Currently, it's hard to debug panic issues caused by kill init,
since there is no debug info from user mode in current panic msg
such as the user_regs and maps info.
This patch adds an option to dump task maps info in panic_print.
Signed-off-by: qiwu.chen <qiwu.chen@xxxxxxxxxxxxx>
---
.../admin-guide/kernel-parameters.txt | 1 +
Documentation/admin-guide/sysctl/kernel.rst | 1 +
kernel/panic.c | 82 +++++++++++++++++++
3 files changed, 84 insertions(+)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 8337d0fed311..f76709deef6c 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4253,6 +4253,7 @@
bit 5: print all printk messages in buffer
bit 6: print all CPUs backtrace (if available in the arch)
bit 7: print only tasks in uninterruptible (blocked) state
+ bit 8: print task maps info
*Be aware* that this option may print a _lot_ of lines,
so there are risks of losing older messages in the log.
Use this option carefully, maybe worth to setup a
diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst
index f8bc1630eba0..558e365b76a9 100644
--- a/Documentation/admin-guide/sysctl/kernel.rst
+++ b/Documentation/admin-guide/sysctl/kernel.rst
@@ -872,6 +872,7 @@ bit 4 print ftrace buffer
bit 5 print all printk messages in buffer
bit 6 print all CPUs backtrace (if available in the arch)
bit 7 print only tasks in uninterruptible (blocked) state
+bit 8 print task maps info
===== ============================================
So for example to print tasks and memory info on panic, user can::
diff --git a/kernel/panic.c b/kernel/panic.c
index 753d12f4dc8f..5b76ff92a6fc 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -77,6 +77,8 @@ EXPORT_SYMBOL_GPL(panic_timeout);
#define PANIC_PRINT_ALL_PRINTK_MSG 0x00000020
#define PANIC_PRINT_ALL_CPU_BT 0x00000040
#define PANIC_PRINT_BLOCKED_TASKS 0x00000080
+#define PANIC_PRINT_TASK_MAPS_INFO 0x00000100
+
unsigned long panic_print;
ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
@@ -208,6 +210,83 @@ void nmi_panic(struct pt_regs *regs, const char *msg)
}
EXPORT_SYMBOL(nmi_panic);
+/*
+ * This function is called in panic proccess if the PANIC_PRINT_TASK_MAPS_INFO
+ * flag is specified in panic_print, which is helpful to debug panic issues due
+ * to an unhandled falut in user mode such as kill init.
+ */
+static void dump_task_maps_info(struct task_struct *tsk)
+{
+ struct pt_regs *user_ret = task_pt_regs(tsk);
+ struct mm_struct *mm = tsk->mm;
+ struct vm_area_struct *vma;
+
+ if (!mm || !user_mode(user_ret))
+ return;
+
+ pr_info("Dump task %s:%d maps start\n", tsk->comm, task_pid_nr(tsk));
+ mmap_read_lock(mm);
+ VMA_ITERATOR(vmi, mm, 0);
+ for_each_vma(vmi, vma) {
+ struct file *file = vma->vm_file;
+ int flags = vma->vm_flags;
+ unsigned long long pgoff = ((loff_t)vma->vm_pgoff) << PAGE_SHIFT;
+ struct anon_vma_name *anon_name = NULL;
+ struct mm_struct *mm = vma->vm_mm;
+ char buf[256] = {0};
+ const char *name = NULL;
+
+ if (mm)
+ anon_name = anon_vma_name(vma);
+
+ if (file) {
+ if (anon_name) {
+ snprintf(buf, sizeof(buf), "[anon_shmem:%s]", anon_name->name);
+ name = buf;
+ } else {
+ char *f_path = d_path(file_user_path(file), buf, sizeof(buf));
+
+ name = IS_ERR(f_path) ? "?" : f_path;
+ }
+ goto print;
+ }
+
+ if (vma->vm_ops && vma->vm_ops->name) {
+ name = vma->vm_ops->name(vma);
+ if (name)
+ goto print;
+ }
+
+ name = arch_vma_name(vma);
+ if (!name) {
+ if (mm) {
+ if (vma_is_initial_heap(vma))
+ name = "[heap]";
+ else if (vma_is_initial_stack(vma))
+ name = "[stack]";
+ } else
+ name = "[vdso]";
+
+ if (anon_name) {
+ snprintf(buf, sizeof(buf), "[anon:%s]", anon_name->name);
+ name = buf;
+ }
+ }
+
+print:
+ if (name)
+ pr_info("%08lx-%08lx %c%c%c%c %08llx %s\n",
+ vma->vm_start, vma->vm_end,
+ flags & VM_READ ? 'r' : '-',
+ flags & VM_WRITE ? 'w' : '-',
+ flags & VM_EXEC ? 'x' : '-',
+ flags & VM_MAYSHARE ? 's' : 'p',
+ pgoff, name);
+ }
+ mmap_read_unlock(mm);
+ pr_info("Dump task %s:%d maps end\n", tsk->comm, task_pid_nr(tsk));
+}
+
static void panic_print_sys_info(bool console_flush)
{
if (console_flush) {
@@ -233,6 +312,9 @@ static void panic_print_sys_info(bool console_flush)
if (panic_print & PANIC_PRINT_BLOCKED_TASKS)
show_state_filter(TASK_UNINTERRUPTIBLE);
+
+ if (panic_print & PANIC_PRINT_TASK_MAPS_INFO)
+ dump_task_maps_info(current);
}
void check_panic_on_warn(const char *origin)
--
2.25.1
