KCOV_TRACE_UNIQ_EDGE stores uniq edge info, which is bitwise xor operation
of prev_pc and current pc.
And only hash the lower 12 bits so the hash is independent of any module
offsets.
Signed-off-by: Jiao, Joey <quic_jiang...@quicinc.com>
---
include/linux/kcov.h | 4 ++-
include/uapi/linux/kcov.h | 2 ++
kernel/kcov.c | 73 ++++++++++++++++++++++++++++++++++++-----------
3 files changed, 61 insertions(+), 18 deletions(-)
diff --git a/include/linux/kcov.h b/include/linux/kcov.h
index
aafd9f88450cb8672c701349300b54662bc38079..56b858205ba16c47fc72bda9938c98f034503c8c
100644
--- a/include/linux/kcov.h
+++ b/include/linux/kcov.h
@@ -23,8 +23,10 @@ enum kcov_mode {
KCOV_MODE_TRACE_CMP = 4,
/* The process owns a KCOV remote reference. */
KCOV_MODE_REMOTE = 8,
- /* COllecting uniq pc mode. */
+ /* Collecting uniq pc mode. */
KCOV_MODE_TRACE_UNIQ_PC = 16,
+ /* Collecting uniq edge mode. */
+ KCOV_MODE_TRACE_UNIQ_EDGE = 32,
};
#define KCOV_IN_CTXSW (1 << 30)
diff --git a/include/uapi/linux/kcov.h b/include/uapi/linux/kcov.h
index
d2a2bff36f285a5e3a03395f8890fcb716cf3f07..9b2019f0ab8b8cb5426d2d6b74472fa1a7293817
100644
--- a/include/uapi/linux/kcov.h
+++ b/include/uapi/linux/kcov.h
@@ -37,6 +37,8 @@ enum {
KCOV_TRACE_CMP = 1,
/* Collecting uniq PC mode. */
KCOV_TRACE_UNIQ_PC = 2,
+ /* Collecting uniq edge mode. */
+ KCOV_TRACE_UNIQ_EDGE = 4,
};
/*
diff --git a/kernel/kcov.c b/kernel/kcov.c
index
bbd7b7503206fe595976458ab685b95f784607d7..5a0ead92729294d99db80bb4e0f5b04c8b025dba
100644
--- a/kernel/kcov.c
+++ b/kernel/kcov.c
@@ -83,10 +83,14 @@ struct kcov {
enum kcov_mode mode;
/* Size of arena (in long's). */
unsigned int size;
+ /* Previous PC. */
+ unsigned long prev_pc;
/* Coverage buffer shared with user space. */
void *area;
/* Coverage hashmap for unique pc. */
struct kcov_map *map;
+ /* Edge hashmap for unique edge. */
+ struct kcov_map *map_edge;
/* Task for which we collect coverage, or NULL. */
struct task_struct *t;
/* Collecting coverage from remote (background) threads. */
@@ -221,7 +225,7 @@ static notrace unsigned int check_kcov_mode(enum kcov_mode
needed_mode, struct t
return mode & needed_mode;
}
-static int kcov_map_init(struct kcov *kcov, unsigned long size)
+static int kcov_map_init(struct kcov *kcov, unsigned long size, bool edge)
{
struct kcov_map *map;
void *area;
@@ -240,8 +244,12 @@ static int kcov_map_init(struct kcov *kcov, unsigned long
size)
spin_lock_irqsave(&kcov->lock, flags);
map->area = area;
- kcov->map = map;
- kcov->area = area;
+ if (edge) {
+ kcov->map_edge = map;
+ } else {
+ kcov->map = map;
+ kcov->area = area;
+ }
spin_unlock_irqrestore(&kcov->lock, flags);
hash_init(map->buckets);
@@ -276,7 +284,7 @@ static inline u32 hash_key(const struct kcov_entry *k)
}
static notrace inline void kcov_map_add(struct kcov_map *map, struct
kcov_entry *ent,
- struct task_struct *t)
+ struct task_struct *t, unsigned int
mode)
{
struct kcov *kcov;
struct kcov_entry *entry;
@@ -298,7 +306,10 @@ static notrace inline void kcov_map_add(struct kcov_map
*map, struct kcov_entry
memcpy(entry, ent, sizeof(*entry));
hash_add_rcu(map->buckets, &entry->node, key);
- area = t->kcov_area;
+ if (mode == KCOV_MODE_TRACE_UNIQ_PC)
+ area = t->kcov_area;
+ else
+ area = kcov->map_edge->area;
pos = READ_ONCE(area[0]) + 1;
if (likely(pos < t->kcov_size)) {
@@ -327,13 +338,15 @@ void notrace __sanitizer_cov_trace_pc(void)
unsigned long ip = canonicalize_ip(_RET_IP_);
unsigned long pos;
struct kcov_entry entry = {0};
+ /* Only hash the lower 12 bits so the hash is independent of any module
