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-rw-r--r--kernel/trace/trace_stack.c582
1 files changed, 582 insertions, 0 deletions
diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
new file mode 100644
index 000000000..5a48dba91
--- /dev/null
+++ b/kernel/trace/trace_stack.c
@@ -0,0 +1,582 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
+ *
+ */
+#include <linux/sched/task_stack.h>
+#include <linux/stacktrace.h>
+#include <linux/security.h>
+#include <linux/kallsyms.h>
+#include <linux/seq_file.h>
+#include <linux/spinlock.h>
+#include <linux/uaccess.h>
+#include <linux/ftrace.h>
+#include <linux/module.h>
+#include <linux/sysctl.h>
+#include <linux/init.h>
+
+#include <asm/setup.h>
+
+#include "trace.h"
+
+#define STACK_TRACE_ENTRIES 500
+
+static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES];
+static unsigned stack_trace_index[STACK_TRACE_ENTRIES];
+
+static unsigned int stack_trace_nr_entries;
+static unsigned long stack_trace_max_size;
+static arch_spinlock_t stack_trace_max_lock =
+ (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
+
+DEFINE_PER_CPU(int, disable_stack_tracer);
+static DEFINE_MUTEX(stack_sysctl_mutex);
+
+int stack_tracer_enabled;
+
+static void print_max_stack(void)
+{
+ long i;
+ int size;
+
+ pr_emerg(" Depth Size Location (%d entries)\n"
+ " ----- ---- --------\n",
+ stack_trace_nr_entries);
+
+ for (i = 0; i < stack_trace_nr_entries; i++) {
+ if (i + 1 == stack_trace_nr_entries)
+ size = stack_trace_index[i];
+ else
+ size = stack_trace_index[i] - stack_trace_index[i+1];
+
+ pr_emerg("%3ld) %8d %5d %pS\n", i, stack_trace_index[i],
+ size, (void *)stack_dump_trace[i]);
+ }
+}
+
+/*
+ * The stack tracer looks for a maximum stack at each call from a function. It
+ * registers a callback from ftrace, and in that callback it examines the stack
+ * size. It determines the stack size from the variable passed in, which is the
+ * address of a local variable in the stack_trace_call() callback function.
+ * The stack size is calculated by the address of the local variable to the top
+ * of the current stack. If that size is smaller than the currently saved max
+ * stack size, nothing more is done.
+ *
+ * If the size of the stack is greater than the maximum recorded size, then the
+ * following algorithm takes place.
+ *
+ * For architectures (like x86) that store the function's return address before
+ * saving the function's local variables, the stack will look something like
+ * this:
+ *
+ * [ top of stack ]
+ * 0: sys call entry frame
+ * 10: return addr to entry code
+ * 11: start of sys_foo frame
+ * 20: return addr to sys_foo
+ * 21: start of kernel_func_bar frame
+ * 30: return addr to kernel_func_bar
+ * 31: [ do trace stack here ]
+ *
+ * The save_stack_trace() is called returning all the functions it finds in the
+ * current stack. Which would be (from the bottom of the stack to the top):
+ *
+ * return addr to kernel_func_bar
+ * return addr to sys_foo
+ * return addr to entry code
+ *
+ * Now to figure out how much each of these functions' local variable size is,
+ * a search of the stack is made to find these values. When a match is made, it
+ * is added to the stack_dump_trace[] array. The offset into the stack is saved
+ * in the stack_trace_index[] array. The above example would show:
+ *
+ * stack_dump_trace[] | stack_trace_index[]
+ * ------------------ + -------------------
+ * return addr to kernel_func_bar | 30
+ * return addr to sys_foo | 20
+ * return addr to entry | 10
+ *
+ * The print_max_stack() function above, uses these values to print the size of
+ * each function's portion of the stack.
+ *
+ * for (i = 0; i < nr_entries; i++) {
+ * size = i == nr_entries - 1 ? stack_trace_index[i] :
+ * stack_trace_index[i] - stack_trace_index[i+1]
+ * print "%d %d %d %s\n", i, stack_trace_index[i], size, stack_dump_trace[i]);
+ * }
+ *
+ * The above shows
+ *
+ * depth size location
+ * ----- ---- --------
+ * 0 30 10 kernel_func_bar
+ * 1 20 10 sys_foo
+ * 2 10 10 entry code
+ *
+ * Now for architectures that might save the return address after the functions
+ * local variables (saving the link register before calling nested functions),
+ * this will cause the stack to look a little different:
+ *
+ * [ top of stack ]
+ * 0: sys call entry frame
+ * 10: start of sys_foo_frame
+ * 19: return addr to entry code << lr saved before calling kernel_func_bar
+ * 20: start of kernel_func_bar frame
+ * 29: return addr to sys_foo_frame << lr saved before calling next function
+ * 30: [ do trace stack here ]
+ *
+ * Although the functions returned by save_stack_trace() may be the same, the
+ * placement in the stack will be different. Using the same algorithm as above
+ * would yield:
+ *
+ * stack_dump_trace[] | stack_trace_index[]
+ * ------------------ + -------------------
+ * return addr to kernel_func_bar | 30
+ * return addr to sys_foo | 29
+ * return addr to entry | 19
+ *
+ * Where the mapping is off by one:
+ *
+ * kernel_func_bar stack frame size is 29 - 19 not 30 - 29!
