer_pid);
+        g_assert(gdbserver_state.processes[0].attached);
+        gdbserver_state.processes[0].pid = getpid();
+    } else {
+        close(gdbserver_user_state.fork_sockets[1]);
+        fd = gdbserver_user_state.fork_sockets[0];
+        gdbserver_user_state.fork_state = GDB_FORK_ACTIVE;
+        gdbserver_user_state.fork_peer_pid = pid;
+        gdbserver_user_state.fork_peer_tid = pid;
+
+        if (!gdbserver_state.allow_stop_reply) {
+            goto fail;
+        }
+        g_string_printf(gdbserver_state.str_buf,
+                        "T%02xfork:p%02x.%02x;thread:p%02x.%02x;",
+                        gdb_target_signal_to_gdb(gdb_target_sigtrap()),
+                        pid, pid, (int)getpid(), qemu_get_thread_id());
+        gdb_put_strbuf();
+    }
+
+    gdbserver_state.state = RS_IDLE;
+    gdbserver_state.allow_stop_reply = false;
+    gdbserver_user_state.running_state = 0;
+    for (;;) {
+        switch (gdbserver_user_state.fork_state) {
+        case GDB_FORK_ENABLED:
+            if (gdbserver_user_state.running_state) {
+                return;
+            }
+            QEMU_FALLTHROUGH;
+        case GDB_FORK_ACTIVE:
+            if (read(gdbserver_user_state.fd, &b, 1) != 1) {
+                goto fail;
+            }
+            gdb_read_byte(b);
+            break;
+        case GDB_FORK_DEACTIVATING:
+            b = GDB_FORK_ACTIVATE;
+            if (write(fd, &b, 1) != 1) {
+                goto fail;
+            }
+            gdbserver_user_state.fork_state = GDB_FORK_INACTIVE;
+            break;
+        case GDB_FORK_INACTIVE:
+            if (read(fd, &b, 1) != 1) {
+                goto fail;
+            }
+            switch (b) {
+            case GDB_FORK_ACTIVATE:
+                gdbserver_user_state.fork_state = GDB_FORK_ACTIVE;
+                break;
+            case GDB_FORK_ENABLE:
+                close(fd);
+                gdbserver_user_state.fork_state = GDB_FORK_ENABLED;
+                break;
+            case GDB_FORK_DISABLE:
+                gdbserver_user_state.fork_state = GDB_FORK_DISABLED;
+                break;
+            default:
+                g_assert_not_reached();
+            }
+            break;
+        case GDB_FORK_ENABLING:
+            b = GDB_FORK_DISABLE;
+            if (write(fd, &b, 1) != 1) {
+                goto fail;
+            }
+            close(fd);
+            gdbserver_user_state.fork_state = GDB_FORK_ENABLED;
+            break;
+        case GDB_FORK_DISABLING:
+            b = GDB_FORK_ENABLE;
+            if (write(fd, &b, 1) != 1) {
+                goto fail;
+            }
+            gdbserver_user_state.fork_state = GDB_FORK_DISABLED;
+            break;
+        case GDB_FORK_DISABLED:
+            close(fd);
+            disable_gdbstub(cpu);
+            return;
+        default:
+            g_assert_not_reached();
+        }
+    }
+
+fail:
+    close(fd);
+    if (pid == 0) {
+        disable_gdbstub(cpu);
+    }
+}
+
+void gdb_handle_query_supported_user(const char *gdb_supported)
+{
+    if (strstr(gdb_supported, "fork-events+")) {
+        gdbserver_user_state.fork_events = true;
+    }
+    g_string_append(gdbserver_state.str_buf, ";fork-events+");
+}
+
+bool gdb_handle_set_thread_user(uint32_t pid, uint32_t tid)
+{
+    if (gdbserver_user_state.fork_state == GDB_FORK_ACTIVE &&
+            pid == gdbserver_user_state.fork_peer_pid &&
+            tid == gdbserver_user_state.fork_peer_tid) {
+        gdbserver_user_state.fork_state = GDB_FORK_DEACTIVATING;
+        gdb_put_packet("OK");
+        return true;
+    }
+    return false;
+}
+
+bool gdb_handle_detach_user(uint32_t pid)
+{
+    bool enable;
+
+    if (gdbserver_user_state.fork_state == GDB_FORK_ACTIVE) {
+        enable = pid == gdbserver_user_state.fork_peer_pid;
+        if (enable || pid == getpid()) {
+            gdbserver_user_state.fork_state = enable ? GDB_FORK_ENABLING :
+                                                       GDB_FORK_DISABLING;
+            gdb_put_packet("OK");
+            return true;
+        }
+    }
+    return false;
 }
 
 /*