Messages in this thread | | | Subject | Re: [PATCH v3] scripts/gdb: fix lx-dmesg when CONFIG_PRINTK_CALLER is set | From | Jan Kiszka <> | Date | Fri, 11 Oct 2019 17:41:46 +0200 |
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On 11.10.19 16:25, Joel Colledge wrote: > When CONFIG_PRINTK_CALLER is set, struct printk_log contains an > additional member caller_id. This affects the offset of the log text. > Account for this by using the type information from gdb to determine all > the offsets instead of using hardcoded values. > > This fixes following error: > > (gdb) lx-dmesg > Python Exception <class 'ValueError'> embedded null character: > Error occurred in Python command: embedded null character > > The read_u* utility functions now take an offset argument to make them > easier to use. > > Signed-off-by: Joel Colledge <joel.colledge@linbit.com> > --- > Changes in v3: > - fix some overlong lines and generally make the code more readable by > pushing the slicing down into the read_u* helper functions > > In general, I would consider slicing to be more "pythonic" than passing > around offsets. However, in this case we always want to slice with > (offset, length), rather than (start, end), so the normal slicing syntax > is not very helpful. Rather than writing [a:a+b] everywhere I just > decided to pass the whole buffer and an offset to the read_u* helpers.
Agreed.
> > scripts/gdb/linux/dmesg.py | 16 ++++++++++++---- > scripts/gdb/linux/utils.py | 25 +++++++++++++------------ > 2 files changed, 25 insertions(+), 16 deletions(-) > > diff --git a/scripts/gdb/linux/dmesg.py b/scripts/gdb/linux/dmesg.py > index 6d2e09a2ad2f..2fa7bb83885f 100644 > --- a/scripts/gdb/linux/dmesg.py > +++ b/scripts/gdb/linux/dmesg.py > @@ -16,6 +16,8 @@ import sys > > from linux import utils > > +printk_log_type = utils.CachedType("struct printk_log") > + > > class LxDmesg(gdb.Command): > """Print Linux kernel log buffer.""" > @@ -42,9 +44,14 @@ class LxDmesg(gdb.Command): > 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 + 8:pos + 10]) > + length = utils.read_u16(log_buf, pos + length_offset) > if length == 0: > if log_buf_2nd_half == -1: > gdb.write("Corrupted log buffer!\n") > @@ -52,10 +59,11 @@ class LxDmesg(gdb.Command): > pos = log_buf_2nd_half > continue > > - text_len = utils.read_u16(log_buf[pos + 10:pos + 12]) > - text = log_buf[pos + 16:pos + 16 + text_len].decode( > + 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:pos + 8]) > + time_stamp = utils.read_u64(log_buf, pos + time_stamp_offset) > > for line in text.splitlines(): > msg = u"[{time:12.6f}] {line}\n".format( > diff --git a/scripts/gdb/linux/utils.py b/scripts/gdb/linux/utils.py > index bc67126118c4..ea94221dbd39 100644 > --- a/scripts/gdb/linux/utils.py > +++ b/scripts/gdb/linux/utils.py > @@ -92,15 +92,16 @@ def read_memoryview(inf, start, length): > return memoryview(inf.read_memory(start, length)) > > > -def read_u16(buffer): > +def read_u16(buffer, offset): > + buffer_val = buffer[offset:offset + 2] > value = [0, 0] > > - if type(buffer[0]) is str: > - value[0] = ord(buffer[0]) > - value[1] = ord(buffer[1]) > + if type(buffer_val[0]) is str: > + value[0] = ord(buffer_val[0]) > + value[1] = ord(buffer_val[1]) > else: > - value[0] = buffer[0] > - value[1] = buffer[1] > + value[0] = buffer_val[0] > + value[1] = buffer_val[1] > > if get_target_endianness() == LITTLE_ENDIAN: > return value[0] + (value[1] << 8) > @@ -108,18 +109,18 @@ def read_u16(buffer): > return value[1] + (value[0] << 8) > > > -def read_u32(buffer): > +def read_u32(buffer, offset): > if get_target_endianness() == LITTLE_ENDIAN: > - return read_u16(buffer[0:2]) + (read_u16(buffer[2:4]) << 16) > + return read_u16(buffer, offset) + (read_u16(buffer, offset + 2) << 16) > else: > - return read_u16(buffer[2:4]) + (read_u16(buffer[0:2]) << 16) > + return read_u16(buffer, offset + 2) + (read_u16(buffer, offset) << 16) > > > -def read_u64(buffer): > +def read_u64(buffer, offset): > if get_target_endianness() == LITTLE_ENDIAN: > - return read_u32(buffer[0:4]) + (read_u32(buffer[4:8]) << 32) > + return read_u32(buffer, offset) + (read_u32(buffer, offset + 4) << 32) > else: > - return read_u32(buffer[4:8]) + (read_u32(buffer[0:4]) << 32) > + return read_u32(buffer, offset + 4) + (read_u32(buffer, offset) << 32) > > > target_arch = None >
Reviewed-by: Jan Kiszka <jan.kiszka@siemens.com>
Jan
-- Siemens AG, Corporate Technology, CT RDA IOT SES-DE Corporate Competence Center Embedded Linux
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