proc: add /proc/*/stack
/proc/*/stack adds the ability to query a task's stack trace. It is more useful than /proc/*/wchan as it provides full stack trace instead of single depth. Example output: $ cat /proc/self/stack [<c010a271>] save_stack_trace_tsk+0x17/0x35 [<c01827b4>] proc_pid_stack+0x4a/0x76 [<c018312d>] proc_single_show+0x4a/0x5e [<c016bdec>] seq_read+0xf3/0x29f [<c015a004>] vfs_read+0x6d/0x91 [<c015a0c1>] sys_read+0x3b/0x60 [<c0102eda>] syscall_call+0x7/0xb [<ffffffff>] 0xffffffff [add save_stack_trace_tsk() on mips, ACK Ralf --adobriyan] Signed-off-by: Ken Chen <kenchen@google.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
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@ -140,6 +140,7 @@ Table 1-1: Process specific entries in /proc
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statm Process memory status information
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status Process status in human readable form
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wchan If CONFIG_KALLSYMS is set, a pre-decoded wchan
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stack Report full stack trace, enable via CONFIG_STACKTRACE
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smaps Extension based on maps, the rss size for each mapped file
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..............................................................................
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@ -32,7 +32,8 @@ static void save_raw_context_stack(struct stack_trace *trace,
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}
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}
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static void save_context_stack(struct stack_trace *trace, struct pt_regs *regs)
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static void save_context_stack(struct stack_trace *trace,
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struct task_struct *tsk, struct pt_regs *regs)
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{
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unsigned long sp = regs->regs[29];
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#ifdef CONFIG_KALLSYMS
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@ -41,7 +42,7 @@ static void save_context_stack(struct stack_trace *trace, struct pt_regs *regs)
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if (raw_show_trace || !__kernel_text_address(pc)) {
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unsigned long stack_page =
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(unsigned long)task_stack_page(current);
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(unsigned long)task_stack_page(tsk);
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if (stack_page && sp >= stack_page &&
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sp <= stack_page + THREAD_SIZE - 32)
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save_raw_context_stack(trace, sp);
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@ -54,7 +55,7 @@ static void save_context_stack(struct stack_trace *trace, struct pt_regs *regs)
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trace->entries[trace->nr_entries++] = pc;
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if (trace->nr_entries >= trace->max_entries)
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break;
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pc = unwind_stack(current, &sp, pc, &ra);
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pc = unwind_stack(tsk, &sp, pc, &ra);
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} while (pc);
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#else
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save_raw_context_stack(trace, sp);
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@ -65,13 +66,24 @@ static void save_context_stack(struct stack_trace *trace, struct pt_regs *regs)
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* Save stack-backtrace addresses into a stack_trace buffer.
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*/
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void save_stack_trace(struct stack_trace *trace)
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{
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save_stack_trace_tsk(current, trace);
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}
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EXPORT_SYMBOL_GPL(save_stack_trace);
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void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
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{
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struct pt_regs dummyregs;
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struct pt_regs *regs = &dummyregs;
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WARN_ON(trace->nr_entries || !trace->max_entries);
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if (tsk != current) {
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regs->regs[29] = tsk->thread.reg29;
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regs->regs[31] = 0;
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regs->cp0_epc = tsk->thread.reg31;
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} else
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prepare_frametrace(regs);
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save_context_stack(trace, regs);
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save_context_stack(trace, tsk, regs);
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}
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EXPORT_SYMBOL_GPL(save_stack_trace);
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EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
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@ -65,6 +65,7 @@
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#include <linux/mm.h>
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#include <linux/rcupdate.h>
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#include <linux/kallsyms.h>
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#include <linux/stacktrace.h>
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#include <linux/resource.h>
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#include <linux/module.h>
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#include <linux/mount.h>
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@ -337,6 +338,37 @@ static int proc_pid_wchan(struct task_struct *task, char *buffer)
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}
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#endif /* CONFIG_KALLSYMS */
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#ifdef CONFIG_STACKTRACE
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#define MAX_STACK_TRACE_DEPTH 64
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static int proc_pid_stack(struct seq_file *m, struct pid_namespace *ns,
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struct pid *pid, struct task_struct *task)
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{
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struct stack_trace trace;
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unsigned long *entries;
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int i;
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entries = kmalloc(MAX_STACK_TRACE_DEPTH * sizeof(*entries), GFP_KERNEL);
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if (!entries)
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return -ENOMEM;
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trace.nr_entries = 0;
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trace.max_entries = MAX_STACK_TRACE_DEPTH;
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trace.entries = entries;
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trace.skip = 0;
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save_stack_trace_tsk(task, &trace);
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for (i = 0; i < trace.nr_entries; i++) {
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seq_printf(m, "[<%p>] %pS\n",
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(void *)entries[i], (void *)entries[i]);
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}
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kfree(entries);
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return 0;
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}
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#endif
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#ifdef CONFIG_SCHEDSTATS
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/*
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* Provides /proc/PID/schedstat
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@ -2500,6 +2532,9 @@ static const struct pid_entry tgid_base_stuff[] = {
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#ifdef CONFIG_KALLSYMS
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INF("wchan", S_IRUGO, proc_pid_wchan),
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#endif
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#ifdef CONFIG_STACKTRACE
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ONE("stack", S_IRUSR, proc_pid_stack),
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#endif
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#ifdef CONFIG_SCHEDSTATS
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INF("schedstat", S_IRUGO, proc_pid_schedstat),
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#endif
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@ -2835,6 +2870,9 @@ static const struct pid_entry tid_base_stuff[] = {
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#ifdef CONFIG_KALLSYMS
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INF("wchan", S_IRUGO, proc_pid_wchan),
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#endif
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#ifdef CONFIG_STACKTRACE
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ONE("stack", S_IRUSR, proc_pid_stack),
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#endif
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#ifdef CONFIG_SCHEDSTATS
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INF("schedstat", S_IRUGO, proc_pid_schedstat),
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#endif
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