From dc9586823f3e06867344e6cf88741688c2c7737f Mon Sep 17 00:00:00 2001
From: Barry Song <song.bao.hua@hisilicon.com>
Date: Thu, 6 May 2021 18:05:06 -0700
Subject: scripts/gdb: document lx_current is only supported by x86
Patch series "scripts/gdb: clarify the platforms supporting lx_current and add arm64 support", v2.
lx_current depends on per_cpu current_task variable which exists on x86
only. so it actually works on x86 only. the 1st patch documents this
clearly; the 2nd patch adds support for arm64.
This patch (of 2):
x86 is the only architecture which has per_cpu current_task:
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.
Link: https://lkml.kernel.org/r/20210314203444.15188-1-song.bao.hua@hisilicon.com
Link: https://lkml.kernel.org/r/20210314203444.15188-2-song.bao.hua@hisilicon.com
Signed-off-by: Barry Song <song.bao.hua@hisilicon.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Kieran Bingham <kbingham@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
Documentation/dev-tools/gdb-kernel-debugging.rst | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
(limited to 'Documentation/dev-tools/gdb-kernel-debugging.rst')
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
--
cgit