diff options
| -rw-r--r-- | gdb/ChangeLog | 5 | ||||
| -rw-r--r-- | gdb/nat/linux-btrace.c | 19 |
2 files changed, 20 insertions, 4 deletions
diff --git a/gdb/ChangeLog b/gdb/ChangeLog index b4398f6..600925f 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,8 @@ +2016-11-14 Markus Metzger <markus.t.metzger@intel.com> + + * nat/linux-btrace.c (perf_event_read): Allow data_head < size. + * nat/linux-btrace.c (perf_event_read_all): Do not adjust size. + 2016-11-12 Tom Tromey <tom@tromey.com> * rust-exp.y (super_name): Use std::vector. diff --git a/gdb/nat/linux-btrace.c b/gdb/nat/linux-btrace.c index 5ac5db2..e4144c6 100644 --- a/gdb/nat/linux-btrace.c +++ b/gdb/nat/linux-btrace.c @@ -119,10 +119,24 @@ perf_event_read (const struct perf_event_buffer *pev, __u64 data_head, if (size == 0) return NULL; + /* We should never ask for more data than the buffer can hold. */ + buffer_size = pev->size; + gdb_assert (size <= buffer_size); + + /* If we ask for more data than we seem to have, we wrap around and read + data from the end of the buffer. This is already handled by the % + BUFFER_SIZE operation, below. Here, we just need to make sure that we + don't underflow. + + Note that this is perfectly OK for perf event buffers where data_head + doesn'grow indefinitely and instead wraps around to remain within the + buffer's boundaries. */ + if (data_head < size) + data_head += buffer_size; + gdb_assert (size <= data_head); data_tail = data_head - size; - buffer_size = pev->size; begin = pev->mem; start = begin + data_tail % buffer_size; stop = begin + data_head % buffer_size; @@ -153,10 +167,7 @@ perf_event_read_all (struct perf_event_buffer *pev, gdb_byte **data, __u64 data_head; data_head = *pev->data_head; - size = pev->size; - if (data_head < size) - size = (size_t) data_head; *data = perf_event_read (pev, data_head, size); *psize = size; |