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e36299efe7
Commit56348560d4("debugfs: do not attempt to create a new file before the filesystem is initalized") forbids creating new debugfs files until debugfs is fully initialized. This means that KCSAN's debugfs file creation, which happened at the end of __init(), no longer works. And was apparently never supposed to work! However, there is no reason to create KCSAN's debugfs file so early. This commit therefore moves its creation to a late_initcall() callback. Cc: "Rafael J. Wysocki" <rafael@kernel.org> Cc: stable <stable@vger.kernel.org> Fixes:56348560d4("debugfs: do not attempt to create a new file before the filesystem is initalized") Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
1047 lines
37 KiB
C
1047 lines
37 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#define pr_fmt(fmt) "kcsan: " fmt
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#include <linux/atomic.h>
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#include <linux/bug.h>
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#include <linux/delay.h>
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#include <linux/export.h>
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/list.h>
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#include <linux/moduleparam.h>
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#include <linux/percpu.h>
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#include <linux/preempt.h>
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#include <linux/sched.h>
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#include <linux/uaccess.h>
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#include "atomic.h"
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#include "encoding.h"
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#include "kcsan.h"
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static bool kcsan_early_enable = IS_ENABLED(CONFIG_KCSAN_EARLY_ENABLE);
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unsigned int kcsan_udelay_task = CONFIG_KCSAN_UDELAY_TASK;
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unsigned int kcsan_udelay_interrupt = CONFIG_KCSAN_UDELAY_INTERRUPT;
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static long kcsan_skip_watch = CONFIG_KCSAN_SKIP_WATCH;
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static bool kcsan_interrupt_watcher = IS_ENABLED(CONFIG_KCSAN_INTERRUPT_WATCHER);
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#ifdef MODULE_PARAM_PREFIX
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#undef MODULE_PARAM_PREFIX
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#endif
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#define MODULE_PARAM_PREFIX "kcsan."
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module_param_named(early_enable, kcsan_early_enable, bool, 0);
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module_param_named(udelay_task, kcsan_udelay_task, uint, 0644);
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module_param_named(udelay_interrupt, kcsan_udelay_interrupt, uint, 0644);
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module_param_named(skip_watch, kcsan_skip_watch, long, 0644);
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module_param_named(interrupt_watcher, kcsan_interrupt_watcher, bool, 0444);
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bool kcsan_enabled;
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/* Per-CPU kcsan_ctx for interrupts */
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static DEFINE_PER_CPU(struct kcsan_ctx, kcsan_cpu_ctx) = {
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.disable_count = 0,
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.atomic_next = 0,
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.atomic_nest_count = 0,
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.in_flat_atomic = false,
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.access_mask = 0,
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.scoped_accesses = {LIST_POISON1, NULL},
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};
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/*
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* Helper macros to index into adjacent slots, starting from address slot
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* itself, followed by the right and left slots.
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*
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* The purpose is 2-fold:
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*
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* 1. if during insertion the address slot is already occupied, check if
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* any adjacent slots are free;
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* 2. accesses that straddle a slot boundary due to size that exceeds a
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* slot's range may check adjacent slots if any watchpoint matches.
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*
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* Note that accesses with very large size may still miss a watchpoint; however,
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* given this should be rare, this is a reasonable trade-off to make, since this
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* will avoid:
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*
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* 1. excessive contention between watchpoint checks and setup;
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* 2. larger number of simultaneous watchpoints without sacrificing
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* performance.
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*
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* Example: SLOT_IDX values for KCSAN_CHECK_ADJACENT=1, where i is [0, 1, 2]:
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*
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* slot=0: [ 1, 2, 0]
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* slot=9: [10, 11, 9]
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* slot=63: [64, 65, 63]
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*/
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#define SLOT_IDX(slot, i) (slot + ((i + KCSAN_CHECK_ADJACENT) % NUM_SLOTS))
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/*
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* SLOT_IDX_FAST is used in the fast-path. Not first checking the address's primary
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* slot (middle) is fine if we assume that races occur rarely. The set of
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* indices {SLOT_IDX(slot, i) | i in [0, NUM_SLOTS)} is equivalent to
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* {SLOT_IDX_FAST(slot, i) | i in [0, NUM_SLOTS)}.
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*/
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#define SLOT_IDX_FAST(slot, i) (slot + i)
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/*
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* Watchpoints, with each entry encoded as defined in encoding.h: in order to be
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* able to safely update and access a watchpoint without introducing locking
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* overhead, we encode each watchpoint as a single atomic long. The initial
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* zero-initialized state matches INVALID_WATCHPOINT.
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*
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* Add NUM_SLOTS-1 entries to account for overflow; this helps avoid having to
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* use more complicated SLOT_IDX_FAST calculation with modulo in the fast-path.
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*/
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static atomic_long_t watchpoints[CONFIG_KCSAN_NUM_WATCHPOINTS + NUM_SLOTS-1];
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/*
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* Instructions to skip watching counter, used in should_watch(). We use a
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* per-CPU counter to avoid excessive contention.
