linux-kernel - Re: [PATCH v9 4/7] extable: Add function to search only kernel exception table

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Message-ID: <877e7gqe5i.fsf@santosiv.in.ibm.com>
Date:   Wed, 14 Aug 2019 15:09:37 +0530
From:   Santosh Sivaraj <santosh@...six.org>
To:     Balbir Singh <bsingharora@...il.com>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Linux Kernel <linux-kernel@...r.kernel.org>
Cc:     "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        Mahesh Salgaonkar <mahesh@...ux.ibm.com>,
        Reza Arbab <arbab@...ux.ibm.com>,
        Chandan Rajendra <chandan@...ux.vnet.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>,
        christophe leroy <christophe.leroy@....fr>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH v9 4/7] extable: Add function to search only kernel exception table

Balbir Singh <bsingharora@...il.com> writes:

> On 12/8/19 7:22 pm, Santosh Sivaraj wrote:
>> Certain architecture specific operating modes (e.g., in powerpc machine
>> check handler that is unable to access vmalloc memory), the
>> search_exception_tables cannot be called because it also searches the
>> module exception tables if entry is not found in the kernel exception
>> table.
>> 
>> Cc: Thomas Gleixner <tglx@...utronix.de>
>> Cc: Ingo Molnar <mingo@...nel.org>
>> Cc: Nicholas Piggin <npiggin@...il.com>
>> Signed-off-by: Santosh Sivaraj <santosh@...six.org>
>> Reviewed-by: Nicholas Piggin <npiggin@...il.com>
>> ---
>>  include/linux/extable.h |  2 ++
>>  kernel/extable.c        | 11 +++++++++--
>>  2 files changed, 11 insertions(+), 2 deletions(-)
>> 
>> diff --git a/include/linux/extable.h b/include/linux/extable.h
>> index 41c5b3a25f67..81ecfaa83ad3 100644
>> --- a/include/linux/extable.h
>> +++ b/include/linux/extable.h
>> @@ -19,6 +19,8 @@ void trim_init_extable(struct module *m);
>>  
>>  /* Given an address, look for it in the exception tables */
>>  const struct exception_table_entry *search_exception_tables(unsigned long add);
>> +const struct exception_table_entry *
>> +search_kernel_exception_table(unsigned long addr);
>> 
>
> Can we find a better name search_kernel still sounds like all of the kernel.
> Can we rename it to search_kernel_linear_map_extable?

I thought search_kernel_exception_table and search_module_extables were
non-ambiguous enough :-) But If you think name will be confusing, I can
change that as suggested.

Thanks,
Santosh

>
>  
>>  #ifdef CONFIG_MODULES
>>  /* For extable.c to search modules' exception tables. */
>> diff --git a/kernel/extable.c b/kernel/extable.c
>> index e23cce6e6092..f6c9406eec7d 100644
>> --- a/kernel/extable.c
>> +++ b/kernel/extable.c
>> @@ -40,13 +40,20 @@ void __init sort_main_extable(void)
>>  	}
>>  }
>>  
>> +/* Given an address, look for it in the kernel exception table */
>> +const
>> +struct exception_table_entry *search_kernel_exception_table(unsigned long addr)
>> +{
>> +	return search_extable(__start___ex_table,
>> +			      __stop___ex_table - __start___ex_table, addr);
>> +}
>> +
>>  /* Given an address, look for it in the exception tables. */
>>  const struct exception_table_entry *search_exception_tables(unsigned long addr)
>>  {
>>  	const struct exception_table_entry *e;
>>  
>> -	e = search_extable(__start___ex_table,
>> -			   __stop___ex_table - __start___ex_table, addr);
>> +	e = search_kernel_exception_table(addr);
>>  	if (!e)
>>  		e = search_module_extables(addr);
>>  	return e;
>> 

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