Messages in this thread | | | Subject | Re: [PATCH] scripts/gdb: fix list_for_each | From | "Prekas, George" <> | Date | Tue, 22 Sep 2020 12:17:00 -0500 |
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On 9/22/2020 9:32 AM, Jan Kiszka wrote: > > On 22.09.20 16:28, George Prekas wrote: >> If the next pointer is NULL, list_for_each gets stuck in an infinite >> loop. >> >> Signed-off-by: George Prekas <prekageo@amazon.com> >> --- >> scripts/gdb/linux/lists.py | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/scripts/gdb/linux/lists.py b/scripts/gdb/linux/lists.py >> index c487ddf09d38..424a91c1aa8b 100644 >> --- a/scripts/gdb/linux/lists.py >> +++ b/scripts/gdb/linux/lists.py >> @@ -27,6 +27,8 @@ def list_for_each(head): >> raise TypeError("Must be struct list_head not {}" >> .format(head.type)) >> >> + if head['next'] == 0: >> + return >> node = head['next'].dereference() >> while node.address != head.address: >> yield node.address > > Obviously, infinite loops are bad and should be avoided. But NULL is > bug, isn't it? Shouldn't we report such a corruption? >
Hi Jan,
Is it a bug? Or does it mean that the list is empty?
Let me give some background. If you do the following:
$ qemu-system-x86_64 -nographic -m 1024 -kernel build/arch/x86/boot/bzImage -s -S < /dev/null > /dev/null & $ gdb -q build/vmlinux -ex 'target remote localhost:1234' -iex 'set auto-load safe-path /' -ex 'lx-symbols'
You will see:
loading vmlinux scanning for modules in /home/ubuntu/linux-5.8.10 no module object found for ''
And the last line repeats forever. This happens because modules.next == NULL. This is the Python stack trace:
File ".../symbols.py", line 174, in invoke self.load_all_symbols() File ".../symbols.py", line 161, in load_all_symbols [self.load_module_symbols(module) for module in module_list] File ".../symbols.py", line 161, in <listcomp> [self.load_module_symbols(module) for module in module_list] File ".../modules.py", line 30, in module_list for module in lists.list_for_each_entry(modules, module_ptr_type, "list"): File ".../lists.py", line 41, in list_for_each_entry for node in list_for_each(head): File ".../lists.py", line 31, in list_for_each traceback.print_stack()
This patch tries to fix the above problem.
George
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