Messages in this thread | ![/](/images/icornerl.gif) | | Date | Mon, 21 Dec 2015 17:09:51 +0000 | From | Catalin Marinas <> | Subject | Re: [PATCH v5] arm64: run-time detection for aarch32 support |
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On Mon, Dec 21, 2015 at 07:44:10AM +0300, 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. > > v4: use new CPU Feature API. > v5: use cpuid_feature_extract_field. > > Signed-off-by: Yury Norov <ynorov@caviumnetworks.com> > --- > arch/arm64/include/asm/cpufeature.h | 7 +++++++ > arch/arm64/include/asm/elf.h | 6 ++++-- > 2 files changed, 11 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h > index 8f271b8..bcb0dbe 100644 > --- a/arch/arm64/include/asm/cpufeature.h > +++ b/arch/arm64/include/asm/cpufeature.h > @@ -184,6 +184,13 @@ static inline bool system_supports_mixed_endian_el0(void) > return id_aa64mmfr0_mixed_endian_el0(read_system_reg(SYS_ID_AA64MMFR0_EL1)); > } > > +static inline bool system_supports_aarch32_el0(void) > +{ > + u64 pfr0 = read_system_reg(SYS_ID_AA64PFR0_EL1); > + return cpuid_feature_extract_field(pfr0, ID_AA64PFR0_EL0_SHIFT) > + != ID_AA64PFR0_EL0_64BIT_ONLY; > +}
Suzuki already suggested to hook this into the existing arm64_features[] array:
http://lkml.kernel.org/g/56748437.2040905@arm.com
> +#define compat_elf_check_arch(x) (system_supports_aarch32_el0() \ > + && ((x)->e_machine == EM_ARM) \ > + && ((x)->e_flags & EF_ARM_EABI_MASK))
And here use something like cpus_have_cap(ARM64_HAS_32BIT_EL0).
And a nitpick: please use the same convention for placing the "&&" operator like in the rest of the file, i.e. on the previous line (similarly for "!=" etc.)
-- Catalin
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