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*/
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static DEFINE_PER_CPU(long, kcsan_skip);
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/* For kcsan_prandom_u32_max(). */
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static DEFINE_PER_CPU(u32, kcsan_rand_state);
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static __always_inline atomic_long_t *find_watchpoint(unsigned long addr,
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size_t size,
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bool expect_write,
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long *encoded_watchpoint)
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{
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const int slot = watchpoint_slot(addr);
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const unsigned long addr_masked = addr & WATCHPOINT_ADDR_MASK;
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atomic_long_t *watchpoint;
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unsigned long wp_addr_masked;
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size_t wp_size;
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bool is_write;
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int i;
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BUILD_BUG_ON(CONFIG_KCSAN_NUM_WATCHPOINTS < NUM_SLOTS);
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for (i = 0; i < NUM_SLOTS; ++i) {
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watchpoint = &watchpoints[SLOT_IDX_FAST(slot, i)];
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*encoded_watchpoint = atomic_long_read(watchpoint);
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if (!decode_watchpoint(*encoded_watchpoint, &wp_addr_masked,
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&wp_size, &is_write))
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continue;
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if (expect_write && !is_write)
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continue;
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/* Check if the watchpoint matches the access. */
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if (matching_access(wp_addr_masked, wp_size, addr_masked, size))
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return watchpoint;
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}
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return NULL;
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}
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static inline atomic_long_t *
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insert_watchpoint(unsigned long addr, size_t size, bool is_write)
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{
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const int slot = watchpoint_slot(addr);
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const long encoded_watchpoint = encode_watchpoint(addr, size, is_write);
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atomic_long_t *watchpoint;
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int i;
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/* Check slot index logic, ensuring we stay within array bounds. */
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BUILD_BUG_ON(SLOT_IDX(0, 0) != KCSAN_CHECK_ADJACENT);
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BUILD_BUG_ON(SLOT_IDX(0, KCSAN_CHECK_ADJACENT+1) != 0);
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BUILD_BUG_ON(SLOT_IDX(CONFIG_KCSAN_NUM_WATCHPOINTS-1, KCSAN_CHECK_ADJACENT) != ARRAY_SIZE(watchpoints)-1);
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BUILD_BUG_ON(SLOT_IDX(CONFIG_KCSAN_NUM_WATCHPOINTS-1, KCSAN_CHECK_ADJACENT+1) != ARRAY_SIZE(watchpoints) - NUM_SLOTS);
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for (i = 0; i < NUM_SLOTS; ++i) {
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long expect_val = INVALID_WATCHPOINT;
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/* Try to acquire this slot. */
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watchpoint = &watchpoints[SLOT_IDX(slot, i)];
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if (atomic_long_try_cmpxchg_relaxed(watchpoint, &expect_val, encoded_watchpoint))
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return watchpoint;
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}
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return NULL;
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}
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/*
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* Return true if watchpoint was successfully consumed, false otherwise.
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*
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* This may return false if:
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*
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* 1. another thread already consumed the watchpoint;
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* 2. the thread that set up the watchpoint already removed it;
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* 3. the watchpoint was removed and then re-used.
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*/
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static __always_inline bool
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try_consume_watchpoint(atomic_long_t *watchpoint, long encoded_watchpoint)
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{
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return atomic_long_try_cmpxchg_relaxed(watchpoint, &encoded_watchpoint, CONSUMED_WATCHPOINT);
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}
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/* Return true if watchpoint was not touched, false if already consumed. */
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static inline bool consume_watchpoint(atomic_long_t *watchpoint)
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{
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return atomic_long_xchg_relaxed(watchpoint, CONSUMED_WATCHPOINT) != CONSUMED_WATCHPOINT;
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}
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/* Remove the watchpoint -- its slot may be reused after. */
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static inline void remove_watchpoint(atomic_long_t *watchpoint)
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{
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atomic_long_set(watchpoint, INVALID_WATCHPOINT);
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}
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static __always_inline struct kcsan_ctx *get_ctx(void)
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{
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/*
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* In interrupts, use raw_cpu_ptr to avoid unnecessary checks, that would
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* also result in calls that generate warnings in uaccess regions.
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*/
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return in_task() ? ¤t->kcsan_ctx : raw_cpu_ptr(&kcsan_cpu_ctx);
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}
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/* Check scoped accesses; never inline because this is a slow-path! */
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static noinline void kcsan_check_scoped_accesses(void)
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{
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struct kcsan_ctx *ctx = get_ctx();
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struct list_head *prev_save = ctx->scoped_accesses.prev;
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struct kcsan_scoped_access *scoped_access;
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ctx->scoped_accesses.prev = NULL; /* Avoid recursion. */
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list_for_each_entry(scoped_access, &ctx->scoped_accesses, list)
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__kcsan_check_access(scoped_access->ptr, scoped_access->size, scoped_access->type);
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ctx->scoped_accesses.prev = prev_save;
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}
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/* Rules for generic atomic accesses. Called from fast-path. */
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static __always_inline bool
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is_atomic(const volatile void *ptr, size_t size, int type, struct kcsan_ctx *ctx)
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{
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if (type & KCSAN_ACCESS_ATOMIC)
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return true;
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/*
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* Unless explicitly declared atomic, never consider an assertion access
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* as atomic. This allows using them also in atomic regions, such as
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* seqlocks, without implicitly changing their semantics.
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*/
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if (type & KCSAN_ACCESS_ASSERT)
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return false;
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if (IS_ENABLED(CONFIG_KCSAN_ASSUME_PLAIN_WRITES_ATOMIC) &&
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(type & KCSAN_ACCESS_WRITE) && size <= sizeof(long) &&
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!(type & KCSAN_ACCESS_COMPOUND) && IS_ALIGNED((unsigned long)ptr, size))
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return true; /* Assume aligned writes up to word size are atomic. */
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if (ctx->atomic_next > 0) {
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/*
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* Because we do not have separate contexts for nested
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* interrupts, in case atomic_next is set, we simply assume that
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* the outer interrupt set atomic_next. In the worst case, we
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* will conservatively consider operations as atomic. This is a
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* reasonable trade-off to make, since this case should be
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* extremely rare; however, even if extremely rare, it could
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* lead to false positives otherwise.
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*/
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if ((hardirq_count() >> HARDIRQ_SHIFT) < 2)
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--ctx->atomic_next; /* in task, or outer interrupt */
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return true;
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}
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return ctx->atomic_nest_count > 0 || ctx->in_flat_atomic;
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}
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static __always_inline bool
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should_watch(const volatile void *ptr, size_t size, int type, struct kcsan_ctx *ctx)
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{
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/*
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* Never set up watchpoints when memory operations are atomic.
