From: Barry Song <song.bao.hua@hisilicon.com>
To: <corbet@lwn.net>, <linux-doc@vger.kernel.org>,
<jan.kiszka@siemens.com>, <kbingham@kernel.org>
Cc: <linux-kernel@vger.kernel.org>, <linuxarm@openeuler.org>,
Barry Song <song.bao.hua@hisilicon.com>
Subject: [PATCH] scripts/gdb: document lx_current is only supported by x86
Date: Mon, 22 Feb 2021 10:35:27 +1300 [thread overview]
Message-ID: <20210221213527.22076-1-song.bao.hua@hisilicon.com> (raw)
lx_current depends on the per_cpu current_task which exists on x86 only:
arch$ git grep current_task | grep -i per_cpu
x86/include/asm/current.h:DECLARE_PER_CPU(struct task_struct *, current_task);
x86/kernel/cpu/common.c:DEFINE_PER_CPU(struct task_struct *, current_task) ____cacheline_aligned =
x86/kernel/cpu/common.c:EXPORT_PER_CPU_SYMBOL(current_task);
x86/kernel/cpu/common.c:DEFINE_PER_CPU(struct task_struct *, current_task) = &init_task;
x86/kernel/cpu/common.c:EXPORT_PER_CPU_SYMBOL(current_task);
x86/kernel/smpboot.c: per_cpu(current_task, cpu) = idle;
On other architectures, lx_current() will lead to a python exception:
(gdb) p $lx_current().pid
Python Exception <class 'gdb.error'> No symbol "current_task" in current context.:
Error occurred in Python: No symbol "current_task" in current context.
To avoid more people struggling and wasting time in other architectures,
document it.
Cc: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Barry Song <song.bao.hua@hisilicon.com>
---
Documentation/dev-tools/gdb-kernel-debugging.rst | 2 +-
scripts/gdb/linux/cpus.py | 10 ++++++++--
2 files changed, 9 insertions(+), 3 deletions(-)
diff --git a/Documentation/dev-tools/gdb-kernel-debugging.rst b/Documentation/dev-tools/gdb-kernel-debugging.rst
index 4756f6b3a04e..1586901b683c 100644
--- a/Documentation/dev-tools/gdb-kernel-debugging.rst
+++ b/Documentation/dev-tools/gdb-kernel-debugging.rst
@@ -114,7 +114,7 @@ Examples of using the Linux-provided gdb helpers
[ 0.000000] BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] reserved
....
-- Examine fields of the current task struct::
+- Examine fields of the current task struct(supported by x86 only)::
(gdb) p $lx_current().pid
$1 = 4998
diff --git a/scripts/gdb/linux/cpus.py b/scripts/gdb/linux/cpus.py
index 008e62f3190d..f382762509d3 100644
--- a/scripts/gdb/linux/cpus.py
+++ b/scripts/gdb/linux/cpus.py
@@ -156,6 +156,13 @@ Note that VAR has to be quoted as string."""
PerCpu()
+def get_current_task(cpu):
+ if utils.is_target_arch("x86"):
+ var_ptr = gdb.parse_and_eval("¤t_task")
+ return per_cpu(var_ptr, cpu).dereference()
+ else:
+ raise gdb.GdbError("Sorry, obtaining the current task is not yet "
+ "supported with this arch")
class LxCurrentFunc(gdb.Function):
"""Return current task.
@@ -167,8 +174,7 @@ number. If CPU is omitted, the CPU of the current context is used."""
super(LxCurrentFunc, self).__init__("lx_current")
def invoke(self, cpu=-1):
- var_ptr = gdb.parse_and_eval("¤t_task")
- return per_cpu(var_ptr, cpu).dereference()
+ return get_current_task(cpu)
LxCurrentFunc()
--
2.25.1
next reply other threads:[~2021-02-21 21:42 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-21 21:35 Barry Song [this message]
2021-02-22 11:06 ` [PATCH] scripts/gdb: document lx_current is only supported by x86 Kieran Bingham
2021-02-22 21:18 ` Song Bao Hua (Barry Song)
2021-02-23 7:26 ` Jan Kiszka
2021-02-23 8:36 ` Song Bao Hua (Barry Song)
2021-02-23 21:27 ` Song Bao Hua (Barry Song)
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