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List:       gdb-patches
Subject:    [PATCH v2] Implement basic threading support in the NetBSD target
From:       n54 () gmx ! com (Kamil Rytarowski)
Date:       2020-03-30 21:17:27
Message-ID: 2c845809-674b-1f48-5922-580e73567386 () gmx ! com
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On 26.03.2020 04:16, Kamil Rytarowski wrote:
> Use sysctl(3) as the portable interface to prompt NetBSD threads on
> all supported NetBSD versions. In future newer versions could switch
> to PT_LWPSTATUS ptrace(2) API that will be supported on NetBSD 10.0
> and newer.
>
> Implement as part of nbsd_nat_target:
>  - thread_name()         - read descriptive thread name
>  - thread_alive()        - check whether a thread is alive
>  - post_attach()         - updates the list of threads after attach
>  - update_thread_list()  - updates the list of threads
>  - pid_to_str()          - translates ptid to a descriptive string
>
> There are two local static functions:
>  - nbsd_thread_lister()  - generic LWP lister for a specified pid
>  - nbsd_add_threads()    - utility to update the list of threads
>
> Now, GDB on NetBSD can attach to a multithreaded process, spawn
> a multithreaded process, list threads, print their LWP+PID numbers
> and descriptive thread names.
>
> gdb/ChangeLog:
>
>        * nbsd-nat.h (struct thread_info): Add forward declaration.
>        (nbsd_nat_target::thread_alive): Add.
>        (nbsd_nat_target::thread_name): Likewise.
>        (nbsd_nat_target::update_thread_list): Likewise.
>        (update_thread_list::post_attach): Likewise.
>        (post_attach::pid_to_str): Likewise.
>        * nbsd-nat.c: Include "gdbthread.h" and "inferior.h".
>        (nbsd_thread_lister): Add.
>        (nbsd_nat_target::thread_alive): Likewise.
>        (nbsd_nat_target::thread_name): Likewise.
>        (nbsd_add_threads): Likewise.
>        (update_thread_list::post_attach): Likewise.
>        (nbsd_nat_target::update_thread_list): Likewise.
>        (post_attach::pid_to_str): Likewise.
> ---
>  gdb/ChangeLog  |  17 +++++
>  gdb/nbsd-nat.c | 166 +++++++++++++++++++++++++++++++++++++++++++++++++
>  gdb/nbsd-nat.h |   8 +++
>  3 files changed, 191 insertions(+)
>
> diff --git a/gdb/ChangeLog b/gdb/ChangeLog
> index 1ee58a541cb..f31a7cf236c 100644
> --- a/gdb/ChangeLog
> +++ b/gdb/ChangeLog
> @@ -1,3 +1,20 @@
> +2020-03-25  Kamil Rytarowski  <n54@gmx.com>
> +
> +	* nbsd-nat.h (struct thread_info): Add forward declaration.
> +	(nbsd_nat_target::thread_alive): Add.
> +	(nbsd_nat_target::thread_name): Likewise.
> +	(nbsd_nat_target::update_thread_list): Likewise.
> +	(update_thread_list::post_attach): Likewise.
> +	(post_attach::pid_to_str): Likewise.
> +	* nbsd-nat.c: Include "gdbthread.h" and "inferior.h".
> +	(nbsd_thread_lister): Add.
> +	(nbsd_nat_target::thread_alive): Likewise.
> +	(nbsd_nat_target::thread_name): Likewise.
> +	(nbsd_add_threads): Likewise.
> +	(update_thread_list::post_attach): Likewise.
> +	(nbsd_nat_target::update_thread_list): Likewise.
> +	(post_attach::pid_to_str): Likewise.
> +
>  2020-03-25  Tom Tromey  <tom@tromey.com>
>
>  	* compile/compile-object-load.c (get_out_value_type): Mention
> diff --git a/gdb/nbsd-nat.c b/gdb/nbsd-nat.c
> index 326bbe3aec3..945699ccfbe 100644
> --- a/gdb/nbsd-nat.c
> +++ b/gdb/nbsd-nat.c
> @@ -20,6 +20,8 @@
>  #include "defs.h"
>
>  #include "nbsd-nat.h"
> +#include "gdbthread.h"
> +#include "inferior.h"
>
>  #include <sys/types.h>
>  #include <sys/ptrace.h>
> @@ -39,3 +41,167 @@ nbsd_nat_target::pid_to_exec_file (int pid)
>      return NULL;
>    return buf;
>  }
> +
> +/* Generic thread (LWP) lister within a specified process.  The callback
> +   parameters is a C++ function that is called for each detected thread.  */
> +
> +static void
> +nbsd_thread_lister (const pid_t pid,
> +		    std::function<bool (const struct kinfo_lwp *)> callback)
> +{
> +  int mib[5] = {CTL_KERN, KERN_LWP, pid, sizeof (struct kinfo_lwp), 0};
> +  size_t size;
> +
> +  if (sysctl (mib, ARRAY_SIZE (mib), NULL, &size, NULL, 0) == -1 || size == 0)