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*
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* Need to check this first, before kcsan_skip check below: (1) atomics
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* should not count towards skipped instructions, and (2) to actually
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* decrement kcsan_atomic_next for consecutive instruction stream.
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*/
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if (is_atomic(ptr, size, type, ctx))
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return false;
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if (this_cpu_dec_return(kcsan_skip) >= 0)
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return false;
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/*
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* NOTE: If we get here, kcsan_skip must always be reset in slow path
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* via reset_kcsan_skip() to avoid underflow.
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*/
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/* this operation should be watched */
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return true;
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}
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/*
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* Returns a pseudo-random number in interval [0, ep_ro). Simple linear
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* congruential generator, using constants from "Numerical Recipes".
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*/
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static u32 kcsan_prandom_u32_max(u32 ep_ro)
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{
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u32 state = this_cpu_read(kcsan_rand_state);
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state = 1664525 * state + 1013904223;
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this_cpu_write(kcsan_rand_state, state);
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return state % ep_ro;
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}
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static inline void reset_kcsan_skip(void)
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{
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long skip_count = kcsan_skip_watch -
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(IS_ENABLED(CONFIG_KCSAN_SKIP_WATCH_RANDOMIZE) ?
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kcsan_prandom_u32_max(kcsan_skip_watch) :
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0);
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this_cpu_write(kcsan_skip, skip_count);
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}
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static __always_inline bool kcsan_is_enabled(void)
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{
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return READ_ONCE(kcsan_enabled) && get_ctx()->disable_count == 0;
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}
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/* Introduce delay depending on context and configuration. */
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static void delay_access(int type)
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{
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unsigned int delay = in_task() ? kcsan_udelay_task : kcsan_udelay_interrupt;
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/* For certain access types, skew the random delay to be longer. */
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unsigned int skew_delay_order =
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(type & (KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_ASSERT)) ? 1 : 0;
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delay -= IS_ENABLED(CONFIG_KCSAN_DELAY_RANDOMIZE) ?
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kcsan_prandom_u32_max(delay >> skew_delay_order) :
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0;
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udelay(delay);
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}
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void kcsan_save_irqtrace(struct task_struct *task)
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{
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#ifdef CONFIG_TRACE_IRQFLAGS
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task->kcsan_save_irqtrace = task->irqtrace;
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#endif
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}
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void kcsan_restore_irqtrace(struct task_struct *task)
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{
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#ifdef CONFIG_TRACE_IRQFLAGS
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task->irqtrace = task->kcsan_save_irqtrace;
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#endif
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}
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/*
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* Pull everything together: check_access() below contains the performance
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* critical operations; the fast-path (including check_access) functions should
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* all be inlinable by the instrumentation functions.
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*
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* The slow-path (kcsan_found_watchpoint, kcsan_setup_watchpoint) are
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* non-inlinable -- note that, we prefix these with "kcsan_" to ensure they can
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* be filtered from the stacktrace, as well as give them unique names for the
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* UACCESS whitelist of objtool. Each function uses user_access_save/restore(),
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* since they do not access any user memory, but instrumentation is still
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* emitted in UACCESS regions.
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*/
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static noinline void kcsan_found_watchpoint(const volatile void *ptr,
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size_t size,
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int type,
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atomic_long_t *watchpoint,
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long encoded_watchpoint)
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{
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unsigned long flags;
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bool consumed;
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if (!kcsan_is_enabled())
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return;
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/*
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* The access_mask check relies on value-change comparison. To avoid
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* reporting a race where e.g. the writer set up the watchpoint, but the
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* reader has access_mask!=0, we have to ignore the found watchpoint.
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*/
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if (get_ctx()->access_mask != 0)
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return;
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/*
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* Consume the watchpoint as soon as possible, to minimize the chances
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* of !consumed. Consuming the watchpoint must always be guarded by
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* kcsan_is_enabled() check, as otherwise we might erroneously
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* triggering reports when disabled.
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*/
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consumed = try_consume_watchpoint(watchpoint, encoded_watchpoint);
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/* keep this after try_consume_watchpoint */
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flags = user_access_save();
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if (consumed) {
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kcsan_save_irqtrace(current);
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kcsan_report(ptr, size, type, KCSAN_VALUE_CHANGE_MAYBE,
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KCSAN_REPORT_CONSUMED_WATCHPOINT,
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watchpoint - watchpoints);
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kcsan_restore_irqtrace(current);
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} else {
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/*
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* The other thread may not print any diagnostics, as it has
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* already removed the watchpoint, or another thread consumed
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* the watchpoint before this thread.
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*/
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atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_REPORT_RACES]);
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}
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if ((type & KCSAN_ACCESS_ASSERT) != 0)
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atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_ASSERT_FAILURES]);
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else
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atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_DATA_RACES]);
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user_access_restore(flags);
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}
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static noinline void
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kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type)
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{
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const bool is_write = (type & KCSAN_ACCESS_WRITE) != 0;
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const bool is_assert = (type & KCSAN_ACCESS_ASSERT) != 0;
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atomic_long_t *watchpoint;
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union {
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u8 _1;
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u16 _2;
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u32 _4;
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u64 _8;
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} expect_value;
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unsigned long access_mask;
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enum kcsan_value_change value_change = KCSAN_VALUE_CHANGE_MAYBE;
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unsigned long ua_flags = user_access_save();
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unsigned long irq_flags = 0;
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/*
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* Always reset kcsan_skip counter in slow-path to avoid underflow; see
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* should_watch().
