// SPDX-License-Identifier: GPL-2.0/* * KCSAN reporting. * * Copyright (C) 2019, Google LLC. */ #include <linux/debug_locks.h>#include <linux/delay.h>#include <linux/jiffies.h>#include <linux/kallsyms.h>#include <linux/kernel.h>#include <linux/lockdep.h>#include <linux/preempt.h>#include <linux/printk.h>#include <linux/sched.h>#include <linux/spinlock.h>#include <linux/stacktrace.h> #include "kcsan.h"#include "encoding.h" /* * Max. number of stack entries to show in the report. */#define NUM_STACK_ENTRIES 64 /* Common access info. */struct access_info { const volatile void *ptr; size_t size; int access_type; int task_pid; int cpu_id; unsigned long ip;}; /* * Other thread info: communicated from other racing thread to thread that set * up the watchpoint, which then prints the complete report atomically. */struct other_info { struct access_info ai; unsigned long stack_entries[NUM_STACK_ENTRIES]; int num_stack_entries; /* * Optionally pass @current. Typically we do not need to pass @current * via @other_info since just @task_pid is sufficient. Passing @current * has additional overhead. * * To safely pass @current, we must either use get_task_struct/ * put_task_struct, or stall the thread that populated @other_info. * * We cannot rely on get_task_struct/put_task_struct in case * release_report() races with a task being released, and would have to * free it in release_report(). This may result in deadlock if we want * to use KCSAN on the allocators. * * Since we also want to reliably print held locks for * CONFIG_KCSAN_VERBOSE, the current implementation stalls the thread * that populated @other_info until it has been consumed. */ struct task_struct *task;}; /* * To never block any producers of struct other_info, we need as many elements * as we have watchpoints (upper bound on concurrent races to report). */static struct other_info other_infos[CONFIG_KCSAN_NUM_WATCHPOINTS + NUM_SLOTS-1]; /* * Information about reported races; used to rate limit reporting. */struct report_time { /* * The last time the race was reported. */ unsigned long time; /* * The frames of the 2 threads; if only 1 thread is known, one frame * will be 0. */ unsigned long frame1; unsigned long frame2;}; /* * Since we also want to be able to debug allocators with KCSAN, to avoid * deadlock, report_times cannot be dynamically resized with krealloc in * rate_limit_report. * * Therefore, we use a fixed-size array, which at most will occupy a page. This * still adequately rate limits reports, assuming that a) number of unique data * races is not excessive, and b) occurrence of unique races within the * same time window is limited. */#define REPORT_TIMES_MAX (PAGE_SIZE / sizeof(struct report_time))#define REPORT_TIMES_SIZE \ (CONFIG_KCSAN_REPORT_ONCE_IN_MS > REPORT_TIMES_MAX ? \ REPORT_TIMES_MAX : \ CONFIG_KCSAN_REPORT_ONCE_IN_MS)static struct report_time report_times[REPORT_TIMES_SIZE]; /* * Spinlock serializing report generation, and access to @other_infos. Although * it could make sense to have a finer-grained locking story for @other_infos, * report generation needs to be serialized either way, so not much is gained. */static DEFINE_RAW_SPINLOCK(report_lock); /* * Checks if the race identified by thread frames frame1 and frame2 has * been reported since (now - KCSAN_REPORT_ONCE_IN_MS). */static bool rate_limit_report(unsigned long frame1, unsigned long frame2) __must_hold(&report_lock){ struct report_time *use_entry = &report_times[0]; unsigned long invalid_before; int i; BUILD_BUG_ON(CONFIG_KCSAN_REPORT_ONCE_IN_MS != 0 && REPORT_TIMES_SIZE == 0); if (CONFIG_KCSAN_REPORT_ONCE_IN_MS == 0) return false; invalid_before = jiffies - msecs_to_jiffies(CONFIG_KCSAN_REPORT_ONCE_IN_MS); /* Check if a matching race report exists. */ for (i = 0; i < REPORT_TIMES_SIZE; ++i) { struct report_time *rt = &report_times[i]; /* * Must always select an entry for use to store info as we * cannot resize report_times; at the end of the scan, use_entry * will be the oldest entry, which ideally also happened before * KCSAN_REPORT_ONCE_IN_MS