Re: [Qemu-devel] [PATCH v3 02/16] gdbstub: introduce GDB processes

[Alistair]

On 10/26/18 1:16 AM, Luc Michel wrote:
> Add a structure GDBProcess that represent processes from the GDB
> semantic point of view.
>
> CPUs can be split into different processes, by grouping them under
> different cpu-cluster objects.  Each occurrence of a cpu-cluster object
> implies the existence of the corresponding process in the GDB stub. The
> GDB process ID is derived from the corresponding cluster ID as follows:
>
>    GDB PID = cluster ID + 1
>
> This is because PIDs -1 and 0 are reserved in GDB and cannot be used by
> processes.
>
> When no such container are found, all the CPUs are put in a unique GDB
> process (create_unique_process()). This is also the case when compiled
> in user mode, where multi-processes do not make much sense for now.
>
> Signed-off-by: Luc Michel <address@hidden>
> ---
>   gdbstub.c | 75 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 75 insertions(+)
>
> diff --git a/gdbstub.c b/gdbstub.c
> index c4e4f9f082..096ac8e99c 100644
> --- a/gdbstub.c
> +++ b/gdbstub.c
> @@ -27,10 +27,11 @@
>   #include "monitor/monitor.h"
>   #include "chardev/char.h"
>   #include "chardev/char-fe.h"
>   #include "sysemu/sysemu.h"
>   #include "exec/gdbstub.h"
> +#include "hw/cpu/cluster.h"
>   #endif
>   
>   #define MAX_PACKET_LENGTH 4096
>   
>   #include "qemu/sockets.h"
> @@ -294,10 +295,15 @@ typedef struct GDBRegisterState {
>       gdb_reg_cb set_reg;
>       const char *xml;
>       struct GDBRegisterState *next;
>   } GDBRegisterState;
>   
> +typedef struct GDBProcess {
> +    uint32_t pid;
> +    bool attached;
> +} GDBProcess;
> +
>   enum RSState {
>       RS_INACTIVE,
>       RS_IDLE,
>       RS_GETLINE,
>       RS_GETLINE_ESC,
> @@ -322,10 +328,13 @@ typedef struct GDBState {
>       int running_state;
>   #else
>       CharBackend chr;
>       Chardev *mon_chr;
>   #endif
> +    bool multiprocess;
> +    GDBProcess *processes;
> +    int process_num;
>       char syscall_buf[256];
>       gdb_syscall_complete_cb current_syscall_cb;
>   } GDBState;
>   
>   /* By default use no IRQs and no timers while single stepping so as to
> @@ -1749,10 +1758,24 @@ void gdb_exit(CPUArchState *env, int code)
>   #ifndef CONFIG_USER_ONLY
>     qemu_chr_fe_deinit(&s->chr, true);
>   #endif
>   }
>   
> +/*
> + * Create a unique process containing all the CPUs.
> + */
> +static void create_unique_process(GDBState *s)
> +{
> +    GDBProcess *process;
> +
> +    s->processes = g_malloc0(sizeof(GDBProcess));
> +    s->process_num = 1;
> +    process = &s->processes[0];
> +
> +    process->pid = 1;
> +}
> +
>   #ifdef CONFIG_USER_ONLY
>   int
>   gdb_handlesig(CPUState *cpu, int sig)
>   {
>       GDBState *s;
> @@ -1846,10 +1869,11 @@ static bool gdb_accept(void)
>       }
>   
>       s = g_malloc0(sizeof(GDBState));
>       s->c_cpu = first_cpu;
>       s->g_cpu = first_cpu;
> +    create_unique_process(s);
>       s->fd = fd;
>       gdb_has_xml = false;
>   
>       gdbserver_state = s;
>       return true;
> @@ -2002,10 +2026,57 @@ static const TypeInfo char_gdb_type_info = {
>       .name = TYPE_CHARDEV_GDB,
>       .parent = TYPE_CHARDEV,
>       .class_init = char_gdb_class_init,
>   };
>   
> +static int find_cpu_clusters(Object *child, void *opaque)
> +{
> +    if (object_dynamic_cast(child, TYPE_CPU_CLUSTER)) {
> +        GDBState *s = (GDBState *) opaque;
> +        CPUClusterState *cluster = CPU_CLUSTER(child);
> +
> +        s->processes = g_renew(GDBProcess, s->processes, ++s->process_num);
> +
> +        GDBProcess *process = &s->processes[s->process_num - 1];

Variables shouldn't be declared mid code.

Otherwise:

Acked-by: Alistair Francis <address@hidden>

Alistair

> +
> +        /* GDB process IDs -1 and 0 are reserved */
> +        process->pid = cluster->cluster_id + 1;
> +        process->attached = false;
> +        return 0;
> +    }
> +
> +    return object_child_foreach(child, find_cpu_clusters, opaque);
> +}
> +
> +static int pid_order(const void *a, const void *b)
> +{
> +    GDBProcess *pa = (GDBProcess *) a;
> +    GDBProcess *pb = (GDBProcess *) b;
> +
> +    return pa->pid - pb->pid;
> +}
> +
> +static void create_processes(GDBState *s)
> +{
> +    object_child_foreach(object_get_root(), find_cpu_clusters, s);
> +
> +    if (!s->processes) {
> +        /* No CPU cluster specified by the machine */
> +        create_unique_process(s);
> +    } else {
> +        /* Sort by PID */
> +        qsort(s->processes, s->process_num, sizeof(s->processes[0]), 
> pid_order);
> +    }
> +}
> +
> +static void cleanup_processes(GDBState *s)
> +{
> +    g_free(s->processes);
> +    s->process_num = 0;
> +    s->processes = NULL;
> +}
> +
>   int gdbserver_start(const char *device)
>   {
>       trace_gdbstub_op_start(device);
>   
>       GDBState *s;
> @@ -2058,15 +2129,19 @@ int gdbserver_start(const char *device)
>                                      NULL, &error_abort);
>           monitor_init(mon_chr, 0);
>       } else {
>           qemu_chr_fe_deinit(&s->chr, true);
>           mon_chr = s->mon_chr;
> +        cleanup_processes(s);
>           memset(s, 0, sizeof(GDBState));
>           s->mon_chr = mon_chr;
>       }
>       s->c_cpu = first_cpu;
>       s->g_cpu = first_cpu;
> +
> +    create_processes(s);
> +
>       if (chr) {
>           qemu_chr_fe_init(&s->chr, chr, &error_abort);
>           qemu_chr_fe_set_handlers(&s->chr, gdb_chr_can_receive, 
> gdb_chr_receive,
>                                    gdb_chr_event, NULL, NULL, NULL, true);
>       }