Re: [Qemu-devel] [PATCH v2 01/15] gdbstub: introduce GDB processes

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

Hi Luc,

On 01/10/2018 13:56, 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 a QOM
> container named after the GDB_CPU_GROUP_NAME macro (`gdb-group[*]').
> Each occurrence of such a container implies the existence of the
> corresponding process in the GDB stub. The gdb_cpu_group_container_get()
> function can be used to create a new container.
> 
> 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 <luc.michel@greensocs.com>
> ---
>  include/exec/gdbstub.h |  8 +++++
>  gdbstub.c              | 67 ++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 75 insertions(+)
> 
> diff --git a/include/exec/gdbstub.h b/include/exec/gdbstub.h
> index 08363969c1..a3e4159bf4 100644
> --- a/include/exec/gdbstub.h
> +++ b/include/exec/gdbstub.h
> @@ -1,8 +1,10 @@
>  #ifndef GDBSTUB_H
>  #define GDBSTUB_H
>  
> +#include "qom/object.h"
> +
>  #define DEFAULT_GDBSTUB_PORT "1234"
>  
>  /* GDB breakpoint/watchpoint types */
>  #define GDB_BREAKPOINT_SW        0
>  #define GDB_BREAKPOINT_HW        1
> @@ -129,6 +131,12 @@ void gdbserver_cleanup(void);
>  extern bool gdb_has_xml;
>  
>  /* in gdbstub-xml.c, generated by scripts/feature_to_c.sh */
>  extern const char *const xml_builtin[][2];
>  
> +#define GDB_CPU_GROUP_NAME  "gdb-group"
> +
> +static inline Object *gdb_cpu_group_container_get(Object *parent)
> +{
> +    return container_get(parent, "/" GDB_CPU_GROUP_NAME "[*]");
> +}
>  #endif
> diff --git a/gdbstub.c b/gdbstub.c
> index d6ab95006c..5c86218f49 100644
> --- a/gdbstub.c
> +++ b/gdbstub.c
> @@ -295,10 +295,17 @@ typedef struct GDBRegisterState {
>      gdb_reg_cb set_reg;
>      const char *xml;
>      struct GDBRegisterState *next;
>  } GDBRegisterState;
>  
> +typedef struct GDBProcess {
> +    uint32_t pid;
> +    bool attached;
> +
> +    char target_xml[1024];

I'd add this field in the patch #7 "support to Xfer:features:read:"
where you start using it.

> +} GDBProcess;
> +
>  enum RSState {
>      RS_INACTIVE,
>      RS_IDLE,
>      RS_GETLINE,
>      RS_GETLINE_ESC,
> @@ -323,10 +330,13 @@ 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
> @@ -1750,10 +1760,24 @@ 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;
> @@ -1847,10 +1871,11 @@ 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;
> @@ -2003,10 +2028,48 @@ static const TypeInfo char_gdb_type_info = {
>      .name = TYPE_CHARDEV_GDB,
>      .parent = TYPE_CHARDEV,
>      .class_init = char_gdb_class_init,
>  };
>  
> +static void create_processes(GDBState *s)
> +{
> +    Object *container;
> +    int i = 0;
> +    char process_str[16];
> +
> +    container = object_resolve_path(GDB_CPU_GROUP_NAME "[0]", NULL);
> +
> +    while (container) {
> +        s->processes = g_renew(GDBProcess, s->processes, i + 1);
> +
> +        GDBProcess *process = &s->processes[i];
> +
> +        /* GDB process IDs -1 and 0 are reserved */
> +        process->pid = i + 1;
> +        process->attached = false;
> +        process->target_xml[0] = '\0';
> +
> +        i++;
> +        snprintf(process_str, sizeof(process_str), GDB_CPU_GROUP_NAME "[%d]", i);
> +        container = object_resolve_path(process_str, NULL);
> +    }
> +
> +    if (!s->processes) {
> +        /* No CPU group specified by the machine */
> +        create_unique_process(s);
> +    } else {
> +        s->process_num = i;
> +    }
> +}
> +
> +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;
> @@ -2055,15 +2118,19 @@ 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);
>      }
>