ago. */ if (time_before(rt->time, use_entry->time)) use_entry = rt; /* * Initially, no need to check any further as this entry as well * as following entries have never been used. */ if (rt->time == 0) break; /* Check if entry expired. */ if (time_before(rt->time, invalid_before)) continue; /* before KCSAN_REPORT_ONCE_IN_MS ago */ /* Reported recently, check if race matches. */ if ((rt->frame1 == frame1 && rt->frame2 == frame2) || (rt->frame1 == frame2 && rt->frame2 == frame1)) return true; } use_entry->time = jiffies; use_entry->frame1 = frame1; use_entry->frame2 = frame2; return false;} /* * Special rules to skip reporting. */static boolskip_report(enum kcsan_value_change value_change, unsigned long top_frame){ /* Should never get here if value_change==FALSE. */ WARN_ON_ONCE(value_change == KCSAN_VALUE_CHANGE_FALSE); /* * The first call to skip_report always has value_change==TRUE, since we * cannot know the value written of an instrumented access. For the 2nd * call there are 6 cases with CONFIG_KCSAN_REPORT_VALUE_CHANGE_ONLY: * * 1. read watchpoint, conflicting write (value_change==TRUE): report; * 2. read watchpoint, conflicting write (value_change==MAYBE): skip; * 3. write watchpoint, conflicting write (value_change==TRUE): report; * 4. write watchpoint, conflicting write (value_change==MAYBE): skip; * 5. write watchpoint, conflicting read (value_change==MAYBE): skip; * 6. write watchpoint, conflicting read (value_change==TRUE): report; * * Cases 1-4 are intuitive and expected; case 5 ensures we do not report * data races where the write may have rewritten the same value; case 6 * is possible either if the size is larger than what we check value * changes for or the access type is KCSAN_ACCESS_ASSERT. */ if (IS_ENABLED(CONFIG_KCSAN_REPORT_VALUE_CHANGE_ONLY) && value_change == KCSAN_VALUE_CHANGE_MAYBE) { /* * The access is a write, but the data value did not change. * * We opt-out of this filter for certain functions at request of * maintainers. */ char buf[64]; int len = scnprintf(buf, sizeof(buf), "%ps", (void *)top_frame); if (!strnstr(buf, "rcu_", len) && !strnstr(buf, "_rcu", len) && !strnstr(buf, "_srcu", len)) return true; } return kcsan_skip_report_debugfs(top_frame);} static const char *get_access_type(int type){ if (type & KCSAN_ACCESS_ASSERT) { if (type & KCSAN_ACCESS_SCOPED) { if (type & KCSAN_ACCESS_WRITE) return "assert no accesses (reordered)"; else return "assert no writes (reordered)"; } else { if (type & KCSAN_ACCESS_WRITE) return "assert no accesses"; else return "assert no writes"; } } switch (type) { case 0: return "read"; case KCSAN_ACCESS_ATOMIC: return "read (marked)"; case KCSAN_ACCESS_WRITE: return "write"; case KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC: return "write (marked)"; case KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE: return "read-write"; case KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC: return "read-write (marked)"; case KCSAN_ACCESS_SCOPED: return "read (reordered)"; case KCSAN_ACCESS_SCOPED | KCSAN_ACCESS_ATOMIC: return "read (marked, reordered)"; case KCSAN_ACCESS_SCOPED | KCSAN_ACCESS_WRITE: return "write (reordered)"; case KCSAN_ACCESS_SCOPED | KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC: return "write (marked, reordered)"; case KCSAN_ACCESS_SCOPED | KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE: return "read-write (reordered)"; case KCSAN_ACCESS_SCOPED | KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC: return "read-write (marked, reordered)"; default: BUG(); }} static const char *get_bug_type(int type){ return (type & KCSAN_ACCESS_ASSERT) != 0 ? "assert: race" : "data-race";} /* Return thread description: in task or interrupt. */static const char *get_thread_desc(int task_id){ if (task_id != -1) { static char buf[32]; /* safe: protected by report_lock */ snprintf(buf, sizeof(buf), "task %i", task_id); return buf; } return "interrupt";} /* Helper to skip KCSAN-related functions in stack-trace. */static int get_stack_skipnr(const unsigned long