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scripts/gdb: fix 'lx-dmesg' on 32 bits arch

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The type atomic_long_t can have size 4 or 8 bytes, depending on
CONFIG_64BIT; it's only content, the field 'counter', is either an
int or a s64 value.

Current code incorrectly uses the fixed size utils.read_u64() to
read the field 'counter' inside atomic_long_t.

On 32 bits architectures reading the last element 'tail_id' of the
struct prb_desc_ring:
	struct prb_desc_ring {
		...
		atomic_long_t tail_id;
	};
causes the utils.read_u64() to access outside the boundary of the
struct and the gdb command 'lx-dmesg' exits with error:
	Python Exception <class 'IndexError'>: index out of range
	Error occurred in Python: index out of range

Query the really used atomic_long_t counter type size.

Link: https://lore.kernel.org/r/20220617143758.137307-1-antonio.borneo@foss.st.com
Fixes: e60768311a ("scripts/gdb: update for lockless printk ringbuffer")
Signed-off-by: Antonio Borneo <antonio.borneo@foss.st.com>
[pmladek@suse.com: Query the really used atomic_long_t counter type size]
Tested-by: Antonio Borneo <antonio.borneo@foss.st.com>
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20220719122831.19890-1-pmladek@suse.com
This commit is contained in:
Antonio Borneo 2022-07-19 14:28:31 +02:00 committed by Petr Mladek
parent 9a3bfa01aa
commit e3c8d33e0d
2 changed files with 15 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
scripts/gdb/linux/dmesg.py
View File

@ -22,7 +22,6 @@ 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."""
@ -68,8 +67,6 @@ class LxDmesg(gdb.Command):
off = prb_data_ring_type.get_type()['data'].bitpos // 8
text_data_addr = utils.read_ulong(text_data_ring, off)
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
@ -89,9 +86,9 @@ class LxDmesg(gdb.Command):
# 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)
tail_id = utils.read_atomic_long(desc_ring, off)
off = prb_desc_ring_type.get_type()['head_id'].bitpos // 8
head_id = utils.read_u64(desc_ring, off + counter_off)
head_id = utils.read_atomic_long(desc_ring, off)
did = tail_id
while True:
@ -102,7 +99,7 @@ class LxDmesg(gdb.Command):
desc = utils.read_memoryview(inf, desc_addr + desc_off, desc_sz).tobytes()
# skip non-committed record
state = 3 & (utils.read_u64(desc, sv_off + counter_off) >> desc_flags_shift)
state = 3 & (utils.read_atomic_long(desc, sv_off) >> desc_flags_shift)
if state != desc_committed and state != desc_finalized:
if did == head_id:
break

14
scripts/gdb/linux/utils.py
View File

@ -35,13 +35,12 @@ class CachedType:
long_type = CachedType("long")
atomic_long_type = CachedType("atomic_long_t")
def get_long_type():
global long_type
return long_type.get_type()
def offset_of(typeobj, field):
element = gdb.Value(0).cast(typeobj)
return int(str(element[field].address).split()[0], 16)
@ -129,6 +128,17 @@ def read_ulong(buffer, offset):
else:
return read_u32(buffer, offset)
atomic_long_counter_offset = atomic_long_type.get_type()['counter'].bitpos
atomic_long_counter_sizeof = atomic_long_type.get_type()['counter'].type.sizeof
def read_atomic_long(buffer, offset):
global atomic_long_counter_offset
global atomic_long_counter_sizeof
if atomic_long_counter_sizeof == 8:
return read_u64(buffer, offset + atomic_long_counter_offset)
else:
return read_u32(buffer, offset + atomic_long_counter_offset)
target_arch = None