[v2,6/8] ARM: enable elf_fdpic on systems with an MMU

[Vincent ABRIOU]

Hi Nicolas,

On 08/17/2017 09:23 AM, Nicolas Pitre wrote:
> Provide the necessary changes to be able to execute ELF-FDPIC binaries
> on ARM systems with an MMU.
> 
> The default for CONFIG_BINFMT_ELF_FDPIC is also set to n if the regular
> ELF loader is already configured so not to force FDPIC support on
> everyone. Given that CONFIG_BINFMT_ELF depends on CONFIG_MMU, this means
> CONFIG_BINFMT_ELF_FDPIC will still default to y when !MMU.
> 
> Signed-off-by: Nicolas Pitre <nico at linaro.org>
Tested-by: Vincent Abriou <vincent.abriou at st.com>

BR
Vincent

> ---
>   arch/arm/include/asm/mmu.h |  4 ++++
>   arch/arm/kernel/elf.c      | 22 ++++++++++++++++++++++
>   fs/Kconfig.binfmt          |  4 ++--
>   fs/binfmt_elf_fdpic.c      |  5 +++++
>   4 files changed, 33 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm/include/asm/mmu.h b/arch/arm/include/asm/mmu.h
> index e0eb16680a..bdec37c6ac 100644
> --- a/arch/arm/include/asm/mmu.h
> +++ b/arch/arm/include/asm/mmu.h
> @@ -14,6 +14,10 @@ typedef struct {
>   #ifdef CONFIG_VDSO
>   	unsigned long	vdso;
>   #endif
> +#ifdef CONFIG_BINFMT_ELF_FDPIC
> +	unsigned long	exec_fdpic_loadmap;
> +	unsigned long	interp_fdpic_loadmap;
> +#endif
>   } mm_context_t;
>   
>   #ifdef CONFIG_CPU_HAS_ASID
> diff --git a/arch/arm/kernel/elf.c b/arch/arm/kernel/elf.c
> index 52fb98358d..569e69ece5 100644
> --- a/arch/arm/kernel/elf.c
> +++ b/arch/arm/kernel/elf.c
> @@ -3,6 +3,7 @@
>   #include <linux/personality.h>
>   #include <linux/binfmts.h>
>   #include <linux/elf.h>
> +#include <linux/elf-fdpic.h>
>   #include <asm/system_info.h>
>   
>   int elf_check_arch(const struct elf32_hdr *x)
> @@ -89,3 +90,24 @@ int arm_elf_read_implies_exec(int executable_stack)
>   	return 0;
>   }
>   EXPORT_SYMBOL(arm_elf_read_implies_exec);
> +
> +#if defined(CONFIG_MMU) && defined(CONFIG_BINFMT_ELF_FDPIC)
> +
> +void elf_fdpic_arch_lay_out_mm(struct elf_fdpic_params *exec_params,
> +			       struct elf_fdpic_params *interp_params,
> +			       unsigned long *start_stack,
> +			       unsigned long *start_brk)
> +{
> +	elf_set_personality(&exec_params->hdr);
> +
> +	exec_params->load_addr = 0x8000;
> +	interp_params->load_addr = ELF_ET_DYN_BASE;
> +	*start_stack = TASK_SIZE - SZ_16M;
> +
> +	if ((exec_params->flags & ELF_FDPIC_FLAG_ARRANGEMENT) == ELF_FDPIC_FLAG_INDEPENDENT) {
> +		exec_params->flags &= ~ELF_FDPIC_FLAG_ARRANGEMENT;
> +		exec_params->flags |= ELF_FDPIC_FLAG_CONSTDISP;
> +	}
> +}
> +
> +#endif
> diff --git a/fs/Kconfig.binfmt b/fs/Kconfig.binfmt
> index 6ef70ce8e9..58c2bbd385 100644
> --- a/fs/Kconfig.binfmt
> +++ b/fs/Kconfig.binfmt
> @@ -34,8 +34,8 @@ config ARCH_BINFMT_ELF_STATE
>   
>   config BINFMT_ELF_FDPIC
>   	bool "Kernel support for FDPIC ELF binaries"
> -	default y
> -	depends on ((ARM && !MMU) || FRV || BLACKFIN || (SUPERH32 && !MMU) || C6X)
> +	default y if !BINFMT_ELF
> +	depends on (ARM || FRV || BLACKFIN || (SUPERH32 && !MMU) || C6X)
>   	select ELFCORE
>   	help
>   	  ELF FDPIC binaries are based on ELF, but allow the individual load
> diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
> index cf93a4fad0..692e2a1fd2 100644
> --- a/fs/binfmt_elf_fdpic.c
> +++ b/fs/binfmt_elf_fdpic.c
> @@ -377,6 +377,11 @@ static int load_elf_fdpic_binary(struct linux_binprm *bprm)
>   				 executable_stack);
>   	if (retval < 0)
>   		goto error;
> +#ifdef ARCH_HAS_SETUP_ADDITIONAL_PAGES
> +	retval = arch_setup_additional_pages(bprm, !!interpreter_name);
> +	if (retval < 0)
> +		goto error;
> +#endif
>   #endif
>   
>   	/* load the executable and interpreter into memory */
>