[Crash-utility] [Crash-Utility][PATCH v2 03/13] Let crash change gdb context

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This patch is a preparation of gdb stack unwinding support. "set" command
is extended with gdb context change:

crash> set <pid>
or
crash> set <task>

Then the task context of crash and gdb will both be switched to
pid/task, and the following command: "bt" "gdb bt" will output
the same task context.

Co-developed-by: Aditya Gupta <adityag@xxxxxxxxxxxxx>
Co-developed-by: Alexey Makhalov <alexey.makhalov@xxxxxxxxxxxx>
Co-developed-by: Tao Liu <ltao@xxxxxxxxxx>
Signed-off-by: Tao Liu <ltao@xxxxxxxxxx>
---
 crash_target.c | 21 +++++++++++++++++----
 defs.h         |  5 ++++-
 kernel.c       | 11 ++++++++---
 task.c         | 21 +++++++++++++--------
 tools.c        |  8 ++++----
 5 files changed, 46 insertions(+), 20 deletions(-)

diff --git a/crash_target.c b/crash_target.c
index 1f62bf6..11134a7 100644
--- a/crash_target.c
+++ b/crash_target.c
@@ -28,7 +28,7 @@ void crash_target_init (void);
 extern "C" int gdb_readmem_callback(unsigned long, void *, int, int);
 extern "C" int crash_get_cpu_reg (int cpu, int regno, const char *regname,
                                   int regsize, void *val);
-
+extern "C" int gdb_change_thread_context ();
 
 /* The crash target.  */
 
@@ -63,16 +63,21 @@ public:
 
 };
 
-/* We just get all the registers, so we don't use regno.  */
 void
 crash_target::fetch_registers (struct regcache *regcache, int regno)
 {
+  int r;
   gdb_byte regval[16];
-  int cpu = inferior_ptid.tid();
   struct gdbarch *arch = regcache->arch ();
 
-  for (int r = 0; r < gdbarch_num_regs (arch); r++)
+  if (regno >= 0) {
+    r = regno;
+    goto onetime;
+  }
+
+  for (r = 0; regno == -1 && r < gdbarch_num_regs (arch); r++)
     {
+onetime:
       const char *regname = gdbarch_register_name(arch, r);
       int regsize = register_size (arch, r);
       if (regsize > sizeof (regval))
@@ -129,3 +134,11 @@ crash_target_init (void)
   /* Now, set up the frame cache. */
   reinit_frame_cache ();
 }
+
+extern "C" int
+gdb_change_thread_context ()
+{
+  target_fetch_registers(get_current_regcache(), -1);
+  reinit_frame_cache();
+  return TRUE;
+}
diff --git a/defs.h b/defs.h
index 3cb8e63..0d872b2 100644
--- a/defs.h
+++ b/defs.h
@@ -6013,7 +6013,7 @@ extern char *help_map[];
  *  task.c
  */ 
 void task_init(void);
-int set_context(ulong, ulong);
+int set_context(ulong, ulong, uint);
 void show_context(struct task_context *);
 ulong pid_to_task(ulong);
 ulong task_to_pid(ulong);
@@ -8051,4 +8051,7 @@ enum x86_64_regnum {
         LAST_REGNUM
 };
 
+/* crash_target.c */
+extern int gdb_change_thread_context ();
+
 #endif /* !GDB_COMMON */
diff --git a/kernel.c b/kernel.c
index 1728b70..78b7b1e 100644
--- a/kernel.c
+++ b/kernel.c
@@ -6494,15 +6494,20 @@ set_cpu(int cpu)
 	if (hide_offline_cpu(cpu))
 		error(FATAL, "invalid cpu number: cpu %d is OFFLINE\n", cpu);
 
