Re: [PATCH v2] Implement basic threading support in the NetBSD target

Kamil Rytarowski
2020-03-30T21:19:08Z

Ping?

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
>