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*/
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reset_kcsan_skip();
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if (!kcsan_is_enabled())
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goto out;
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/*
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* Special atomic rules: unlikely to be true, so we check them here in
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* the slow-path, and not in the fast-path in is_atomic(). Call after
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* kcsan_is_enabled(), as we may access memory that is not yet
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* initialized during early boot.
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*/
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if (!is_assert && kcsan_is_atomic_special(ptr))
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goto out;
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if (!check_encodable((unsigned long)ptr, size)) {
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atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_UNENCODABLE_ACCESSES]);
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goto out;
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}
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/*
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* Save and restore the IRQ state trace touched by KCSAN, since KCSAN's
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* runtime is entered for every memory access, and potentially useful
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* information is lost if dirtied by KCSAN.
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*/
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kcsan_save_irqtrace(current);
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if (!kcsan_interrupt_watcher)
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local_irq_save(irq_flags);
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watchpoint = insert_watchpoint((unsigned long)ptr, size, is_write);
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if (watchpoint == NULL) {
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/*
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* Out of capacity: the size of 'watchpoints', and the frequency
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* with which should_watch() returns true should be tweaked so
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* that this case happens very rarely.
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|
*/
|
|
atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_NO_CAPACITY]);
|
|
goto out_unlock;
|
|
}
|
|
|
|
atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_SETUP_WATCHPOINTS]);
|
|
atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_USED_WATCHPOINTS]);
|
|
|
|
/*
|
|
* Read the current value, to later check and infer a race if the data
|
|
* was modified via a non-instrumented access, e.g. from a device.
|
|
*/
|
|
expect_value._8 = 0;
|
|
switch (size) {
|
|
case 1:
|
|
expect_value._1 = READ_ONCE(*(const u8 *)ptr);
|
|
break;
|
|
case 2:
|
|
expect_value._2 = READ_ONCE(*(const u16 *)ptr);
|
|
break;
|
|
case 4:
|
|
expect_value._4 = READ_ONCE(*(const u32 *)ptr);
|
|
break;
|
|
case 8:
|
|
expect_value._8 = READ_ONCE(*(const u64 *)ptr);
|
|
break;
|
|
default:
|
|
break; /* ignore; we do not diff the values */
|
|
}
|
|
|
|
if (IS_ENABLED(CONFIG_KCSAN_DEBUG)) {
|
|
kcsan_disable_current();
|
|
pr_err("watching %s, size: %zu, addr: %px [slot: %d, encoded: %lx]\n",
|
|
is_write ? "write" : "read", size, ptr,
|
|
watchpoint_slot((unsigned long)ptr),
|
|
encode_watchpoint((unsigned long)ptr, size, is_write));
|
|
kcsan_enable_current();
|
|
}
|
|
|
|
/*
|
|
* Delay this thread, to increase probability of observing a racy
|
|
* conflicting access.
|
|
*/
|
|
delay_access(type);
|
|
|
|
/*
|
|
* Re-read value, and check if it is as expected; if not, we infer a
|
|
* racy access.
|
|
*/
|
|
access_mask = get_ctx()->access_mask;
|
|
switch (size) {
|
|
case 1:
|
|
expect_value._1 ^= READ_ONCE(*(const u8 *)ptr);
|
|
if (access_mask)
|
|
expect_value._1 &= (u8)access_mask;
|
|
break;
|
|
case 2:
|
|
expect_value._2 ^= READ_ONCE(*(const u16 *)ptr);
|
|
if (access_mask)
|
|
expect_value._2 &= (u16)access_mask;
|
|
break;
|
|
case 4:
|
|
expect_value._4 ^= READ_ONCE(*(const u32 *)ptr);
|
|
if (access_mask)
|
|
expect_value._4 &= (u32)access_mask;
|
|
break;
|
|
case 8:
|
|
expect_value._8 ^= READ_ONCE(*(const u64 *)ptr);
|
|
if (access_mask)
|
|
expect_value._8 &= (u64)access_mask;
|
|
break;
|
|
default:
|
|
break; /* ignore; we do not diff the values */
|
|
}
|
|
|
|
/* Were we able to observe a value-change? */
|
|
if (expect_value._8 != 0)
|
|
value_change = KCSAN_VALUE_CHANGE_TRUE;
|
|
|
|
/* Check if this access raced with another. */
|
|
if (!consume_watchpoint(watchpoint)) {
|
|
/*
|
|
* Depending on the access type, map a value_change of MAYBE to
|
|
* TRUE (always report) or FALSE (never report).
|
|
*/
|
|
if (value_change == KCSAN_VALUE_CHANGE_MAYBE) {
|
|
if (access_mask != 0) {
|
|
/*
|
|
* For access with access_mask, we require a
|
|
* value-change, as it is likely that races on
|
|
* ~access_mask bits are expected.
|
|
*/
|
|
value_change = KCSAN_VALUE_CHANGE_FALSE;
|
|
} else if (size > 8 || is_assert) {
|
|
/* Always assume a value-change. */
|
|
value_change = KCSAN_VALUE_CHANGE_TRUE;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* No need to increment 'data_races' counter, as the racing
|
|
* thread already did.
|
|
*
|
|
* Count 'assert_failures' for each failed ASSERT access,
|
|
* therefore both this thread and the racing thread may
|
|
* increment this counter.
