[PATCH v4 1/2] panic: add option to dump task maps info in panic_print
qiwu.chen
qiwuchen55 at gmail.com
Tue Sep 24 00:43:40 PDT 2024
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.
- changes history:
v3:
https://lore.kernel.org/all/20240922095504.7182-1-qiwu.chen@transsion.com/
https://lore.kernel.org/all/20240922095504.7182-2-qiwu.chen@transsion.com/
v2: https://lore.kernel.org/all/20231110031553.33186-1-qiwu.chen@transsion.com/
v1: https://lore.kernel.org/all/20231110022720.GA3087@rlk/
Signed-off-by: qiwu.chen <qiwu.chen at transsion.com>
---
.../admin-guide/kernel-parameters.txt | 1 +
Documentation/admin-guide/sysctl/kernel.rst | 1 +
fs/proc/task_mmu.c | 3 +-
include/linux/mm.h | 4 ++
kernel/panic.c | 52 +++++++++++++++++++
5 files changed, 60 insertions(+), 1 deletion(-)
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/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index ade74a396968..37169ae36542 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -240,7 +240,7 @@ static int do_maps_open(struct inode *inode, struct file *file,
sizeof(struct proc_maps_private));
}
-static void get_vma_name(struct vm_area_struct *vma,
+void get_vma_name(struct vm_area_struct *vma,
const struct path **path,
const char **name,
const char **name_fmt)
@@ -300,6 +300,7 @@ static void get_vma_name(struct vm_area_struct *vma,
return;
}
}
+EXPORT_SYMBOL(get_vma_name);
static void show_vma_header_prefix(struct seq_file *m,
unsigned long start, unsigned long end,
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 13bff7cf03b7..2fa403aae1de 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3566,6 +3566,10 @@ static inline bool range_in_vma(struct vm_area_struct *vma,
#ifdef CONFIG_MMU
pgprot_t vm_get_page_prot(unsigned long vm_flags);
void vma_set_page_prot(struct vm_area_struct *vma);
+void get_vma_name(struct vm_area_struct *vma,
+ const struct path **path,
+ const char **name,
+ const char **name_fmt);
#else
static inline pgprot_t vm_get_page_prot(unsigned long vm_flags)
{
diff --git a/kernel/panic.c b/kernel/panic.c
index 753d12f4dc8f..2217e1d0ad44 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 +210,53 @@ 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) {
+ int flags = vma->vm_flags;
+ unsigned long long pgoff = ((loff_t)vma->vm_pgoff) << PAGE_SHIFT;
+ const struct path *path;
+ const char *name_fmt, *name;
+ char name_buf[SZ_256];
+
+ get_vma_name(vma, &path, &name, &name_fmt);
+ if (path) {
+ name = d_path(path, name_buf, sizeof(name_buf));
+ name = IS_ERR(name) ? "?" : name;
+ } else if (name || name_fmt) {
+ snprintf(name_buf, sizeof(name_buf), name_fmt ?: "%s", name);
+ name = name_buf;
+ }
+
+ 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 +282,9 @@ 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
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