Messages in this thread | | | Subject | Re: [PATCH] scripts/gdb: fix 'lx-dmesg' on 32 bits arch | From | Antonio Borneo <> | Date | Fri, 1 Jul 2022 11:15:38 +0200 |
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On Thu, 2022-06-30 at 15:13 +0200, Petr Mladek wrote: > On Fri 2022-06-17 16:37:58, Antonio Borneo wrote: > > 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 > > > > Use the existing utils.read_ulong() to read 'counter' inside the > > atomic_long_t. > > I was about to accept this. But then I wondered if we could somehow > detect the really used atomic_long_t counter type size. > > I have updated your patch. It works for me on x86_64. > Could you please check it on 32-bit system?
Tested on 32 bits Cortex-A7 STM32MP157, it works fine. Yes, agree on your rework; definitively cleaner.
Thanks, Antonio
> Here is the patch: > > From bb5b6a7ad6f4339a1102585c691cb725182c0acf Mon Sep 17 00:00:00 > 2001 > From: Antonio Borneo <antonio.borneo@foss.st.com> > Date: Fri, 17 Jun 2022 16:37:58 +0200 > Subject: [PATCH] scripts/gdb: fix 'lx-dmesg' on 32 bits arch > > 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. > > Fixes: e60768311af8 ("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] > Link: > https://lore.kernel.org/r/20220617143758.137307-1-antonio.borneo@foss.st.com > --- > scripts/gdb/linux/dmesg.py | 9 +++------ > scripts/gdb/linux/utils.py | 14 ++++++++++++-- > 2 files changed, 15 insertions(+), 8 deletions(-) > > diff --git a/scripts/gdb/linux/dmesg.py b/scripts/gdb/linux/dmesg.py > index d5983cf3db7d..c771831eb077 100644 > --- a/scripts/gdb/linux/dmesg.py > +++ b/scripts/gdb/linux/dmesg.py > @@ -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 > diff --git a/scripts/gdb/linux/utils.py b/scripts/gdb/linux/utils.py > index ff7c1799d588..1553f68716cc 100644 > --- a/scripts/gdb/linux/utils.py > +++ b/scripts/gdb/linux/utils.py > @@ -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 >
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