[PATCH v3 0/2] GDB: Support getting current task struct in UML

[PATCH v3 0/2] GDB: Support getting current task struct in UML

[Glenn Washburn]

Changes in v3:
  - Rebase onto tip.

Changes in v2:
  - Use cpu_tasks symbols instead of uml_kmalloc when determining if the
    kernel is a UML kernel.
  - Improve formatting.

Glenn

Glenn Washburn (2):
  scripts/gdb: Correct indentation in get_current_task
  scripts/gdb: Support getting current task struct in UML

 scripts/gdb/linux/cpus.py | 24 +++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)

Range-diff against v2:
1:  918bc1299bdb ! 1:  2e117b82240d scripts/gdb: Correct indentation in get_current_task
    @@ scripts/gdb/linux/cpus.py: def get_current_task(cpu):
          task_ptr_type = task_type.get_type().pointer()
      
          if utils.is_target_arch("x86"):
    --         var_ptr = gdb.parse_and_eval("&current_task")
    +-         var_ptr = gdb.parse_and_eval("&pcpu_hot.current_task")
     -         return per_cpu(var_ptr, cpu).dereference()
    -+        var_ptr = gdb.parse_and_eval("&current_task")
    ++        var_ptr = gdb.parse_and_eval("&pcpu_hot.current_task")
     +        return per_cpu(var_ptr, cpu).dereference()
          elif utils.is_target_arch("aarch64"):
     -         current_task_addr = gdb.parse_and_eval("$SP_EL0")
2:  93fc6584ea16 ! 2:  b839d611e290 scripts/gdb: Support getting current task struct in UML
    @@ scripts/gdb/linux/cpus.py: def get_current_task(cpu):
          task_ptr_type = task_type.get_type().pointer()
      
          if utils.is_target_arch("x86"):
    --        var_ptr = gdb.parse_and_eval("&current_task")
    +-        var_ptr = gdb.parse_and_eval("&pcpu_hot.current_task")
     -        return per_cpu(var_ptr, cpu).dereference()
     +        if gdb.lookup_global_symbol("cpu_tasks"):
     +            # This is a UML kernel, which stores the current task
    @@ scripts/gdb/linux/cpus.py: def get_current_task(cpu):
     +            var_ptr = gdb.parse_and_eval("(struct task_struct *)cpu_tasks[0].task")
     +            return var_ptr.dereference()
     +        else:
    -+            var_ptr = gdb.parse_and_eval("&current_task")
    ++            var_ptr = gdb.parse_and_eval("&pcpu_hot.current_task")
     +            return per_cpu(var_ptr, cpu).dereference()
          elif utils.is_target_arch("aarch64"):
              current_task_addr = gdb.parse_and_eval("$SP_EL0")
-- 
2.30.2


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[PATCH v3 1/2] scripts/gdb: Correct indentation in get_current_task

[Glenn Washburn]

There is an extra space in a couple blocks in get_current_task.
Though python does not care, let's make the spacing consistent.
Also, format better an if expression, removing unneeded parenthesis.

Signed-off-by: Glenn Washburn <development@efficientek.com>
Reviewed-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 scripts/gdb/linux/cpus.py | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/scripts/gdb/linux/cpus.py b/scripts/gdb/linux/cpus.py
index 9ee99f9fae8d..e8d2a62ff119 100644
--- a/scripts/gdb/linux/cpus.py
+++ b/scripts/gdb/linux/cpus.py
@@ -163,16 +163,16 @@ def get_current_task(cpu):
     task_ptr_type = task_type.get_type().pointer()
 
     if utils.is_target_arch("x86"):
-         var_ptr = gdb.parse_and_eval("&pcpu_hot.current_task")
-         return per_cpu(var_ptr, cpu).dereference()
+        var_ptr = gdb.parse_and_eval("&pcpu_hot.current_task")
+        return per_cpu(var_ptr, cpu).dereference()
     elif utils.is_target_arch("aarch64"):
-         current_task_addr = gdb.parse_and_eval("$SP_EL0")
-         if((current_task_addr >> 63) != 0):
-             current_task = current_task_addr.cast(task_ptr_type)
-             return current_task.dereference()
-         else:
-             raise gdb.GdbError("Sorry, obtaining the current task is not allowed "
-                                "while running in userspace(EL0)")
+        current_task_addr = gdb.parse_and_eval("$SP_EL0")
+        if (current_task_addr >> 63) != 0:
+            current_task = current_task_addr.cast(task_ptr_type)
+            return current_task.dereference()
+        else:
+            raise gdb.GdbError("Sorry, obtaining the current task is not allowed "
+                               "while running in userspace(EL0)")
     else:
         raise gdb.GdbError("Sorry, obtaining the current task is not yet "
                            "supported with this arch")
-- 
2.30.2


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[PATCH v3 2/2] scripts/gdb: Support getting current task struct in UML

[Glenn Washburn]

A running x86 UML kernel reports with architecture "i386:x86-64" as
it is a sub-architecture. However, a difference with bare-metal x86
kernels is in how it manages tasks and the current task struct. To
identify that the inferior is a UML kernel and not bare-metal, check
for the existence of the UML specific symbol "cpu_tasks" which
contains the current task struct.

Signed-off-by: Glenn Washburn <development@efficientek.com>
Reviewed-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 scripts/gdb/linux/cpus.py | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/scripts/gdb/linux/cpus.py b/scripts/gdb/linux/cpus.py
index e8d2a62ff119..255dc18cb9da 100644
--- a/scripts/gdb/linux/cpus.py
+++ b/scripts/gdb/linux/cpus.py
@@ -163,8 +163,14 @@ def get_current_task(cpu):
     task_ptr_type = task_type.get_type().pointer()
 
     if utils.is_target_arch("x86"):
-        var_ptr = gdb.parse_and_eval("&pcpu_hot.current_task")
-        return per_cpu(var_ptr, cpu).dereference()
+        if gdb.lookup_global_symbol("cpu_tasks"):
+            # This is a UML kernel, which stores the current task
+            # differently than other x86 sub architectures
+            var_ptr = gdb.parse_and_eval("(struct task_struct *)cpu_tasks[0].task")
+            return var_ptr.dereference()
+        else:
+            var_ptr = gdb.parse_and_eval("&pcpu_hot.current_task")
+            return per_cpu(var_ptr, cpu).dereference()
     elif utils.is_target_arch("aarch64"):
         current_task_addr = gdb.parse_and_eval("$SP_EL0")
         if (current_task_addr >> 63) != 0:
-- 
2.30.2


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