On Tue, Sep 01, 2015 at 03:41:12PM +0100, Yury Norov wrote:
> Kernel option COMPAT defines the ability of executing aarch32 binaries.
> Some platforms does not support aarch32 mode, and so cannot execute that
> binaries. But we cannot just disable COMPAT for them because the same
> kernel binary may be used by multiple platforms.
>
> In this patch, system_supports_aarch32_el0() is introduced to detect
> aarch32 support at run-time.
>
> Signed-off-by: Yury Norov <yno...@caviumnetworks.com>
> ---
> arch/arm64/include/asm/cpufeature.h | 1 +
> arch/arm64/include/asm/elf.h | 6 ++++--
> arch/arm64/kernel/cpuinfo.c | 9 +++++++++
> 3 files changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/include/asm/cpufeature.h
> b/arch/arm64/include/asm/cpufeature.h
> index 20cdc26..d24ea15 100644
> --- a/arch/arm64/include/asm/cpufeature.h
> +++ b/arch/arm64/include/asm/cpufeature.h
> @@ -81,6 +81,7 @@ void check_local_cpu_errata(void);
> void check_local_cpu_features(void);
> bool cpu_supports_mixed_endian_el0(void);
> bool system_supports_mixed_endian_el0(void);
> +bool system_supports_aarch32_el0(void);
>
> #endif /* __ASSEMBLY__ */
>
> diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
> index faad6df..461897b 100644
> --- a/arch/arm64/include/asm/elf.h
> +++ b/arch/arm64/include/asm/elf.h
> @@ -21,6 +21,7 @@
> /*
> * ELF register definitions..
> */
> +#include <asm/cpufeature.h>
> #include <asm/ptrace.h>
> #include <asm/user.h>
>
> @@ -173,8 +174,9 @@ typedef compat_elf_greg_t
> compat_elf_gregset_t[COMPAT_ELF_NGREG];
>
> /* AArch32 EABI. */
> #define EF_ARM_EABI_MASK 0xff000000
> -#define compat_elf_check_arch(x) (((x)->e_machine == EM_ARM) && \
> - ((x)->e_flags & EF_ARM_EABI_MASK))
> +#define compat_elf_check_arch(x) (system_supports_aarch32_el0() \
> + && ((x)->e_machine == EM_ARM) \
> + && ((x)->e_flags & EF_ARM_EABI_MASK))
>
> #define compat_start_thread compat_start_thread
> #define COMPAT_SET_PERSONALITY(ex) set_thread_flag(TIF_32BIT);
> diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c
> index 75d5a86..95d953f 100644
> --- a/arch/arm64/kernel/cpuinfo.c
> +++ b/arch/arm64/kernel/cpuinfo.c
> @@ -79,6 +79,15 @@ bool system_supports_mixed_endian_el0(void)
> return mixed_endian_el0;
> }
>
> +#define AARCH64 1
> +#define AARCH32_64 2
These should be better namespaced. Perhaps ID_AA64PFR0_EL1_EL0_64 and
ID_AA64PFR0_EL1_EL0_6432 ?
> +bool system_supports_aarch32_el0(void)
> +{
> + struct cpuinfo_arm64 *info = this_cpu_ptr(&cpu_data);
> + u64 arm64_el0 = info->reg_id_aa64pfr0 & 0xf;
> + return arm64_el0 == AARCH32_64;
> +}
We should handle this the same way as we do for endianness support and
check that all CPUs support AArch32, and set a global flag, rather than
assuming that all CPUs are symmetric. Likewise for any other feature we
have to dynamically detect.
Thanks,
Mark.
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