-	if ((task = get_active_task(cpu))) 
-		set_context(task, NO_PID);
+	task = get_active_task(cpu);
+
+	/* Check if context is already set to given cpu */
+	if (task == CURRENT_TASK())
+		return;
+
+	if (task)
+		set_context(task, NO_PID, TRUE);
 	else
 		error(FATAL, "cannot determine active task on cpu %ld\n", cpu);
 
 	show_context(CURRENT_CONTEXT());
 }
 
-
 /*
  *  Collect the irq_desc[] entry along with its associated handler and
  *  action structures.
diff --git a/task.c b/task.c
index ebdb5be..d47d268 100644
--- a/task.c
+++ b/task.c
@@ -672,7 +672,7 @@ task_init(void)
 	if (ACTIVE()) {
 		active_pid = REMOTE() ? pc->server_pid :
 			LOCAL_ACTIVE() ? pc->program_pid : 1;
-		set_context(NO_TASK, active_pid);
+		set_context(NO_TASK, active_pid, FALSE);
 		tt->this_task = pid_to_task(active_pid);
 	}
 	else {
@@ -684,7 +684,7 @@ task_init(void)
 		else if (ELF_NOTES_VALID() && DISKDUMP_DUMPFILE())
 			map_cpus_to_prstatus_kdump_cmprs();
 		please_wait("determining panic task");
-		set_context(get_panic_context(), NO_PID);
+		set_context(get_panic_context(), NO_PID, TRUE);
 		please_wait_done();
 	}
 
@@ -2985,9 +2985,9 @@ refresh_context(ulong curtask, ulong curpid)
 	struct task_context *tc;
 
 	if (task_exists(curtask) && pid_exists(curpid)) {
-                set_context(curtask, NO_PID);
+                set_context(curtask, NO_PID, FALSE);
         } else {
-                set_context(tt->this_task, NO_PID);
+                set_context(tt->this_task, NO_PID, FALSE);
 
                 complain = TRUE;
                 if (STREQ(args[0], "set") && (argcnt == 2) &&
@@ -3053,7 +3053,7 @@ sort_context_array(void)
 	curtask = CURRENT_TASK();
 	qsort((void *)tt->context_array, (size_t)tt->running_tasks,
         	sizeof(struct task_context), sort_by_pid);
-	set_context(curtask, NO_PID);
+	set_context(curtask, NO_PID, TRUE);
 
 	sort_context_by_task();
 }
@@ -3100,7 +3100,7 @@ sort_context_array_by_last_run(void)
 	curtask = CURRENT_TASK();
 	qsort((void *)tt->context_array, (size_t)tt->running_tasks,
         	sizeof(struct task_context), sort_by_last_run);
-	set_context(curtask, NO_PID);
+	set_context(curtask, NO_PID, TRUE);
 
 	sort_context_by_task();
 }
@@ -5281,7 +5281,7 @@ comm_exists(char *s)
  *  that pid is selected.
  */
 int
-set_context(ulong task, ulong pid)
+set_context(ulong task, ulong pid, uint update_gdb_thread)
 {
 	int i;
 	struct task_context *tc;
@@ -5301,7 +5301,12 @@ set_context(ulong task, ulong pid)
 
 	if (found) {
 		CURRENT_CONTEXT() = tc;
-		return TRUE;
+
+		/* change the selected thread in gdb, according to current context */
+		if (update_gdb_thread)
+			return gdb_change_thread_context();
+		else
+			return TRUE;
 	} else {
 		if (task) 
 			error(INFO, "cannot set context for task: %lx\n", task);
diff --git a/tools.c b/tools.c
index 0f2db10..80d4244 100644
--- a/tools.c
+++ b/tools.c
@@ -1871,7 +1871,7 @@ cmd_set(void)
 				return;
 
 			if (ACTIVE()) {
-				set_context(tt->this_task, NO_PID);
+				set_context(tt->this_task, NO_PID, TRUE);
 				show_context(CURRENT_CONTEXT());
 				return;
 			}
@@ -1880,7 +1880,7 @@ cmd_set(void)
                 		error(INFO, "no panic task found!\n");
 				return;
 			}
-        		set_context(tt->panic_task, NO_PID);
+			set_context(tt->panic_task, NO_PID, TRUE);
 			show_context(CURRENT_CONTEXT());
 			return;
 
@@ -2559,14 +2559,14 @@ cmd_set(void)
 	                case STR_PID:
                                 pid = value;
                                 task = NO_TASK;
-                        	if (set_context(task, pid))
+                                if (set_context(task, pid, TRUE))
                                 	show_context(CURRENT_CONTEXT());
 	                        break;
 	
 	                case STR_TASK:
                                 task = value;
                                 pid = NO_PID;
-                                if (set_context(task, pid))
+                                if (set_context(task, pid, TRUE))
                                         show_context(CURRENT_CONTEXT()); 
 	                        break;
 	
-- 
2.40.1
--
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