+ *
+ * To fix this, if the architecture sets ARCH_RET_ADDR_AFTER_LOCAL_VARS the
+ * values in stack_trace_index[] are shifted by one to and the number of
+ * stack trace entries is decremented by one.
+ *
+ * stack_dump_trace[] | stack_trace_index[]
+ * ------------------ + -------------------
+ * return addr to kernel_func_bar | 29
+ * return addr to sys_foo | 19
+ *
+ * Although the entry function is not displayed, the first function (sys_foo)
+ * will still include the stack size of it.
+ */
+static void check_stack(unsigned long ip, unsigned long *stack)
+{
+ unsigned long this_size, flags; unsigned long *p, *top, *start;
+ static int tracer_frame;
+ int frame_size = READ_ONCE(tracer_frame);
+ int i, x;
+
+ this_size = ((unsigned long)stack) & (THREAD_SIZE-1);
+ this_size = THREAD_SIZE - this_size;
+ /* Remove the frame of the tracer */
+ this_size -= frame_size;
+
+ if (this_size <= stack_trace_max_size)
+ return;
+
+ /* we do not handle interrupt stacks yet */
+ if (!object_is_on_stack(stack))
+ return;
+
+ /* Can't do this from NMI context (can cause deadlocks) */
+ if (in_nmi())
+ return;
+
+ local_irq_save(flags);
+ arch_spin_lock(&stack_trace_max_lock);
+
+ /* In case another CPU set the tracer_frame on us */
+ if (unlikely(!frame_size))
+ this_size -= tracer_frame;
+
+ /* a race could have already updated it */
+ if (this_size <= stack_trace_max_size)
+ goto out;
+
+ stack_trace_max_size = this_size;
+
+ stack_trace_nr_entries = stack_trace_save(stack_dump_trace,
+ ARRAY_SIZE(stack_dump_trace) - 1,
+ 0);
+
+ /* Skip over the overhead of the stack tracer itself */
+ for (i = 0; i < stack_trace_nr_entries; i++) {
+ if (stack_dump_trace[i] == ip)
+ break;
+ }
+
+ /*
+ * Some archs may not have the passed in ip in the dump.
+ * If that happens, we need to show everything.
+ */
+ if (i == stack_trace_nr_entries)
+ i = 0;
+
+ /*
+ * Now find where in the stack these are.
+ */
+ x = 0;
+ start = stack;
+ top = (unsigned long *)
+ (((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE);
+
+ /*
+ * Loop through all the entries. One of the entries may
+ * for some reason be missed on the stack, so we may
+ * have to account for them. If they are all there, this
+ * loop will only happen once. This code only takes place
+ * on a new max, so it is far from a fast path.
+ */
+ while (i < stack_trace_nr_entries) {
+ int found = 0;
+
+ stack_trace_index[x] = this_size;
+ p = start;
+
+ for (; p < top && i < stack_trace_nr_entries; p++) {
+ /*
+ * The READ_ONCE_NOCHECK is used to let KASAN know that
+ * this is not a stack-out-of-bounds error.
+ */
+ if ((READ_ONCE_NOCHECK(*p)) == stack_dump_trace[i]) {
+ stack_dump_trace[x] = stack_dump_trace[i++];
+ this_size = stack_trace_index[x++] =
+ (top - p) * sizeof(unsigned long);
+ found = 1;
+ /* Start the search from here */
+ start = p + 1;
+ /*
+ * We do not want to show the overhead
+ * of the stack tracer stack in the
+ * max stack. If we haven't figured
+ * out what that is, then figure it out
+ * now.
+ */
+ if (unlikely(!tracer_frame)) {
+ tracer_frame = (p - stack) *
+ sizeof(unsigned long);
+ stack_trace_max_size -= tracer_frame;
+ }
+ }
+ }
+
+ if (!found)
+ i++;
+ }
+
+#ifdef ARCH_FTRACE_SHIFT_STACK_TRACER
+ /*
+ * Some archs will store the link register before calling
+ * nested functions. This means the saved return address
+ * comes after the local storage, and we need to shift
+ * for that.
