From: John Ogness john.ogness@linutronix.de
[ Upstream commit deaee2704a157dfcca77301ddaa10c62a9840952 ]
For the gdb command lx-dmesg, the entire descriptor, info, and text data regions are read into memory before printing any records. For large kernel log buffers, this not only causes a huge delay before seeing any records, but it may also lead to python errors of too much memory allocation.
Rather than reading in all these regions in advance, read them as needed and only read the regions for the particular record that is being printed.
The gdb macro "dmesg" in Documentation/admin-guide/kdump/gdbmacros.txt already prints out the kernel log buffer like this.
Signed-off-by: John Ogness john.ogness@linutronix.de Signed-off-by: Petr Mladek pmladek@suse.com Link: https://lore.kernel.org/r/874k79c3a9.fsf@jogness.linutronix.de Signed-off-by: Sasha Levin sashal@kernel.org --- scripts/gdb/linux/dmesg.py | 35 ++++++++++++++++++----------------- 1 file changed, 18 insertions(+), 17 deletions(-)
diff --git a/scripts/gdb/linux/dmesg.py b/scripts/gdb/linux/dmesg.py index a92c55bd8de5..d5983cf3db7d 100644 --- a/scripts/gdb/linux/dmesg.py +++ b/scripts/gdb/linux/dmesg.py @@ -44,19 +44,17 @@ class LxDmesg(gdb.Command): sz = prb_desc_ring_type.get_type().sizeof desc_ring = utils.read_memoryview(inf, addr, sz).tobytes()
- # read in descriptor array + # read in descriptor count, size, and address off = prb_desc_ring_type.get_type()['count_bits'].bitpos // 8 desc_ring_count = 1 << utils.read_u32(desc_ring, off) desc_sz = prb_desc_type.get_type().sizeof off = prb_desc_ring_type.get_type()['descs'].bitpos // 8 - addr = utils.read_ulong(desc_ring, off) - descs = utils.read_memoryview(inf, addr, desc_sz * desc_ring_count).tobytes() + desc_addr = utils.read_ulong(desc_ring, off)
- # read in info array + # read in info size and address info_sz = printk_info_type.get_type().sizeof off = prb_desc_ring_type.get_type()['infos'].bitpos // 8 - addr = utils.read_ulong(desc_ring, off) - infos = utils.read_memoryview(inf, addr, info_sz * desc_ring_count).tobytes() + info_addr = utils.read_ulong(desc_ring, off)
# read in text data ring structure off = printk_ringbuffer_type.get_type()['text_data_ring'].bitpos // 8 @@ -64,12 +62,11 @@ class LxDmesg(gdb.Command): sz = prb_data_ring_type.get_type().sizeof text_data_ring = utils.read_memoryview(inf, addr, sz).tobytes()
- # read in text data + # read in text data size and address off = prb_data_ring_type.get_type()['size_bits'].bitpos // 8 text_data_sz = 1 << utils.read_u32(text_data_ring, off) off = prb_data_ring_type.get_type()['data'].bitpos // 8 - addr = utils.read_ulong(text_data_ring, off) - text_data = utils.read_memoryview(inf, addr, text_data_sz).tobytes() + text_data_addr = utils.read_ulong(text_data_ring, off)
counter_off = atomic_long_type.get_type()['counter'].bitpos // 8
@@ -102,17 +99,20 @@ class LxDmesg(gdb.Command): desc_off = desc_sz * ind info_off = info_sz * ind
+ desc = utils.read_memoryview(inf, desc_addr + desc_off, desc_sz).tobytes() + # skip non-committed record - state = 3 & (utils.read_u64(descs, desc_off + sv_off + - counter_off) >> desc_flags_shift) + state = 3 & (utils.read_u64(desc, sv_off + counter_off) >> desc_flags_shift) if state != desc_committed and state != desc_finalized: if did == head_id: break did = (did + 1) & desc_id_mask continue
- begin = utils.read_ulong(descs, desc_off + begin_off) % text_data_sz - end = utils.read_ulong(descs, desc_off + next_off) % text_data_sz + begin = utils.read_ulong(desc, begin_off) % text_data_sz + end = utils.read_ulong(desc, next_off) % text_data_sz + + info = utils.read_memoryview(inf, info_addr + info_off, info_sz).tobytes()
# handle data-less record if begin & 1 == 1: @@ -125,16 +125,17 @@ class LxDmesg(gdb.Command): # skip over descriptor id text_start = begin + utils.get_long_type().sizeof
- text_len = utils.read_u16(infos, info_off + len_off) + text_len = utils.read_u16(info, len_off)
# handle truncated message if end - text_start < text_len: text_len = end - text_start
- text = text_data[text_start:text_start + text_len].decode( - encoding='utf8', errors='replace') + text_data = utils.read_memoryview(inf, text_data_addr + text_start, + text_len).tobytes() + text = text_data[0:text_len].decode(encoding='utf8', errors='replace')
- time_stamp = utils.read_u64(infos, info_off + ts_off) + time_stamp = utils.read_u64(info, ts_off)
for line in text.splitlines(): msg = u"[{time:12.6f}] {line}\n".format(