offsets. */
+ unsigned long mask = (1 << 12) - 1;
unsigned int mode;
t = current;
- if (!check_kcov_mode(KCOV_MODE_TRACE_PC | KCOV_MODE_TRACE_UNIQ_PC, t))
+ if (!check_kcov_mode(KCOV_MODE_TRACE_PC | KCOV_MODE_TRACE_UNIQ_PC |
+ KCOV_MODE_TRACE_UNIQ_EDGE, t))
return;
- area = t->kcov_area;
mode = t->kcov_mode;
if (mode == KCOV_MODE_TRACE_PC) {
area = t->kcov_area;
@@ -352,8 +365,15 @@ void notrace __sanitizer_cov_trace_pc(void)
area[pos] = ip;
}
} else {
- entry.ent = ip;
- kcov_map_add(t->kcov->map, &entry, t);
+ if (mode & KCOV_MODE_TRACE_UNIQ_PC) {
+ entry.ent = ip;
+ kcov_map_add(t->kcov->map, &entry, t,
KCOV_MODE_TRACE_UNIQ_PC);
+ }
+ if (mode & KCOV_MODE_TRACE_UNIQ_EDGE) {
+ entry.ent = (hash_long(t->kcov->prev_pc & mask,
BITS_PER_LONG) & mask) ^ ip;
+ t->kcov->prev_pc = ip;
+ kcov_map_add(t->kcov->map_edge, &entry, t,
KCOV_MODE_TRACE_UNIQ_EDGE);
+ }
}
}
EXPORT_SYMBOL(__sanitizer_cov_trace_pc);
@@ -555,14 +575,17 @@ static void kcov_get(struct kcov *kcov)
refcount_inc(&kcov->refcount);
}
-static void kcov_map_free(struct kcov *kcov)
+static void kcov_map_free(struct kcov *kcov, bool edge)
{
int bkt;
struct hlist_node *tmp;
struct kcov_entry *entry;
struct kcov_map *map;
- map = kcov->map;
+ if (edge)
+ map = kcov->map_edge;
+ else
+ map = kcov->map;
if (!map)
return;
rcu_read_lock();
@@ -581,7 +604,8 @@ static void kcov_put(struct kcov *kcov)
{
if (refcount_dec_and_test(&kcov->refcount)) {
kcov_remote_reset(kcov);
- kcov_map_free(kcov);
+ kcov_map_free(kcov, false);
+ kcov_map_free(kcov, true);
kfree(kcov);
}
}
@@ -636,18 +660,27 @@ static int kcov_mmap(struct file *filep, struct
vm_area_struct *vma)
unsigned long size, off;
struct page *page;
unsigned long flags;
+ void *area;
spin_lock_irqsave(&kcov->lock, flags);
size = kcov->size * sizeof(unsigned long);
- if (kcov->area == NULL || vma->vm_pgoff != 0 ||
- vma->vm_end - vma->vm_start != size) {
+ if (!vma->vm_pgoff) {
+ area = kcov->area;
+ } else if (vma->vm_pgoff == size >> PAGE_SHIFT) {
+ area = kcov->map_edge->area;
+ } else {
+ spin_unlock_irqrestore(&kcov->lock, flags);
+ return -EINVAL;
+ }
+
+ if (!area || vma->vm_end - vma->vm_start != size) {
res = -EINVAL;
goto exit;
}
spin_unlock_irqrestore(&kcov->lock, flags);
vm_flags_set(vma, VM_DONTEXPAND);
for (off = 0; off < size; off += PAGE_SIZE) {
- page = vmalloc_to_page(kcov->area + off);
+ page = vmalloc_to_page(area + off);
res = vm_insert_page(vma, vma->vm_start + off, page);
if (res) {
pr_warn_once("kcov: vm_insert_page() failed\n");
@@ -693,6 +726,8 @@ static int kcov_get_mode(unsigned long arg)
#endif
else if (arg == KCOV_TRACE_UNIQ_PC)
return KCOV_MODE_TRACE_UNIQ_PC;
+ else if (arg == KCOV_TRACE_UNIQ_EDGE)
+ return KCOV_MODE_TRACE_UNIQ_EDGE;
else
return -EINVAL;
}
@@ -747,7 +782,8 @@ static int kcov_ioctl_locked(struct kcov *kcov, unsigned
int cmd,
* at task exit or voluntary by KCOV_DISABLE. After that it can
* be enabled for another task.
*/
- if (kcov->mode != KCOV_MODE_INIT || !kcov->area)
+ if (kcov->mode != KCOV_MODE_INIT || !kcov->area ||
+ !kcov->map_edge->area)
return -EINVAL;
t = current;
if (kcov->t != NULL || t->kcov != NULL)
@@ -859,7 +895,10 @@ static long kcov_ioctl(struct file *filep, unsigned int
cmd, unsigned long arg)
size = arg;
if (size < 2 || size > INT_MAX / sizeof(unsigned long))
return -EINVAL;
- res = kcov_map_init(kcov, size);
+ res = kcov_map_init(kcov, size, false);
+ if (res)
+ return res;
+ res = kcov_map_init(kcov, size, true);
if (res)
return res;
spin_lock_irqsave(&kcov->lock, flags);
--
2.47.1
