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@xxxxxxxxxxxxx/ https://lore.kernel.org/all/20240922095504.7182-2-qiwu.chen@xxxxxxxxxxxxx/ v2: https://lore.kernel.org/all/20231110031553.33186-1-qiwu.chen@xxxxxxxxxxxxx/ v1: https://lore.kernel.org/all/20231110022720.GA3087@rlk/ Signed-off-by: qiwu.chen <qiwu.chen@xxxxxxxxxxxxx> --- .../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