|
|
*/
|
|
if (is_assert && value_change == KCSAN_VALUE_CHANGE_TRUE)
|
|
atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_ASSERT_FAILURES]);
|
|
|
|
kcsan_report(ptr, size, type, value_change, KCSAN_REPORT_RACE_SIGNAL,
|
|
watchpoint - watchpoints);
|
|
} else if (value_change == KCSAN_VALUE_CHANGE_TRUE) {
|
|
/* Inferring a race, since the value should not have changed. */
|
|
|
|
atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_RACES_UNKNOWN_ORIGIN]);
|
|
if (is_assert)
|
|
atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_ASSERT_FAILURES]);
|
|
|
|
if (IS_ENABLED(CONFIG_KCSAN_REPORT_RACE_UNKNOWN_ORIGIN) || is_assert)
|
|
kcsan_report(ptr, size, type, KCSAN_VALUE_CHANGE_TRUE,
|
|
KCSAN_REPORT_RACE_UNKNOWN_ORIGIN,
|
|
watchpoint - watchpoints);
|
|
}
|
|
|
|
/*
|
|
* Remove watchpoint; must be after reporting, since the slot may be
|
|
* reused after this point.
|
|
*/
|
|
remove_watchpoint(watchpoint);
|
|
atomic_long_dec(&kcsan_counters[KCSAN_COUNTER_USED_WATCHPOINTS]);
|
|
out_unlock:
|
|
if (!kcsan_interrupt_watcher)
|
|
local_irq_restore(irq_flags);
|
|
kcsan_restore_irqtrace(current);
|
|
out:
|
|
user_access_restore(ua_flags);
|
|
}
|
|
|
|
static __always_inline void check_access(const volatile void *ptr, size_t size,
|
|
int type)
|
|
{
|
|
const bool is_write = (type & KCSAN_ACCESS_WRITE) != 0;
|
|
atomic_long_t *watchpoint;
|
|
long encoded_watchpoint;
|
|
|
|
/*
|
|
* Do nothing for 0 sized check; this comparison will be optimized out
|
|
* for constant sized instrumentation (__tsan_{read,write}N).
|
|
*/
|
|
if (unlikely(size == 0))
|
|
return;
|
|
|
|
/*
|
|
* Avoid user_access_save in fast-path: find_watchpoint is safe without
|
|
* user_access_save, as the address that ptr points to is only used to
|
|
* check if a watchpoint exists; ptr is never dereferenced.
|
|
*/
|
|
watchpoint = find_watchpoint((unsigned long)ptr, size, !is_write,
|
|
&encoded_watchpoint);
|
|
/*
|
|
* It is safe to check kcsan_is_enabled() after find_watchpoint in the
|
|
* slow-path, as long as no state changes that cause a race to be
|
|
* detected and reported have occurred until kcsan_is_enabled() is
|
|
* checked.
|
|
*/
|
|
|
|
if (unlikely(watchpoint != NULL))
|
|
kcsan_found_watchpoint(ptr, size, type, watchpoint,
|
|
encoded_watchpoint);
|
|
else {
|
|
struct kcsan_ctx *ctx = get_ctx(); /* Call only once in fast-path. */
|
|
|
|
if (unlikely(should_watch(ptr, size, type, ctx)))
|
|
kcsan_setup_watchpoint(ptr, size, type);
|
|
else if (unlikely(ctx->scoped_accesses.prev))
|
|
kcsan_check_scoped_accesses();
|
|
}
|
|
}
|
|
|
|
/* === Public interface ===================================================== */
|
|
|
|
void __init kcsan_init(void)
|
|
{
|
|
int cpu;
|
|
|
|
BUG_ON(!in_task());
|
|
|
|
for_each_possible_cpu(cpu)
|
|
per_cpu(kcsan_rand_state, cpu) = (u32)get_cycles();
|
|
|
|
/*
|
|
* We are in the init task, and no other tasks should be running;
|
|
* WRITE_ONCE without memory barrier is sufficient.
|
|
*/
|
|
if (kcsan_early_enable) {
|
|
pr_info("enabled early\n");
|
|
WRITE_ONCE(kcsan_enabled, true);
|
|
}
|
|
}
|
|
|
|
/* === Exported interface =================================================== */
|
|
|
|
void kcsan_disable_current(void)
|
|
{
|
|
++get_ctx()->disable_count;
|
|
}
|
|
EXPORT_SYMBOL(kcsan_disable_current);
|
|
|
|
void kcsan_enable_current(void)
|
|
{
|
|
if (get_ctx()->disable_count-- == 0) {
|
|
/*
|
|
* Warn if kcsan_enable_current() calls are unbalanced with
|
|
* kcsan_disable_current() calls, which causes disable_count to
|
|
* become negative and should not happen.
|
|
*/
|
|
kcsan_disable_current(); /* restore to 0, KCSAN still enabled */
|
|
kcsan_disable_current(); /* disable to generate warning */
|
|
WARN(1, "Unbalanced %s()", __func__);
|
|
kcsan_enable_current();
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(kcsan_enable_current);
|
|
|
|
void kcsan_enable_current_nowarn(void)
|
|
{
|
|
if (get_ctx()->disable_count-- == 0)
|
|
kcsan_disable_current();
|
|
}
|
|
EXPORT_SYMBOL(kcsan_enable_current_nowarn);
|
|
|
|
void kcsan_nestable_atomic_begin(void)
|
|
{
|
|
/*
|
|
* Do *not* check and warn if we are in a flat atomic region: nestable
|
|
* and flat atomic regions are independent from each other.
|
|
* See include/linux/kcsan.h: struct kcsan_ctx comments for more
|
|
* comments.
|
|
*/
|
|
|
|
++get_ctx()->atomic_nest_count;
|
|
}
|
|
EXPORT_SYMBOL(kcsan_nestable_atomic_begin);
|
|
|
|
void kcsan_nestable_atomic_end(void)
|
|
{
|
|
if (get_ctx()->atomic_nest_count-- == 0) {
|
|
/*
|
|
* Warn if kcsan_nestable_atomic_end() calls are unbalanced with
|
|
* kcsan_nestable_atomic_begin() calls, which causes
|
|
* atomic_nest_count to become negative and should not happen.
