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SubjectRe: [PATCHv3 4/7] powerpc64: Add .opd based function descriptor dereference
On Sat 2017-09-30 11:53:16, 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].
>
> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
> Tested-by: Helge Deller <deller@gmx.de> # parisc64
> Tested-by: Santosh Sivaraj <santosh@fossix.org> # powerpc64
> Acked-by: Michael Ellerman <mpe@ellerman.id.au> # powerpc64
> Tested-by: Tony Luck <tony.luck@intel.com> # ia64
> ---
> arch/powerpc/include/asm/module.h | 3 +++
> arch/powerpc/include/asm/sections.h | 11 +++++++++++
> arch/powerpc/kernel/module_64.c | 16 ++++++++++++++++
> arch/powerpc/kernel/vmlinux.lds.S | 2 ++
> 4 files changed, 32 insertions(+)
>
> diff --git a/arch/powerpc/include/asm/module.h b/arch/powerpc/include/asm/module.h
> index 6c0132c7212f..7e28442827f1 100644
> --- a/arch/powerpc/include/asm/module.h
> +++ b/arch/powerpc/include/asm/module.h
> @@ -45,6 +45,9 @@ struct mod_arch_specific {
> unsigned long tramp;
> #endif
>
> + /* For module function descriptor dereference */
> + unsigned long start_opd;
> + unsigned long end_opd;
> #else /* powerpc64 */
> /* Indices of PLT sections within module. */
> unsigned int core_plt_section;
> diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
> index 67379b8945e8..6b4ee0d1645f 100644
> --- a/arch/powerpc/include/asm/sections.h
> +++ b/arch/powerpc/include/asm/sections.h
> @@ -75,6 +75,17 @@ static inline unsigned long dereference_function_descriptor(unsigned long ptr)
> ptr = (unsigned long)p;
> return ptr;
> }
> +
> +#undef dereference_kernel_function_descriptor
> +static inline unsigned long
> +dereference_kernel_function_descriptor(unsigned long addr)
> +{
> + if (addr < (unsigned long)__start_opd ||
> + addr >= (unsigned long)__end_opd)
> + return addr;
> +
> + return dereference_function_descriptor(addr);
> +}
> #endif /* PPC64_ELF_ABI_v1 */
>
> #endif
> diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
> index 0b0f89685b67..94caec045a90 100644
> --- a/arch/powerpc/kernel/module_64.c
> +++ b/arch/powerpc/kernel/module_64.c
> @@ -344,6 +344,11 @@ int module_frob_arch_sections(Elf64_Ehdr *hdr,
> else if (strcmp(secstrings+sechdrs[i].sh_name,"__versions")==0)
> dedotify_versions((void *)hdr + sechdrs[i].sh_offset,
> sechdrs[i].sh_size);
> + else if (!strcmp(secstrings + sechdrs[i].sh_name, ".opd")) {
> + me->arch.start_opd = sechdrs[i].sh_addr;
> + me->arch.end_opd = sechdrs[i].sh_addr +
> + sechdrs[i].sh_size;
> + }
>
> /* We don't handle .init for the moment: rename to _init */
> while ((p = strstr(secstrings + sechdrs[i].sh_name, ".init")))
> @@ -712,6 +717,17 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
> return 0;
> }
>
> +#ifdef PPC64_ELF_ABI_v1
> +unsigned long dereference_module_function_descriptor(struct module *mod,
> + unsigned long addr)
> +{
> + if (addr < mod->arch.start_opd || addr >= mod->arch.end_opd)
> + return addr;
> +
> + return dereference_function_descriptor(addr);
> +}
> +#endif /* PPC64_ELF_ABI_v1 */

I would personally move this up in the source file. It is related to
the definition of func_desc() and other functions that are
also PPC_ELF_ABI-specific.

Otherwise, it looks good to me.

Reviewed-by: Petr Mladek <pmladek@suse.com>

Best Regards,
Petr

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