> +    perror_with_name (("sysctl"));
> +
> +  mib[4] = size / sizeof (size_t);
> +
> +  gdb::unique_xmalloc_ptr<struct kinfo_lwp> kl
> +    ((struct kinfo_lwp *) xcalloc (size, 1));
> +  if (kl == NULL)
> +    perror_with_name (("calloc"));
> +
> +  if (sysctl (mib, ARRAY_SIZE (mib), kl.get (), &size, NULL, 0) == -1 ||
> +      size == 0)
> +    perror_with_name (("sysctl"));
> +
> +  for (size_t i = 0; i < size / sizeof (struct kinfo_lwp); i++)
> +    {
> +      struct kinfo_lwp *l = &kl.get ()[i];
> +
> +      /* Return true if the specified thread is alive.  */
> +      auto lwp_alive =
> +	[&l]()
> +	{
> +	  switch (l->l_stat)
> +	    {
> +	    case LSSLEEP:
> +	    case LSRUN:
> +	    case LSONPROC:
> +	    case LSSTOP:
> +	    case LSSUSPENDED:
> +	      return true;
> +	    default:
> +	      return false;
> +	    }
> +	};
> +
> +      /* Ignore embryonic or demised threads.  */
> +      if (!lwp_alive ())
> +	continue;
> +
> +      if (callback (l))
> +	break;
> +    }
> +}
> +
> +/* Return true if PTID is still active in the inferior.  */
> +
> +bool
> +nbsd_nat_target::thread_alive (ptid_t ptid)
> +{
> +  pid_t pid = ptid.pid ();
> +  int lwp = ptid.lwp ();
> +  bool found = false;
> +
> +  auto fn =
> +    [&lwp, &found] (const struct kinfo_lwp *kl)
> +    {
> +      if (kl->l_lid == lwp)
> +	{
> +	  found = true;
> +	  return true;
> +	}
> +      return false;
> +    };
> +
> +  nbsd_thread_lister (pid, fn);
> +
> +  return found;
> +}
> +
> +/* Return the name assigned to a thread by an application.  Returns
> +   the string in a static buffer.  */
> +
> +const char *
> +nbsd_nat_target::thread_name (struct thread_info *thr)
> +{
> +  ptid_t ptid = thr->ptid;
> +  pid_t pid = ptid.pid ();
> +  int lwp = ptid.lwp ();
> +
> +  static char buf[KI_LNAMELEN] = {};
> +
> +  auto fn =
> +    [&lwp] (const struct kinfo_lwp *kl)
> +    {
> +      if (kl->l_lid == lwp)
> +	{
> +	  xsnprintf (buf, sizeof buf, "%s", kl->l_name);
> +	  return true;
> +	}
> +      return false;
> +    };
> +
> +  nbsd_thread_lister (pid, fn);
> +
> +  return buf;
> +}
> +
> +/* Implement the "post_attach" target_ops method.  */
> +
> +static void
> +nbsd_add_threads (nbsd_nat_target *target, pid_t pid)
> +{
> +  auto fn =
> +    [&target, &pid] (const struct kinfo_lwp *kl)
> +    {
> +      ptid_t ptid = ptid_t (pid, kl->l_lid, 0);
> +      if (!in_thread_list (target, ptid))
> +	{
> +	  if (inferior_ptid.lwp () == 0)
> +	    thread_change_ptid (target, inferior_ptid, ptid);
> +	  else
> +	    add_thread (target, ptid);
> +	}
> +      return false;
> +    };
> +
> +  nbsd_thread_lister (pid, fn);
> +}
> +
> +/* Implement the "post_attach" target_ops method.  */
> +
> +void
> +nbsd_nat_target::post_attach (int pid)
> +{
> +  nbsd_add_threads (this, pid);
> +}
> +
> +/* Implement the "update_thread_list" target_ops method.  */
> +
> +void
> +nbsd_nat_target::update_thread_list ()
> +{
> +  prune_threads ();
> +
> +  nbsd_add_threads (this, inferior_ptid.pid ());
> +}
> +
> +/* Convert PTID to a string.  */
> +
> +std::string
> +nbsd_nat_target::pid_to_str (ptid_t ptid)
> +{
> +  int lwp = ptid.lwp ();
> +
> +  if (lwp != 0)
> +    {
> +      pid_t pid = ptid.pid ();
> +
> +      return string_printf ("LWP %d of process %d", lwp, pid);
> +    }
> +
> +  return normal_pid_to_str (ptid);
> +}
> diff --git a/gdb/nbsd-nat.h b/gdb/nbsd-nat.h
> index a752fbe572d..3606048cd07 100644
> --- a/gdb/nbsd-nat.h
> +++ b/gdb/nbsd-nat.h
> @@ -22,11 +22,19 @@
>
>  #include "inf-ptrace.h"
>
> +struct thread_info;
> +
>  /* A prototype NetBSD target.  */
>
>  struct nbsd_nat_target : public inf_ptrace_target
>  {
>    char *pid_to_exec_file (int pid) override;
> +
> +  bool thread_alive (ptid_t ptid) override;
> +  const char *thread_name (struct thread_info *thr) override;
> +  void post_attach (int pid) override;
> +  void update_thread_list () override;
> +  std::string pid_to_str (ptid_t ptid) override;
>  };
>
>  #endif /* nbsd-nat.h */
> --
> 2.25.0
>


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