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.
Fixes: e60768311af8 ("scripts/gdb: update for lockless printk ringbuffer")
Signed-off-by: Antonio Borneo <[email protected]>
---
scripts/gdb/linux/dmesg.py | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/scripts/gdb/linux/dmesg.py b/scripts/gdb/linux/dmesg.py
index d5983cf3db7d..e2d9ab3aa836 100644
--- a/scripts/gdb/linux/dmesg.py
+++ b/scripts/gdb/linux/dmesg.py
@@ -89,9 +89,9 @@ 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_ulong(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)
+ head_id = utils.read_ulong(desc_ring, off + counter_off)
did = tail_id
while True:
@@ -102,7 +102,7 @@ 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_ulong(desc, sv_off + counter_off) >> desc_flags_shift)
if state != desc_committed and state != desc_finalized:
if did == head_id:
break
base-commit: b13baccc3850ca8b8cccbf8ed9912dbaa0fdf7f3
--
2.36.1
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 <[email protected]>
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 <[email protected]>
[[email protected]: Query the really used atomic_long_t counter type size]
Link: https://lore.kernel.org/r/[email protected]
---
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
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 <[email protected]>
> 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 <[email protected]>
> [[email protected]: Query the really used atomic_long_t counter type
> size]
> Link:
> https://lore.kernel.org/r/[email protected]
> ---
> 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
>