Re: [PATCH v3 1/2] kretprobe: produce sane stack traces

From: kbuild test robot
Date: Fri Nov 02 2018 - 00:02:15 EST

Hi Aleksa,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on tip/perf/core]
[also build test ERROR on v4.19 next-20181101]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url: https://github.com/0day-ci/linux/commits/Aleksa-Sarai/kretprobe-produce-sane-stack-traces/20181102-034111
config: i386-randconfig-h1-11021006 (attached as .config)
compiler: gcc-4.9 (Debian 4.9.4-2) 4.9.4
reproduce:
# save the attached .config to linux build tree
make ARCH=i386

All errors (new ones prefixed by >>):

kernel/kprobes.c: In function 'pre_handler_kretprobe':
kernel/kprobes.c:1846:10: error: variable 'trace' has initializer but incomplete type
struct stack_trace trace = {};
^
kernel/kprobes.c:1846:22: error: storage size of 'trace' isn't known
struct stack_trace trace = {};
^
>> kernel/kprobes.c:1858:3: error: implicit declaration of function 'save_stack_trace_regs' [-Werror=implicit-function-declaration]
save_stack_trace_regs(regs, &trace);
^
kernel/kprobes.c:1846:22: warning: unused variable 'trace' [-Wunused-variable]
struct stack_trace trace = {};
^
kernel/kprobes.c: In function 'kretprobe_save_stack_trace':
>> kernel/kprobes.c:1922:16: error: dereferencing pointer to incomplete type
for (i = trace->skip; i < krt->nr_entries; i++) {
^
kernel/kprobes.c:1923:12: error: dereferencing pointer to incomplete type
if (trace->nr_entries >= trace->max_entries)
^
kernel/kprobes.c:1923:33: error: dereferencing pointer to incomplete type
if (trace->nr_entries >= trace->max_entries)
^
kernel/kprobes.c:1925:8: error: dereferencing pointer to incomplete type
trace->entries[trace->nr_entries++] = krt->entries[i];
^
kernel/kprobes.c:1925:23: error: dereferencing pointer to incomplete type
trace->entries[trace->nr_entries++] = krt->entries[i];
^
cc1: some warnings being treated as errors

vim +/save_stack_trace_regs +1858 kernel/kprobes.c

1819
1820 #ifdef CONFIG_KRETPROBES
1821 /*
1822 * This kprobe pre_handler is registered with every kretprobe. When probe
1823 * hits it will set up the return probe.
1824 */
1825 static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs)
1826 {
1827 struct kretprobe *rp = container_of(p, struct kretprobe, kp);
1828 unsigned long hash, flags = 0;
1829 struct kretprobe_instance *ri;
1830
1831 /*
1832 * To avoid deadlocks, prohibit return probing in NMI contexts,
1833 * just skip the probe and increase the (inexact) 'nmissed'
1834 * statistical counter, so that the user is informed that
1835 * something happened:
1836 */
1837 if (unlikely(in_nmi())) {
1838 rp->nmissed++;
1839 return 0;
1840 }
1841
1842 /* TODO: consider to only swap the RA after the last pre_handler fired */
1843 hash = hash_ptr(current, KPROBE_HASH_BITS);
1844 raw_spin_lock_irqsave(&rp->lock, flags);
1845 if (!hlist_empty(&rp->free_instances)) {
> 1846 struct stack_trace trace = {};
1847
1848 ri = hlist_entry(rp->free_instances.first,
1849 struct kretprobe_instance, hlist);
1850 hlist_del(&ri->hlist);
1851 raw_spin_unlock_irqrestore(&rp->lock, flags);
1852
1853 ri->rp = rp;
1854 ri->task = current;
1855
1856 trace.entries = &ri->entry.entries[0];
1857 trace.max_entries = KRETPROBE_TRACE_SIZE;
> 1858 save_stack_trace_regs(regs, &trace);
1859 ri->entry.nr_entries = trace.nr_entries;
1860
1861 if (rp->entry_handler && rp->entry_handler(ri, regs)) {
1862 raw_spin_lock_irqsave(&rp->lock, flags);
1863 hlist_add_head(&ri->hlist, &rp->free_instances);
1864 raw_spin_unlock_irqrestore(&rp->lock, flags);
1865 return 0;
1866 }
1867
1868 arch_prepare_kretprobe(ri, regs);
1869
1870 /* XXX(hch): why is there no hlist_move_head? */
1871 INIT_HLIST_NODE(&ri->hlist);
1872 kretprobe_table_lock(hash, &flags);
1873 hlist_add_head(&ri->hlist, &kretprobe_inst_table[hash]);
1874 kretprobe_table_unlock(hash, &flags);
1875 } else {
1876 rp->nmissed++;
1877 raw_spin_unlock_irqrestore(&rp->lock, flags);
1878 }
1879 return 0;
1880 }
1881 NOKPROBE_SYMBOL(pre_handler_kretprobe);
1882
1883 /*
1884 * Return the kretprobe_instance associated with the current_kprobe. Calling
1885 * this is only reasonable from within a kretprobe handler context (otherwise
1886 * return NULL).
1887 *
1888 * Must be called within a kretprobe_hash_lock(current, ...) context.
1889 */
1890 struct kretprobe_instance *current_kretprobe_instance(void)
1891 {
1892 struct kprobe *kp;
1893 struct kretprobe *rp;
1894 struct kretprobe_instance *ri;
1895 struct hlist_head *head;
1896 unsigned long hash = hash_ptr(current, KPROBE_HASH_BITS);
1897
1898 kp = kprobe_running();
1899 if (!kp || !kprobe_is_retprobe(kp))
1900 return NULL;
1901 if (WARN_ON(!kretprobe_hash_is_locked(current)))
1902 return NULL;
1903
1904 rp = container_of(kp, struct kretprobe, kp);
1905 head = &kretprobe_inst_table[hash];
1906
1907 hlist_for_each_entry(ri, head, hlist) {
1908 if (ri->task == current && ri->rp == rp)
1909 return ri;
1910 }
1911 return NULL;
1912 }
1913 EXPORT_SYMBOL_GPL(current_kretprobe_instance);
1914 NOKPROBE_SYMBOL(current_kretprobe_instance);
1915
1916 void kretprobe_save_stack_trace(struct kretprobe_instance *ri,
1917 struct stack_trace *trace)
1918 {
1919 int i;
1920 struct kretprobe_trace *krt = &ri->entry;
1921
> 1922 for (i = trace->skip; i < krt->nr_entries; i++) {
1923 if (trace->nr_entries >= trace->max_entries)
1924 break;
1925 trace->entries[trace->nr_entries++] = krt->entries[i];
1926 }
1927 }
1928

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