linux-kernel - Re: [PATCH] modules: Fix display of wrong module .text address

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Date:   Tue, 17 Apr 2018 10:24:35 +0200
From:   Christian Borntraeger <borntraeger@...ibm.com>
To:     Thomas Richter <tmricht@...ux.ibm.com>, jeyu@...nel.org,
        torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org
Cc:     schwidefsky@...ibm.com, brueckner@...ux.vnet.ibm.com,
        heiko.carstens@...ibm.com, peterz@...radead.org, acme@...nel.org,
        me@...in.cc, keescook@...omium.org
Subject: Re: [PATCH] modules: Fix display of wrong module .text address



On 04/17/2018 10:20 AM, Thomas Richter wrote:
> In kernel v4.16.0 the module .text address is displayed
> wrong when using /sys/module/*/sections/.text file.
> Commit ef0010a30935 ("vsprintf: don't use 'restricted_pointer()' when
> not restricting")
> is the first bad commit.
> 
> Here is the issue, using module qeth_l2 on s390 which is the
> ethernet device driver:
> 
> [root@...lp76 ~]# lsmod
> Module                  Size  Used by
> qeth_l2                94208  1
> ...
> 
> [root@...lp76 ~]# cat /proc/modules | egrep '^qeth_l2'
> qeth_l2 94208 1 - Live 0x000003ff80401000
>                        ^ This is the correct address in memory
> [root@...lp76 ~]# cat /sys/module/qeth_l2/sections/.text
> 0x0000000018ea8363      <---- This is a wrong address
> [root@...lp76 ~]#
> 
> This breaks the perf tool which uses this address on s390
> to calculate start of .text section in memory.
> 
> Fix this by printing the correct (unhashed) address.
> 
> Thanks to Jessica Yu for helping on this.
> 
> Suggested-by: Linus Torvalds <torvalds@...ux-foundation.org>
> Signed-off-by: Thomas Richter <tmricht@...ux.ibm.com>
> Cc: Jessica Yu <jeyu@...nel.org>

CC stable?

> ---
>  kernel/module.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/module.c b/kernel/module.c
> index a6e43a5806a1..77ab7211ddef 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -1472,7 +1472,7 @@ static ssize_t module_sect_show(struct module_attribute *mattr,
>  {
>  	struct module_sect_attr *sattr =
>  		container_of(mattr, struct module_sect_attr, mattr);
> -	return sprintf(buf, "0x%pK\n", (void *)sattr->address);
> +	return sprintf(buf, "%#lx\n", kptr_restrict < 2 ? sattr->address : 0);
>  }
>  
>  static void free_sect_attrs(struct module_sect_attrs *sect_attrs)
>