stack_entries[], int num_entries){ char buf[64]; char *cur; int len, skip; for (skip = 0; skip < num_entries; ++skip) { len = scnprintf(buf, sizeof(buf), "%ps", (void *)stack_entries[skip]); /* Never show tsan_* or {read,write}_once_size. */ if (strnstr(buf, "tsan_", len) || strnstr(buf, "_once_size", len)) continue; cur = strnstr(buf, "kcsan_", len); if (cur) { cur += strlen("kcsan_"); if (!str_has_prefix(cur, "test")) continue; /* KCSAN runtime function. */ /* KCSAN related test. */ } /* * No match for runtime functions -- @skip entries to skip to * get to first frame of interest. */ break; } return skip;} /* * Skips to the first entry that matches the function of @ip, and then replaces * that entry with @ip, returning the entries to skip with @replaced containing * the replaced entry. */static intreplace_stack_entry(unsigned long stack_entries[], int num_entries, unsigned long ip, unsigned long *replaced){ unsigned long symbolsize, offset; unsigned long target_func; int skip; if (kallsyms_lookup_size_offset(ip, &symbolsize, &offset)) target_func = ip - offset; else goto fallback; for (skip = 0; skip < num_entries; ++skip) { unsigned long func = stack_entries[skip]; if (!kallsyms_lookup_size_offset(func, &symbolsize, &offset)) goto fallback; func -= offset; if (func == target_func) { *replaced = stack_entries[skip]; stack_entries[skip] = ip; return skip; } } fallback: /* Should not happen; the resulting stack trace is likely misleading. */ WARN_ONCE(1, "Cannot find frame for %pS in stack trace", (void *)ip); return get_stack_skipnr(stack_entries, num_entries);} static intsanitize_stack_entries(unsigned long stack_entries[], int num_entries, unsigned long ip, unsigned long *replaced){ return ip ? replace_stack_entry(stack_entries, num_entries, ip, replaced) : get_stack_skipnr(stack_entries, num_entries);} /* Compares symbolized strings of addr1 and addr2. */static int sym_strcmp(void *addr1, void *addr2){ char buf1[64]; char buf2[64]; snprintf(buf1, sizeof(buf1), "%pS", addr1); snprintf(buf2, sizeof(buf2), "%pS", addr2); return strncmp(buf1, buf2, sizeof(buf1));} static voidprint_stack_trace(unsigned long stack_entries[], int num_entries, unsigned long reordered_to) __must_hold(&report_lock){ stack_trace_print(stack_entries, num_entries, 0); if (reordered_to) pr_err(" |\n +-> reordered to: %pS\n", (void *)reordered_to);} static void print_verbose_info(struct task_struct *task) __must_hold(&report_lock){ if (!task) return; /* Restore IRQ state trace for printing. */ kcsan_restore_irqtrace(task); pr_err("\n"); debug_show_held_locks(task); print_irqtrace_events(task);} static void print_report(enum kcsan_value_change value_change, const struct access_info *ai, struct other_info *other_info, u64 old, u64 new, u64 mask) __must_hold(&report_lock){ unsigned long reordered_to = 0; unsigned long stack_entries[NUM_STACK_ENTRIES] = { 0 }; int num_stack_entries = stack_trace_save(stack_entries, NUM_STACK_ENTRIES, 1); int skipnr = sanitize_stack_entries(stack_entries, num_stack_entries, ai->ip, &reordered_to); unsigned long this_frame = stack_entries[skipnr]; unsigned long other_reordered_to = 0; unsigned long other_frame = 0; int other_skipnr = 0; /* silence uninit warnings */ /* * Must check report filter rules before starting to print. */ if (skip_report(KCSAN_VALUE_CHANGE_TRUE, stack_entries[skipnr])) return; if (other_info) { other_skipnr = sanitize_stack_entries(other_info->stack_entries, other_info->num_stack_entries, other_info->ai.ip, &other_reordered_to); other_frame = other_info->stack_entries[other_skipnr]; /* @value_change is only known for the other thread */ if (skip_report(value_change, other_frame)) return; } if (rate_limit_report(this_frame, other_frame)) return; /* Print report header. */ pr_err("==================================================================\n"); if (other_info) { int cmp; /* * Order functions lexographically for consistent bug titles. * Do not print offset of functions to keep title short. */ cmp = sym_strcmp((void *)other_frame, (void *)this_frame); pr_err("BUG: