The patch titled
Subject: scripts/gdb: add $lx_per_cpu_ptr()
has been added to the -mm mm-nonmm-unstable branch. Its filename is
scripts-gdb-add-lx_per_cpu_ptr.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/scripts-gdb-add-lx_per_cpu_ptr.patch
This patch will later appear in the mm-nonmm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Brendan Jackman <jackmanb@xxxxxxxxxx>
Subject: scripts/gdb: add $lx_per_cpu_ptr()
Date: Thu, 20 Feb 2025 12:23:40 +0000
We currently have $lx_per_cpu() which works fine for stuff that kernel
code would access via per_cpu(). But this doesn't work for stuff that
kernel code accesses via per_cpu_ptr():
(gdb) p $lx_per_cpu(node_data[1].node_zones[2]->per_cpu_pageset)
Cannot access memory at address 0xffff11105fbd6c28
This is because we take the address of the pointer and use that as the
offset, instead of using the stored value.
Add a GDB version that mirrors the kernel API, which uses the pointer
value.
To be consistent with per_cpu_ptr(), we need to return the pointer value
instead of dereferencing it for the user. Therefore, move the existing
dereference out of the per_cpu() Python helper and do that only in the
$lx_per_cpu() implementation.
Link: https://lkml.kernel.org/r/20250220-lx-per-cpu-ptr-v2-1-945dee8d8d38@xxxxxxxxxx
Signed-off-by: Brendan Jackman <jackmanb@xxxxxxxxxx>
Reviewed-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
Cc: Florian Rommel <mail@xxxxxxxxxxxx>
Cc: Kieran Bingham <kbingham@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
scripts/gdb/linux/cpus.py | 22 ++++++++++++++++++++--
1 file changed, 20 insertions(+), 2 deletions(-)
--- a/scripts/gdb/linux/cpus.py~scripts-gdb-add-lx_per_cpu_ptr
+++ a/scripts/gdb/linux/cpus.py
@@ -46,7 +46,7 @@ def per_cpu(var_ptr, cpu):
# !CONFIG_SMP case
offset = 0
pointer = var_ptr.cast(utils.get_long_type()) + offset
- return pointer.cast(var_ptr.type).dereference()
+ return pointer.cast(var_ptr.type)
cpu_mask = {}
@@ -149,11 +149,29 @@ Note that VAR has to be quoted as string
super(PerCpu, self).__init__("lx_per_cpu")
def invoke(self, var, cpu=-1):
- return per_cpu(var.address, cpu)
+ return per_cpu(var.address, cpu).dereference()
PerCpu()
+
+class PerCpuPtr(gdb.Function):
+ """Return per-cpu pointer.
+
+$lx_per_cpu_ptr("VAR"[, CPU]): Return the per-cpu pointer called VAR for the
+given CPU number. If CPU is omitted, the CPU of the current context is used.
+Note that VAR has to be quoted as string."""
+
+ def __init__(self):
+ super(PerCpuPtr, self).__init__("lx_per_cpu_ptr")
+
+ def invoke(self, var, cpu=-1):
+ return per_cpu(var, cpu)
+
+
+PerCpuPtr()
+
+
def get_current_task(cpu):
task_ptr_type = task_type.get_type().pointer()
_
Patches currently in -mm which might be from jackmanb@xxxxxxxxxx are
mm-mmu_gather-update-comment-on-rcu-freeing.patch
selftests-mm-report-errno-when-things-fail-in-gup_longterm.patch
selftests-mm-fix-assumption-that-sudo-is-present.patch
selftests-mm-skip-uffd-stress-if-userfaultfd-not-available.patch
selftests-mm-skip-uffd-wp-mremap-if-userfaultfd-not-available.patch
selftests-mm-uffd-rename-nr_cpus-nr_threads.patch
selftests-mm-print-some-details-when-uffd-stress-gets-bad-params.patch
selftests-mm-dont-fail-uffd-stress-if-too-many-cpus.patch
selftests-mm-skip-map_populate-on-weird-filesystems.patch
selftests-mm-skip-gup_longerm-tests-on-weird-filesystems.patch
scripts-gdb-add-lx_per_cpu_ptr.patch
