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Re: [PATCH v4 8/9] Implement kernel live patching for ppc64le (ABIv2)

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  Re: [PATCH v4 8/9] Implement kernel live patching for ppc64le (ABIv2) Petr Mladek <pmladek@suse.com> - 2015-12-03 17:30 +0100
    Re: [PATCH v4 8/9] Implement kernel live patching for ppc64le  (ABIv2) Torsten Duwe <duwe@lst.de> - 2015-12-04 10:10 +0100

#1283174 — Re: [PATCH v4 8/9] Implement kernel live patching for ppc64le (ABIv2)

On Wed 2015-11-25 17:48:36, Torsten Duwe wrote:
>   * create the appropriate files+functions
>     arch/powerpc/include/asm/livepatch.h
>         klp_check_compiler_support,
>         klp_arch_set_pc
>     arch/powerpc/kernel/livepatch.c with a stub for
>         klp_write_module_reloc
>     This is architecture-independent work in progress.
>   * introduce a fixup in arch/powerpc/kernel/entry_64.S
>     for local calls that are becoming global due to live patching.
>     And of course do the main KLP thing: return to a maybe different
>     address, possibly altered by the live patching ftrace op.
> 
> --- /dev/null
> +++ b/arch/powerpc/include/asm/livepatch.h
> @@ -0,0 +1,45 @@
[...]
> +#include <linux/module.h>
> +#include <linux/ftrace.h>
> +
> +#ifdef CONFIG_LIVEPATCH
> +static inline int klp_check_compiler_support(void)
> +{
> +#if !defined(_CALL_ELF) || _CALL_ELF != 2

I am just curious why we do not check CC_USING_MPROFILE_KERNEL
like in the other similar locations. It would look less cryptic.
But I am not sure if it is precise enough.

Best Regards,
Petr

> +	return 1;
> +#endif
> +	return 0;
> +}
> +
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#1283664 — Re: [PATCH v4 8/9] Implement kernel live patching for ppc64le (ABIv2)

On Thu, Dec 03, 2015 at 05:24:45PM +0100, Petr Mladek wrote:
> > +++ b/arch/powerpc/include/asm/livepatch.h
> > @@ -0,0 +1,45 @@
> [...]
> > +#include <linux/module.h>
> > +#include <linux/ftrace.h>
> > +
> > +#ifdef CONFIG_LIVEPATCH
> > +static inline int klp_check_compiler_support(void)
> > +{
> > +#if !defined(_CALL_ELF) || _CALL_ELF != 2
> 
> I am just curious why we do not check CC_USING_MPROFILE_KERNEL
> like in the other similar locations. It would look less cryptic.
> But I am not sure if it is precise enough.

Because a ppc with a gcc > 4.8.5 is not sufficient. The code
currently only works for the PPC ELF ABI v2, a.k.a. ppc64le.
But now that you say it, CC_USING_MPROFILE_KERNEL should go
into that condition as well. Thanks!

	Torsten

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