KCSAN: %s in %ps / %ps\n", get_bug_type(ai->access_type | other_info->ai.access_type), (void *)(cmp < 0 ? other_frame : this_frame), (void *)(cmp < 0 ? this_frame : other_frame)); } else { pr_err("BUG: KCSAN: %s in %pS\n", get_bug_type(ai->access_type), (void *)this_frame); } pr_err("\n"); /* Print information about the racing accesses. */ if (other_info) { pr_err("%s to 0x%px of %zu bytes by %s on cpu %i:\n", get_access_type(other_info->ai.access_type), other_info->ai.ptr, other_info->ai.size, get_thread_desc(other_info->ai.task_pid), other_info->ai.cpu_id); /* Print the other thread's stack trace. */ print_stack_trace(other_info->stack_entries + other_skipnr, other_info->num_stack_entries - other_skipnr, other_reordered_to); if (IS_ENABLED(CONFIG_KCSAN_VERBOSE)) print_verbose_info(other_info->task); pr_err("\n"); pr_err("%s to 0x%px of %zu bytes by %s on cpu %i:\n", get_access_type(ai->access_type), ai->ptr, ai->size, get_thread_desc(ai->task_pid), ai->cpu_id); } else { pr_err("race at unknown origin, with %s to 0x%px of %zu bytes by %s on cpu %i:\n", get_access_type(ai->access_type), ai->ptr, ai->size, get_thread_desc(ai->task_pid), ai->cpu_id); } /* Print stack trace of this thread. */ print_stack_trace(stack_entries + skipnr, num_stack_entries - skipnr, reordered_to); if (IS_ENABLED(CONFIG_KCSAN_VERBOSE)) print_verbose_info(current); /* Print observed value change. */ if (ai->size <= 8) { int hex_len = ai->size * 2; u64 diff = old ^ new; if (mask) diff &= mask; if (diff) { pr_err("\n"); pr_err("value changed: 0x%0*llx -> 0x%0*llx\n", hex_len, old, hex_len, new); if (mask) { pr_err(" bits changed: 0x%0*llx with mask 0x%0*llx\n", hex_len, diff, hex_len, mask); } } } /* Print report footer. */ pr_err("\n"); pr_err("Reported by Kernel Concurrency Sanitizer on:\n"); dump_stack_print_info(KERN_DEFAULT); pr_err("==================================================================\n"); check_panic_on_warn("KCSAN");}Lines 1–500 of 720. 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// SPDX-License-Identifier: GPL-2.0 /* * KCSAN reporting. * * Copyright (C) 2019, Google LLC. */ #include <linux/debug_locks.h> #include <linux/delay.h> #include <linux/jiffies.h> #include <linux/kallsyms.h> #include <linux/kernel.h> #include <linux/lockdep.h> #include <linux/preempt.h> #include <linux/printk.h> #include <linux/sched.h> #include <linux/spinlock.h> #include <linux/stacktrace.h> #include "kcsan.h" #include "encoding.h" /* * Max. number of stack entries to show in the report. */ #define NUM_STACK_ENTRIES 64 /* Common access info. */ struct access_info { const volatile void *ptr; size_t size; int access_type; int task_pid; int cpu_id; unsigned long ip; }; /* * Other thread info: communicated from other racing thread to thread that set * up the watchpoint, which then prints the complete report atomically. */ struct other_info { struct access_info ai; unsigned long stack_entries[NUM_STACK_ENTRIES]; int num_stack_entries; /* * Optionally pass @current. Typically we do not need to pass @current * via @other_info since just @task_pid is sufficient. Passing @current * has additional overhead. * * To safely pass @current, we must either use get_task_struct/ * put_task_struct, or stall the thread that populated @other_info. * * We cannot rely on get_task_struct/put_task_struct in case * release_report() races with a task being released, and would have to * free it in release_report(). This may result in deadlock if we want * to use KCSAN on the allocators. * * Since we also want to reliably print held locks for * CONFIG_KCSAN_VERBOSE, the current implementation stalls the thread * that populated @other_info until it has been consumed. */ struct task_struct *task; }; /* * To never block any producers of struct other_info, we need as many elements * as we have watchpoints (upper bound on concurrent races to report). */ static struct other_info other_infos[CONFIG_KCSAN_NUM_WATCHPOINTS + NUM_SLOTS-1]; /* * Information about reported races; used to rate limit reporting. */ struct