On 18/06/2024 06:43, Jonathan Corbet wrote:
> Li Zhijian <lizhijian@xxxxxxxxxxx> writes:
>
>> When it was in text format, it correctly hardcoded steps 8a to 8c.
>> However, after it was converted to RST, the sequence numbers were
>> auto-generated during rendering and became incorrect after some
>> steps were inserted.
>>
>> Change it to refer to steps a to c in a relative way.
>>
>> Signed-off-by: Li Zhijian <lizhijian@xxxxxxxxxxx>
>> ---
>> Documentation/arch/x86/exception-tables.rst | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/Documentation/arch/x86/exception-tables.rst b/Documentation/arch/x86/exception-tables.rst
>> index efde1fef4fbd..562d1bc6d448 100644
>> --- a/Documentation/arch/x86/exception-tables.rst
>> +++ b/Documentation/arch/x86/exception-tables.rst
>> @@ -297,7 +297,7 @@ vma occurs?
>> c) execution continues at local label 2 (address of the
>> instruction immediately after the faulting user access).
>>
>> -The steps 8a to 8c in a certain way emulate the faulting instruction.
>> +The steps a to c above in a certain way emulate the faulting instruction.
>>
>
> Those steps render as 1, 2, and 3 ... where did "a to c" come from?
>>> c) execution continues at local label 2 (address of the
>>> instruction immediately after the faulting user access).
IIUC, this is the __c__, and __a__ is documented above __c__.
Check the original commit, it did hardcode __8a__ and __8c__,
for example,
commit c368b4921bc6e309aba2fbee0efcbbc965008d9f
Author: Amerigo Wang <amwang@xxxxxxxxxx>
Date: Fri Jul 10 15:02:44 2009 -0700
Doc: move Documentation/exception.txt into x86 subdir
<...snip...>
+1.) access to invalid address:
+ > c017e7a5 <do_con_write+e1> movb (%ebx),%dl
+2.) MMU generates exception
+3.) CPU calls do_page_fault
+4.) do page fault calls search_exception_table (regs->eip == c017e7a5);
+5.) search_exception_table looks up the address c017e7a5 in the
+ exception table (i.e. the contents of the ELF section __ex_table)
+ and returns the address of the associated fault handle code c0199ff5.
+6.) do_page_fault modifies its own return address to point to the fault
+ handle code and returns.
+7.) execution continues in the fault handling code.
+8.) 8a) EAX becomes -EFAULT (== -14)
+ 8b) DL becomes zero (the value we "read" from user space)
+ 8c) execution continues at local label 2 (address of the
+ instruction immediately after the faulting user access).
+
+The steps 8a to 8c in a certain way emulate the faulting instruction.
+
+That's it, mostly. If you look at our example, you might ask why
>
> Thanks,
>
> jon