+ */
+ if (x > 1) {
+ memmove(&stack_trace_index[0], &stack_trace_index[1],
+ sizeof(stack_trace_index[0]) * (x - 1));
+ x--;
+ }
+#endif
+
+ stack_trace_nr_entries = x;
+
+ if (task_stack_end_corrupted(current)) {
+ print_max_stack();
+ BUG();
+ }
+
+ out:
+ arch_spin_unlock(&stack_trace_max_lock);
+ local_irq_restore(flags);
+}
+
+/* Some archs may not define MCOUNT_INSN_SIZE */
+#ifndef MCOUNT_INSN_SIZE
+# define MCOUNT_INSN_SIZE 0
+#endif
+
+static void
+stack_trace_call(unsigned long ip, unsigned long parent_ip,
+ struct ftrace_ops *op, struct ftrace_regs *fregs)
+{
+ unsigned long stack;
+
+ preempt_disable_notrace();
+
+ /* no atomic needed, we only modify this variable by this cpu */
+ __this_cpu_inc(disable_stack_tracer);
+ if (__this_cpu_read(disable_stack_tracer) != 1)
+ goto out;
+
+ /* If rcu is not watching, then save stack trace can fail */
+ if (!rcu_is_watching())
+ goto out;
+
+ ip += MCOUNT_INSN_SIZE;
+
+ check_stack(ip, &stack);
+
+ out:
+ __this_cpu_dec(disable_stack_tracer);
+ /* prevent recursion in schedule */
+ preempt_enable_notrace();
+}
+
+static struct ftrace_ops trace_ops __read_mostly =
+{
+ .func = stack_trace_call,
+};
+
+static ssize_t
+stack_max_size_read(struct file *filp, char __user *ubuf,
+ size_t count, loff_t *ppos)
+{
+ unsigned long *ptr = filp->private_data;
+ char buf[64];
+ int r;
+
+ r = snprintf(buf, sizeof(buf), "%ld\n", *ptr);
+ if (r > sizeof(buf))
+ r = sizeof(buf);
+ return simple_read_from_buffer(ubuf, count, ppos, buf, r);
+}
+
+static ssize_t
+stack_max_size_write(struct file *filp, const char __user *ubuf,
+ size_t count, loff_t *ppos)
+{
+ long *ptr = filp->private_data;
+ unsigned long val, flags;
+ int ret;
+
+ ret = kstrtoul_from_user(ubuf, count, 10, &val);
+ if (ret)
+ return ret;
+
+ local_irq_save(flags);
+
+ /*
+ * In case we trace inside arch_spin_lock() or after (NMI),
+ * we will cause circular lock, so we also need to increase
+ * the percpu disable_stack_tracer here.
+ */
+ __this_cpu_inc(disable_stack_tracer);
+
+ arch_spin_lock(&stack_trace_max_lock);
+ *ptr = val;
+ arch_spin_unlock(&stack_trace_max_lock);
+
+ __this_cpu_dec(disable_stack_tracer);
+ local_irq_restore(flags);
+
+ return count;
+}
+
+static const struct file_operations stack_max_size_fops = {
+ .open = tracing_open_generic,
+ .read = stack_max_size_read,
+ .write = stack_max_size_write,
+ .llseek = default_llseek,
+};
+
+static void *
+__next(struct seq_file *m, loff_t *pos)
+{
+ long n = *pos - 1;
+
+ if (n >= stack_trace_nr_entries)
+ return NULL;
+
+ m->private = (void *)n;
+ return &m->private;
+}
+
+static void *
+t_next(struct seq_file *m, void *v, loff_t *pos)
+{
+ (*pos)++;
+ return __next(m, pos);
+}
+
+static void *t_start(struct seq_file *m, loff_t *pos)
+{
+ local_irq_disable();
+
+ __this_cpu_inc(disable_stack_tracer);
+
+ arch_spin_lock(&stack_trace_max_lock);
+
+ if (*pos == 0)
+ return SEQ_START_TOKEN;
+
+ return __next(m, pos);
+}
+
+static void t_stop(struct seq_file *m, void *p)
+{
+ arch_spin_unlock(&stack_trace_max_lock);
+
+ __this_cpu_dec(disable_stack_tracer);
+
+ local_irq_enable();
+}
+
+static void trace_lookup_stack(struct seq_file *m, long i)
+{
+ unsigned long addr = stack_dump_trace[i];
+
+ seq_printf(m, "%pS\n", (void *)addr);
+}
+
+static void print_disabled(struct seq_file *m)
+{
+ seq_puts(m, "#\n"
+ "# Stack tracer disabled\n"
+ "#\n"
+ "# To enable the stack tracer, either add 'stacktrace' to the\n"