report_time { /* * The last time the race was reported. */ unsigned long time; /* * The frames of the 2 threads; if only 1 thread is known, one frame * will be 0. */ unsigned long frame1; unsigned long frame2; }; /* * Since we also want to be able to debug allocators with KCSAN, to avoid * deadlock, report_times cannot be dynamically resized with krealloc in * rate_limit_report. * * Therefore, we use a fixed-size array, which at most will occupy a page. This * still adequately rate limits reports, assuming that a) number of unique data * races is not excessive, and b) occurrence of unique races within the * same time window is limited. */ #define REPORT_TIMES_MAX (PAGE_SIZE / sizeof(struct report_time)) #define REPORT_TIMES_SIZE \ (CONFIG_KCSAN_REPORT_ONCE_IN_MS > REPORT_TIMES_MAX ? \ REPORT_TIMES_MAX : \ CONFIG_KCSAN_REPORT_ONCE_IN_MS) static struct report_time report_times[REPORT_TIMES_SIZE]; /* * Spinlock serializing report generation, and access to @other_infos. Although * it could make sense to have a finer-grained locking story for @other_infos, * report generation needs to be serialized either way, so not much is gained. */ static DEFINE_RAW_SPINLOCK(report_lock); /* * Checks if the race identified by thread frames frame1 and frame2 has * been reported since (now - KCSAN_REPORT_ONCE_IN_MS). */ static bool rate_limit_report(unsigned long frame1, unsigned long frame2) __must_hold(&report_lock) { struct report_time *use_entry = &report_times[0]; unsigned long invalid_before; int i; BUILD_BUG_ON(CONFIG_KCSAN_REPORT_ONCE_IN_MS != 0 && REPORT_TIMES_SIZE == 0); if (CONFIG_KCSAN_REPORT_ONCE_IN_MS == 0) return false; invalid_before = jiffies - msecs_to_jiffies(CONFIG_KCSAN_REPORT_ONCE_IN_MS); /* Check if a matching race report exists. */ for (i = 0; i < REPORT_TIMES_SIZE; ++i) { struct report_time *rt = &report_times[i]; /* * Must always select an entry for use to store info as we * cannot resize report_times; at the end of the scan, use_entry * will be the oldest entry, which ideally also happened before * KCSAN_REPORT_ONCE_IN_MS ago. */ if (time_before(rt->time, use_entry->time)) use_entry = rt; /* * Initially, no need to check any further as this entry as well * as following entries have never been used. */ if (rt->time == 0) break; /* Check if entry expired. */ if (time_before(rt->time, invalid_before)) continue; /* before KCSAN_REPORT_ONCE_IN_MS ago */ /* Reported recently, check if race matches. */ if ((rt->frame1 == frame1 && rt->frame2 == frame2) || (rt->frame1 == frame2 && rt->frame2 == frame1)) return true; } use_entry->time = jiffies; use_entry->frame1 = frame1; use_entry->frame2 = frame2; return false; } /* * Special rules to skip reporting. */ static bool skip_report(enum kcsan_value_change value_change, unsigned long top_frame) { /* Should never get here if value_change==FALSE. */ WARN_ON_ONCE(value_change == KCSAN_VALUE_CHANGE_FALSE); /* * The first call to skip_report always has value_change==TRUE, since we * cannot know the value written of an instrumented access. For the 2nd * call there are 6 cases with CONFIG_KCSAN_REPORT_VALUE_CHANGE_ONLY: * * 1. read watchpoint, conflicting write (value_change==TRUE): report; * 2. read watchpoint, conflicting write (value_change==MAYBE): skip; * 3. write watchpoint, conflicting write (value_change==TRUE): report; * 4. write watchpoint, conflicting write (value_change==MAYBE): skip; * 5. write watchpoint, conflicting read (value_change==MAYBE): skip; * 6. write watchpoint, conflicting read (value_change==TRUE): report; * * Cases 1-4 are intuitive and expected; case 5 ensures we do not report * data races where the write may have rewritten the same value; case 6 * is possible either if the size is larger than what we check value * changes for or the access type is KCSAN_ACCESS_ASSERT. */ if (IS_ENABLED(CONFIG_KCSAN_REPORT_VALUE_CHANGE_ONLY) && value_change == KCSAN_VALUE_CHANGE_MAYBE) { /* * The access is a write, but the data value did not change. * * We opt-out of this filter for certain functions at request of * maintainers. */ char buf[64]; int len = scnprintf(buf, sizeof(buf), "%ps", (void *)top_frame); if (!strnstr(buf, "rcu_", len) && !strnstr(buf, "_rcu", len) && !strnstr(buf, "_srcu", len)) return true; } return kcsan_skip_report_debugfs(top_frame); } static const char *get_access_type(int type) { if (type & KCSAN_ACCESS_ASSERT) { if (type & KCSAN_ACCESS_SCOPED) { if (type & KCSAN_ACCESS_WRITE) return "assert no accesses (reordered)"; else return "assert no writes (reordered)"; } else { if (type & KCSAN_ACCESS_WRITE) return "assert no accesses"; else return "assert no writes"; } } switch (type) { case 0: return "read"; case KCSAN_ACCESS_ATOMIC: return "read (marked)"; case KCSAN_ACCESS_WRITE: return "write"; case KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC: return "write (marked)"; case KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE: return "read-write"; case KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC: return "read-write (marked)"; case KCSAN_ACCESS_SCOPED: return "read (reordered)"; case KCSAN_ACCESS_SCOPED | KCSAN_ACCESS_ATOMIC: return "read (marked, reordered)"; case KCSAN_ACCESS_SCOPED | KCSAN_ACCESS_WRITE: return "write (reordered)"; case KCSAN_ACCESS_SCOPED | KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC: return "write (marked, reordered)"; case KCSAN_ACCESS_SCOPED | KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE: return "read-write (reordered)"; case KCSAN_ACCESS_SCOPED | KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC: return "read-write (marked, reordered)"; default: BUG(); } } static const char *get_bug_type(int type) { return (type & KCSAN_ACCESS_ASSERT) != 0 ? "assert: race" : "data-race"; } /* Return thread description: in task or interrupt. */ static const char *get_thread_desc(int task_id) { if (task_id != -1) { static char buf[32]; /* safe: protected by report_lock */ snprintf(buf, sizeof(buf), "task %i", task_id); return buf; } return "interrupt"; } /* Helper to skip KCSAN-related functions in stack-trace. */ static int get_stack_skipnr(const unsigned long stack_entries[], int num_entries) { char buf[64]; char *cur; int len, skip; for (skip = 0; skip < num_entries; ++skip) { len = scnprintf(buf, sizeof(buf), "%ps", (void *)stack_entries[skip]); /* Never show tsan_* or {read,write}_once_size. */ if (strnstr(buf, "tsan_", len) || strnstr(buf, "_once_size", len)) continue; cur = strnstr(buf, "kcsan_", len); if (cur) { cur += strlen("kcsan_"); if (!str_has_prefix(cur, "test")) continue; /* KCSAN runtime function. */ /* KCSAN related test. */ } /* * No match for runtime functions -- @skip entries to skip to * get to first frame of interest. */ break; } return skip; } /* * Skips to the first entry that matches the function of @ip, and then replaces * that entry with @ip, returning the entries to skip with @replaced containing * the replaced entry. */ static int replace_stack_entry(unsigned long stack_entries[], int num_entries, unsigned long ip, unsigned long *replaced) { unsigned long symbolsize, offset; unsigned long target_func; int skip; if (kallsyms_lookup_size_offset(ip, &symbolsize, &offset)) target_func = ip - offset; else goto fallback; for (skip = 0; skip < num_entries; ++skip) { unsigned long func = stack_entries[skip]; if (!kallsyms_lookup_size_offset(func, &symbolsize, &offset)) goto fallback; func -= offset; if (func == target_func) { *replaced = stack_entries[skip]; stack_entries[skip] = ip; return skip; } } fallback: /* Should not happen; the resulting stack trace is likely misleading. */ WARN_ONCE(1, "Cannot find frame for %pS in stack trace", (void *)ip); return get_stack_skipnr(stack_entries, num_entries); } static int sanitize_stack_entries(unsigned long stack_entries[], int num_entries, unsigned long ip, unsigned long *replaced) { return ip ? replace_stack_entry(stack_entries, num_entries, ip, replaced) : get_stack_skipnr(stack_entries, num_entries); } /* Compares symbolized strings of addr1 and addr2. */ static int sym_strcmp(void *addr1, void *addr2) { char buf1[64]; char