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Re: bsd-kvm target, always a thread
On Saturday 09 August 2008 13:11:16, Mark Kettenis wrote:
> > From: Pedro Alves <pedro@codesourcery.com>
> > Date: Sat, 9 Aug 2008 12:27:34 +0100
> >
> > On Saturday 09 August 2008 09:32:57, Mark Kettenis wrote:
> > > > From: Pedro Alves <pedro@codesourcery.com>
> > >
> > > Hmm, it is unfortunate that a process ID of 0 is "verboten", since
> > > that's what you are really looking at with "target kvm". And it
> > > should be possible for me to actually make all the running processes
> > > visible as kernel "threads".
> > >
> > >
> > > I guess your diff is right, although I'd prefer a less arbitrary ptid
> > > to be used. Would something like ptid_build(0, 1, 0) work?
> >
> > I'd prefer to get away without pid == 0. I'm going to
> > introduce later a "struct inferior" which holds an "int pid", and
> > we will match a ptid to a struct inferior by its ptid.pid.
> > I'd rather avoid having an inferior with pid == 0.
> >
> > Does something like this work for you?
>
> Something like that'd work fine for the OpenBSD kernel.
> Sure, I'd just think you should use something that's a bit less
> arbitrary than 42000 (which could be confused with a real process ID)
> here.
Eh, 42 carries some history. :-) It was used in several targets already,
even before I started changing then to use ptid(pid,0,tid), and always
registering a thread. monitor used 42000, remote used 42000, remote-sim
used 42, go32-nat.c uses 42. I just thought that carrying it around
would make it easier to spot what it is.
> I see that remote.c uses negative numbers for special cases.
> Would using -1 or -2 work for you?
Those are in the tid field, which I just carried around when I
made the remote target use ptid(pid,0,tid) for threads instead
of ptid(tid,0,0). The magic is in using lwp != 0. The
special -1,-2 numbers have has some binding to the remote
stub current thread.
Let's not use -1, as that conflicts a bit with the special
ptid(-1,0,0) (aka, minus_one_ptid).
I actually have a patchlet in my series to bring back the 42000:
remote.c:
/* Take advantage of the fact that the LWP field is not used, to tag
special ptids with it set to != 0. */
- magic_null_ptid = ptid_build (0, 1, -1);
- not_sent_ptid = ptid_build (0, 1, -2);
- any_thread_ptid = ptid_build (0, 1, 0);
+ magic_null_ptid = ptid_build (42000, 1, -1);
+ not_sent_ptid = ptid_build (42000, 1, -2);
+ any_thread_ptid = ptid_build (42000, 1, 0);
I guess we're numerically converging :-)
How about the attached?
With your fix for the %eip in, I now get,
(gdb) tar kvm
#0 0xd034ee05 in ?? ()
(gdb) info threads
* 1 <kvm> 0xd034ee05 in ?? ()
OK?
--
Pedro Alves
2008-08-09 Pedro Alves <pedro@codesourcery.com>
* bsd-kvm.c: Include "gdbthread.h".
(bsd_kvm_ptid): New.
(bsd_kvm_open): Add a main thread.
(bsd_kvm_close): Delete it.
(bsd_kvm_thread_alive): New.
(bsd_kvm_pid_to_str): New.
(bsd_kvm_add_target): Register bsd_kvm_thread_alive and
bsd_kvm_pid_to_str.
(bsd_kvm_add_target): Initialize bsd_kvm_ptid.
---
gdb/bsd-kvm.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 44 insertions(+)
Index: src/gdb/bsd-kvm.c
===================================================================
--- src.orig/gdb/bsd-kvm.c 2008-08-09 15:04:34.000000000 +0100
+++ src/gdb/bsd-kvm.c 2008-08-09 15:28:08.000000000 +0100
@@ -25,6 +25,7 @@
#include "target.h"
#include "value.h"
#include "gdbcore.h" /* for get_exec_file */
+#include "gdbthread.h"
#include "gdb_assert.h"
#include <fcntl.h>
@@ -56,6 +57,11 @@ static int (*bsd_kvm_supply_pcb)(struct
/* Target ops for libkvm interface. */
static struct target_ops bsd_kvm_ops;
+/* This is the ptid we use while we're connected to kvm. The kvm
+ target currently doesn't export any view of the running processes,
+ so this represents the kernel task. */
+static ptid_t bsd_kvm_ptid;
+
static void
bsd_kvm_open (char *filename, int from_tty)
{
@@ -89,6 +95,9 @@ bsd_kvm_open (char *filename, int from_t
core_kd = temp_kd;
push_target (&bsd_kvm_ops);
+ add_thread_silent (bsd_kvm_ptid);
+ inferior_ptid = bsd_kvm_ptid;
+
target_fetch_registers (get_current_regcache (), -1);
reinit_frame_cache ();
@@ -104,6 +113,9 @@ bsd_kvm_close (int quitting)
warning (("%s"), kvm_geterr(core_kd));
core_kd = NULL;
}
+
+ inferior_ptid = null_ptid;
+ delete_thread_silent (bsd_kvm_ptid);
}
static LONGEST
@@ -297,6 +309,20 @@ bsd_kvm_pcb_cmd (char *arg, int fromtty)
print_stack_frame (get_selected_frame (NULL), -1, 1);
}
+static int
+bsd_kvm_thread_alive (ptid_t ptid)
+{
+ return 1;
+}
+
+static char *
+bsd_kvm_pid_to_str (ptid_t ptid)
+{
+ static char buf[64];
+ xsnprintf (buf, sizeof buf, "<kvm>");
+ return buf;
+}
+
/* Add the libkvm interface to the list of all possible targets and
register CUPPLY_PCB as the architecture-specific process control
block interpreter. */
@@ -316,6 +342,8 @@ Optionally specify the filename of a cor
bsd_kvm_ops.to_fetch_registers = bsd_kvm_fetch_registers;
bsd_kvm_ops.to_xfer_partial = bsd_kvm_xfer_partial;
bsd_kvm_ops.to_files_info = bsd_kvm_files_info;
+ bsd_kvm_ops.to_thread_alive = bsd_kvm_thread_alive;
+ bsd_kvm_ops.to_pid_to_str = bsd_kvm_pid_to_str;
bsd_kvm_ops.to_stratum = process_stratum;
bsd_kvm_ops.to_has_memory = 1;
bsd_kvm_ops.to_has_stack = 1;
@@ -335,4 +363,20 @@ Generic command for manipulating the ker
add_cmd ("pcb", class_obscure, bsd_kvm_pcb_cmd,
/* i18n: PCB == "Process Control Block" */
_("Set current context from pcb address"), &bsd_kvm_cmdlist);
+
+ /* Some notes on the ptid usage on this target.
+
+ The pid field represents the kvm inferior instance. Currently,
+ we don't support multiple kvm inferiors, but we start at 1
+ anyway. The lwp field is set to != 0, in case the core wants to
+ refer to the whole kvm inferior with ptid(1,0,0).
+
+ If kvm is made to export running processes as gdb threads,
+ the following form can be used:
+ ptid (1, 1, 0) -> kvm inferior 1, in kernel
+ ptid (1, 1, 1) -> kvm inferior 1, process 1
+ ptid (1, 1, 2) -> kvm inferior 1, process 2
+ ptid (1, 1, n) -> kvm inferior 1, process n
+ */
+ bsd_kvm_ptid = ptid_build (1, 1, 0);
}