|
|
*/
|
|
kcsan_nestable_atomic_begin(); /* restore to 0 */
|
|
kcsan_disable_current(); /* disable to generate warning */
|
|
WARN(1, "Unbalanced %s()", __func__);
|
|
kcsan_enable_current();
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(kcsan_nestable_atomic_end);
|
|
|
|
void kcsan_flat_atomic_begin(void)
|
|
{
|
|
get_ctx()->in_flat_atomic = true;
|
|
}
|
|
EXPORT_SYMBOL(kcsan_flat_atomic_begin);
|
|
|
|
void kcsan_flat_atomic_end(void)
|
|
{
|
|
get_ctx()->in_flat_atomic = false;
|
|
}
|
|
EXPORT_SYMBOL(kcsan_flat_atomic_end);
|
|
|
|
void kcsan_atomic_next(int n)
|
|
{
|
|
get_ctx()->atomic_next = n;
|
|
}
|
|
EXPORT_SYMBOL(kcsan_atomic_next);
|
|
|
|
void kcsan_set_access_mask(unsigned long mask)
|
|
{
|
|
get_ctx()->access_mask = mask;
|
|
}
|
|
EXPORT_SYMBOL(kcsan_set_access_mask);
|
|
|
|
struct kcsan_scoped_access *
|
|
kcsan_begin_scoped_access(const volatile void *ptr, size_t size, int type,
|
|
struct kcsan_scoped_access *sa)
|
|
{
|
|
struct kcsan_ctx *ctx = get_ctx();
|
|
|
|
__kcsan_check_access(ptr, size, type);
|
|
|
|
ctx->disable_count++; /* Disable KCSAN, in case list debugging is on. */
|
|
|
|
INIT_LIST_HEAD(&sa->list);
|
|
sa->ptr = ptr;
|
|
sa->size = size;
|
|
sa->type = type;
|
|
|
|
if (!ctx->scoped_accesses.prev) /* Lazy initialize list head. */
|
|
INIT_LIST_HEAD(&ctx->scoped_accesses);
|
|
list_add(&sa->list, &ctx->scoped_accesses);
|
|
|
|
ctx->disable_count--;
|
|
return sa;
|
|
}
|
|
EXPORT_SYMBOL(kcsan_begin_scoped_access);
|
|
|
|
void kcsan_end_scoped_access(struct kcsan_scoped_access *sa)
|
|
{
|
|
struct kcsan_ctx *ctx = get_ctx();
|
|
|
|
if (WARN(!ctx->scoped_accesses.prev, "Unbalanced %s()?", __func__))
|
|
return;
|
|
|
|
ctx->disable_count++; /* Disable KCSAN, in case list debugging is on. */
|
|
|
|
list_del(&sa->list);
|
|
if (list_empty(&ctx->scoped_accesses))
|
|
/*
|
|
* Ensure we do not enter kcsan_check_scoped_accesses()
|
|
* slow-path if unnecessary, and avoids requiring list_empty()
|
|
* in the fast-path (to avoid a READ_ONCE() and potential
|
|
* uaccess warning).
|
|
*/
|
|
ctx->scoped_accesses.prev = NULL;
|
|
|
|
ctx->disable_count--;
|
|
|
|
__kcsan_check_access(sa->ptr, sa->size, sa->type);
|
|
}
|
|
EXPORT_SYMBOL(kcsan_end_scoped_access);
|
|
|
|
void __kcsan_check_access(const volatile void *ptr, size_t size, int type)
|
|
{
|
|
check_access(ptr, size, type);
|
|
}
|
|
EXPORT_SYMBOL(__kcsan_check_access);
|
|
|
|
/*
|
|
* KCSAN uses the same instrumentation that is emitted by supported compilers
|
|
* for ThreadSanitizer (TSAN).
|
|
*
|
|
* When enabled, the compiler emits instrumentation calls (the functions
|
|
* prefixed with "__tsan" below) for all loads and stores that it generated;
|
|
* inline asm is not instrumented.
|
|
*
|
|
* Note that, not all supported compiler versions distinguish aligned/unaligned
|
|
* accesses, but e.g. recent versions of Clang do. We simply alias the unaligned
|
|
* version to the generic version, which can handle both.
|
|
*/
|
|
|
|
#define DEFINE_TSAN_READ_WRITE(size) \
|
|
void __tsan_read##size(void *ptr); \
|
|
void __tsan_read##size(void *ptr) \
|
|
{ \
|
|
check_access(ptr, size, 0); \
|
|
} \
|
|
EXPORT_SYMBOL(__tsan_read##size); \
|
|
void __tsan_unaligned_read##size(void *ptr) \
|
|
__alias(__tsan_read##size); \
|
|
EXPORT_SYMBOL(__tsan_unaligned_read##size); \
|
|
void __tsan_write##size(void *ptr); \
|
|
void __tsan_write##size(void *ptr) \
|
|
{ \
|
|
check_access(ptr, size, KCSAN_ACCESS_WRITE); \
|
|
} \
|
|
EXPORT_SYMBOL(__tsan_write##size); \
|
|
void __tsan_unaligned_write##size(void *ptr) \
|
|
__alias(__tsan_write##size); \
|
|
EXPORT_SYMBOL(__tsan_unaligned_write##size); \
|
|
void __tsan_read_write##size(void *ptr); \
|
|
void __tsan_read_write##size(void *ptr) \
|
|
{ \
|
|
check_access(ptr, size, \
|
|
KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE); \
|
|
} \
|
|
EXPORT_SYMBOL(__tsan_read_write##size); \
|
|
void __tsan_unaligned_read_write##size(void *ptr) \
|
|
__alias(__tsan_read_write##size); \
|
|
EXPORT_SYMBOL(__tsan_unaligned_read_write##size)
|
|
|
|
DEFINE_TSAN_READ_WRITE(1);
|
|
DEFINE_TSAN_READ_WRITE(2);
|
|
DEFINE_TSAN_READ_WRITE(4);
|
|
DEFINE_TSAN_READ_WRITE(8);
|
|
DEFINE_TSAN_READ_WRITE(16);
|
|
|
|
void __tsan_read_range(void *ptr, size_t size);
|
|
void __tsan_read_range(void *ptr, size_t size)
|
|
{
|
|
check_access(ptr, size, 0);
|
|
}
|
|
EXPORT_SYMBOL(__tsan_read_range);
|
|
|
|
void __tsan_write_range(void *ptr, size_t size);
|
|
void __tsan_write_range(void *ptr, size_t size)
|
|
{
|
|
check_access(ptr, size, KCSAN_ACCESS_WRITE);
|
|
}
|
|
EXPORT_SYMBOL(__tsan_write_range);
|
|
|
|
/*
|
|
* Use of explicit volatile is generally disallowed [1], however, volatile is
|
|
* still used in various concurrent context, whether in low-level
|
|
* synchronization primitives or for legacy reasons.