buf2[64]; snprintf(buf1, sizeof(buf1), "%pS", addr1); snprintf(buf2, sizeof(buf2), "%pS", addr2); return strncmp(buf1, buf2, sizeof(buf1)); } static void print_stack_trace(unsigned long stack_entries[], int num_entries, unsigned long reordered_to) __must_hold(&report_lock) { stack_trace_print(stack_entries, num_entries, 0); if (reordered_to) pr_err(" |\n +-> reordered to: %pS\n", (void *)reordered_to); } static void print_verbose_info(struct task_struct *task) __must_hold(&report_lock) { if (!task) return; /* Restore IRQ state trace for printing. */ kcsan_restore_irqtrace(task); pr_err("\n"); debug_show_held_locks(task); print_irqtrace_events(task); } static void print_report(enum kcsan_value_change value_change, const struct access_info *ai, struct other_info *other_info, u64 old, u64 new, u64 mask) __must_hold(&report_lock) { unsigned long reordered_to = 0; unsigned long stack_entries[NUM_STACK_ENTRIES] = { 0 }; int num_stack_entries = stack_trace_save(stack_entries, NUM_STACK_ENTRIES, 1); int skipnr = sanitize_stack_entries(stack_entries, num_stack_entries, ai->ip, &reordered_to); unsigned long this_frame = stack_entries[skipnr]; unsigned long other_reordered_to = 0; unsigned long other_frame = 0; int other_skipnr = 0; /* silence uninit warnings */ /* * Must check report filter rules before starting to print. */ if (skip_report(KCSAN_VALUE_CHANGE_TRUE, stack_entries[skipnr])) return; if (other_info) { other_skipnr = sanitize_stack_entries(other_info->stack_entries, other_info->num_stack_entries, other_info->ai.ip, &other_reordered_to); other_frame = other_info->stack_entries[other_skipnr]; /* @value_change is only known for the other thread */ if (skip_report(value_change, other_frame)) return; } if (rate_limit_report(this_frame, other_frame)) return; /* Print report header. */ pr_err("==================================================================\n"); if (other_info) { int cmp; /* * Order functions lexographically for consistent bug titles. * Do not print offset of functions to keep title short. */ cmp = sym_strcmp((void *)other_frame, (void *)this_frame); pr_err("BUG: KCSAN: %s in %ps / %ps\n", get_bug_type(ai->access_type | other_info->ai.access_type), (void *)(cmp < 0 ? other_frame : this_frame), (void *)(cmp < 0 ? this_frame : other_frame)); } else { pr_err("BUG: KCSAN: %s in %pS\n", get_bug_type(ai->access_type), (void *)this_frame); } pr_err("\n"); /* Print information about the racing accesses. */ if (other_info) { pr_err("%s to 0x%px of %zu bytes by %s on cpu %i:\n", get_access_type(other_info->ai.access_type), other_info->ai.ptr, other_info->ai.size, get_thread_desc(other_info->ai.task_pid), other_info->ai.cpu_id); /* Print the other thread's stack trace. */ print_stack_trace(other_info->stack_entries + other_skipnr, other_info->num_stack_entries - other_skipnr, other_reordered_to); if (IS_ENABLED(CONFIG_KCSAN_VERBOSE)) print_verbose_info(other_info->task); pr_err("\n"); pr_err("%s to 0x%px of %zu bytes by %s on cpu %i:\n", get_access_type(ai->access_type), ai->ptr, ai->size, get_thread_desc(ai->task_pid), ai->cpu_id); } else { pr_err("race at unknown origin, with %s to 0x%px of %zu bytes by %s on cpu %i:\n", get_access_type(ai->access_type), ai->ptr, ai->size, get_thread_desc(ai->task_pid), ai->cpu_id); } /* Print stack trace of this thread. */ print_stack_trace(stack_entries + skipnr, num_stack_entries - skipnr, reordered_to); if (IS_ENABLED(CONFIG_KCSAN_VERBOSE)) print_verbose_info(current); /* Print observed value change. */ if (ai->size <= 8) { int hex_len = ai->size * 2; u64 diff = old ^ new; if (mask) diff &= mask; if (diff) { pr_err("\n"); pr_err("value changed: 0x%0*llx -> 0x%0*llx\n", hex_len, old, hex_len, new); if (mask) { pr_err(" bits changed: 0x%0*llx with mask 0x%0*llx\n", hex_len, diff, hex_len, mask); } } } /* Print report footer. */ pr_err("\n"); pr_err("Reported by Kernel Concurrency Sanitizer on:\n"); dump_stack_print_info(KERN_DEFAULT); pr_err("==================================================================\n"); check_panic_on_warn("KCSAN"); }