linux-kernel - Re: [v5 4/6] extable: Add function to search only kernel exception table

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Message-Id: <1562837939.bik9erongk.astroid@bobo.none>
Date:   Thu, 11 Jul 2019 19:47:18 +1000
From:   Nicholas Piggin <npiggin@...il.com>
To:     linux-kernel@...r.kernel.org,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Santosh Sivaraj <santosh@...six.org>
Cc:     "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        Reza Arbab <arbab@...ux.ibm.com>,
        Balbir Singh <bsingharora@...il.com>,
        Chandan Rajendra <chandan@...ux.vnet.ibm.com>,
        christophe leroy <christophe.leroy@....fr>,
        Mahesh Salgaonkar <mahesh@...ux.ibm.com>,
        Ingo Molnar <mingo@...nel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [v5 4/6] extable: Add function to search only kernel exception
 table

Santosh Sivaraj's on July 9, 2019 10:15 pm:
> In real mode, the search_exception tables cannot be called because
> it also searches the module exception tables if entry is not found
> in the kernel exception tables.

This is a patch for generic kernel code, it may not go through
powerpc tree and someone doing git blame or something won't have
any idea what this changelog means.

Can you re-word this and just say something like, "certain architecture
$specific operating modes (e.g., in powerpc machine check handler that
is unable to access vmalloc memory)."

> 
> 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>
> ---
>  include/linux/extable.h |  2 ++
>  kernel/extable.c        | 16 +++++++++++++---
>  2 files changed, 15 insertions(+), 3 deletions(-)
> 
> diff --git a/include/linux/extable.h b/include/linux/extable.h
> index 41c5b3a25f67..0c2819ba67f0 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);
>  
>  #ifdef CONFIG_MODULES
>  /* For extable.c to search modules' exception tables. */
> diff --git a/kernel/extable.c b/kernel/extable.c
> index e23cce6e6092..6d544cb79fff 100644
> --- a/kernel/extable.c
> +++ b/kernel/extable.c
> @@ -40,13 +40,23 @@ void __init sort_main_extable(void)
>  	}
>  }
>  
> -/* Given an address, look for it in the exception tables. */
> +/* For the given address, look for it in the kernel exception table */

Nitpick, no reason to vary the structure of the comment.

Code wise it looks fine, so with the comments and changelog fixed,

Reviewed-by: Nicholas Piggin <npiggin@...il.com>

> +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 kernel and the module 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;
> -- 
> 2.20.1
> 
>