|
|
* [1] https://lwn.net/Articles/233479/
|
|
*
|
|
* We only consider volatile accesses atomic if they are aligned and would pass
|
|
* the size-check of compiletime_assert_rwonce_type().
|
|
*/
|
|
#define DEFINE_TSAN_VOLATILE_READ_WRITE(size) \
|
|
void __tsan_volatile_read##size(void *ptr); \
|
|
void __tsan_volatile_read##size(void *ptr) \
|
|
{ \
|
|
const bool is_atomic = size <= sizeof(long long) && \
|
|
IS_ALIGNED((unsigned long)ptr, size); \
|
|
if (IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS) && is_atomic) \
|
|
return; \
|
|
check_access(ptr, size, is_atomic ? KCSAN_ACCESS_ATOMIC : 0); \
|
|
} \
|
|
EXPORT_SYMBOL(__tsan_volatile_read##size); \
|
|
void __tsan_unaligned_volatile_read##size(void *ptr) \
|
|
__alias(__tsan_volatile_read##size); \
|
|
EXPORT_SYMBOL(__tsan_unaligned_volatile_read##size); \
|
|
void __tsan_volatile_write##size(void *ptr); \
|
|
void __tsan_volatile_write##size(void *ptr) \
|
|
{ \
|
|
const bool is_atomic = size <= sizeof(long long) && \
|
|
IS_ALIGNED((unsigned long)ptr, size); \
|
|
if (IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS) && is_atomic) \
|
|
return; \
|
|
check_access(ptr, size, \
|
|
KCSAN_ACCESS_WRITE | \
|
|
(is_atomic ? KCSAN_ACCESS_ATOMIC : 0)); \
|
|
} \
|
|
EXPORT_SYMBOL(__tsan_volatile_write##size); \
|
|
void __tsan_unaligned_volatile_write##size(void *ptr) \
|
|
__alias(__tsan_volatile_write##size); \
|
|
EXPORT_SYMBOL(__tsan_unaligned_volatile_write##size)
|
|
|
|
DEFINE_TSAN_VOLATILE_READ_WRITE(1);
|
|
DEFINE_TSAN_VOLATILE_READ_WRITE(2);
|
|
DEFINE_TSAN_VOLATILE_READ_WRITE(4);
|
|
DEFINE_TSAN_VOLATILE_READ_WRITE(8);
|
|
DEFINE_TSAN_VOLATILE_READ_WRITE(16);
|
|
|
|
/*
|
|
* The below are not required by KCSAN, but can still be emitted by the
|
|
* compiler.
|
|
*/
|
|
void __tsan_func_entry(void *call_pc);
|
|
void __tsan_func_entry(void *call_pc)
|
|
{
|
|
}
|
|
EXPORT_SYMBOL(__tsan_func_entry);
|
|
void __tsan_func_exit(void);
|
|
void __tsan_func_exit(void)
|
|
{
|
|
}
|
|
EXPORT_SYMBOL(__tsan_func_exit);
|
|
void __tsan_init(void);
|
|
void __tsan_init(void)
|
|
{
|
|
}
|
|
EXPORT_SYMBOL(__tsan_init);
|
|
|
|
/*
|
|
* Instrumentation for atomic builtins (__atomic_*, __sync_*).
|
|
*
|
|
* Normal kernel code _should not_ be using them directly, but some
|
|
* architectures may implement some or all atomics using the compilers'
|
|
* builtins.
|
|
*
|
|
* Note: If an architecture decides to fully implement atomics using the
|
|
* builtins, because they are implicitly instrumented by KCSAN (and KASAN,
|
|
* etc.), implementing the ARCH_ATOMIC interface (to get instrumentation via
|
|
* atomic-instrumented) is no longer necessary.
|
|
*
|
|
* TSAN instrumentation replaces atomic accesses with calls to any of the below
|
|
* functions, whose job is to also execute the operation itself.