+ "# kernel command line\n"
+ "# or 'echo 1 > /proc/sys/kernel/stack_tracer_enabled'\n"
+ "#\n");
+}
+
+static int t_show(struct seq_file *m, void *v)
+{
+ long i;
+ int size;
+
+ if (v == SEQ_START_TOKEN) {
+ seq_printf(m, " Depth Size Location"
+ " (%d entries)\n"
+ " ----- ---- --------\n",
+ stack_trace_nr_entries);
+
+ if (!stack_tracer_enabled && !stack_trace_max_size)
+ print_disabled(m);
+
+ return 0;
+ }
+
+ i = *(long *)v;
+
+ if (i >= stack_trace_nr_entries)
+ return 0;
+
+ if (i + 1 == stack_trace_nr_entries)
+ size = stack_trace_index[i];
+ else
+ size = stack_trace_index[i] - stack_trace_index[i+1];
+
+ seq_printf(m, "%3ld) %8d %5d ", i, stack_trace_index[i], size);
+
+ trace_lookup_stack(m, i);
+
+ return 0;
+}
+
+static const struct seq_operations stack_trace_seq_ops = {
+ .start = t_start,
+ .next = t_next,
+ .stop = t_stop,
+ .show = t_show,
+};
+
+static int stack_trace_open(struct inode *inode, struct file *file)
+{
+ int ret;
+
+ ret = security_locked_down(LOCKDOWN_TRACEFS);
+ if (ret)
+ return ret;
+
+ return seq_open(file, &stack_trace_seq_ops);
+}
+
+static const struct file_operations stack_trace_fops = {
+ .open = stack_trace_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = seq_release,
+};
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+
+static int
+stack_trace_filter_open(struct inode *inode, struct file *file)
+{
+ struct ftrace_ops *ops = inode->i_private;
+
+ /* Checks for tracefs lockdown */
+ return ftrace_regex_open(ops, FTRACE_ITER_FILTER,
+ inode, file);
+}
+
+static const struct file_operations stack_trace_filter_fops = {
+ .open = stack_trace_filter_open,
+ .read = seq_read,
+ .write = ftrace_filter_write,
+ .llseek = tracing_lseek,
+ .release = ftrace_regex_release,
+};
+
+#endif /* CONFIG_DYNAMIC_FTRACE */
+
+int
+stack_trace_sysctl(struct ctl_table *table, int write, void *buffer,
+ size_t *lenp, loff_t *ppos)
+{
+ int was_enabled;
+ int ret;
+
+ mutex_lock(&stack_sysctl_mutex);
+ was_enabled = !!stack_tracer_enabled;
+
+ ret = proc_dointvec(table, write, buffer, lenp, ppos);
+
+ if (ret || !write || (was_enabled == !!stack_tracer_enabled))
+ goto out;
+
+ if (stack_tracer_enabled)
+ register_ftrace_function(&trace_ops);
+ else
+ unregister_ftrace_function(&trace_ops);
+ out:
+ mutex_unlock(&stack_sysctl_mutex);
+ return ret;
+}
+
+static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata;
+
+static __init int enable_stacktrace(char *str)
+{
+ int len;
+
+ if ((len = str_has_prefix(str, "_filter=")))
+ strncpy(stack_trace_filter_buf, str + len, COMMAND_LINE_SIZE);
+
+ stack_tracer_enabled = 1;
+ return 1;
+}
+__setup("stacktrace", enable_stacktrace);
+
+static __init int stack_trace_init(void)
+{
+ int ret;
+
+ ret = tracing_init_dentry();
+ if (ret)
+ return 0;
+
+ trace_create_file("stack_max_size", TRACE_MODE_WRITE, NULL,
+ &stack_trace_max_size, &stack_max_size_fops);
+
+ trace_create_file("stack_trace", TRACE_MODE_READ, NULL,
+ NULL, &stack_trace_fops);
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+ trace_create_file("stack_trace_filter", TRACE_MODE_WRITE, NULL,
+ &trace_ops, &stack_trace_filter_fops);
+#endif
+
+ if (stack_trace_filter_buf[0])
+ ftrace_set_early_filter(&trace_ops, stack_trace_filter_buf, 1);
+
+ if (stack_tracer_enabled)
+ register_ftrace_function(&trace_ops);
+
+ return 0;
+}
+
+device_initcall(stack_trace_init);
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-01 09:41:27 +0000