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Message-ID: <Yr2hcGLDNT0k91aS@alley>
Date: Thu, 30 Jun 2022 15:13:20 +0200
From: Petr Mladek <pmladek@...e.com>
To: Antonio Borneo <antonio.borneo@...s.st.com>
Cc: Jan Kiszka <jan.kiszka@...mens.com>,
Kieran Bingham <kbingham@...nel.org>,
John Ogness <john.ogness@...utronix.de>,
linux-kernel@...r.kernel.org,
linux-stm32@...md-mailman.stormreply.com
Subject: Re: [PATCH] scripts/gdb: fix 'lx-dmesg' on 32 bits arch
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?
Here is the patch:
>From bb5b6a7ad6f4339a1102585c691cb725182c0acf Mon Sep 17 00:00:00 2001
From: Antonio Borneo <antonio.borneo@...s.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@...s.st.com>
[pmladek@...e.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
--
2.35.3
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