|
|
*/
|
|
|
|
#define DEFINE_TSAN_ATOMIC_LOAD_STORE(bits) \
|
|
u##bits __tsan_atomic##bits##_load(const u##bits *ptr, int memorder); \
|
|
u##bits __tsan_atomic##bits##_load(const u##bits *ptr, int memorder) \
|
|
{ \
|
|
if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) { \
|
|
check_access(ptr, bits / BITS_PER_BYTE, KCSAN_ACCESS_ATOMIC); \
|
|
} \
|
|
return __atomic_load_n(ptr, memorder); \
|
|
} \
|
|
EXPORT_SYMBOL(__tsan_atomic##bits##_load); \
|
|
void __tsan_atomic##bits##_store(u##bits *ptr, u##bits v, int memorder); \
|
|
void __tsan_atomic##bits##_store(u##bits *ptr, u##bits v, int memorder) \
|
|
{ \
|
|
if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) { \
|
|
check_access(ptr, bits / BITS_PER_BYTE, \
|
|
KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC); \
|
|
} \
|
|
__atomic_store_n(ptr, v, memorder); \
|
|
} \
|
|
EXPORT_SYMBOL(__tsan_atomic##bits##_store)
|
|
|
|
#define DEFINE_TSAN_ATOMIC_RMW(op, bits, suffix) \
|
|
u##bits __tsan_atomic##bits##_##op(u##bits *ptr, u##bits v, int memorder); \
|
|
u##bits __tsan_atomic##bits##_##op(u##bits *ptr, u##bits v, int memorder) \
|
|
{ \
|
|
if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) { \
|
|
check_access(ptr, bits / BITS_PER_BYTE, \
|
|
KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE | \
|
|
KCSAN_ACCESS_ATOMIC); \
|
|
} \
|
|
return __atomic_##op##suffix(ptr, v, memorder); \
|
|
} \
|
|
EXPORT_SYMBOL(__tsan_atomic##bits##_##op)
|
|
|
|
/*
|
|
* Note: CAS operations are always classified as write, even in case they
|
|
* fail. We cannot perform check_access() after a write, as it might lead to
|
|
* false positives, in cases such as:
|
|
*
|
|
* T0: __atomic_compare_exchange_n(&p->flag, &old, 1, ...)
|
|
*
|
|
* T1: if (__atomic_load_n(&p->flag, ...)) {
|
|
* modify *p;
|
|
* p->flag = 0;
|
|
* }
|
|
*
|
|
* The only downside is that, if there are 3 threads, with one CAS that
|
|
* succeeds, another CAS that fails, and an unmarked racing operation, we may
|
|
* point at the wrong CAS as the source of the race. However, if we assume that
|
|
* all CAS can succeed in some other execution, the data race is still valid.
|
|
*/
|
|
#define DEFINE_TSAN_ATOMIC_CMPXCHG(bits, strength, weak) \
|
|
int __tsan_atomic##bits##_compare_exchange_##strength(u##bits *ptr, u##bits *exp, \
|
|
u##bits val, int mo, int fail_mo); \
|
|
int __tsan_atomic##bits##_compare_exchange_##strength(u##bits *ptr, u##bits *exp, \
|
|
u##bits val, int mo, int fail_mo) \
|
|
{ \
|
|
if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) { \
|
|
check_access(ptr, bits / BITS_PER_BYTE, \
|
|
KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE | \
|
|
KCSAN_ACCESS_ATOMIC); \
|
|
} \
|
|
return __atomic_compare_exchange_n(ptr, exp, val, weak, mo, fail_mo); \
|
|
} \
|
|
EXPORT_SYMBOL(__tsan_atomic##bits##_compare_exchange_##strength)
|
|
|
|
#define DEFINE_TSAN_ATOMIC_CMPXCHG_VAL(bits) \
|
|
u##bits __tsan_atomic##bits##_compare_exchange_val(u##bits *ptr, u##bits exp, u##bits val, \
|
|
int mo, int fail_mo); \
|
|
u##bits __tsan_atomic##bits##_compare_exchange_val(u##bits *ptr, u##bits exp, u##bits val, \
|
|
int mo, int fail_mo) \
|
|
{ \
|
|
if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) { \
|
|
check_access(ptr, bits / BITS_PER_BYTE, \
|
|
KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE | \
|
|
KCSAN_ACCESS_ATOMIC); \
|
|
} \
|
|
__atomic_compare_exchange_n(ptr, &exp, val, 0, mo, fail_mo); \
|
|
return exp; \
|
|
} \
|
|
EXPORT_SYMBOL(__tsan_atomic##bits##_compare_exchange_val)
|
|
|
|
#define DEFINE_TSAN_ATOMIC_OPS(bits) \
|
|
DEFINE_TSAN_ATOMIC_LOAD_STORE(bits); \
|
|
DEFINE_TSAN_ATOMIC_RMW(exchange, bits, _n); \
|
|
DEFINE_TSAN_ATOMIC_RMW(fetch_add, bits, ); \
|
|
DEFINE_TSAN_ATOMIC_RMW(fetch_sub, bits, ); \
|
|
DEFINE_TSAN_ATOMIC_RMW(fetch_and, bits, ); \
|
|
DEFINE_TSAN_ATOMIC_RMW(fetch_or, bits, ); \
|
|
DEFINE_TSAN_ATOMIC_RMW(fetch_xor, bits, ); \
|
|
DEFINE_TSAN_ATOMIC_RMW(fetch_nand, bits, ); \
|
|
DEFINE_TSAN_ATOMIC_CMPXCHG(bits, strong, 0); \
|
|
DEFINE_TSAN_ATOMIC_CMPXCHG(bits, weak, 1); \
|
|
DEFINE_TSAN_ATOMIC_CMPXCHG_VAL(bits)
|
|
|
|
DEFINE_TSAN_ATOMIC_OPS(8);
|
|
DEFINE_TSAN_ATOMIC_OPS(16);
|
|
DEFINE_TSAN_ATOMIC_OPS(32);
|
|
DEFINE_TSAN_ATOMIC_OPS(64);
|
|
|
|
void __tsan_atomic_thread_fence(int memorder);
|
|
void __tsan_atomic_thread_fence(int memorder)
|
|
{
|
|
__atomic_thread_fence(memorder);
|
|
}
|
|
EXPORT_SYMBOL(__tsan_atomic_thread_fence);
|
|
|
|
void __tsan_atomic_signal_fence(int memorder);
|
|
void __tsan_atomic_signal_fence(int memorder) { }
|
|
EXPORT_SYMBOL(__tsan_atomic_signal_fence);
|