Re: [PATCH 3/5] powerpc64: Add .opd based function descriptor dereference

From	Michael Ellerman <mpe@ellerman.id.au>
Newsgroups	linux.kernel
Subject	Re: [PATCH 3/5] powerpc64: Add .opd based function descriptor dereference
Date	2017-09-20 04:00 +0200
Message-ID	<urCsV-4FV-3@gated-at.bofh.it> (permalink)
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Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> writes:

> On (09/19/17 20:22), Michael Ellerman wrote:
>> > On 2017/09/16 12:53PM, Sergey Senozhatsky wrote:
>> >> We are moving towards separate kernel and module function descriptor
>> >> dereference callbacks. This patch enables it for powerpc64.
>> >> 
>> >> For pointers that belong to the kernel
>> >> -  Added __start_opd and __end_opd pointers, to track the kernel
>> >>    .opd section address range;
>> >> 
>> >> -  Added dereference_kernel_function_descriptor(). Now we
>> >>    will dereference only function pointers that are within
>> >>    [__start_opd, __end_opd];
>> >> 
>> >> For pointers that belong to a module
>> >> -  Added dereference_module_function_descriptor() to handle module
>> >>    function descriptor dereference. Now we will dereference only
>> >>    pointers that are within [module->opd.start, module->opd.end].
>> >
>> > Would it be simpler to just use kernel_text_address() and dereference 
>> > everything else? See commit 83e840c770f2c5 ("powerpc64/elfv1: Only 
>> > dereference function descriptor for non-text symbols") for a related 
>> > patch.
>> 
>> Yeah that would be a lot simpler and probably work perfectly well.
>
> unlike ppc_function_entry(), printk() can get called on any symbol,
> not just function pointers.
>
> for example,
>
> cat /proc/kallsyms | grep shrinker_rwsem
> ffffffff81a4b1e0 d shrinker_rwsem

Yep, good point. So your patch is probably good then. Maybe someone
other than me can find time to test it ;)

cheers

Thread

[PATCH 0/5] [RFC] printk/ia64/ppc64/parisc64: let's deprecate %pF/%pf printk specifiers Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2017-09-16 06:00 +0200
  [PATCH 5/5] symbol lookup: use new kernel and module dereference functions Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2017-09-16 06:00 +0200
  [PATCH 1/5] sections: split dereference_function_descriptor() Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2017-09-16 06:00 +0200
  [PATCH 3/5] powerpc64: Add .opd based function descriptor dereference Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2017-09-16 06:00 +0200
    Re: [PATCH 3/5] powerpc64: Add .opd based function descriptor  dereference "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> - 2017-09-16 11:50 +0200
      Re: [PATCH 3/5] powerpc64: Add .opd based function descriptor  dereference Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2017-09-16 13:40 +0200
      Re: [PATCH 3/5] powerpc64: Add .opd based function descriptor dereference Michael Ellerman <mpe@ellerman.id.au> - 2017-09-19 12:30 +0200
        Re: [PATCH 3/5] powerpc64: Add .opd based function descriptor  dereference Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-09-19 12:40 +0200
          Re: [PATCH 3/5] powerpc64: Add .opd based function descriptor dereference Michael Ellerman <mpe@ellerman.id.au> - 2017-09-20 04:00 +0200
            Re: [PATCH 3/5] powerpc64: Add .opd based function descriptor  dereference Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-09-20 08:20 +0200
  [PATCH 4/5] parisc64: Add .opd based function descriptor dereference Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2017-09-16 06:00 +0200
  [PATCH 2/5] ia64: Add .opd based function descriptor dereference Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2017-09-16 06:00 +0200
  Re: [PATCH 0/5] [RFC] printk/ia64/ppc64/parisc64: let's deprecate  %pF/%pf printk specifiers "Luck, Tony" <tony.luck@intel.com> - 2017-09-18 19:50 +0200
    Re: [PATCH 0/5] [RFC] printk/ia64/ppc64/parisc64: let's deprecate  %pF/%pf printk specifiers Helge Deller <deller@gmx.de> - 2017-09-18 20:40 +0200
      Re: [PATCH 0/5] [RFC] printk/ia64/ppc64/parisc64: let's deprecate  %pF/%pf printk specifiers Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-09-19 04:10 +0200
        RE: [PATCH 0/5] [RFC] printk/ia64/ppc64/parisc64: let's deprecate  %pF/%pf printk specifiers David Laight <David.Laight@ACULAB.COM> - 2017-09-19 15:40 +0200
          Re: [PATCH 0/5] [RFC] printk/ia64/ppc64/parisc64: let's deprecate  %pF/%pf printk specifiers Helge Deller <deller@gmx.de> - 2017-09-19 22:10 +0200
            RE: [PATCH 0/5] [RFC] printk/ia64/ppc64/parisc64: let's deprecate  %pF/%pf printk specifiers David Laight <David.Laight@ACULAB.COM> - 2017-09-20 10:50 +0200
              Re: [PATCH 0/5] [RFC] printk/ia64/ppc64/parisc64: let's deprecate  %pF/%pf printk specifiers Helge Deller <deller@gmx.de> - 2017-09-20 12:30 +0200
                Re: [PATCH 0/5] [RFC] printk/ia64/ppc64/parisc64: let's deprecate  %pF/%pf printk specifiers Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2017-09-20 18:40 +0200
        Re: [PATCH 0/5] [RFC] printk/ia64/ppc64/parisc64: let's deprecate  %pF/%pf printk specifiers Helge Deller <deller@gmx.de> - 2017-09-19 16:10 +0200
          Re: [PATCH 0/5] [RFC] printk/ia64/ppc64/parisc64: let's deprecate  %pF/%pf printk specifiers Helge Deller <deller@gmx.de> - 2017-09-19 22:10 +0200
            Re: [PATCH 0/5] [RFC] printk/ia64/ppc64/parisc64: let's deprecate  %pF/%pf printk specifiers Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-09-20 02:50 +0200
    Re: [PATCH 0/5] [RFC] printk/ia64/ppc64/parisc64: let's deprecate  %pF/%pf printk specifiers Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-09-19 04:10 +0200

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