From e60768311af854734ce2bbfc50f24cff67b54a91 Mon Sep 17 00:00:00 2001 From: John Ogness Date: Fri, 14 Aug 2020 23:31:25 +0206 Subject: scripts/gdb: update for lockless printk ringbuffer With the introduction of the lockless printk ringbuffer, the data structure for the kernel log buffer was changed. Update the gdb scripts to be able to parse/print the new log buffer structure. Fixes: 896fbe20b4e2333fb55 ("printk: use the lockless ringbuffer") Signed-off-by: John Ogness Reported-by: Nick Desaulniers Tested-by: Nick Desaulniers Tested-by: Petr Mladek [akpm@linux-foundation.org: A typo fix.] Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20200814212525.6118-3-john.ogness@linutronix.de --- scripts/gdb/linux/dmesg.py | 139 +++++++++++++++++++++++++++++++++------------ 1 file changed, 102 insertions(+), 37 deletions(-) (limited to 'scripts/gdb/linux') diff --git a/scripts/gdb/linux/dmesg.py b/scripts/gdb/linux/dmesg.py index 2fa7bb83885f..6c6022012ea8 100644 --- a/scripts/gdb/linux/dmesg.py +++ b/scripts/gdb/linux/dmesg.py @@ -16,8 +16,13 @@ import sys from linux import utils -printk_log_type = utils.CachedType("struct printk_log") - +printk_info_type = utils.CachedType("struct printk_info") +prb_data_blk_lpos_type = utils.CachedType("struct prb_data_blk_lpos") +prb_desc_type = utils.CachedType("struct prb_desc") +prb_desc_ring_type = utils.CachedType("struct prb_desc_ring") +prb_data_ring_type = utils.CachedType("struct prb_data_ring") +printk_ringbuffer_type = utils.CachedType("struct printk_ringbuffer") +atomic_long_type = utils.CachedType("atomic_long_t") class LxDmesg(gdb.Command): """Print Linux kernel log buffer.""" @@ -26,44 +31,102 @@ class LxDmesg(gdb.Command): super(LxDmesg, self).__init__("lx-dmesg", gdb.COMMAND_DATA) def invoke(self, arg, from_tty): - log_buf_addr = int(str(gdb.parse_and_eval( - "(void *)'printk.c'::log_buf")).split()[0], 16) - log_first_idx = int(gdb.parse_and_eval("'printk.c'::log_first_idx")) - log_next_idx = int(gdb.parse_and_eval("'printk.c'::log_next_idx")) - log_buf_len = int(gdb.parse_and_eval("'printk.c'::log_buf_len")) - inf = gdb.inferiors()[0] - start = log_buf_addr + log_first_idx - if log_first_idx < log_next_idx: - log_buf_2nd_half = -1 - length = log_next_idx - log_first_idx - log_buf = utils.read_memoryview(inf, start, length).tobytes() - else: - log_buf_2nd_half = log_buf_len - log_first_idx - a = utils.read_memoryview(inf, start, log_buf_2nd_half) - b = utils.read_memoryview(inf, log_buf_addr, log_next_idx) - log_buf = a.tobytes() + b.tobytes() - - length_offset = printk_log_type.get_type()['len'].bitpos // 8 - text_len_offset = printk_log_type.get_type()['text_len'].bitpos // 8 - time_stamp_offset = printk_log_type.get_type()['ts_nsec'].bitpos // 8 - text_offset = printk_log_type.get_type().sizeof - - pos = 0 - while pos < log_buf.__len__(): - length = utils.read_u16(log_buf, pos + length_offset) - if length == 0: - if log_buf_2nd_half == -1: - gdb.write("Corrupted log buffer!\n") + + # read in prb structure + prb_addr = int(str(gdb.parse_and_eval("(void *)'printk.c'::prb")).split()[0], 16) + sz = printk_ringbuffer_type.get_type().sizeof + prb = utils.read_memoryview(inf, prb_addr, sz).tobytes() + + # read in descriptor ring structure + off = printk_ringbuffer_type.get_type()['desc_ring'].bitpos // 8 + addr = prb_addr + off + sz = prb_desc_ring_type.get_type().sizeof + desc_ring = utils.read_memoryview(inf, addr, sz).tobytes() + + # read in descriptor array + 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() + + # read in text data ring structure + off = printk_ringbuffer_type.get_type()['text_data_ring'].bitpos // 8 + addr = prb_addr + off + sz = prb_data_ring_type.get_type().sizeof + text_data_ring = utils.read_memoryview(inf, addr, sz).tobytes() + + # read in text data + 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() + + counter_off = atomic_long_type.get_type()['counter'].bitpos // 8 + + sv_off = prb_desc_type.get_type()['state_var'].bitpos // 8 + + off = prb_desc_type.get_type()['text_blk_lpos'].bitpos // 8 + begin_off = off + (prb_data_blk_lpos_type.get_type()['begin'].bitpos // 8) + next_off = off + (prb_data_blk_lpos_type.get_type()['next'].bitpos // 8) + + off = prb_desc_type.get_type()['info'].bitpos // 8 + ts_off = off + printk_info_type.get_type()['ts_nsec'].bitpos // 8 + len_off = off + printk_info_type.get_type()['text_len'].bitpos // 8 + + # definitions from kernel/printk/printk_ringbuffer.h + desc_sv_bits = utils.get_long_type().sizeof * 8 + desc_committed_mask = 1 << (desc_sv_bits - 1) + desc_reuse_mask = 1 << (desc_sv_bits - 2) + desc_flags_mask = desc_committed_mask | desc_reuse_mask + desc_id_mask = ~desc_flags_mask + + # read in tail and head descriptor ids + off = prb_desc_ring_type.get_type()['tail_id'].bitpos // 8 + tail_id = utils.read_u64(desc_ring, off + counter_off) + off = prb_desc_ring_type.get_type()['head_id'].bitpos // 8 + head_id = utils.read_u64(desc_ring, off + counter_off) + + did = tail_id + while True: + ind = did % desc_ring_count + desc_off = desc_sz * ind + + # skip non-committed record + state = utils.read_u64(descs, desc_off + sv_off + counter_off) & desc_flags_mask + if state != desc_committed_mask: + if did == head_id: break - pos = log_buf_2nd_half + did = (did + 1) & desc_id_mask continue - text_len = utils.read_u16(log_buf, pos + text_len_offset) - text_start = pos + text_offset - text = log_buf[text_start:text_start + text_len].decode( - encoding='utf8', errors='replace') - time_stamp = utils.read_u64(log_buf, pos + time_stamp_offset) + begin = utils.read_ulong(descs, desc_off + begin_off) % text_data_sz + end = utils.read_ulong(descs, desc_off + next_off) % text_data_sz + + # handle data-less record + if begin & 1 == 1: + text = "" + else: + # handle wrapping data block + if begin > end: + begin = 0 + + # skip over descriptor id + text_start = begin + utils.get_long_type().sizeof + + text_len = utils.read_u16(descs, desc_off + 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') + + time_stamp = utils.read_u64(descs, desc_off + ts_off) for line in text.splitlines(): msg = u"[{time:12.6f}] {line}\n".format( @@ -75,7 +138,9 @@ class LxDmesg(gdb.Command): msg = msg.encode(encoding='utf8', errors='replace') gdb.write(msg) - pos += length + if did == head_id: + break + did = (did + 1) & desc_id_mask LxDmesg() -- cgit v1.2.3